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Dissertations / Theses on the topic 'Forced convection heat transfer'
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1
Lee, Man. "Forced convection heat transfer in integrated microchannel heat sinks /." View abstract or full-text, 2006. http://library.ust.hk/cgi/db/thesis.pl?MECH%202006%20LEE.
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Chick, Eric. "Problems in forced and free convection." Thesis, Keele University, 1995. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.241449.
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Alhamdan, Abdullah M. "Experimental studies on natural and forced convection around spherical and mushroom shaped particles." The Ohio State University, 1989. http://rave.ohiolink.edu/etdc/view?acc_num=osu1145369315.
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Thiele, Roman. "Prediction of forced convection heat transfer to Lead-Bismuth-Eutectic." Licentiate thesis, KTH, Reaktorteknologi, 2013. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-121983.
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The goal of this work is to investigate the capabilities of two different commercial codes, OpenFOAM and ANSYS CFX, to predict forced convection heat transfer in low Prandtl number fluids and investigate the sensitivity of these predictions to the type of code and to several input parameters.The goal of the work is accomplished by predicting forced convection heat transfer in two different experimental setups with the codes OpenFOAM and ANSYS CFX using three different turbulence models and varying the input parameters in an extensive sensitivity analysis. The computational results are compared two the experimental data and analyzed for qualitative and quantitative parameters, such as shape of velocity and temperature profiles, thickness of the boundary layers and wall temperatures.The results show that predictions of the temperature and velocity field are generally sufficient to good, however, the sensitivity especially to the turbulent Prandtl number has to be taken into account when computing forced convection heat transfer in low Prandtl number fluids. The results also show that methods applied to OpenFOAM cannot directly be applied to ANSYS CFX.<br><p>QC 20130531</p><br>GENIUS
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Hama, Katsuhiko. "Film boiling heat transfer in various liquids under natural convection and forced convection conditions." Kyoto University, 2006. http://hdl.handle.net/2433/143793.
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Vijay, Dig. "Forced convective heat transfer through open cell foams." Doctoral thesis, Technische Universitaet Bergakademie Freiberg Universitaetsbibliothek "Georgius Agricola", 2017. http://nbn-resolving.de/urn:nbn:de:bsz:105-qucosa-226330.
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The purpose of this study is to investigate forced convection of air through open cell foams. It can be numerically investigated either by implementing the time efficient macroscopic models or computationally expensive microscopic models. However, during the course of this study, it was observed that the macroscopic models are not sufficient for determining the desired key parameters. Nevertheless, it is still possible that these macroscopic models can be used to design an application accurately with minimum time efforts if the concerned key parameters are already known through other means. Accordingly, in this work, a methodology is developed to determine the desired key parameters by implementing the microscopic models, which are further used into the macroscopic models for designing different applications. To validate the proposed methodology, a set of steady state and transient forced convection experiments were performed for a set of ceramic foams having different pore diameter (10−30 PPI) and porosity (0.79−0.87) for a superficial velocity in the range of 0.5−10 m/s.
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Park, Do Seo. "Experimental and numerical study of laminar forced convection heat transfer for a dimpled heat sink." Thesis, [College Station, Tex. : Texas A&M University, 2007. http://hdl.handle.net/1969.1/ETD-TAMU-1571.
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Kirez, Oguz. "A Numerical Forced Convection Heat Transfer Analysis Of Nanofluids Considering Performance Criteria." Master's thesis, METU, 2012. http://etd.lib.metu.edu.tr/upload/12615167/index.pdf.
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A nanofluid is a new heat transfer fluid produced by mixing a base fluid and solid nano sized particles. This fluid has great potential in heat transfer applications, because of its increased thermal conductivity and even increased Nusselt number due to higher thermal conductivity, Brownian motion of nanoparticles, and other various effects on heat transfer phenomenon.
In this work, the first aim is to predict convective heat transfer of nanofluids. A numerical code is created and run to obtain results in a pipe with two different boundary conditions, constant wall temperature and constant wall heat flux. The results for laminar flow for thermally developing region in a pipe are obtained for Al2O3/water nanofluid with different volumetric fraction and particle sizes with local temperature dependent conductivity approach. Various effects that influence nanofluid heat transfer enhancement are investigated. As a result, a better heat transfer performance is obtained for all cases, compared to pure water. The important parameters that have impact on nanofluid heat transfer are particle diameter of the nanoparticles, nanoparticle volumetric fraction, Peclet number, and viscous dissipation.
Next, a heat transfer performance evaluation methodology is proposed considering increased pumping power of nanofluids. Two different criteria are selected for two boundary conditions at constant pumping power. These are heat transfer rate ratio of the nanofluid and the base fluid for constant wall temperature boundary condition and difference between wall temperature of the pipe at the exit and inlet mean temperature of the fluid ratio for constant wall heat flux case. Three important parameters that influence the heat transfer performance of nanofluids are extracted from a parametric study. Lastly, optimum particle size and volumetric fraction values are obtained depending on Graetz number, Nusselt number, heat transfer fluid temperature, and nanofluid type.
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Koski, Jennifer Rose. "Radiatively induced ignition of PMMA in the presence of forced convection." Thesis, Georgia Institute of Technology, 1993. http://hdl.handle.net/1853/15886.
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Tough, M. C. "A heat transfer model of forced convection, cross flow heat exchangers used in space heating." Thesis, Cardiff University, 1989. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.259171.
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Sun, Guang. "Heat transfer in forced convective flow boiling." Thesis, Imperial College London, 1996. http://hdl.handle.net/10044/1/11255.
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Thorpe, Roger. "Heat transfer by forced convection in beds of granular adsorbent material for solid sorption heat pumps." Thesis, University of Warwick, 1996. http://wrap.warwick.ac.uk/34618/.
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A novel adsorption cycle in which enhanced heat transfer between the adsorbent and external heat sinks and sources is achieved by forced convection of refrigerant gas through the adsorbent bed is presented This cycle is further developed by the use of inert beds to store the heat of desorption and sensible heat between phases. The performance and utility of such a cycle will depend on the heat transfer coefficients and pressure drops that result when the refrigerant gas is circulated through the beds The heat transfer and pressure drop characteristics of a bed of granular active carbon were investigated using argon, carbon dioxide and ammonia. Equipment was designed and built to pass a stream of gas through a bed at a controlled rate, pressure and temperature. The pressure drop characteristic was found to conform to Ergun equation and the constants for the application of that relation to a commonly available granular active carbon established. A mathematical model based on a finite difference technique was created and used to predict the progress of a temperature front in the bed and derive the heat transfer characteristics from experimental data. Heat transfer coefficients measured with argon and ammonia appeared inconsistent with each other and after investigations of the data and comparison with established correlations were made it was concluded that carbon during the argon experiments had been contaminated. The heat transfer results with ammonia and carbon were compared with a modified version of the Colburn analogy between heat transfer and pressure loss. A correlation between the Nusselt number and Reynolds number for design purposes was established.
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Ozerinc, Sezer. "Heat Transfer Enhancement With Nanofluids." Master's thesis, METU, 2010. http://etd.lib.metu.edu.tr/upload/12611862/index.pdf.
