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1

Khandekar, Sameer. "Thermo-hydrodynamics of closed loop pulsating heat pipes." [S.l. : s.n.], 2004. http://www.bsz-bw.de/cgi-bin/xvms.cgi?SWB11312755.

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2

MAMELI, Mauro. "Pulsating heat pipes. Numerical Modelling and Experimental Assessment." Doctoral thesis, Università degli studi di Bergamo, 2012. http://hdl.handle.net/10446/222122.

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The present thesis is the result of a three year research study on the developing and experimental validation of a numerical model for the thermal-hydraulic simulation of Closed Loop Pulsating Heat Pipes. The project has been carried out in the framework of the PRIN-2009 and put the basis for a fruitful collaboration between the University of Bergamo and the Indian Institute of Technology Kanpur (IITK, India). The first two years were mainly devoted to improve the theoretical model and to the subsequent implementation of new subroutines. During this first stage the model has been validated by means of experimental data available from the literature. In the last year an actual CLPHP test-rig has been designed, built and tested. The outcome of the proprietor experimental apparatus provided new data on the heat transfer capability of two phase flows in mini-channels and allowed to perform a more accurate quantitative comparison with the simulation results. Although the final version of the numerical model is able to satisfactorily reproduce many trends of actual PHP devices, further work is needed in order to understand some open issues related to the physics and to release a reliable software tool for the PHP design.
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3

Mameli, Mauro. "Pulsating heat pipes. Numerical Modelling and Experimental Assessment." Doctoral thesis, Università degli studi di Bergamo, 2012. http://hdl.handle.net/10446/26720.

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The present thesis is the result of a three year research study on the developing and experimental validation of a numerical model for the thermal-hydraulic simulation of Closed Loop Pulsating Heat Pipes. The project has been carried out in the framework of the PRIN-2009 and put the basis for a fruitful collaboration between the University of Bergamo and the Indian Institute of Technology Kanpur (IITK, India). The first two years were mainly devoted to improve the theoretical model and to the subsequent implementation of new subroutines. During this first stage the model has been validated by means of experimental data available from the literature. In the last year an actual CLPHP test-rig has been designed, built and tested. The outcome of the proprietor experimental apparatus provided new data on the heat transfer capability of two phase flows in mini-channels and allowed to perform a more accurate quantitative comparison with the simulation results. Although the final version of the numerical model is able to satisfactorily reproduce many trends of actual PHP devices, further work is needed in order to understand some open issues related to the physics and to release a reliable software tool for the PHP design.
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4

Barba, Higueras María Asunción. "Study of Meter-scale Horizontal Cryogenic Pulsating Heat Pipes." Thesis, Université Paris-Saclay (ComUE), 2019. http://www.theses.fr/2019SACLS224/document.

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Un caloduc pulsé diphasique est un lien thermique composé d'un tube capillaire lisse sous forme de serpentin reliant un évaporateur à un condenseur, séparés par une partie adiabatique. Les conditions de température et de pression du fluide à l'intérieur du caloduc sont proches des conditions de changement de phase. De ce fait, et grâce aux dimensions capillaires du tube, le fluide se distribue en différentes parties liquide et vapeur distribuées de manière alternée. Les instabilités thermo-hydrauliques permanentes sont à l'origine d'un écoulement oscillant qui permet le transfert de chaleur de l'évaporateur jusqu'au condenseur.L'objectif du présent projet de recherche consiste à étudier le comportement thermo-hydraulique de trois caloducs cryogéniques pulsés diphasiques testés avec différents fluides cryogéniques (azote, néon et argon) pour le refroidissement d'aimants à haute température critique. De plus, un code numérique a été développé pour les futures simulations 2D des caloducs pulsés diphasiques.Au cours de ce projet de recherche, de nombreux tests expérimentaux ont été réalisés avec trois fluides cryogéniques différents: azote, néon et argon. Les résultats expérimentaux des tests avec une augmentation de puissance progressive dans l'évaporateur ont révélé des capacités de transfert thermiques très différentes en fonction du fluide, chaque fluide présentant un comportement thermo-hydraulique différent. L'état thermodynamique du fluide lors du fonctionnement stable du PHP et la phase d'assèchement (dry-out) ont été étudiés. Les différences dans le comportement des différents fluides ont été expliquées après l'analyse de leurs propriétés physiques. De plus, les taux de remplissage de fluide dans le PHP donnant les meilleures performances thermiques ont été définis. Ajouté à cela, de nombreux tests réalisés en configuration ouverte (avec le PHP connecté au volume tampon) et en configuration fermé (avec le PHP isolé du volume tampon) ont permis de conclure sur la capacité de régulation du volume tampon en cas de surpression dans le PHP. Aussi, les résultats expérimentaux des longs tests de stabilité ont permis de vérifier la stabilité du système PHP pendant des longues périodes de fonctionnement. Par ailleurs, des tests spécifiques ont été réalisés pour déterminer des conditions optimales de démarrage, l'influence de la température du condenseur dans les performances thermiques du système et l'influence du nombre de tubes en parallèle dans la capacité de transfert thermique du système. Finalement, une série de tests avec une forte puissance thermique imposée au niveau de l'évaporateur imitant une situation de quench dans un aimant supraconducteur ont données des précieuses informations sur les limites thermiques du système. Concernant les simulations numériques, un modèle a été développé avec le solveur Fluent pour des simulations dans une géométrie 2D axisymétrique en utilisant la méthode VOF. La dynamique du fluide dans un tube capillaire a été modélisée et les simulations thermiques ont permis de conclure que les instabilités thermodynamiques restent insuffisantes pour maintenir les oscillations du fluide. Ce modèle est présenté comme une nouvelle plateforme pour de futures modélisations 2D des caloducs pulsés diphasiques<br>A pulsating (or oscillating) heat pipe (PHP or OHP) is a heat transfer device composed of a single capillary tube bent in many U-turns, connecting an evaporator to a condenser, separated by an adiabatic part. In the PHP, temperature and pressure conditions of the working fluid are close to phase-change conditions. Due to this and to the capillary dimensions of the tube, the fluid is distributed in alternating liquid slugs and vapor plugs. Permanent thermal instabilities in the PHP create the oscillating flow which allows the transfer of heat from one end (the evaporator) to the other (the condenser).The objective of the present work consists in characterizing the thermo-hydraulic behavior of the meter-scale horizontal cryogenic pulsating heat pipes as a cooling solution for space superconducting magnets. To this, several experiments have been conducted in a cryogenic facility containing three different horizontal pulsating heat pipes. In addition, a numerical 2D model has been proposed for future horizontal pulsating heat pipes simulations.During the research project, numerous tests have been performed using three different working fluids: nitrogen, neon and argon. From experimental results of progressive heat load tests it has been possible to compare the maximum heat load transfer capacity of the PHP with each fluid and the corresponding thermal performance. It has also been noticed that each fluid presents a specific behavior concerning the fluid oscillations. In addition, the thermodynamic state of the fluid in operating conditions and the dry-out process have been characterized. Differences between fluid's behaviors have been partly explained by analyzing the evolution of the fluid physical properties related to the movement and the heat transfer capacity. Furthermore, it has been possible to conclude about the relation between the liquid filling ratio in the PHP and its thermal performance, determining the filling ratios giving the highest thermal performances. Moreover, similar tests have been performed in open configuration (with the PHP connected to the buffer volume) and closed configuration (with the PHP isolated from the buffer volume). From this, it has been possible to conclude about the regulation made by the buffer volume in case of overpressure in the PHP. Also, experimental results from long stability tests have confirmed that these pulsating heat pipe are able to work in stable conditions during long periods as a reliable cooling system. In addition to that, specific tests have been done to determine the optimum start-tup conditions, the influence of the temperature of the condenser in the thermal performance and the influence of the number of turns in the global heat transfer capacity. A final series of tests have been achieved with a sudden extra heat load at the surface of the evaporator while the PHP is operating in stable conditions, simulating a quench event of a superconducting magnet. Experimental results gave us precious information about the transient thermal behavior and operating limits of this kind of device during transient heat loads like quench situations. Concerning the numerical part, a numerical model has been proposed for transient simulations with a pressure-based Fluent solver using the Volume of Fluid (VOF) method in a 2D axisymmetric geometry. Certain characteristics of fluid dynamics in capillary tubes have been confirmed. It has also been noticed that thermodynamic instabilities are not enough to generate the fluid oscillations in capillary tubes. Even if the 2D axisymmetric simulation is still at its early stages, several aspects of the models have been validated after analyzing the evolution of different parameters, suggesting that this kind of model can be considered as a new platform for future 2D pulsating heat pipes simulations
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5

Simonetti, Marco. "Study of convective heat transfer phenomena for turbulent pulsating flows in pipes." Thesis, Orléans, 2017. http://www.theses.fr/2017ORLE2057/document.

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Dans le but de réduire la consommation en carburant et les émissions de CO2 des moteurs à combustion interne, un des leviers, qui a intéressé diffèrent acteurs dans le secteur automobile, est la récupération de l’énergie thermique disponible dans les gaz d’échappement. Malgré différents technologie ont été investigués dans le passé; les transferts de chaleur qui apparient dans les gaz d’échappement n’ont pas encore étés suffisamment étudiés. Le fait que les échanges de la chaleur apparent dans des conditions pulsatives, notamment due aux conditions de fonctionnement moteur, rende les connaissances acquis jusqu’à présent limités et ne pas exploitables. A l’état actuel on n’est pas capable de pouvoir prédire le transfert thermique convectif des écoulements pulsé. Les travaux de cette thèse s’instaurent dans la continuité de ce besoin, l’objectif principal est donc l’étude expérimentale du transfert thermique convectif des écoulements turbulent pulsés dans un conduit cylindrique. La première partie de ce travail a été consacrée à le dimensionnement d’un moyen d’essais permettant la création d’un écoulement pulsé type moteur; en suite différents méthodes de mesures ont étés développes afin de connaitre les variations instantanés de vitesse et température de l’écoulement. Plusieurs essais ont été reproduits afin de caractériser l’impact de la pulsation sur le transfert de la chaleur. Les résultats expérimentaux ont été analysés avec deux approches différentes: dans un premier temps une approche analytique 1D a permis de mettre en évidence le mécanisme principal responsable de l’amélioration du transfert thermique convectif,ainsi, il a fourni des éléments supplémentaires pour le futur développement de modèles mathématiques plus adaptés à la prédiction des transferts d’énergie. En suite une approche 2D, supporté d’une phase de modélisation numérique, a permis de caractériser le mécanisme de transport radial d’énergie thermique<br>Waste Energy Recovery represents a promising way to go further in fuel saving and greenhouse emissions control for Internal Combustion Engine applications. Although several technologies have been investigated in the past few years, the convective heat transfers, playing an important role in the energy exchanges at the engine exhaust, has not receive enough attention. Heat transfers, in such applications, occur in pulsating conditions because of the engine operating conditions, making thus the actual knowledge of the heat transfer phenomena limited and not exploitable. Nowadays there is not any model capable to predict convective heat transfers for pulsating flows. In this context, the present thesis addresses the purpose to study the convective heat transfer phenomena, by an experimental approach, occurring for turbulent pulsating flows in pipes. In the first part of this work, an experimental apparatus has been designed to reproduce an exhaust type pulsating flow in fully managed conditions, as well as, several measurement techniques have been developed to know the instantaneous profiles of air temperature and velocity. Many experiments have been performed in order to characterize the impact of the flow pulsation on the convective heat transfers. In the second part of this work, the experimental results have been analyzed with two different approaches: firstly, with a 1D assumption the time-average convective heat transfers has been computed, and the major mechanism responsible of the heat transfer enhancement has been pointed out. Furthermore, it has been possible to highlight the mathematical term representative of such mechanism, which should be accounted in future to define a more adapted numerical model for the heat transfer prediction. In a second phase with a 2D assumption, and, with an energy and a fluid-mechanic computational phase, the radial transport of thermal energy has been characterized for a pulsating flow
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6

MANZONI, Miriam. "Design of pulsating heat pipes. A novel non-equilibrium lumped parameter model for transient gravity levels." Doctoral thesis, Università degli studi di Bergamo, 2016. http://hdl.handle.net/10446/52296.

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As relatively new and promising members of the wickless heat pipe family, Pulsating Heat Pipes (PHPs), with high effective thermal conductivity and construction simplicity, may answer to the present industrial demand of efficient thermal control, flexibility and low costs. In the last twenty years, many experimental and numerical works focused on PHPs, but despite the great efforts, their non linear, two-phase, internal flow remains essentially an unknown and, thus, none of the existing models is actually able to simulate it. One of the most important unsolved questions regards the influence that gravity may have on the device thermal-hydraulic behavior. Literature, indeed, reports very poor and contradictory data, even if modified gravity conditions arise in various applications from automotive to aerospace, from chemistry to material synthesis. This work aims to fill this serious lack of knowledge. Thus, a capillary, closed loop PHP made of a copper tube bended into 32 parallel channels and filled with FC-72 has been investigated both on the ESA ESTEC Large Diameter Centrifuge (ESA Educational project Spin Your Thesis! 2013), and on board of the ESA-NoveSpace Airbus A300 Zero-G flying parabolic trajectories (58th and 59th ESA Parabolic Flight Campaigns). For the first time, a planar PHP with circular cross section channels, equipped with 14 thermocouples and a pressure transducer has been fully, thermally characterized in several operative conditions from 0.01g to 20g. In addition, in order to provide a numerical tool able to help and support the experimental research in enlarging the present knowhow and spreading PHPs industrial application, the results of these experimental campaigns have been used to develop and validate a novel lumped parameters model. It uses an advanced numerical technique to allow fast simulations, extending sensitivity analysis and device designs. Lumped parameter models are not a novelty for PHPs per se: however, for the first time this kind of numerical tools has been applied to simulate transient operative conditions removing physical simplified assumptions and embedding directly phase changes processes. The resulting code showed very good prediction capability, being able to reproduce with high accuracy the experimental recorded data both in steady and transient conditions.
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7

MANZONI, Miriam. "Design of pulsating heat pipes. A novel non-equilibrium lumped parameter model for transient gravity levels." Doctoral thesis, Università degli studi di Bergamo, 2016. http://hdl.handle.net/10446/222108.

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As relatively new and promising members of the wickless heat pipe family, Pulsating Heat Pipes (PHPs), with high effective thermal conductivity and construction simplicity, may answer to the present industrial demand of efficient thermal control, flexibility and low costs. In the last twenty years, many experimental and numerical works focused on PHPs, but despite the great efforts, their non linear, two-phase, internal flow remains essentially an unknown and, thus, none of the existing models is actually able to simulate it. One of the most important unsolved questions regards the influence that gravity may have on the device thermal-hydraulic behavior. Literature, indeed, reports very poor and contradictory data, even if modified gravity conditions arise in various applications from automotive to aerospace, from chemistry to material synthesis. This work aims to fill this serious lack of knowledge. Thus, a capillary, closed loop PHP made of a copper tube bended into 32 parallel channels and filled with FC-72 has been investigated both on the ESA ESTEC Large Diameter Centrifuge (ESA Educational project Spin Your Thesis! 2013), and on board of the ESA-NoveSpace Airbus A300 Zero-G flying parabolic trajectories (58th and 59th ESA Parabolic Flight Campaigns). For the first time, a planar PHP with circular cross section channels, equipped with 14 thermocouples and a pressure transducer has been fully, thermally characterized in several operative conditions from 0.01g to 20g. In addition, in order to provide a numerical tool able to help and support the experimental research in enlarging the present knowhow and spreading PHPs industrial application, the results of these experimental campaigns have been used to develop and validate a novel lumped parameters model. It uses an advanced numerical technique to allow fast simulations, extending sensitivity analysis and device designs. Lumped parameter models are not a novelty for PHPs per se: however, for the first time this kind of numerical tools has been applied to simulate transient operative conditions removing physical simplified assumptions and embedding directly phase changes processes. The resulting code showed very good prediction capability, being able to reproduce with high accuracy the experimental recorded data both in steady and transient conditions.
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8

Rao, Manoj. "Thermo-hydrodynamics of an extended meniscus as unit-cell approach of pulsating heat pipe." Thesis, Lyon, INSA, 2015. http://www.theses.fr/2015ISAL0080/document.

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Ce travail fait une tentative pour expliquer les oscillations induites thermiquement auto-entretenue d'un système à deux phases constitué d'un liquide-vapeur confinée ménisque isolé (un bouchon de liquide unique attenant à une bulle de vapeur) à l'intérieur d'un tube capillaire circulaire, la longueur du tube être exposé à un gradient de température net, créant ainsi un cycle continu de l'évaporation et la condensation. Ce système représente la simple « unité-cellule" version d'un caloduc oscillant (PHP). La compréhension fondamentale de son comportement de transport menant à oscillations auto-soutenue est essentielle pour la construction des modèles mathématiques jusque-là inexistants du système PHP complet. Tout d'abord, la visualisation des oscillations de l'unité de cellules a été effectuée dans des conditions aux limites thermiques contrôlées. Ici, une compréhension nouvelle et unique de la dynamique du système a été atteint par une synchronisation en temps réel de la mesure de pression interne avec la vidéographie haute vitesse qui a été utilisé pour visualiser et enregistrer les oscillations du ménisque et le mince film de liquide qui est mis sur le mur lorsque le ménisque quitte l'évaporateur. Un modèle numérique a été développé pour le système constitué par un bouchon de vapeur et un bouchon de liquide oscillant dans un tube fermé à une extrémité et relié à un réservoir à une pression constante à l'autre extrémité. Le principe de modélisation avait été posé lors de travaux antérieurs. Quelques modifications ont été jamais moins introduites dans ce travail pour prendre en compte les particularités de la nouvelle expérimental et pour améliorer le liquide modèle film de l'évaporation à la lumière des résultats expérimentaux. Une étude paramétrique a également été réalisée pour comprendre les implications des différents facteurs sur le fonctionnement d'un tel système<br>This work makes an attempt to explain the self-sustained thermally-induced oscillations of a two-phase system consisting of an isolated confined liquid–vapour meniscus (a single liquid plug adjoining a vapour bubble) inside a circular capillary tube, the tube length being exposed to a net temperature gradient, thereby creating a continuous cycle of evaporation and condensation. This system represents the simplest ‘unit-cell’ version of a Pulsating Heat Pipe (PHP). The fundamental understanding of its transport behavior leading to self-sustained oscillations is vital for building the hitherto non-existent mathematical models of the complete PHP system. First, visualization of the oscillations of the unit-cell has been done under controlled thermal boundary conditions. Here, a unique and novel understanding of the system dynamics has been achieved by real-time synchronization of the internal pressure measurement with high-speed videography that was used to visualize and record the meniscus oscillations and the thin liquid film that is laid on the wall when the meniscus leaves the evaporator. A numerical model was developed for the system consisting of a vapour plug and a liquid slug oscillating in a tube closed at one end and connected to a reservoir at a constant pressure at the other end. The modeling principle had been posed in previous work. Some modifications were never the less introduced in this work to take into account the peculiarities of the new experimental set-up and to improve the liquid film evaporation model in the light of the experimental results. Also a parametric study was carried out to understand the implications of the various factors on the working of such system
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MANGINI, Daniele. "Hybrid Thermosyphon/Pulsating Heat Pipe for Ground and Space Applications: A novel two-phase passive heat transfer device." Doctoral thesis, Università degli studi di Bergamo, 2017. http://hdl.handle.net/10446/77206.

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Pulsating heat pipes (PHP) are very promising passive heat transfer devices, simply made of a capillary tube and characterized by high thermal performance and extraordinary space adaptability. One of the main advantages with respect to Thermosyphons (TS) is that PHPs can work also without gravity assistance, making such technology interesting also for space applications. Nevertheless, the global heat power input that they can absorb is limited due to the capillary dimensions of the tube. The actual literature shows that it would be theoretically possible to build a hybrid TS/PHP with an Inner Diameter larger than the capillary limit, evaluated in normal gravity conditions, that works indeed as a loop thermosyphon on ground and switches to the typical PHP slug/plug operation when microgravity occurs. The aim of the present work is to prove the feasibility of such hybrid two-phase passive heat transfer device concept by means of a complete multi-parametric experimental campaign. Therefore, during the first year of the doctoral thesis, a fully equipped hybrid TS/PHP experiment is designed and built at the Thermal Physics Laboratories of the University of Bergamo. Then, such device is tested both on ground and in hyper-micro gravity conditions during the 61th and the 63th ESA Parabolic Flight Campaign. A thorough thermo-hydraulic characterization is performed on ground, varying important parameters such as the heat power input, the inclination angle, the ambient temperature and the heating elements position. It is found that a strategic arrangement of multiple heaters may be used in order to enhance the flow motion and consequently the thermal performance. In micro-gravity, parabolic flight tests point out a PHP working mode. The sudden absence of buoyancy force activates an oscillating slug/plug flow regime, typical of the PHP operation, allowing the device to work in any orientation. Although the present work demonstrates the feasibility of the TS/PHP concept, and that a strategic position of the heating elements promotes the two-phase flow motion, further tests in prolonged micro-gravity conditions (i.e. onboard a sub-orbital flight or, even better, the International Space) can point out the effective heat transfer performance in weightlessness conditions.
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Dufraisse, David. "Analyse expérimentale du comportement thermo-hydraulique de caloduc oscillant (Pulsating Heat Pipe (PHP) en environnement sévère : Application aux systèmes embarqués." Thesis, Chasseneuil-du-Poitou, Ecole nationale supérieure de mécanique et d'aérotechnique, 2017. http://www.theses.fr/2017ESMA0007.