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A nanofluid is the suspension of nanoparticles in a base fluid. Nanofluids are promising for heat transfer enhancement due to their high thermal conductivity. Presently, discrepancy exists in nanofluid thermal conductivity data in the literature, and enhancement mechanisms have not been fully understood yet. In the first part of this study, a literature review of nanofluid thermal conductivity is performed. Experimental studies are discussed through the effects of some parameters such as particle volume fraction, particle size, and temperature on conductivity. Enhancement mechanisms of conductivity are summarized, theoretical models are explained, model predictions are compared with experimental data, and discrepancies are indicated.
Nanofluid forced convection research is important for practical application of nanofluids. Recent experiments showed that nanofluid heat transfer enhancement exceeds the associated thermal conductivity enhancement, which might be explained by thermal dispersion, which occurs due to random motion of nanoparticles. In the second part of the study, to examine the validity of a thermal dispersion model, hydrodynamically developed, thermally developing laminar Al2O3/water nanofluid flow inside a circular tube under constant wall temperature and heat flux boundary conditions is analyzed by using finite difference method with Alternating Direction Implicit Scheme. Numerical results are compared with experimental and numerical data in the literature and good agreement is observed especially with experimental data, which indicates the validity of the thermal dispersion model for explaining nanofluid heat transfer. Additionally, a theoretical analysis is performed, which shows that usage of classical correlations for heat transfer analysis of nanofluids is not valid.
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Okamura, Takahiro. "Forced convection heat transfer of He 1 and He 2 up to supercritical pressures." Kyoto University, 2004. http://hdl.handle.net/2433/145258.
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Kyoto University (京都大学)<br>0048<br>新制・課程博士<br>博士(エネルギー科学)<br>甲第11206号<br>エネ博第103号<br>新制||エネ||28(附属図書館)<br>22790<br>UT51-2004-T175<br>京都大学大学院エネルギー科学研究科エネルギー応用科学専攻<br>(主査)教授 塩津 正博, 教授 宅田 裕彦, 助教授 白井 康之<br>学位規則第4条第1項該当
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Youcef-Ali, Sabri. "Etude numérique et expérimentale des séchoirs solaires indirects à convection forcée : Application à la pomme de terre." Valenciennes, 2001. https://ged.uphf.fr/nuxeo/site/esupversions/7db5b7f1-e247-4d7f-9a14-5040200b9cb4.
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Nous avons développé un code de calcul permettant de simuler le comportement d'une chaine énergétique (insolateur-séchoir) fonctionnant en convection forcée pour des applications au séchage de produits agro-alimentaires. L’insolateur plan, relié à l'armoire de séchage, est à simple passe arrière, la veine d'air mobile pouvant être munie d'ailettes permettant d'améliorer les performances de ce capteur. Le séchoir est une armoire en bois comportant quatre grilles superposées, sur lesquelles le produit a séché et disposées en lits de rondelles. Dans le modèle théorique décrivant son comportement, nous tenons compte en particulier des pertes calorifiques à travers les parois latérales et du rétrécissement volumique du produit en cours de séchage, phénomènes généralement négligés. Le premier sous-programme itératif développé détermine les performances thermiques instantanées de l'insolateur. Le second gère un modèle théorique qui repose sur les équations de bilan de chaleur et de masse dans les milieux poreux. Dans ce modèle, intervient un coefficient de migration de l'eau dans la masse des particules propre au produit utilisé. Nous avons déterminé ce coefficient expérimentalement, pour plusieurs températures de l'air asséchant, en fonction de l'humidité absolue moyenne des rondelles, ce qui nous a permis de le représenter sous une forme mathématique exploitable dans l'algorithme de calcul. Le modèle théorique est validé par un grand nombre d'expériences en utilisant la pomme de terre, en ensoleillement artificiel et naturel. Cette validation nous a donc permis de tester les possibilités de la chaine étudiée (notamment à travers le coefficient d'efficacité que nous définissons par le rapport de la masse de produit à sécher au temps de séchage global) et de dégager certains principes permettant d'en tirer le maximum de production. Nous présentons enfin quelques prédictions du modèle numérique pour différentes valeurs des paramètres aérothermiques de l'air de séchage.
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Fritzgerald, Claire Louise. "Forced-convection condensation heat-transfer on horizontal integral-fin tubes including effects of liquid retention." Thesis, Queen Mary, University of London, 2011. http://qmro.qmul.ac.uk/xmlui/handle/123456789/2353.
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Accurate and repeatable heat-transfer data are reported for forced-convection filmwise condensation of steam and ethylene glycol flowing vertically downward over two single, horizontal instrumented integral-fin tubes and one plain tube. Vapour-side, heat-transfer coefficients were obtained by direct measurement of the tube wall temperature using specially manufactured, instrumented tubes with thermocouples embedded in the tube walls. Both tubes had fin height of 1.6 mm and fin root diameter of 12.7 mm, with fin thickness and spacing of 0.3 mm and 0.6 mm, respectively for the first tube and 0.5 mm and 1.0 mm respectively for the second. Tests were performed at atmospheric pressure for steam with nominal vapour velocities from 2.4 m/s to 10.5 m/s and at three pressures below atmospheric with nominal vapour velocities from 8.4 m/s to 57 m/s for steam and 13 m/s to 82 m/s for ethylene glycol. The data show that both the finned tubes provide an increase in heat flux at the same vapour-side temperature difference with increasing vapour velocity. Visual observations were made and photographs obtained of the condensate retention angle at each combination of vapour velocity and pressure. It was observed that the curvature of the meniscus was distorted by the increase in vapour velocity and in many cases, the extent of condensate flooding changed compared to its value in the quiescent vapour case. In parallel, experiments involving simulated condensation on finned tubes were conducted using horizontal finned tubes in a vertical wind tunnel. Condensate was simulated by liquid (water, ethylene glycol and R-113) supplied to the tube via small holes between the fins along the top of the tube. Downward air velocities up to 24 m/s were used and retention angles were determined from still photograph. Eight tubes with a diameter at the fin root of 12.7 mm were tested. Five tubes of which had fin height of 0.8 mm and spacing between fins of 0.5 mm, 0.75 mm, 1.0 mm, 1.25 mm and 1.5 mm and three tubes had fin height 1.6 mm with fin spacings 0.6 mm, 1.0 mm and 1.5 mm. The results were repeatable on different days and suggested, for all tubes and fluids, that the retention angle asymptotically approached a value around 80o to 85o (from either lower or higher values at zero vapour velocity) with increase in air velocity. Good agreement was found with observations taken during the condensation experiments.
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Diette, Christophe. "Measurement and analysis of forced convection phenomena in blade cooling channels." Valenciennes, 2003. http://ged.univ-valenciennes.fr/nuxeo/site/esupversions/c76547a4-820c-48f8-9717-ced740f0cb38.