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Le caloduc oscillant est étudié depuis plus d'une vingtaine d'années, mais n'est utilisé, pour l'instant,que pour le refroidissement de composants électroniques. Il y a actuellement un engouement pour élargir l'utilisation de cette technologie au refroidissement d'équipements dissipatifs embarqués. Toutefois, malgré de nombreuses études expérimentales et numériques, Je comportement chaotique d'un caloduc oscillant rend difficile la prévision de son fonctionnement dans des conditions encore jamais rencontrées. Avant de pouvoir l'implémenter dans une application liée au transport, il est nécessaire de s'intéresser aux conditions sévères qu'un caloduc oscillant pourrait rencontrer dans un tel contexte.La présente étude porte sur la validation expérimentale de l'utilisation d'un caloduc oscillant sous diverses conditions sévères. Pour cela, un premier dispositif permet l'observation du comportement du caloduc oscillant lors de variations temporelles des conditions opératoires observées durant un trajet aérien type, ou durant La présence de vibrations mécaniques. Le caloduc oscillant prouve ainsi son utilisation possible dans ce contexte. Deux autres dispositifs permettent l'analyse des performances et limites de fonctionnement pour des puissances (8,4 kW) et densités de puissances thermiques (53 W/cm2) bien supérieures à ce qui est observé classiquement dans la littérature. L'eau s'est montrée le fluide. le plus propice à ces niveaux de puissances,comparée au pentane et au méthanol. Ces deux dispositifs permettent également l'observation du comportement lors d'une répartition uniforme ou non de la puissance thermique injectée sur différentes sources chaudes. Des études paramétriques ont été menées sur les différents dispositifs pour les trois fluides de travail, couplées à des visualisations infrarouges, et permettent d'approfondir la compréhension de l'influence des conditions opératoires: le taux de remplissage, la répartition de la puissance et la température de source froide influencent de façon importante non seulement les performances, mais aussi la limite d'assèchement du caloduc oscillant<br>The pulsating heat pipe has been studied for more than twenty years, but is, for the time being, only used for the cooling of electronic components. Tbere is currently a keen interest in expanding the use of this technology to the cooling of embedded dissipative equipment. However, despite numerous experimental and numerical studies, the chaotic behavior of an pulsating heat pipe makes it difficult to predict its functioning under conditions never before encountered. Before being able to implement it in a transport-related application,it is necessary to consider the severe conditions that a pulsating heat pipe could encounter in such a context.The present study deals with the experimental validation of the use of a pulsating heat pipe under various severe conditions. For this purpose, a first device is made to observe the behavior of the pulsating heat pipe during temporal variations of the operating conditions observed during a typical flight or during the presence of mechanical vibrations. The pulsating heat pipe thus proves its possible use in this context. Two other devices serve the analysis of performance and operating limits for powers (8.4 kW) and heat flux densities(53 W/cm2) much higher than conventionally observed in the literature. Water is the most favorable fluid at these power levels, compared to pentane and methanol. These two devices also make it possible to observe the behavior during a uniform or non-uniform distribution of the injected thermal power on various hot sources. Parametric studies have been carried out on the various devices for the three working fluids, coupled with infrared visualizations, to deepen the understanding of the influence of the operating conditions: the filling ratio,power distribution and cold source temperature not only significantly influence performance but also the drying limit of the pulsating heat pipe
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Voirand, Antoine. "Etude théorique de la dynamique d'une bulle dans un tube capillaire chauffé." Thesis, Chasseneuil-du-Poitou, Ecole nationale supérieure de mécanique et d'aérotechnique, 2016. http://www.theses.fr/2016ESMA0008/document.

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Dans le cadre d’une contribution à la modélisation des caloducs oscillants, le modèle mis en place se résume à une bulle seule se déplaçant dans un tube de dimension capillaire.Une densité volumique de chaleur est considérée dans la paroi du capillaire, et la température de référence considérée n’est pas la température de saturation de la phase vapeur,mais la température extérieure au tube ce qui permet la variation de la température de saturation dans le temps et une meilleur adéquation du modèle avec la réalité. La résolution du modèle est effectuée par étapes selon la technique de perturbation du domaine,et les effets physiques de moindres importances peuvent être ajoutés au problème simplifié, en particulier les effets inertiels. Cette résolution a permis de définir une nouvelle corrélation portant sur la hauteur de film déposé par le bouchon liquide en mouvement en fonction du nombre capillaire et d’un nombre d’évaporation représentant l’intensité du chargement thermique. Ce modèle permettra aussi d’étudier l’influence réciproque des champs de vitesse et de température sur le bouchon de liquide devant le ménisque en déplacement. La résolution du problème associé à la partie arrière de la bulle met en évidence la formation d’un bourrelet de liquide entre le film de liquide déposé à la paroi et le ménisque arrière. La taille de ce bourrelet est fortement dépendante de la densité de flux de chaleur imposée à la paroi. Dans le cas o`u le ménisque arrière remouille un film adsorbé laissé à la paroi après assèchement du film, la ligne triple présente des ondulations axiales dues à son déplacement, et non au chargement thermique. La densité de flux de masse évaporée à l’interface liquide-vapeur entraîne une modification non seulement de la température de saturation, mais aussi de la masse de la bulle. Un modèle thermodynamique de la phase vapeur a ´et´e mis en place pour étudier les paramètres importants influençant les variations temporelles des caractéristiques géométriques et thermodynamiques de la bulle<br>The model of a single bubble moving in a capillary tube is written as a contribution to the modeling of Pulsating Heat Pipes. A constant heat load is considered at the wall, and the reference temperature of the problem is defined to be the outside medium temperature, which is closer to reality, and thus allowing the saturation temperature of the vapor phase to vary. Using domain perturbation techniques, a step-by-step resolution ofthe model is implemented, allowing minor physical effects to be taken into consideration,for example the inertial effect on the receding meniscus. A new correlation is proposed on the thickness of the liquid film deposited by the receding meniscus, by means of the capillary number and an evaporation number representing the thermal condition. The velocity and temperature fields in the liquid plug ahead of the meniscus can also be obtained. The resolution of the problem associated with the rear-end of the bubble,where the rear meniscus advances on either a micrometric liquid film or an adsorbed film left by the dry-out of the capillary wall, shows a corrugating liquid-vapor interface.The magnitude of these corrugations is strongly dependent on the value of the heat load applied at the wall. In the case of wall rewetting, the interface corrugations at the triple line are due to its displacement, and not to the thermal boundary condition. Because the evaporative mass flux through the liquid-vapor interface modifies the vapor bubble mass, a complete transient thermodynamical model of the bubble is implemented. In this case, the important parameters controlling the kinematics, dynamics and thermodynamics of the bubble were identified
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12

Fourgeaud, Laura. "Analyse de la dynamique du film liquide dans un caloduc oscillant." Thesis, Université Grenoble Alpes (ComUE), 2016. http://www.theses.fr/2016GREAY038/document.

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Nous étudions expérimentalement le comportement d'un film liquide, dit de Landau-Levich, lorsqu'il s'évapore dans une atmosphère constituée uniquement de sa vapeur.La dynamique de ce type de film est un paramètre-clef qui gouverne le fonctionnement des caloducs oscillant (en anglais PHP - Pulsating Heat Pipes). Les PHP sont des liens thermiques de forte conductance. Les recherches récentes leur attribuent un pouvoir de refroidissement très élevé, ce qui les rend particulièrement convoités par l'industrie. Leur géométrie est simple : il s'agit d'un tube capillaire enroulé en plusieurs branches entre une partie froide (condenseur) et une partie chaude (évaporateur). Le tube est rempli d'un fluide pur diphasique, c'est-à-dire présent sous la forme d'une succession de bulles de vapeur et de bouchons de liquide. Lorsque la différence de température entre l’évaporateur et le condenseur dépasse un certain seuil, les bulles et bouchons commencent à osciller dans le tube, entre les deux parties, ce qui permet au PHP de transférer la chaleur.Notre installation expérimentale représente un PHP dans sa configuration la plus simple, à branche unique. Une interface liquide-vapeur oscille dans un tube de section rectangulaire, et dépose un film liquide à chaque passage. Nous nous intéressons au mécanisme qui permet l'entretien de l'oscillation de l'interface, et fixe sa fréquence. L'équation de mouvement obtenue prend en compte la dissipation visqueuse engendrée par un écoulement oscillant. Dans les modèles actuels de PHP, l'hypothèse d'un écoulement de type Poiseuille est formulée. Or, notre approche montre que l'hypothèse d'un écoulement faiblement inertiel est mieux adaptée, conduit à une dissipation deux fois supérieure.Le dispositif expérimental permet l'observation du film. Une combinaison originale de méthodes optiques permet également de mesurer sa longueur et son épaisseur, et de reconstruire son profil 3D à chaque instant. Nous pouvons suivre l'évolution du film tout au long de sa durée de vie, et ainsi analyser son comportement dynamique. Le film est presque plat (pente inférieure à 0,1°). Sur toute sa longueur, qui est de quelques centimètres, cela correspond à une variation de son épaisseur de moitié, la valeur moyenne étant de 50 microns. Sous l'effet du chauffage, le film se rétracte progressivement. Dès le début de son évaporation, un bourrelet de démouillage est formé sur le pourtour du film, près de la ligne triple. L'apparition de ce bourrelet est caractéristique d'un démouillage visqueux sous conditions de non-mouillage. Ce comportement est surprenant, dans la mesure où nous avons choisi un fluide mouillant parfaitement la paroi en conditions isothermes. A l'échelle nanométrique, au plus près de la ligne triple, l'angle de contact entre le liquide et la paroi est donc très faible. Nous mesurons cependant un grand angle apparent (c'est-à-dire visible à l'échelle millimétrique), qui augmente avec la surchauffe de la paroi. Dès l'augmentation de cet angle, le bourrelet de démouillage se forme, et le film se rétracte. Ce phénomène est expliqué par l'évaporation à l'échelle microscopique. Les résultats expérimentaux sont en accord quantitatif avec la théorie développée par d'autres chercheurs<br>We experimentally study the behavior of liquid films - so called Landau-Levich films - when they evaporate in their pure vapor atmosphere.The dynamics of this film is a key parameter that rules out the functioning of Pulsating Heat Pipes (PHPs). PHPs are high conductive thermal links. Their heat transfert capability is known to be extremely high. For this reason they are promising for numerous industrial applications. Their geometry is simple. It is a capillary tube bent in several branches that meander between a hot part (called evaporator) and a cold part (called condenser), and filled up with a pure two-phase fluid. When the temperature difference between evaporator and condenser exceeds a certain threshold, gas bubbles and liquid plugs begin to oscillate spontaneously back and forth inside the tube and PHP starts transferring the heat.Our experimental setup features the simplest, single branch PHP. A liquid/vapor interface oscillates in a tube. It deposits a liquid film at each passage. We focus first on the mecanism which makes possible self-sustained interface oscillations and defines its frequency. The obtained motion equation accounts for the viscous dissipation caused by oscillatory flow. In existing PHP modelling, a laminar flow is supposed. Yet, our approach shows that the assumption of weakly inertial flow is preferable and leads to a dissipation rate twice larger that the Poiseuille flow.The experimental setup allows the film visualization. An original combination of optical measurement techniques lets us measure the film length, thickness and 3D-profile at all times. The film evolution has been measured during its whole lifetime. The film is nearly flat (its slope is smaller than 0,1°). The film length is of several centimeters, and the average thickness is 50 microns. Thus, along the total length, its thickness decreases by half. Under heating conditions, the film gradually recedes. A dewetting ridge is formed, near the triple contact line. Such a behavior is typical under non-wetting conditions. At the nanometric scale the contact angle between the liquid and the solid wall is very low. However, we measure a large apparent contact angle (visible at the millimetric scale) which increases with the wall superheating. Once this angle increases, the dewetting ridge is formed and the film recedes. The large apparent contact angle is explained by evaporation in the microscopic vicinity of the contact line. The measured apparent contact angle value agrees quantitatively with theoretical results obtained by other researchers
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13

Наумова, Альона Миколаївна. "Теплопередаючі характеристики пульсаційних капілярних теплових труб, призначених для малогабаритних систем охолодження". Thesis, НТУУ "КПІ", 2016. https://ela.kpi.ua/handle/123456789/14940.

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Дисертація присвячена дослідженню теплопередаючих характеристик пульсаційних капілярних теплових труб (ПТТ) в залежності від режимних та експлуатаційних параметрів. Дослідження проводились зі скляною та мідною ПТТ з внутрішнім діаметром, відповідно, 3,8мм та 1мм; кількість петель 4 та 7. Теплоносієм слугувала вода з коефіцієнтом заповнення приблизно 50% від внутрішнього об’єму. Охолодження скляної ПТТ відбувалося за рахунок вільної конвекції повітря, мідної – за рахунок вимушеної конвекції рідини з різними значеннями температури та витрати. Кут нахилу мідної ПТТ до горизонту змінювався від -90° до +90° з кроком 45°. Робота ПТТ умовно розділена на два режими передачі тепла: конвективно-кондуктивний, що відповідає малим значенням підведеної теплової потужності, та пульсаційний, що відповідає середнім та високим значенням підведеної теплової потужності та початку кипіння теплоносія. Величину теплового потоку, за якої відбувається перехід від одного режиму передачі тепла до другого, названо перехідним QПЕРЕХ. В результаті досліджень виявлено вплив режимних (підведений тепловий потік, витрата та температура охолоджувальної рідини) і експлуатаційних (орієнтації в просторі, зовнішні механічні вібрації) на температурний режим, термічний опір та коефіцієнти тепловіддачі ПТТ. Отримана напівемпірична залежність для приблизного розрахунку QПЕРЕХ. Отримані формули для обчислення кількості петель замкнутої та розімкнутої ПТТ в залежності від геометрії капілярної трубки, довжин зон нагріву та конденсації. На базі пульсаційного механізму теплопередачі розроблені новітні пристрої. Порівняння роботи ПТТ з іншими радіаторами показало, що пульсаційні теплові труби найбільш ефективні при необхідності відведення високих теплових потоків (більш ніж 6 Вт/см2).<br>The dissertation is dedicated to the heat transfer characteristics of pulsating capillary heat pipes (PHP) depending on the regime and operational parameters. The experiments were conducted with glass and copper PHP with the internal diameter, respectively, 3,8mm and 1mm; number of turns 4 and 7. The water was used as a heat carrier; the filling ratio was approximately 50% of the internal volume. Cooling of the glass PHP was carried out by free air convection, and cooling of the copper one was carried out by forced convection of the liquid with different values of temperature and flow rate. The inclination angle of the copper PHP varied from -90° to + 90° in increments of 45 °. The PHP operation can be conditionally divided into two modes of heat transfer that are: convection-conductive mode that corresponds to small values of input heat power and pulsation mode that corresponds to middle and high of input heat power and to the heat carrier boiling. The heat flux called transient takes place at the transition from one mode of heat transfer to another. As a result of experimental studies the temperature of the PHP heating, transport, and condensation areas as well as thermal resistance and heat transfer coefficients are presented depending on the input heat flux and parameters of the cooling fluid. The dependence of the PHP heat transfer characteristics on external mechanical vibrations and PHP orientation in space was researched. The simplified semi-empirical formula for transient heat flux calculating is obtained. Given dissertation also presents a constructional calculation of the PHP number of loops when manufactured depending on the geometry of the capillary tube, and the lengths of the heater and the condenser. On the basis of the pulsation heat transfer mechanism some new heat transfer devices were designed, such as pulsating thermosyphon radiator with PHP. Comparing of the PHP with other cooling systems has shown that it is most effective for rejection of the heat fluxes over 6 W/cm2.<br>Диссертация посвящена исследованию теплопередающих характеристик пульсационных капиллярных тепловых труб (ПТТ) в зависимости от режимных и эксплуатационных параметров. Исследования проводились со стеклянной и медной ПТТ с внутренним диаметром, соответственно, 3,8мм и 1мм; количество петель 4 и 7. Теплоносителем служила вода с коэффициентом заполнения примерно 50% от внутреннего объема. Охлаждение стеклянной ПТТ осуществлялось за счет свободной конвекции воздуха, медной – за счет принудительной конвекции жидкости с разными значениями температуры и расхода. Угол наклона медной ПТТ к горизонту изменялся от -90° до +90° с шагом 45°. Работа ПТТ условно разделена на два режима передачи тепла: конвективно-кондуктивный, соответствующий малым значениям подведенной тепловой мощности, и пульсационный, соответствующий средним и высоким значениям подведенной тепловой мощности и началу кипения теплоносителя. Величина теплового по- тока, при котором происходит переход от одного режима передачи тепла к другому, называется переходным QПЕРЕХ. В результате экспериментальных исследований представлены зависимости температур в зонах нагрева (ЗН), транспорта (ЗТ) и конденсации (ЗК) ПТТ от времени и подведенного теплового потока. Показано влияние параметров охлаждающей жидкости – расхода и температуры – на величину QПЕРЕХ. Для медной ПТТ стабильный пульсационный режим теплопередачи устанавливается при 30-50 Вт в зависимости от параметров эксперимента. Величина термического сопротивления ПТТ различается только в области конвективно-кондуктивного режима теплопередачи и достигает значений 4-5 °С/Вт, после начала кипения эта цифра снижается на порядок и составляет примерно 0,3-0,6 °С/Вт. Влияние режима теплопередачи сказывается и на величину средних коэффициентов теплоотдачи в ЗН и ЗК ПТТ. Если для конвективно-кондуктивного режима теплопередачи средние коэффициенты теплоотдачи для ЗН составляют 400-450 Вт/(м2·К), а для ЗК – 200-250 Вт/(м2·К), то для пульсационного режима передачи тепла в ПТТ средние коэффициенты теплоотдачи в ЗН достигают 3,5-4 кВт/(м2·К), а в ЗК – 1,8 кВт/(м2·К), т.е. почти в 9 раз больше. Впервые исследована зависимость теплопередающих характеристик ПТТ от внешних механических колебаний. Эксперименты показали, что вибрации практически не оказывают влияния на величину термического сопротивления, однако способствуют тому, что QПЕРЕХ наступает при меньших значениях подведенной мощности. Например, если без вибраций QПЕРЕХ = 45-50 Вт, то для частоты 10 Гц это значение снижается до 40 Вт, а для частоты порядка 40 Гц – до 20-25 Вт. Приведена физическая модель процессов, возникающих в ЗН в момент начала кипения теплоносителя. На основе теплового баланса построена математическая модель, учитывающая зарождение, рост и дальнейший отрыв парового пузырька в ЗН. В результате решения математической модели получена упрощенная полуэмпирическая формула для расчета QПЕРЕХ. Расчетные значения величины QПЕРЕХ превышают экспериментальные данные в среднем на 21%, что не уменьшает работоспособности формулы. В работе представлен конструктивный расчет количества петель ПТТ при её изготовлении в зависимости от геометрии капиллярной трубки, а также длин ЗН и ЗК. Приведена методика инженерного расчета ПТТ. Зная максимальную температуру и геометрические параметры теплонагруженного элемента, а также отводимую мощность и условия охлаждения, можно рассчитать среднюю температуру и термическое сопротивление ПТТ. На основе пульсационного механизма передачи тепла разработаны новые конструкции теплопередающих устройств: пульсационный термосифон и радиатор с ПТТ.
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Chen, Yi-Rong, and 陳奕融. "Horizontal Operation of Flat-Plate Closed-Loop Pulsating Heat Pipes." Thesis, 2009. http://ndltd.ncl.edu.tw/handle/52212456125152649683.

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碩士<br>元智大學<br>機械工程學系<br>97<br>In recent years, Pulsating Heat Pipes (PHPs) without wick structures have drawn much attention of many researchers for enhancing heat transfer through passive two-phase flow heat transfer mechanism. The characteristics of flat-plate closed-loop pulsating heat pipes are applied on spreaders widely and viewed as competitive passive heat transfer devices. This research aims to experimentally investigate thermal performance of flat-plate closed-loop Pulsating Heat Pipes (CLPHPs) in horizontal operating condition. Two tested CLPHPs are made of copper capillary tubes with overall size 122×57×5.5 mm3, one of them has 16 parallel square channels with cross-section 2×2 mm2, called uniform CLPHPs, and the other one, called non-uniform CLPHPs, has 8 parallel square channels with cross-section 2×2 mm2 and 8 parallel square channels with cross-section 1×2 mm2. The working fluid used on the two CLPHPs is distilled water. Both of them are covered by acrylic plates for visualization study. By using a high-speed video camera, the effects of two-phase flow patterns on the evaporator temperature and the heat transfer mechanism for various heat loads are investigated. The results show that the optimal performance of heat transfer occurs at a steady circulating flow pattern. It is also found that, non-uniform CLPHPs with a filling ratio of 60% can operate in horizontal position and the optimal performance of overall thermal resistance is 0.81(°C/W). The operation limit of the filling ratio is 50%, below which oscillating two-phase flows disappear and the heat transfer mechanism approximates to conduction. The uniform one can’t work with any filling ratios in horizontal position.
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15

陳聖文. "On the Performance of Flat-Plate Closed-Loop Pulsating Heat Pipes." Thesis, 2008. http://ndltd.ncl.edu.tw/handle/09212336298502050968.