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Dealing with gas turbine aircraft engines, the Turbine Entry Temperature (TET) is generally targeted as high as possible. Increasing this parameter leads to higher thermodynamic efficiency and power output and reduces the weight-to-thrust ratio and the Specific Fuel Consumption (SFC). Since the maximum permissible TET is determined by the temperature limitations of the turbine assembly, the choice of turbine material and the design of cooling systems applied to turbine blades are essential. This work reports both an experimental and numerical investigation on internal blade cooling cavities. Various cross sections are examined depending on the region of the blade to cool down. Numerous parameters regarding the promoters of turbulence and the flow conditions are varied to find an optimum solution in terms of both heat transfer and pressure losses. Numerical simulations are performed to support the analysis of the flow behaviour. A good agreement is found between the simulations and the aerodynamic measurements. Theoretical diagrams to interpret the flow field are finally proposed. This study provides a better understanding of flow features occuring in cooling channels together with a very detailed database. The later is useful for further numerical validations and the optimisation of cooling cavities<br>En matière de moteurs d'avion à turbine à gaz, une Température d'Entrée de Turbine (TET) aussi élevée que possible est souhaitée. Augmenter sa valeur permet en effet d'obtenir un rendement thermodynamique plus élevé tout en réduisant le rapport poids-poussée et la consommation spécifique (SFC). Parce que la TET maximum permise est liée aux limites de température supportées par les composants de la turbine, le choix des matériaux et la conception des circuits de refroidissement d'aubes sont cruciaux. Cette recherche rend compte d'une étude expérimentale et numérique sur les cavités internes de refroidissement d'aubes. Des sections de passage différentes sont examinées, en fonction de la région de l'aube à refroidir. Plusieurs paramètres en ce qui concerne les promoteurs de turbulence et les conditions de l'écoulement, sont variés pour définir une solution optimale en termes de transfert de chaleur et pertes de charges. Des simulations numériques sont réalisées pour appuyer l'analyse de l'écoulement. La comparaison de ces résultats avec les mesures aérodynamiques se révèle très satisfaisante. Enfin, des diagrammes sont proposés, pour décrire l'écoulement dans chaque cavité étudiée. De cette étude, il ressort une meilleure compréhension des phénomènes mis en jeu dans les cavités de refroidissement, ainsi qu'une base de données détaillée. Cette dernière est utile pour la validation de codes de calcul et l'optimisation des systèmes de refroidissement
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Lin, Kuan-Ting. "Experimental and Computational Study of Novel Plate-Fin-Surfaces for Enhancing Forced Convection Heat Transfer in Compact Heat Exchangers." University of Cincinnati / OhioLINK, 2021. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1623166309984355.
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Bulliard-Sauret, Odin. "Étude expérimentale de l'Intensification des transferts thermiques par les ultrasons en convection forcée." Thesis, Université Grenoble Alpes (ComUE), 2016. http://www.theses.fr/2016GREAI034/document.
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Le but de l'étude présentée dans ce mémoire de thèse est de caractériser localement l'intensification des transferts thermiques observée le long d'une plaque chauffante lorsqu'elle est soumise à des ultrasons. Ces derniers induisent des effets hydrodynamique dans les fluides qu'ils traversent. Premièrement, la cavitation acoustique, qui permet de produire de forts effets mécaniques dans les liquides. Viens ensuite le courant acoustique qui génère une écoulement convectif sous l'action d'une dissipation visqueuse de l’énergie acoustique. Ce travaille à permis de mettre en évidence la relation existant entre ces effets hydrodynamiques et l'intensification des transferts thermiques observée. Ces résultats ont permis de définir quelles conditions expérimentales sont favorables à l'intégration d'ultrasons dans un échangeur de chaleur<br>The aim of the study presented in this thesis is to characterize heat transfer enhancement by ultrasound observed along a hot plate in forced convection. These induced hydrodynamic effects in the fluids they cross. The first one is the acoustic cavitation, which can produce strong mechanical effects in liquids. The second one is the acoustic streaming which generates convective flows thanks to viscous dissipation of the acoustic energy. This work helped to highlight the relationship between ultrasound hydrodynamic effects and heat transfer enhancement. Thanks to those results, experimental conditions which allowed ultrasound integration in a heat exchangers, could be determined
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Shahin, Gus A. "The effect of pulsating flow on forced convective heat transfer." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1999. http://www.collectionscanada.ca/obj/s4/f2/dsk2/ftp01/MQ39881.pdf.
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Abuserwal, Ahmed. "Pressure drop and forced convective heat transfer in porous media." Thesis, University of Sheffield, 2018. http://etheses.whiterose.ac.uk/19512/.
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Metal foams, a new class of porous material with highly permeable structure and higher porosity (>0.60) compared with classical porous granular beds, are a viable solution to enlarge the thermal exchange area and provide a high heat capacity and high specific area. These metal foams are available in a number of solid materials with different porosities and pore size. There is a current lack of understanding regarding metal foam microstructure parameters’ effects on hydraulic and thermal parameters. This is a barrier to the design and implementation of various industrial applications. The current study aims to discover the effects of the pore shape and morphological parameters in terms of pore size and porosity at relatively low ranges of porosity on fluid flow and conductive and convective thermal transport phenomena. The manufacturing defects were tracked using the image processing technique for scanned surfaces samples. The effect of these defects on the thermal and hydraulic parameters was also studied.
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Dehghannya, Jalal. "Mathematical modeling of airflow, heat and mass transfer during forced convection cooling of produce in ventilated packages." Thesis, McGill University, 2008. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=115663.
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Forced convection cooling process is the most widely used method of cooling to extend shelf life of horticultural produce after harvest. However, heterogeneous cooling of produce inside different parts of ventilated packages is a serious problem. Therefore, it is essential to design packages that facilitate air circulation throughout the entire package to provide uniform cooling. Selection of appropriate combinations of air temperature and velocity for a given vent design is currently done largely by experimental trial and error approach. A more logical approach in designing new packages, to provide uniform cooling, is to develop mathematical models that would be able to predict package performance without requiring costly experiments.<br>In this study, mathematical models of simultaneous airflow, heat and mass transfer during forced convection cooling process were developed and validated with experimental data. The study showed that produce cooling is strongly influenced by different ventilated package designs. Generally, cooling uniformity was increased by increasing number of vents from 1 (2.4% vent area) to 5 (12.1% vent area). More uniform produce cooling was obtained at less cooling time when vents were uniformly distributed on package walls with at least 4.8% opening areas. Aerodynamic studies showed that heterogeneity of airflow distribution during the process is strongly influenced by different package vent configurations. The highest cooling heterogeneity index (108%) was recorded at 2.4% vent area whereas lowest heterogeneity index (0%) was detected in a package with 12.1% vent area.<br>The magnitudes of produce evaporative cooling (EC) and heat generation by respiration (HG) as well as the interactive effects of EC, HG and package vent design on produce cooling time were also investigated. Considerable differences in cooling times were obtained with regard to independent and simultaneous effects of EC and HG in different package vent configurations. Cooling time was increased to about 47% in a package with 1 vent compared to packages with 3 and 5 vents considering simultaneous effects of EC and HG. Therefore, the effects of EC and HG can be influential in designing the forced-air precooling system and consequently, in the accurate determination of cooling time and the corresponding refrigeration load.
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Osborne, Rodney Layne. "An experimental determination of mixed and forced convection heat transfer coefficients in a modeled nuclear waste repository /." The Ohio State University, 1992. http://rave.ohiolink.edu/etdc/view?acc_num=osu1487759914762946.