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碩士<br>國立清華大學<br>動力機械工程學系<br>96<br>Due to the lack of wick structures, Pulsating Heat Pipes (PHPs) have drawn the attention of many researchers for enhancing heat transfer through passive two-phase flow heat transfer mechanisms. The characteristics of flat-plate closed-loop pulsating heat pipes are recently applied on spreaders and are viewed as competitive passive heat transfer devices. In the present study, flat-plate PHP structures (rectangular cross-section area are 1.5mmx2mm, hydraulic diameter =1.714mm), which are directly machined onto an aluminum substrate (110mmx44mmx3mm) and are covered by an acrylic plate, are made for visualization study. The working fluid is DI water. By using a high-speed video camera, the effects of two-phase flow patterns on the evaporator temperature and the heat transfer mechanism for varied heat load are investigated. The optimal performance of heat transfer occurs when a steadily circulating flow pattern appears. To further examine the thermal performance, a flat-plate PHP made of copper(112mmx48mmx4mm) with the same groove dimensions as that for visualization study is made for the problem of interest. It is found that, with a filling ratio of 50% and a tilting angle of 90°, the optimal performance yields an overall thermal resistance of 0.52(°C/W) and a maximum heat capacity of 100W. The operation limit of the tilting angle is 20° below which oscillating two-phase flows disappear and the heat transfer mechanism approximately becomes a process of pure conduction. Finally, this thesis proposes some workable ways to improve the visualization study of flat-plate PHPs in the future.
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16

Shiang, Hung-Chi, and 洪啟翔. "Experimental studies of flow patterns in closed loop pulsating heat pipes." Thesis, 2011. http://ndltd.ncl.edu.tw/handle/72985667493685374081.

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碩士<br>淡江大學<br>機械與機電工程學系碩士班<br>99<br>A Closed Loop Pulsating Heat Pipe (CLPHP) is a complex heat transfer device with a strong thermo-hydrodynamic coupling governing its thermal performance. This research utilized 6 mm outer diameter and 3 mm inner diameter glass tubes to manufacture 9 turns closed loop Pulsating Heat Pipe(PHP) with a total length of 1980mm. For achieving the loop circulation easily, a water cooling system kept at 25 ℃ was used as the condenser, and used methanol as working fluid. Experiment was conducted to measure temperature difference and to evaluate the thermal resistance under at a series change of power inputs (30W, 60W, 90W, 120W, 150W, 180W). A digital video camera was used to record the working situation of the working fluid inside the channel. The flow pattern can be categorized into clockwise, counter-clockwise and transition status. The results showed the flow direction of PHP was changed with the temperature difference of tubes. The lowest resistance is 0.217(K/W) at an input power of 180W in this study.
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Wu, Ho-Meng, and 吳河孟. "Performance Tests on Pulsating Heat Pipes (PHPs) and Water-Cooling System under Two Heat Sources." Thesis, 2018. http://ndltd.ncl.edu.tw/handle/a9d6cp.

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18

Khandekar, Sameer [Verfasser]. "Thermo-hydrodynamics of closed loop pulsating heat pipes / vorgelegt von Sameer Khandekar." 2004. http://d-nb.info/972098682/34.

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19

Liao, Wei-Chen, and 廖偉辰. "The Research and Development of Oil Immersed Transformer by Using Pulsating Heat Pipes (PHP)." Thesis, 2018. http://ndltd.ncl.edu.tw/handle/572249.

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Nikkanen, Kathryn. "A study of pulsating heat pipes for electronics cooling applications : structure, fluid, and performance parameters." 2005. http://link.library.utoronto.ca/eir/EIRdetail.cfm?Resources__ID=370108&T=F.

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21

Wang, Pei-Kang, and 王培綱. "Flat Plate Pulsating Heat Pipe Heat Spreader." Thesis, 2007. http://ndltd.ncl.edu.tw/handle/78471415576473642443.

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碩士<br>國立中央大學<br>能源工程研究所<br>95<br>This article is trying to develop a new kind heat spreader, which were used the theory of pulsating heat pipes. Channels were manufactured on copper plate, to finish the flat plate pulsating heat pipes. When heat input, fluid makes phase changes, produce the vapor pressure difference between the evaporation area and condensation area, the major heat transfer mechanism in a pulsating heat pipe is the sensible heat of liquid. Channels arrangement designed to two types, which were single loop and double side loop. In order to understand the influence by the wide of channel, there are two kinds of channel size, which wide were 0.5 mm and 1 mm. In this article, also experiment three fill rate, which were 20 %、50 % and 80 %. The heat transfer characteristics of flat plat pulsating heat pipes were investigated experimentally. The experimental results at the same input heat and same fill rate, the single loop design which heat transfer performance better than the double side loop. When fix the fill rate as 50 %, the minimum heating power is 15 W at 1 mm wide channel, 20 W at 0.5 mm wide channel. In the experiment of different fill rate, when fill rate 20 %, pulsation only occurs at heating power 15 W, as the heating power increase, pulsation stop. Also found that the optimal fill rate is around 50 % and 80 %. The drag force which caused by the channel walls will decrease the liquidity, also decrease the range of pulsation. In order to decrease the spreading resistance, we should make the design of channel better.
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22

Wu, Tsung-Yu, and 吳宗祐. "Fabrication of Polydimethylsiloxane Pulsating Heat Pipe." Thesis, 2007. http://ndltd.ncl.edu.tw/handle/70474598124806879265.

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碩士<br>淡江大學<br>機械與機電工程學系碩士班<br>95<br>This paper reports on preliminary experimental results by using polydimethylsiloxane (PDMS) to manufacture a visual pulsating heat pipe with length, width and internal diameter are 56mm, 50mm and 2mm respectively. That includes manufacturing process and the vacuuming management for filling and packaging. Try to design a standard process to manufacture the prototype and to complete the test platform structure. Make use of the methanol and ethanol to be the working fluid. According to the fix filled ratio (about 60%) and different heating power (3W, 4W, 5W, 6W, 7W, 8W respectively) to test the thermal performance. By utilizing the high speed video camera, shoot working situation of the working fluid inside the channel will be discussed and analyzed. The experimental shows that when the working fluid is methanol and placed it in vertical orientation could have shown the best efficiency result. When the heating power is 3W, the thermal resistance is less to 4.5ºC/W than the ethanol working fluid. When the heating power is 4W, the average temperature will decrease to 15ºC of the evaporator. In the mean time, the gravity will have the impact on PHP performance, therefore the vertical orientation is easier to work as compared to the horizontal orientation. According to the visual observation, utilize the high speed video camera; observe that working situation of the complex vapor plug and liquid slug inside the channel to study the behavior of flows. It is clear to observe the different heating power of the pulsating heat pipe which changes the working situation and flow type of the working fluid. We can find out that change from minute bubble flow into slug bubble flow and change into continuous slug bubble flow, nucleation of bubble in the evaporator, bubble combination, break, collapsed and vanishes. When PHP is inputting higher heat flux, vapor plug and liquid slug will begin in a regular direction inside the channel to make it circulate with high oscillation amplitude.
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23

Lin, Yi-Pang, and 林益邦. "Manufacture and Measure of Pulsating Heat Pipe." Thesis, 2004. http://ndltd.ncl.edu.tw/handle/87067598670904021236.

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碩士<br>國立臺北科技大學<br>製造科技研究所<br>92<br>The Purpose of this thesis is to investigate Pulsating Heat Pipe which is one new concept of microelectronics thermal management .A two phase loop is constructed with a copper capillary tube ( ID:2.4mm)having no internal wick structure. The loop is through estimation to overcome the shortcomings and limits of the convectional Heat Pipe. While PHP has an advantage of simple structure; as simply manufacture process. The Vacuum Process of heat pipe, which is base on the vacuum after injection into water principle of NTFL Lab. To ensure the ratio of water loss inside 2%.To improves the heat pipe process in the past. The problem of can not accurately control degree of vacuum and the rest water in the heat pipe. The flow pattern visualization module of this paper, which using a charge coupled device (CCD).It was observed the complex act condition of slug-plug train flow in the tubes, and during the start —up period, the working fluid oscillates principles. So as to observed the practice behavior mode of flow pattern. The loop at steady operating state, the working fluid heat transfer circulates was observed by Infrared Rays Thermal Screen Imager. According to the NTFL Lab testing procedures. To obtain the best Filling Ratio is 50%, While the working fluid is water, the best operate orientation is vertical. The lowest Rth is 0.29(℃/W).The results strongly demonstrate the effect of input heat flux ,and change of flow pattern , turn number and filling ratio of the working fluid on the thermal performance of the device. Even more further understand the whole characteristic and performance of PHP. To invest in microelectronics thermal management and to solve the problem of waste heat in the future.
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24

Ramesh, Uppala. "Thermal Analysis of Closed Loop Pulsating Heat Pipe." 2004. http://www.cetd.com.tw/ec/thesisdetail.aspx?etdun=U0001-2507200514185500.

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25

Uppala, Ramesh, and 迦文西. "Thermal Analysis of Closed Loop Pulsating Heat Pipe." Thesis, 2005. http://ndltd.ncl.edu.tw/handle/91437765245664491044.

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碩士<br>國立臺灣大學<br>機械工程學研究所<br>93<br>This study aims to flow visualization and thermal analysis of a closed loop pulsating heat pipe based on inclination angle, charging ratio, type of fluid and heat flux for thermal control of micro electronic equipments. Although a variety of designs are in use, understanding of the fundamental processes and parameters affecting the PHP operation are still vague. A vertical, closed loop, glass PHP with water, methanol and 2-propanol as working fluids is first experimentally investigated for a range of heat inputs, inclination angles and charging ratios. Experimental studies are performed on a PHP, consisting of a heating section, an adiabatic section and a condensation section incorporating heat sink. The capillary tube used in this study has an inside diameter of 2mm and a wall thickness of 3mm.Total length of the pulsating heat pipe is 350cm. The experiments are conducted under forced convection cooling at the condenser section, with heating powers from 10 to 110W, with different heating modes (locations) and charging ratios from 30% to 80%. The experimental results show that the system presented better performance when operating at vertical orientation. Optimal charging ratio is 50% for DI water, 40% for methanol and 40% for 2-propanol. Regarding working fluid the PHP shows better performance when Methanol is used in vertical orientation with the lowest evaporator section temperatures.
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26

Peng, Hsien-Kai, and 彭賢凱. "The Visualization of Flat Plate Pulsating Heat Pipe." Thesis, 2009. http://ndltd.ncl.edu.tw/handle/07735348152154965157.

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碩士<br>國立中央大學<br>機械工程研究所<br>98<br>This article is trying to etching manufactured pulsating heat pipes on copper plate, and design two kind of loop type channel, In this article, experiment three filling ratio 50 %, and different incline, which were 0°、30°、60° and 90°, also record vapor motion in the channel by high speed camera,and want to know different operate conditions effect to flat plate pulsating heat pipes by visualization observe. By visualization observe and thermal resistance analysis, it is found out that, with a filling ratio 50 % and incline angle 90° have optimal performance yields a thermal resistance, and the phenomenon of oscillating can observe from30°~90°, when heating rate at 45W, thermal resistance decrease 44% than heating rate at 15W. In the double loop pulsating heat pipes, thermal resistance change is unobvious with heat input. In this article we found that the flow oscillating can enhance heat transfer, but there is a critical in low incline angle.
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27

Huang, Hsin-Fu, and 黃信輔. "The Study of Double Closed-Loop Pulsating Heat Pipe Heat Exchangers." Thesis, 2017. http://ndltd.ncl.edu.tw/handle/bs3434.

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28

Tu, Tang-Hung, and 涂堂烘. "Fabrication and Test of Closed-loop Pulsating Heat Pipe." Thesis, 2005. http://ndltd.ncl.edu.tw/handle/25477134870862668660.

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碩士<br>國立清華大學<br>動力機械工程學系<br>93<br>Pulsating heat pipe (PHP) is a newly developed two-phase-flow heat transfer device, which can transfer heat very efficiently in both sensible and latent forms. Due to the simple structure and the bent characteristics, PHP becomes a prosperous heat transfer machine. The purpose of this study is to build several closed-loop PHPs made by copper tube (outer diameter 1/8”, inner diameter 2mm) or glass tube (outer diameter 3mm, inner diameter 2mm), which is partially filled with a working fluid such as water. Based on the above developed PHP, the experiments were conducted as follows: (1) to observe visualization of flow pattern inside the PHP tube, (2) to measure the thermal transport performance of PHPs, and (3) to compare the performance of PHP and traditional heat pipe (THP). The experimental results show that (1) the type of flow pattern inside the PHP tube depends on the input heat loading. It was found that the flow pattern changes from the oscillating to transiting and then to stable period with increasing input heat loading; (2) the thermal resistance of PHP decreases with increasing heat loading. In addition, when the filling ratio is equal to 30%, it reaches the best heat transfer efficiency. When the angle of inclination changes, main parameter that effects efficiency of PHP, will be different; and (3) in case that both heat loading and area of heat transfer surface are equal, PHP may have the better heat transfer efficiency than THP at the vertical operating condition.
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29

Hsu, Chang-Jung, and 許展榕. "Nondimensional Parameters’ Simulation of Open-Loop Pulsating Heat Pipe." Thesis, 2008. http://ndltd.ncl.edu.tw/handle/r6a8at.

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碩士<br>國立臺北科技大學<br>製造科技研究所<br>96<br>This research is to make a description of open-loop pulsating heat pipe’s parameter by using four nondimentional parameterα(energy ratio),β(density empty ratio),γ(empty filling ratio),Rm(mass ratio).After simulating,we can find no oscillation zone and oscillation zone.In our simulation,α is meaning of internal energy divided by kinetic energy’s ,βis meaning of empty volume ratio divided by density ratio,γis meaning of empty filling ratio divided by filling ratio,Rm is meaning of mass evaporating rate divided by flow rate. In this research,we develop two software by EES(Engineering Equation Solver),one is PHP.ees ,this software is using slug’s continuity and momemtum equation , plug’s continuity and energy equation and state equation,these five equation will solve by EES in order to understand open-loop pulsating heat pipe’s thermal property’s variety;another is Txt.ees,this software is using slug’s energy equation to slove a slug’s temprature distribution,then calcuting the slug’s heat transfer rate.EES is a software with bulid-in thermal property’s database and can create GUI ,it is why we use this software in this research .After creating GUI ,it will be easier to operate for people who doesn’t understand EES very much ,and it will let open-loop pulsating heat pipe’s design more easier. When we let geometry fixed ,β becomes function of filling ratio .Then we could find out an oscillation area changed with filling ratio ,when α is 4126 .As Fig 4.11 ,Fig 4.12,Fig 4.13 and Fig 4.14 ,filling ratio changes from 0.6 to 0.68 in oscillation area. After simulating Table 4.1 , we could find there is a maximum heat transfer rate 16.15(W) in one slug , and there are two equal slugs in this system , the maximum heat transfer rate in this system is 32.3(W).
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30

Hsuan, Chuang Yu, and 莊宇軒. "The Effectiveness Analysis of Double Closed-Loop Pulsating Heat Pipe." Thesis, 2016. http://ndltd.ncl.edu.tw/handle/h5atfs.

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31

WEI, LIN CHIN, and 林金緯. "Radial-type Closed Loop Pulsating Heat Pipe Design and Fabrication." Thesis, 2009. http://ndltd.ncl.edu.tw/handle/96486077280910849802.

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碩士<br>聖約翰科技大學<br>自動化及機電整合研究所<br>97<br>In this paper, in order to create a number of different length and bend the new type of Radial-type closed loop pulsating heat pipe and to analyze its effectiveness; "RCLPHP" is the abbreviation of Radial-type closed loop pulsating heat pipe. The production process of RCLPHP, in addition to do flow visualization to observe the situation, but also joined the different design parameters such as copper pipe and brass pipe (external diameter = 3 mm, internal diameter = 2.5 mm), the number of radiation (8, 10, 12) and radiation length (50mm, 100mm, 150mm) as a change in mix and match parameters, the working fluid is pure water, filling rate are 40%, 50%, 60%, and use the different heating power (10W, 20W, 30W, 40W, 50W, 60W) compared with solid and filling the heat transfer performance of RCLPHP. The evaporation side of RCLPHP are heated by the square copper of the central bottom 40 mm , and the condensation side use the forced air cooling for heat dissipation. Experimental results show, that the radiation length 150 mm and radiation number of 12, filling rate of 60%, due to liquid and vapor bubble pulsating cycle frequency, and significantly lower temperature, it is better heat dissipation.
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32

Chan, Chien-Hsuan, and 詹前軒. "Study on Circulation Flow in Closed Loop Pulsating Heat Pipe." Thesis, 2010. http://ndltd.ncl.edu.tw/handle/61314848247762995792.

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碩士<br>淡江大學<br>機械與機電工程學系碩士班<br>98<br>This research utilized 6 mm outer diameter and 3 mm inner diameter glass tubes to manufacture 9 turns closed loop Pulsating Heat Pipe(PHP) with a total length of 1980mm. For achieving the loop circulation easily, a water cooling system kept at 35 ° C was used as the condenser. The experiment was conducted to evaluate the thermal resistance under different fluid filling ratios (20%, 30%, 40%, 50%, 60%, 70% and 80%), and at a series change of heat inputs (40W, 80W, 120W, 160W, 200W). Through a digital video camera, the visualization experiment was carried out to observe the circulation flow period in the PHP. A styrofoam ball was designed to put into the tube for a better observation and a correct estimation of fluid flow direction. Circulation times and circulation period were observed and calculated from different filling ratio tests. We also analyze the effect of inclination angles to the performance and circulation period in the PHP. The results showed that PHP reached fully circulation under the filling ratio of 60%, 70%, and 80%, at an input power of 200W. The circulation can be categorized into clockwise circulation, counter-clockwise circulation and transition circulation status. The shorter circulation period happened as filling ratio was 80%. We also found that there were more counter-clockwise circulation occurred in each experiment. Due to gravity effects, better performance and shorter period took place when the inclination angle was 45 °. Key words: pulsating heat pipes, PHP, circulation flow, circulation period
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33

Cheng, Po-Hsuan, and 鄭博軒. "Fabrication of Polydimethylsiloxane Mixing with Copper Powder Pulsating Heat Pipe." Thesis, 2008. http://ndltd.ncl.edu.tw/handle/79414202990954535469.

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碩士<br>淡江大學<br>機械與機電工程學系碩士班<br>96<br>This paper reports on using polydimethylsiloxane (PDMS) and copper powder to manufacture a visual pulsating heat pipe (PHP) with a length of 56mm, a width of 50mm, an internal diameter of 2mm, and total length of 580mm. Evaporator and condenser were put into copper blocks as the media for heating and heat dissipation. In order to increase the speed of heat conduction, PDMS mixed with copper powder in these two sections and finishing making the vacuum management. According to the fix filled ratio (60%) and different heating power (3W, 4W, 5W, 6W, 7W, 8W) to test the efficiency of the Polydimethylsiloxane mixing with Copper Powder (PCP) PHP. When the working fluid is methanol, and the PHP is in a vertical orientation, increasing the heating power, then the PHP is working. When the heating power reaches 8 watts and the PHP will work obviously. So we can get the lowest thermal resistance of 7.7℃/W. A video camera was used to record the fluid pulsating motion inside the PHP. Different heating powers were employed to observe the working situation, flow direction of the vapor plug, liquid slug and the structure form of the flow. We can find the change from minute bubble flow into slug bubble flow and change into continuous slug bubble flow. When PHP is putting higher heat flux, vapor plug and liquid slug will become longer.
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34

Lin, Chien-Cheng, and 林建成. "Optimization Study of Pulsating Heat Pipe Performance Using Taguchi Method." Thesis, 2012. http://ndltd.ncl.edu.tw/handle/87080434181706796320.

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碩士<br>淡江大學<br>機械與機電工程學系碩士班<br>100<br>Pulsating heat pipe experimental process often need to spend much time, and then in this study reduce experimental time by applied Taguchi method to pulsating heat pipe, explore the pulsating heat pipe optimization in different control factors and levels. In this research, there are three factors which are filling ratio (50%, 60% and 70%), condensate flow rate (0.05, 0.1, 0.15 L/min), and heating power (90W, 120W, 150W), then thermal resistance for quality analysis by using L9 orthogonal array of Taguchi method. The working fluid is water, and 35°C constant temperature water for cooling; evaporator part is heated by the heat coil. The result show that the best combination is 0.05 L/min condensate flow rate with 150W heating power in 60% filling ratio, moreover confirmed by experiment to obtain the best quality for the thermal resistance is 0.187. Using literature experimental data to discuss and compare the best quality by Taguchi method.
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35

XU, PENG-XIANG, and 徐鵬翔. "Study on the performance of Flat-Plate pulsating heat pipe." Thesis, 2019. http://ndltd.ncl.edu.tw/handle/d7rnux.