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Ahn, Hee Seok. "Heat transfer enhancement in single-phase forced convection with blockages and in two-phase pool boiling with nano-structured surfaces." Texas A&M University, 2003. http://hdl.handle.net/1969.1/5869.
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The first study researched turbulent forced convective heat (mass) transfer down-
stream of blockages with round and elongated holes in a rectangular channel. The
blockages and the channel had the same cross section, and a distance equal to twice
the channel height separated consecutive blockages. Naphthalene sublimation experiments were conducted with four hole aspect ratios (hole-width-to-height ratios) and
two hole-to-blockage area ratios (ratios of total hole cross-sectional area to blockage
area). The effects of the hole aspect ratio, for each hole-to-blockage area ratio, on the
local heat (mass) transfer distribution on the exposed primary channel wall between
consecutive blockages were examined. Results showed that the blockages with holes
enhanced the average heat (mass) transfer by up to 8.5 and 7.0 times that for fully
developed turbulent flow through a smooth channel at the same mass flow rate, respectively, in the smaller and larger hole-to-blockage area ratio (or smaller and larger
hole diameter) cases. The elongated holes caused a higher average heat (mass) transfer and a larger spanwise variation of the local heat (mass) transfer on the channel
wall than did the round holes.
The second study explored the heat transfer enhancement for pool boiling on
nano-structured surfaces. Experiments were conducted with three horizontal silicon surfaces, two of which were coated with vertically aligned multi-walled carbon nanotubes (MWCNT) with heights of 9 and 25 ùm, respectively, and diameters between
8 and 15 nm. The MWCNT arrays were synthesized on the two silicon wafers using
chemical vapor deposition. Experimental results were obtained over the nucleate boiling and film boiling regimes under saturated and sub-cooled (5ñC and 10ñC) boiling
conditions. PF-5060 was the test fluid. Results showed that the MWCNT array with
a height of 25 ùm enhanced the nucleate and film boiling heat fluxes on the silicon
surface by up to 380% and 60%, respectively, under saturated boiling conditions, and
by up to 300% and 80%, respectively, under 10ñC sub-cooled boiling conditions, over
corresponding heat fluxes on a smooth silicon surface. The MWCNT array with a
height of 9 ùm enhanced the nucleate boiling heat flux as much as the taller array,
but did not significantly enhance the wall heat flux in the film boiling regime.
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Mlcak, Justin Dale. "Simulation of three-dimensional laminar flow and heat transfer in an array of parallel microchannels." [College Station, Tex. : Texas A&M University, 2007. http://hdl.handle.net/1969.1/ETD-TAMU-1671.
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Van, der Merwe Nicola Mary. "Fully developed forced convection heat transfer and pressure drop in a smooth tube in the transitional flow regime." Diss., University of Pretoria, 2005. http://hdl.handle.net/2263/66251.
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Extensive work has been done on characterising convective heat transfer and pressure drop in smooth tubes in the laminar and turbulent flow regimes. However, little work was completed in the transitional flow regime. In all previous transitional studies, experiments that were conducted between the laminar and turbulent flow regimes were with mixed convection in the laminar flow regime and not in the forced convection flow regime. The secondary flow that occurs during mixed convection should most probably influence the characteristics in the transitional flow regime. It can therefore be expected that the transitional flow characteristics of forced convection and mixed convection will be different. However, the transitional characteristics of forced convection flow have not yet been determined. The purpose of this study was therefore to determine the heat transfer and pressure drop transitional characteristics specifically in the forced convection flow regime. Furthermore, to focus on determining these factors for a circular, horizontal smooth tube for fully developed flow. The characteristics were determined in an experimental set-up through which flow occurred through a test section consisting of a horizontal and circular smooth tube. The test-section inside diameter was 4.04 mm, and the tube length was 8.4 m. Water was used as the test fluid and was circulated through the test section which was heated at a constant heat flux. A calming section with a square edge inlet was upstream of the test section. Temperatures at the tube inlet, outlet and outer surface of the test section were measured with a total of 58 thermocouples. Two pressure taps was also installed on the test section and was connected to a pressure transducer for pressure drop measurements. Experiments were conducted mainly on the last part of the test section where fully developed flow occurred. Experiments were conducted between Reynolds numbers of 1 000 to 10 000, Prandtl numbers of 3 to 8, and Rayleigh numbers of 330 and 11 000 (heat fluxes of 0.89 kW/m2 to 3.26 kW/m2). It was found that the heat transfer transitional range coincided with the friction factor transition range with a Reynolds number range of 2 484 to 2 849. Forced convection results in the laminar regime was achieved and compared well to literature. The results were mapped on published flow regime maps. This was inconclusive as the published flow regime maps have been specifically developed for fixed parameters that did not match the parameters of this study.<br>Dissertation (MEng)--University of Pretoria, 2017.<br>Mechanical and Aeronautical Engineering<br>MEng<br>Unrestricted
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Roland, Jason Howard. "Forced Convection Over Flat and Curved Isothermal Surfaces with Unheated Starting Length." University of Dayton / OhioLINK, 2014. http://rave.ohiolink.edu/etdc/view?acc_num=dayton1418343439.
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Astrouski, Ilya. "Polymeric Hollow Fiber Heat Exchanger Design." Doctoral thesis, Vysoké učení technické v Brně. Fakulta strojního inženýrství, 2016. http://www.nusl.cz/ntk/nusl-240499.
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This Ph.D. thesis is focused on theory and experimental investigations developing of new knowledge about polymeric hollow fiber heat exchanger (PHFHE). The state-of-the-art study of plastic heat exchangers shows that their usage is limited by several niches where their advantages significantly dominates, or where the use of non-plastic competitors is not impossible. On the other hand, plastic heat exchangers (and PHFHEs in particular) are devices of increasing interest. It is shown that use of small tubes (fibers) allows PHFHEs to be more competitive than conventional plastic heat exchangers. Small hydraulic diameter of a fiber causes high heat transfer coefficients, reduces thermal resistance of plastic wall and allows it to create light and compact design. Detailed study of fluid flow and heat transfer inside the hollow fiber showed that conventional approaches for single-phase laminar flow can be utilized. Poiseuille number equal to 64 and Nussel number about 4 are recommended to be used to predict pressure drops and heat transfer coefficient, respectively. Additional attention should be paid to careful determination of fiber diameter and liquid properties (viscosity). Scaling effects, such as axial heat conduction, thermal entrance region and viscous dissipation can be neglected. The study of outside heat transfer showed that heat transfer on fiber bunches are intense and are competitive to contemporary compact finned-tube heat exchangers. The Grimson approach showed clear correlation with experimental results and, thus is recommended to predict heat transfer coefficients on fiber bunches. Two types of fouling (particulate- and biofouling) of outer fiber surface were experimentally studied. It was found that particulate fouling by titanium oxide particles is not intense and deposits can be removed relatively easy. However, fouling is much more intense when it is associated with biofouling caused by wastewater. In this case, smooth and low-adhesive surface of plastic is not sufficient precaution to prevent deposit formation.