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碩士<br>國立勤益科技大學<br>冷凍空調與能源系<br>107<br>In this study, a complex pulse-type heat pipe is used to connect the single point or a plurality of points to make the fluid unbalanced. Even if there are only a small number of bends, the fluid can be continuously operated to evaporate and condense The two-phase flow. With the flow field visual analysis, the heat transfer performance of the working fluid using water and HFE-7000 under different input wattages was observed. The filling rate was 50%, the operating angle was placed vertically, tilted, And placed horizontally. The results show that the working fluid HFE-7000 has better performance than the water in the middle and low wattage. When the double pipe pulsating heat pipes filled with HFE-7000 has a wattage of 80W and is placed vertically, the system has the lowest Thermal resistance 0.32 K/W, compared with the single pipe pulsating heat pipe with the same parameters, the thermal resistance is 0.378 K/W, which differs by 15.3%. When placed horizontally, the double pipe pulsating heat pipes allows the fluid filled with HFE-7000 to flow back to the evaporation. Compared to the same input wattage of 20W, the double pipe pulsating heat pipes reduces thermal resistance by 18.5% compared to the single pipe pulsating heat pipes. Indicates that the design of the double pipe pulsating heat pipe improves part of the heat transfer performance.
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36

Singh, Ashutosh Kr. "Numerical Analysis of Performance of Closed-Loop Pulsating Heat Pipe." Thesis, 2013. http://ethesis.nitrkl.ac.in/5427/1/211ME3193.pdf.

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This presents a computational study on the heat transfer characteristics of closed loop pulsating heat pipe (CLPHPs). However modeling of a CLPHP system in GAMBIT has many challenging issues due to the complexity and multi-physics nature of the system. So, the closed loop pulsating heat pipe modeled here has no wick material inside it as it present in heat pipe. The closed loop pulsating heat pipe has no complex structure so it is to be modeled. Flow visualization was conducted for the closed loop pulsating heat pipe using ANSYS Fluent 13.0. With appropriate boundary conditions we can visualize the behavior of the model and make predictions regarding its performance. Water-water vapor and ethyl alcohol ant ethyl alcohol vapor are taken as the working fluid and heat flux is supplied at the inlet. Phenomena such as nucleation boiling, formation of slug and propagation of inertia wave were observed in the closed loop PHPs. Also the analysis has been done to know the behavior of CLPHPs under varying supply of heat flux at the inlet (evaporator).for this, the output heat flux is obtain at outlet (condenser) and find out how the heat flux is varying for different heat flux and the different working fluid.
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37

Sha, Bibhu Bhusan. "Numerical and experimental investigation of common header pulsating heat pipe." Thesis, 2018. http://ethesis.nitrkl.ac.in/9755/1/2018_MT_216ME3480_BBSha_Numerical.pdf.

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Pulsating heat pipe is a successful passive two-phase heat transfer device used mainly for cooling such as electronic cooling in spacecraft and other applications. The present work is based on numerical as well as an experimental investigation carried out for a novel design common header pulsating heat pipe (CHPHP) which is different from conventional pulsating heat pipe (PHP). The heat transfer performance of this unique PHP is studied numerically as well as experimentally. For both approaches, copper CHPHP of 2 mm inner diameter is studied by varying the heat input from 10 w ̶100 W at a filling ratio of 50% for DI-water, ethanol and methanol as the working fluid. CFD modeling is done using ANSYS FLUENT 18.1 (Academic version). A Volume-of-Fluid (VOF) model in conjunction with continuum surface force model is applied considering the two phase flow occuring inside the device. The experimental results validate with the Numerical result and found that the experimental result within the 10% error. The lowest thermal resistance achieved for DI-water is around 1.03 K/W whereas for ethanol it is about 0.1781 K/W and for Methanol is about 0.23 K/W which clarifies that ethanol and methanol proved to be a better working fluid than water. The highest thermal conductivity for DI-water, ethanol and methanol are about 8830.6 W/m-K, 12735.8 W/m-K and 10067.1021 W/m-K respectively which shows the heat transfer efficiency of the CHPHP device. The highest local convective heat transfer coefficient hevap in the evaporator is found for DI-water, ethanol and methanol are about 5972.18.6 W/m2- K,4543.91W/m2-K and 9632.93 W/m2-K respectively which shows the heat transfer efficiency of the CHPHP device. As the heat transfer performance of a PHP is depend upon the combination of various parameter such as latent heat, surface tension, specific heat and water has the higher value than other two and by comparing all the three fluid ethanol is proved as the best working fluid among all the fluid, methanol also found as better fluid than water for the copper CHPHP.
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38

JIANG, MING-YEN, and 蔣明諺. "An Experimental Study on the Thermal Performance of Pulsating Heat Pipe Heat Exchanger." Thesis, 2018. http://ndltd.ncl.edu.tw/handle/jk5697.

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碩士<br>國立高雄應用科技大學<br>機械工程系<br>106<br>In this study, the experimental test on the pulsating heat pipe heat exchanger filled with either water or HFE-7000 under various testing conditions was conducted. The filling ratio of the pulsating heat pipe was 35%, 50%, 65% tested with frontal air velocity between 0.5 m/s and 2 m/s at operating temperature between 60C and 120C. The heat transfer capability, the effectiveness, and the heat transfer coefficient of the heat exchanger were estimated to investigate the thermal performance of the pulsating heat pipe heat exchanger. The pulsating heat pipe was installed in the plate-fin array, which consists of 124 plates with fin pitch of 1.6 mm, with staggered arrangement in three rows. The overall size of the heat exchanger is 132 mm in length, 44 mm in width and 200 mm in height. Both the evaporator section and the condenser section of the heat exchanger were installed in individual air ducts to achieve heat exchange between hot airflow and cold airflow. The results showed that as the operating temperature was between 60C and 120C with frontal air velocity of 0.5 m/s, the effectiveness of the pulsating heat pipe heat exchanger filled with 35% water was 35.7%, 43.98%, 46.43%, 47.36%, while that of the pulsating heat pipe heat exchanger filled with 35% HFE-7000 was 42.96%, 45.71%, 46.14%, 46.80%. Besides, it was found that the effectiveness of the heat exchanger filled with HFE-7000 was higher than that filled with water at low operating temperature. This is likely because HFE-7000 has a lower saturation temperature and a higher slope of saturation pressure versus temperature than those of water, resulting in easier start-up of the pulsating heat pipe. However, the pulsating heat pipe filled with water in filling ratio of 50% and 65% operated at low temperature was not able to start-up of the pulsating motion, causing a low heat transfer capability. As the operating temperature increased, the pressure difference between the evaporation section and the condensation section could be established, so that the pulsating heat pipe was able to function. In order to enhance the maximum possible heat transfer capability, two pulsating heat pipe heat exchangers arranged in series with the water-filled pulsating heat pipe heat exchanger at vacuum condition being placed ahead of the HFE-7000-filled pulsating heat pipe heat exchanger at vacuum condition. The results showed that such arrangement with filling ratio of 35% could reach a heat transfer capability of 186 W, at frontal velocity of 2 m/s at higher temperature, which is an increase of 32% compared to the heat exchanger with a single heat exchanger.
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39

Chen, Hui-Lun, and 陳慧倫. "Experimental investigation of silver nanofluid on pulsating heat pipe thermal performance." Thesis, 2004. http://ndltd.ncl.edu.tw/handle/35217462948040315738.

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碩士<br>淡江大學<br>機械與機電工程學系碩士班<br>94<br>This paper reports on preliminary experimental results on using copper tube having internal and external diameter with 2.4 mm and 3 mm respectively to carry out the experimental pulsating heat pipe. In order to study and measure the efficiency, we compare with 20 mm silver nano-fluid at different concentration (100ppm and 450ppm) or in the different filled ratio (20%, 40%, 60% and 80%), also applying with different heating power (5W, 15W, 35W, 45W, 55W, 65W, 75W and 85W). Finally we make a comparison with pure water. In a word, the result in the mid value (40%, 60%) of filled ratio is better. In the majority 60% of efficiency is considered much better. May be in these two filled ratio at high heating power, the power in the bubble production amount and pulsation gets balanced. The result is analogous in sensible heat exchange, 60% has more liquid slugs that are suitable for sensible heat exchange as to 40%, so in 60% of filled ratio, heat dissipation result is better than 40%. On the whole the best filled ratio is 60%, and the best filled fluid is 100ppm in silver nano-fluid. When the filled ratio is 60% and the heating power is 85 W, the difference of temperature is less than 7.79 ℃ at this same filled ratio, and the thermal resistance is also less than 0.092℃/W.
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40

Hsiao, Pai-Chun, and 蕭百鈞. "Study on Single Direction Circulation Flow inClosed-Loop Pulsating Heat Pipe." Thesis, 2013. http://ndltd.ncl.edu.tw/handle/29403255581542648013.

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碩士<br>淡江大學<br>機械與機電工程學系碩士班<br>101<br>This research utilized 6 mm outer diameter and 3 mm inner diameter glass tubes to manufacture 9 turns Closed-Loop Pulsating Heat Pipe (CLPHP) with a total length of 1980mm. For achieving the loop circulation, heaters were installed unilaterally and bilaterally in the evaporator respectively, and a water cooling system kept at 25°C was used as the condenser. The experiment was conducted under both heating methods to compare the thermal resistance at an input power of 20W, 60W, 100W and 140W. Through a digital video camera, the visualization experiment was carried out to observe the ethanol fluid flow in the PHP. From the observation, when the input power is greater than 100W, circulation in the working fluid occurs. Randomness direction of circulation and local oscillation can be found in the bilateral heating. Unilateral heating may allow the consistent direction circulation happened at lower input power to perform lower thermal resistance.
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41

Wu, Hung-Hsing, and 吳弘信. "The Development and Experiment of using Pulsating Heat Pipe as Thawing." Thesis, 2018. http://ndltd.ncl.edu.tw/handle/3jx95q.

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42

Hsiao, Ming-Yuan, and 蕭鳴遠. "Parameter Research and Numerical Simulation of Open Loop Pulsating Heat Pipe." Thesis, 2006. http://ndltd.ncl.edu.tw/handle/9564g4.

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碩士<br>國立臺北科技大學<br>製造科技研究所<br>94<br>The main topic of this thesis is to develop the Open Loop Pulsating Heat Pipe. It is composed of copper capillary tube with inner diameter 1.2mm. The inner structure is used to overcome the current heat transfer difficulty in Heat Pipe. Since it has the advantages in simple structure and simplified fabrication technique, this is a new heat transfer concept. The research developed an Open Loop Pulsating Heat Pipe module and manufacturing process. The program developing from Lab is also used to predict the performance and the relationship between vibration frequency and coefficients. 「The Active and Passive Thermal testing system of thermal resistance」 are employed in the experiment. When the working fluid is coolant R134a, the optimized thickness of plate is 4mm. The operation modes (vertical/ horizontal) did not affect the heat performance. The optimized ratio is 40%, and periodic vibrations occurred around the heat pipe. When the Heat Load is 280W, and H is 80, the lowest system heat resistance is 0.19(℃/W). The best ratio of optimized vaporizing length and cooling length is for module with H=80 and the magnitude of cooling wind did not affect the convection heat resistance much. Whenever increasing 20CFM, the average convection heat resistances decrease 0.01(℃/W). The simulation error for the experiment module(H80、FR=60%) is 30%. Thus, we can understand more about the characteristics and performance of the Open Loop Heat Pipe, and hope this research can be employed widely in the future thermal system of electronic products.
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43

liu, Yi-Ching, and 劉義勤. "Manufacture and Measure of Opened-Loop Pulsating Heat Pipe with Different Shape." Thesis, 2010. http://ndltd.ncl.edu.tw/handle/rv5s62.

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碩士<br>國立臺北科技大學<br>能源與冷凍空調工程系碩士班<br>98<br>Opened-loop pulsating heat pipe (OLPHP) is a newly developed two-phase-flow heat transfer device, which transfer heat very efficiently in both sensible and latent forms. Due to the simple structure and the bent characteristics, OLPHP becomes a prosperous heat transfer implement. The purpose of this study is to explore experimentally the behavior model of the actual flow field inside the OLPHP and discuss in detail about the establishment of standard design parameters and mode of operation etc. Both infrared thermal camera and high speed camera are used to observe the array configuration of gas-liquid column within the pipe, cyclic restart principle, and flow properties of OLPHP The results show that (1) if the OLPHP is setup in a way that the two end points are close to the condensation side, the working fluid will accumulate at both end points due to inadequate recovery force resulting in poor performance, (2) The spiraled-type OLPHP has the better heat rejection capability than the meandered-type one because of the longer-length evaporator section for heat input; (3) the effective heat transfer coefficient of OLPHP is proportional to the heat load; (4) The OLPHP with 70% filling ratio has better heat rejection property, and (5) a vertical tilt angle provides the best mode of operation. After establishing the basic theory and phenomenon, this paper has also pursued vigorously the development of multi-deformation type and line-Stereoscopic type OLPHPs, which are designed based on the above observed phenomenon and theories so that they can work properly. The heat transfer rate per unit area for the ultimate line-Stereoscopic type OLPHP reaches 3.07 w/cm^2
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44

Chen, Kuan-Ting, and 陳冠廷. "Apply the Neural Networks Predict the Thermal Performance of Pulsating Heat Pipe." Thesis, 2009. http://ndltd.ncl.edu.tw/handle/56357599611085114005.

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碩士<br>淡江大學<br>機械與機電工程學系碩士班<br>97<br>This research utilizes stainless steel tube having external and internal diameter with 3.5 mm and 3 mm to manufacture closed loop pulsating heat pipe. The study includes manufacturing process and the vacuuming management for filling and packaging. The experiment use D.I. water as the working fluid. Different filling ratio, wind velocity and heating power are used to test the thermal performance. An Artificial Neural Network (ANN) is then trained with the above available test data. Fully connected feed forward multi-layer ANN configuration is adopted. The experiment result shows that the applicable filling ratio is between 30% and 70%. The ANN consists of three input nodes corresponding to the filling ratio, the heat input and the wind velocity and a single output node corresponding to the total thermal resistance. The result shows the best series of filling ratio are 15%, 40%, 60% and 80%. And the one hidden layer is better than two hidden layer, the best mean error is 0.0541K/W. The final part of the thesis also reports on preliminary experimental results of using Pyrex glass to manufacture a visual pulsating heat pipe to compare pulsating motion at different filling ratio.
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Ding-Rui, Yang, and 楊定睿. "Taguchi method is applied to a radial-type Pulsating Heat Pipe of optimizing." Thesis, 2015. http://ndltd.ncl.edu.tw/handle/59109849473989932117.

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碩士<br>聖約翰科技大學<br>機械與電腦輔助工程系碩士班<br>103<br>This study is the use of radial shock Taguchi method heat pipe to do the analysis for the new patterns of different lengths and number of bends ; radial oscillation heat pipe (Radial-type closed-loop pulsating heat pipe) referred RCLPHP, by changing the length of the radiation , radiation number , fill rate and heating power to carry out experiments and analysis . And use Minitab to perform the experimental results of variance analysis, assume that the predicted regression curve and compared with experimental results and look forward to get the optimum design parameters . As used herein, the parameters are the number of radiation ( 8,10,12 ) and radiation length (50mm, 100mm, 150mm) to mix and match as the parameter changes , the working fluid is water , the filling rate of 40 %, 50% , 60% and heating power of 20W, 40W, 60W to do the experiment . And the use of Taguchi orthogonal table (L9) experiment planning and quality analysis , re-use signal -noise ratio (S / N) were each prediction , and then get to do with the optimal combination of experiments to compare. The results show , in which the length of 50 mm and the number of radiation radiation 8 , the filling rate of 40% , a better cooling effect , the reason for the liquid and vapor column frequent shock cycle, resulting in significantly reduced temperature formed in accordance . Then calculate the quadratic regression equation which showed 99.9% total deviation R2 , and R2 standard value of 95% consistent , re-use MATLAB subtraction experiments and predicted values do contour maps , which analysis showed that the highest rate similar reached 97.26% .
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46

Yu, Bo-Huai, and 游博淮. "A Study of Cuo Nanofluid and Water on Closed-loop Pulsating Heat pipe." Thesis, 2006. http://ndltd.ncl.edu.tw/handle/54dktt.

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碩士<br>國立臺北科技大學<br>冷凍空調工程系所<br>94<br>Modern microelectronics thermal management is facing considerable challenges in the wake of miniaturizing of components leading to higher demands on net heat flux dissipation. A new heat transfer device (called pulsating heat pipe (PHP)), which can transfer effectively the heat from one of its end to the other end by a pulsating action of the liquid-vapor system, can fit to the above need. Due to the simple design, cost effectiveness and excellent thermal performance may find wide applications (especially using in the electronic cooling). In this project, an experimentally investigation is conducted to explore the thermal performance of PHP. Several closed-loop pulsating heat pipes filled with slug-plug-train two-phase flow field are developed by implementation for the purpose of flow pattern visualization. In addition, the effects of various design parameters, e.g., working fluid (Cuo nanofluid, water, and methanol), filling ratio, input heat flux, and inclined angle on the thermal performance of PHP, are also analyzed. The experimental results show that (1) The input heat flux will change the flow pattern inside the PHP tube, which can be divided into three periods-oscillating, transitional and stable periods; (2) The PHP heat resistance decreases with increasing heat load; (3) The PHP exhibits the best thermal performance when FR=30% for CuO nanofluid or water, and when FR=50% for methanol; (4) The PHP filling with 1.0 %wt CuO nanofluid presents the better thermal performance compared to other fluid when 30°≦β≦90°. While PHP filling with methanol can start to work at lowest heat load (20W) when β=0°. It should be noted that the CuO particles may precipitate from the nanofluid and stick on inner surface of tubes during PHP operation, which reduces the CuO concentration and changes the heat transport performance of PHP.
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47

Wang, Yao-Chun, and 王耀羣. "Study of Magnetic Field Effect on the Magnetic Nanofluid Pulsating Heat Pipe Performance." Thesis, 2014. http://ndltd.ncl.edu.tw/handle/dr2dgg.

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碩士<br>淡江大學<br>機械與機電工程學系碩士班<br>102<br>Abstract: The present research a pulsating heat pipe (PHP) is made of glass material with an inner and outer diameters of 3 mm and 6 mm for 70 % fill ratio was employed. The heat input was applied at 20, 55, 90, 125 and 160 W. Distilled Water and Fe3O4 nanofluid with different concentrations of 90, 270, 450ppm were used as working fluid, and cooling water temperature was set at 25 °C. Experiment was conducted under no magnetic field and three different magnetic fields that magnet located in the middle area of evaporator (Mid mag), both sides of evaporator (Both mag) and along the evaporator (Along mag). In order to investigate the effects of nanofluid and magnetic field on the thermal resistance of PHP, a video camera was set to observe the motion of working fluid in PHP, and temperatures were measured. The results show that the thermal performance enhanced with PHP filled magnetic nanofluid, and thermal resistances reduced with an increase of heat input for all experimental parameters. With high heat input from 125 to 160 W, annular flows were observed and the thermal resistances tend to be approximately the same in all the tests. It indicates that magnetic nanofluid and magnetic field have no obvious effects on PHP in high heat input. At low heat input of 20 W, compared with no magnetic field was set, nanoparticles were observed to have a more significant attachment on the evaporator side wall when a magnetic field was applied, and the thermal resistance of the PHP was lower. It was also found that more nanoparticles attachment and lower thermal resistance happened both in the case of (Both mag) and (Along mag) than in the case of (Mid mag). However, a high concentration of 450 ppm in the case of (Along mag), excessive nanoparticles attached and PHP had higher thermal resistance. Finally, enhancement of heat transfer in a PHP utilizing magnetic nanofluid and magnetic field has been designed and predicted using Taguchi method.
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48

Chen, Jian-Ting, and 陳建廷. "Thermal Enhancement of Pulsating Heat Pipe by using Ag、TiO2 Nanofluid as working Medium." Thesis, 2008. http://ndltd.ncl.edu.tw/handle/xxtqpf.

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碩士<br>國立臺北科技大學<br>能源與冷凍空調工程系碩士班<br>96<br>Pulsating heat pipe (PHP) is a new heat transfer device, which can transfer the heat from one end to the other end by the mechanism of pulsating action of the liquid-vapor system. The thesis aimed to discover area on the nano-fluid increasing heat transfer further. To discover bubble type of PHP system, changeful temperature condition by observing their actions with high speed, thermal imaging machine. Through analysis of the features, I explore the influence under different parameters of work fluid, fill ratio, angle of inclination and heating load . The experimental results show that: (1) The input heat flux will change the flow pattern inside the PHP tube, which can be divided into three periods-oscillating, transitional and stable periods. (2) PHP fluid field type can be divided into dispersed bubble, confined bubble, slug and annular flows. Dispersed bubble only appears in periods-oscillating. After stability, the condenser exit will be confined bubble and the evaporator exit will be straight confined bubble and annular flows. (3) When the work fluid properties are different, observing the difference of confined bubble. For example, water is confined bubble, silver and titanium dioxide are dividedly elliptic mode and pipa mode. (4) The experience will make a PHP performance model. The PHP heat resistance value will be the lowest when the work fluid of nano-fluid(silver and titanium dioxide) and water under the conditions of FR 30%, angle of inclination 90°. (5) When nano-fluid is testing through the long time, its performances close to water and unuseful in long. (6) It is the two-phases circle along steady direction on spreading temperature field of stable periods. The temperature of fluid would rather be uneven spreading temperature than appear increasing along circular direction.
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49

Shieh, Lin Chieh, and 謝令傑. "A Study of Flat-Plate Pulsating Heat Pipe Optimal Filling Ratio and Spreading Resistance Measurements." Thesis, 2015. http://ndltd.ncl.edu.tw/handle/p69e77.

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50

Wai, Chiang Yi. "Experimental investigation of pulsating heat pipe performance: Effects of working fluid, geometrical parameters and nanoparticles." 2007. http://link.library.utoronto.ca/eir/EIRdetail.cfm?Resources__ID=788877&T=F.

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