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Wright, Lesley Mae. "Experimental investigation of turbine blade platform film cooling and rotational effect on trailing edge internal cooling." [College Station, Tex. : Texas A&M University, 2006. http://hdl.handle.net/1969.1/ETD-TAMU-1826.
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Watel, Barbara. "Etude des échanges convectifs sur un cylindre aileté en rotation, soumis a un courant d'air parallèle aux ailettes." Valenciennes, 1997. https://ged.uphf.fr/nuxeo/site/esupversions/29267151-660f-45b9-af69-34482a8dce42.
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L'évaluation expérimentale des échanges convectifs avec l'air est faite sur des ailettes circulaires d'un arbre en rotation à vitesse uniforme et soumises ou non à un courant d'air parallèle à leurs faces. Un banc d'essais a été conçu pour mesurer, par thermographie infrarouge, l'évolution temporelle des températures suivant un rayon d'une ailette durant son refroidissement, cette dernière ayant été préalablement chauffée. Une analyse théorique des phénomènes thermiques se produisant dans une ailette, en régime transitoire, permet de déterminer le coefficient d'échange moyen de celle-ci avec l'air. L’étude bibliographique de la structure d'écoulement entre les ailettes en fonction de leur espacement, de leur vitesse de rotation et de la vitesse du courant d'air a été réalisée. Cette étude sert de base à l'analyse physique de la variation du coefficient d'échange en fonction des différents paramètres. Les essais avec les ailettes en rotation, soumises ou non à un courant d'air parallèle, ont permis de mettre en évidence les domaines d'influence de la convection forcée due à la rotation, de la convection forcée due au courant d'air et de la convection naturelle. Les résultats obtenus sur le coefficient d'échange en convection forcée sont justifiés par la représentation du champ des vitesses de l'écoulement entre les ailettes par vélocimétrie par images de particules. L’ensemble des essais réalisés peuvent être corrélés avec un écart relatif inférieur à 5% par une équation générale.
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Faust, Adriane (Adriane Jean) 1976. "Forced convective heat transfer to supercritical water in micro-rocket cooling passages." Thesis, Massachusetts Institute of Technology, 2000. http://hdl.handle.net/1721.1/9296.
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Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Aeronautics and Astronautics, 2000.<br>Includes bibliographical references (p. 101-102).<br>An investigation of heat transfer to supercritical fluids in micro-channels was completed to assess the cooling characteristics of the MIT micro-rocket engine. Previous results from supercritical ethanol heat transfer tests were compared to water tests to establish a baseline for future fuel testing. Existing literature on supercritical heat transfer was also consulted to corroborate the water test results. It was found that the characteristics of the water tests matched those observed in the literature, as well as those of ethanol tests run at similar conditions.<br>by Adriane Faust.<br>S.M.
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Alves, Thiago Antonini. "Resfriamento conjugado de aquecedores discretos em canais." [s.n.], 2010. http://repositorio.unicamp.br/jspui/handle/REPOSIP/264147.
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Orientador: Carlos Alberto Carrasco Altemani<br>Tese (doutorado) - Universidade Estadual de Campinas, Faculdade de Engenharia Mecânica<br>Made available in DSpace on 2018-08-16T09:22:29Z (GMT). No. of bitstreams: 1
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Previous issue date: 2010<br>Resumo: A transferência de calor conjugada por convecção forçada e condução de três aquecedores 2D montados rentes ou protuberantes na placa inferior (substrato) de um canal de placas paralelas foi investigada numericamente em regime permanente. Uma taxa uniforme de geração de calor foi assumida em cada aquecedor e seu resfriamento ocorreu por meio de um escoamento forçado de ar com propriedades constantes em regime laminar. Na entrada do canal, os perfis de velocidade e de temperatura do escoamento eram uniformes. Este problema está relacionado ao resfriamento de componentes eletrônicos montados numa placa de circuito impresso. Para um substrato adiabático, o resfriamento dos aquecedores ocorre apenas por convecção forçada. Para um substrato condutivo, dois mecanismos para a transferência de calor dos aquecedores para o escoamento fluido foram considerados. Um, por convecção forçada, diretamente das superfícies dos aquecedores em contato com o escoamento e outro, por condução através das interfaces substrato-aquecedor. As equações de conservação foram resolvidas dentro de um domínio único, que englobou as regiões sólidas e de fluido, através de um procedimento acoplado. Nesta Tese foi proposto um descritor invariante do processo conjugado de transferência de calor por convecção forçada e condução, por meio de coeficientes de influência conjugados g+, agrupados numa matriz quadrada G+. Com este descritor, a temperatura de cada aquecedor foi determinada a partir de taxas arbitrárias de geração de calor nos aquecedores. Os resultados foram obtidos para números de Reynolds na faixa de 600 a 1900, correspondendo a velocidades médias de entrada do ar no canal na faixa de 0,5 m/s a 1,5 m/s. Os efeitos da razão entre a condutividade térmica do substrato e a do ar foram estudados na faixa de 0 (substrato adiabático) a 80, uma faixa típica de materiais de circuito impresso. A altura dos aquecedores variou entre 0 (aquecedores rentes) e 35% em relação à altura do canal, sendo que em todos os casos o aquecedor possuía uma condutividade térmica 500 vezes maior do que a do ar.<br>Abstract: The conjugate heat transfer by forced convection and conduction from three 2D heaters either flush mounted or protruding from the lower plate (substrate) of a parallel plates channel was investigated numerically under steady state conditions. A uniform heat generation rate was assumed in each heater and the cooling was performed by means of a forced air flow with constant properties in the laminar regime. At the channel entrance the flow velocity and temperature profiles were assumed uniform. This problem is related to the cooling of electronic components mounted on a circuit board. For an adiabatic substrate, the heaters are cooled only by forced convection. For a conductive substrate, two mechanisms were considered for the heat transfer from the heaters to the fluid flow. One, by forced convection, directly from the heaters surfaces in contact with the flow, and the other, by conduction through the heaters-substrate interfaces. The conservation equations were solved through a coupled procedure within a single calculation domain comprising the solid and fluid regions. In this Thesis an invariant descriptor of the conjugate forced convection and conduction heat transfer was proposed by means of conjugate influence coefficients g+ which were grouped in a square matrix G+. With this descriptor, the temperature of each heater was obtained from an arbitrary distribution of the heat generation rate in the heaters. The results were obtained for Reynolds numbers Re in the range from 600 to 1900, corresponding to average air velocities in the channel entrance from 0.5 m/s to 1.5 m/s. The ratio of the substrate plate thermal conductivity relative to that of the air was considered in the range from 0 (adiabatic substrate) to 80, typical of printed circuit boards. The heaters' height in the channel ranged from 0 (flush mounted) to 35 % of the channel height, while their thermal conductivity was always assumed equal to 500 that of the air.<br>Doutorado<br>Termica e Fluidos<br>Doutor em Engenharia Mecânica
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Loiola, Bruna Rafaella 1987. "Resfriamento conjugado de aquecedores protuberantes em um duto retangular." [s.n.], 2013. http://repositorio.unicamp.br/jspui/handle/REPOSIP/265971.
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Orientador: Carlos Alberto Carrasco Altemani<br>Dissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Engenharia Mecânica<br>Made available in DSpace on 2018-08-24T09:07:23Z (GMT). No. of bitstreams: 1
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Previous issue date: 2013<br>Resumo: A transferência de calor conjugada por convecção forçada-condução de dois aquecedores protuberantes montados na parede inferior (substrato) de um duto retangular foi investigada através de medidas experimentais em laboratório. Potência elétrica era dissipada em resistências embutidas nos aquecedores feitos de alumínio, que eram resfriados em regime permanente por um escoamento forçado de ar no duto. Cada aquecedor transferia calor por convecção diretamente das suas superfícies em contato com o escoamento e por condução para a placa do substrato através da interface comum. Esta condução de calor espalhava na placa do substrato e era transferida por convecção da placa para o escoamento de ar no duto. O resfriamento conjugado dos aquecedores na placa de substrato foi descrito por uma matriz de coeficientes conjugados obtidos por meio de testes experimentais realizados com um aquecedor ativo por vez, em uma faixa do número de Reynolds do escoamento entre 1600 e 6400. Foram utilizadas duas montagens experimentais praticamente idênticas, uma com a placa do substrato de acrílico e a outra, de alumínio. O número de Nusselt adiabático, que é um descritor invariante do processo convectivo de troca de calor, também foi avaliado nos testes com o substrato de acrílico. Os coeficientes conjugados obtidos nestes testes foram então utilizados para prever as temperaturas dos aquecedores em testes adicionais com os dois simultaneamente ativos, sob condições variadas de escoamento e aquecimento. A concordância dessas temperaturas indicou que esses coeficientes são descritores invariantes do resfriamento conjugado dos aquecedores discretos no duto. Simulações numéricas do escoamento e da transferência de calor no duto considerado foram efetuadas com o pacote computacional PHOENICS em um domínio tridimensional semelhante ao duto experimental. Os resultados numéricos obtidos foram comparados com as medidas experimentais<br>Abstract: Conjugate heat transfer by forced convection-conduction of two protruding heaters mounted on the lower wall (substrate) of a rectangular duct was investigated through experiments in laboratory. Electric power dissipation in the Aluminum heaters¿ embedded resistances was transferred under steady state conditions to forced airflow in the duct. Heat losses from each heater included direct convection from its surfaces in contact with the airflow and conduction to the substrate plate through their common interface. This heat conduction was spread in the substrate plate and eventually transferred by convection from the plate to the airflow in the duct. The heaters¿ conjugate cooling was described by a conjugate matrix with coefficients obtained from experimental tests with a single active heater at a time, in the range of the airflow Reynolds number from 1,600 to 6,400. Two almost identical assemblies were used, one with a Plexiglas plate and the other with Aluminum. The adiabatic Nusselt number, an invariant descriptor of the convective heat transfer, was also evaluated in the tests with the Plexiglas plate. The conjugate coefficients were used to predict the heaters¿ temperatures from additional tests with both active heaters, for arbitrary airflow rates and heaters¿ power dissipation. An agreement of these temperatures indicated that the conjugate coefficients are invariant descriptors of their conjugate cooling. Numerical CFD simulations were performed using the PHOENICS software in a three dimensional domain similar to the experimental assembly. The numerical results were compared to those of the experiments<br>Mestrado<br>Termica e Fluidos<br>Mestra em Engenharia Mecânica
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Nelson, Ian Carl. "Characterization of thermo-physical properties and forced convective heat transfer of poly-alpha-olefin (PAO) nanofluids." Thesis, [College Station, Tex. : Texas A&M University, 2007. http://hdl.handle.net/1969.1/ETD-TAMU-1569.
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Ahmed, Nisaar. "Thermo-fluid modelling of electrical generator frames under forced convection in an oscillating water column environment." Thesis, University of Edinburgh, 2018. http://hdl.handle.net/1842/31363.
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This PhD involved computational fluid dynamic simulations of finned generators cooling under forced convection in an oscillating water column environment. Various design changes to the upstream Wells turbine and its effect on the consequent cooling of the generator were investigated. Simulations were run in steady-state to obtain an initial condition, thereafter, unsteady simulations revealed a steadying of heat transfer over the course of multiple blade rotation cycles. This justified the use of steady-state for the remaining simulations over a range of flow coefficients. The results revealed that the heat transfer from the generator increased for tighter blade tip clearances, thicker blade profiles and greater turbine solidity. The heat transfer was found to increase with rising flow rate coefficient, which was adjusted by increasing the inlet velocity whilst maintaining the angular velocity of the turbine at a constant 2000 RPM. Additionally, the variation of turbine angular velocity at a fixed flow rate coefficient was investigated, the heat transfer was also found to increase with angular velocity, albeit by a far lesser extent. The inclusion of the Wells turbine upstream of the generator was investigated initially and was found to increase heat transfer due to the resulting impingement of airflow across the generator. In all design scenarios in which the heat transfer increases, there is also an observed increase in the mass flow rate of air, radially, towards the generator.
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Gurer, Turker. "Numerical Investigation Of Incompressible Flow In Grooved Channels- Heat Transfer Enhancment By Self Sustained Oscillatins." Phd thesis, METU, 2003. http://etd.lib.metu.edu.tr/upload/12604891/index.pdf.
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In this study, forced convection cooling of package of 2-D parallel boards with heat generating chips is investigated. The main objective of this study is to determine the optimal board-to-board spacing to maintain the temperature of the components below the allowable temperature limit and maximize the rate of heat transfer from parallel heat generating boards cooled by forced convection under constant pressure drop across the package. Constant heat flux and constant wall temperature boundary conditions on the chips are applied for laminar and turbulent flows.
Finite elements method is used to solve the governing continuity, momentum and energy equations. Ansys-Flotran computational fluid dynamics solver is utilized to obtain the numerical results. The solution approach and results are compared with the experimental, numerical and theoretical results in the literature.
The results are presented for both the laminar and turbulent flows. Laminar flow results improve existing relations in the literature. It introduces the effect of chip spacing on the optimum board spacing and corresponding maximum heat transfer. Turbulent flow results are original in the sense that a complete solution of turbulent flow through the boards with discrete heat sources with constant temperature and constant heat flux boundary conditions are obtained for the first time. Moreover, optimization of board-to-board spacing and maximum heat transfer rate is introduced, including the effects of chip spacing.
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Racine, Evan Michael. "Experimental Study - High Altitude Forced Convective Cooling of Electromechanical Actuation Systems." University of Dayton / OhioLINK, 2015. http://rave.ohiolink.edu/etdc/view?acc_num=dayton1450286609.
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Bishara, Fady. "Numerical Simulation of Fully Developed Laminar Flow and Heat Transfer in Isothermal Helically Twisted Tubes with Elliptical Cross-Sections." University of Cincinnati / OhioLINK, 2010. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1291146958.
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Szabo, Peter Sebastian Benedek. "Heat transfer through thermomagnetic convection in magnetic fluids induced by varying magnetic fields." Thesis, Heriot-Watt University, 2017. http://hdl.handle.net/10399/3365.
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Magnetic fluid flow by thermomagnetic convection with and without buoyancy was studied in experiments and computational simulations. A mineral oil based ferro magnetic fluid was subjected to varying magnetic fields to induce thermomagnetic convection. As such fluids are mainly developed to increase heat transfer for cooling the fundamental effects on magnetic fluid flow was investigated using various magnetic field distributions. Computational simulations of natural and thermomagnetic convection are based on a Finite-Element technique and considered a constant magnetic field gradient, a realistic magnetic field generated by a permanent magnet and alternating magnetic fields. The magnetic field within the fluid domain was calculated by the magneto-static Maxwell equations and considered in an additional magnetic body force known as the Kelvin body force by numerical simulations. The computational model coupled the solutions of the magnetic field equations with the heat and fluid flow equations. Experiments to investigate thermomagnetic convection in the presence of terrestrial gravity used infrared thermography to record temperature fields that are validated by a corresponding numerical analysis. All configurations were chosen to investigate the response of the magnetic fluid to the applied body forces and their competition by varying the magnetic field intensity and its spatial distribution. As both body forces are temperature dependent, situations were analysed numerically and experimentally to give an indication of the degree by which heat transfer may be enhanced or reduced. Results demonstrate that the Kelvin body force can be much stronger than buoyancy and can induce convection where buoyancy is not able to. This was evident in a transition area if parts of a fluid domain are not fully magnetically saturated. Results for the transition from natural convection to thermomagnetic convection suggest that the domain of influence of the Kelvin body force is aligned with the dominance of the respective body force. To characterise the transition a body force ratio of the Kelvin body force to buoyancy was developed that identified the respective driving forces of the convection cells. The effects on heat transfer was quantified by the Nusselt number and a suitable Rayleigh number. A modified Rayleigh number was used when both body forces were active to define an effective body force by taking the relative orientation of both forces into account. Results for the alternating magnetic field presented flow fields that altered with the frequency of the applied magnetic field but with varying amplitude. This affected the heat transfer that alternated with the frequency but failed to respond instantaneously and a phase lag was observed which was characterised by three different time scales.
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Ren, Tieying. "An experimental study of the local mean and turbulent flow field affecting forced convection heat transfer for finned tubes in cross flow." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1999. http://www.collectionscanada.ca/obj/s4/f2/dsk2/ftp01/MQ39872.pdf.
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Metwally, Hossam Eldin Mahmoud Hassan. "A computational study of enhanced laminar forced convection heat transfer to Newtonian and non-Newtonian fluid flows in sinusoidal corrugated-plate channels." Cincinnati, Ohio : University of Cincinnati, 2002. http://rave.ohiolink.edu/etdc/view?acc%5Fnum=ucin1022762582.
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Hudjetz, Stefan. "Experimental investigation of heat exchange between thermal mass and room environments." Thesis, De Montfort University, 2012. http://hdl.handle.net/2086/9021.
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The different technologies of passive cooling concepts have to rely on a good thermal coupling between a building's thermal mass and indoor air. In many cases, the ceiling is the only surface remaining for a good coupling. Further research is necessary to investigate discrepancies between existing correlations. Therefore, the overall aim of the work described in this thesis is the investigation of heat transfer at a heated ceiling in an experimental chamber. Acoustic baffles obstruct the surface of the ceiling and impede heat transfer. However, there is nearly no published data about the effect of such baffles on heat transfer. Available results from simulations should be verified with an experimental investigation. Consequently, one of the primary aims of this work was to experimentally determine the influence of such acoustic baffles. A suitable experimental chamber has been built at Biberach University of Applied Sciences. The thesis describes the experimental chamber, the experimental programme as well as results from five different test series. With a value of ±0.1Wm⁻²K⁻¹ for larger temperature differences, uncertainty in resulting convective heat transfer coefficients for natural convection is comparable to that of results from an existing recent experimental work often recommended for use. Additionally, total heat transfer (by convection and radiation) results are presented. Results are given for natural, forced and mixed convection conditions at an unobstructed heated ceiling. Furthermore, results for acoustic baffles in both an unventilated and a ventilated chamber are shown. Natural convection results show a very good agreement with existing correlations. Under mixed convection conditions, convective heat transfer at an unobstructed ceiling decreases to the limiting case described by natural convection. Installation of acoustic baffles leads to a reduction in total heat transfer (convection and radiation) between 20% and 30% when compared to the case of an unobstructed ceiling.
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Loosmann, Felix [Verfasser], Cameron [Akademischer Betreuer] Tropea, and Sanjeev [Akademischer Betreuer] Chandra. "Forced Convective Heat Transfer in Channels with Complex Internal Structures / Felix Loosmann ; Cameron Tropea, Sanjeev Chandra." Darmstadt : Universitäts- und Landesbibliothek Darmstadt, 2019. http://d-nb.info/1194547796/34.
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Avelar, Ana Cristina. "Analise teorica e experimental da tranferencia de calor em placas de circuito impresso formando canais verticais abertos." [s.n.], 1997. http://repositorio.unicamp.br/jspui/handle/REPOSIP/263433.
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Orientador: Marcelo Moreira Ganzarolli<br>Dissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Engenharia Mecanica<br>Made available in DSpace on 2018-07-22T20:18:14Z (GMT). No. of bitstreams: 1
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Previous issue date: 1997<br>Resumo: Os constantes avanços tecnológicos em eletrônica e informática tem tornado os sistemas eletrônicos cada vez mais compactos, aumentando-se a quantidade de calor a ser removida dos componentes e placas de circuito impresso. Por este motivo, atualmente são exigidos sistemas de dissipação de calor altamente eficientes. Este estudo analisa teórica e experimentalmente a transferência de calor em canais verticais formados por placas de circuito impresso dispostas paralelamente, resfriadas por convecção natural e propõe uma modelagem, baseada em relações existentes na literatura, que busca prever a distribuição de temperaturas em pontos significativos nos canais e placas em função da potência dissipada e da distância entre as placas. Este estudo visa também analisar os efeitos do aquecimento não-uniforme das placas que formam o canal. Na simulação teórica, devido à pequena espessura da placa o gradiente de temperatura ao longo da espessura da mesma foi desprezado e resolveu-se numericamente a equação de transferência de calor em coordenadas cartesianas bidimensionais e em regime permanente. Equacionou-se balanços de energia para os componentes e para o ar no canal e o problema foi resolvido numericamente através de um programa computacional. As placas de circuito impresso utilizadas nos testes experimentais, concebidas exclusivamente para fins de estudos térmicos, possuem uma base de epóxi com 25 resistores discretamente distribuídos sobre sua superfície de 200x164mm. Realizou-se testes com aquecimento uniforme e não-uniforme, variando-se a potência por componentes nas placas. Variou-se também as potências por placas e as distâncias entre as mesmas. Testou-se as potências de 2, 4,6 e 8 W e as distâncias entre placas de 12,24, e 48mm. Verificou-se boa concordância entre os resultados numéricos e experimentais, principalmente para a menor distância entre placas, 12 mm, onde a diferença entre os resultados teóricos e experimentais foi muito pequena<br>Abstract: The constant technological advances in electronics and computations have made the electronic system increasingly more compact, thus increasing the amount of heat to be removed ITomthe components and printed circuit boards. For this reason, highly efficient system of heat removal are presently required. This study analyses both theoretically and experimentallyheat transfer in an array of vertical parallel printed circuit boards, cooled off by natural convection and proposes a modeling, based on correlation found in literature which tries to predict temperature distribution in significant places in the channels and boards as regards dissipated power and distance among boards. This study also aims at analyzing nonuniform heating effets of the channel made boards. In the theoritical simulation, due to the board' s small thickness, the temperature gradient across the board has been neglected, and the equation of heat transfer in two-dimensional Cartesian was numericallysolved, and on a steady state. Energy balances for the componentes were formulated, and the problem was numerically solved by a computer programo The printed circuit boards used in the experimental tests, manufactured speciallyfor heat trasnfer studies have an epoxy basis with 25 resistors discretely distributed on 200 x 164 mm. Uniform and non-uniform heating tests were performed, thus a variation of power and distance among them had a variation. The 2, 4, 6 and 8 W power and distance among 12, 24 and 48 mm boards were tested. Good agreements between numerical and experimentalresults were observed, mainlyfor the smaller distance among boards, 12 mm, the differencesbetween the theoretical and experimentalresults were small<br>Mestrado<br>Termica e Fluidos<br>Mestre em Engenharia Mecânica
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Kashani, Ali. "Forced convection heat transfer in He II." 1986. http://catalog.hathitrust.org/api/volumes/oclc/15340950.html.
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Thesis (Ph. D.)--University of Wisconsin--Madison, 1986.<br>Typescript. Vita. eContent provider-neutral record in process. Description based on print version record. Includes bibliographical references (leaves 127-129).
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HUANG, YU-KAI, and 黃堉凱. "Parametric study of conjugate forced convection heat transfer." Thesis, 2016. http://ndltd.ncl.edu.tw/handle/69688519881008495453.
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碩士<br>中華大學<br>機械工程學系<br>104<br>Conjugate heat transfer problem is solved by a differential algorithm based on the compressible Navier-Stokes equations and a heat conduction solver. A parametric study on the height of the block, thermal conductivity ratio, Prandtl number, and the shape of the top surface is investigated on the heat transfer characteristics. The effect of conjugate heat transfer is analyzed by the temperature contour, streamlines, velocity and temperature profiles, local surface temperature and Nusselt number distributions. The current numerical scheme provides a skill to handle complicate heat transfer problems.
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Ting, Hsien-Hung, and 丁獻宏. "Heat Transfer Enhancement of Nanofluids in Forced Convection Flows." Thesis, 2016. http://ndltd.ncl.edu.tw/handle/46472974674906633359.
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博士<br>崑山科技大學<br>機械與能源工程研究所<br>104<br>In recent years, much attention has been focused on the heat transfer characteristics of nanofluids in circular and non-circular tubes. However, few numerical results were compared with experimental literature, especially for non-circular ducts. The purpose of this study is to numerically investigate heat transfer enhancement of nanofluids in forced convection flows. The finite volume formulation is used with the semi-implicit method for pressure-linked equations (SIMPLE) algorithm to solve the discretized equations derived from the partial nonlinear differential equations of the mathematical model. The numerical results are also compared with published experimental data.
Firstly, the forced convection heat transfer and flow characteristics of water-based Al2O3 nanofluids inside a horizontal circular tube in the laminar flow regime under the constant wall temperature boundary condition are numerically investigated. The results show that heat transfer coefficient of nanofluids increases with increasing Reynolds number or particle volume concentration. The heat transfer coefficient of the water-based nanofluid with 2 vol.% Al2O3 nanoparticles is enhanced by 32% compared with that of pure water. Increasing particle volume concentration causes an increase in pressure drop. At 2 vol.% of particle concentration, the pressure drop reaches a maximum that is nearly 5.7 times compared with that of pure water. Note that the numerical results are in good agreement with published experimental data.
Secondly, the convective heat transfer of water-based Al2O3 nanofluids flowing through a square cross-section duct with a constant heat flux under laminar flow conditions is numerically investigated. The results show that the heat transfer coefficients and Nusselt numbers of Al2O3-water nanofluids increase with increases in the Peclet number as well as particle volume concentration. The heat transfer coefficient of nanofluids is increased by 25.5% at a particle volume concentration of 2.5% and a Peclet number of 7500 as compared with that of the base fluid (pure water). It is noteworthy that at the same particle volume concentration of 2.5%, the enhancement of the convective heat transfer coefficient of Al2O3-water nanofluid (25.5%) is much higher than that of the effective thermal conductivity (9.98%). Thus, the enhancement of the convective heat transfer cannot be solely attributed to the enhancement of the effective thermal conductivity. Additionally, the numerical results coincide well with the published experimental data.
Thirdly, turbulent flow forced convection of CuO-water nanofluid in a square cross-section duct subjected to a constant heat flux is numerically studied. The results show that the heat transfer coefficient and Nusselt number increase with increasing Peclet number and particle volume concentration. The heat transfer coefficient of CuO-water nanofluids increased by 19.63 percent at a particle concentration of 0.8 vol% compared with that of pure water at Pe=49,000. It is worth noting that at this particle volume concentration (0.8 percent), the enhancement of the convective heat transfer coefficient of the CuO-water nanofluid (19.63 percent) is much higher than that of the effective thermal conductivity (3.15 percent). Hence, the enhancement of the convective heat transfer cannot be solely attributed to the enhancement of the effective thermal conductivity. Other factors such as dispersion, Brownian motion, thermophoresis, and nanoparticle migration may also be responsible for the enhancement of convective heat transfer. Additionally, theoretical correlations calculated from the Dittus-Boelter equation are not able to predict nanofluid thermal performance. Moreover, the present numerical results are in good agreement with the published experimental data.
Finally, the heat transfer augmentation using water-based Al2O3 and CuO nanofluids flowing in a triangular cross-sectional duct under constant heat flux in laminar flow conditions is numerically explored. The heat transfer rate becomes more remarkable when employing nanofluids. As compared with pure water, at a Peclet number of 7000, a 35% enhancement in the convective heat transfer coefficient, is obtained for an Al2O3/water nanofluid with 2% particle volume fraction; at the same Peclet number, a 41% enhancement in the convective heat transfer coefficient is achieved for a CuO/water nanofluid with 0.8% particle volume concentration. Heat transfer enhancement increases with increases in particle volume concentration and Peclet number. Moreover, the numerical results are found to be in good agreement with published experimental data.
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Huang, I.-Chia, and 黃怡家. "Heat Transfer Characteristics of Aluminum Foam Metal in Forced Convection." Thesis, 1994. http://ndltd.ncl.edu.tw/handle/10124773485512307993.
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碩士<br>國立臺灣大學<br>機械工程研究所<br>82<br>In this research, the heat transfer characteristics of aluminum
foam metal was experimentally investigated in the wind tunnel.
And the overall heat transfer coefficients are compared with
some fins now used in applications.The employment of porous
media could be considered as a alternative for traditional
fins. This work examines the effects of different heat flux,
velocity, pore structure, volume and different ratio of the
channel height to the height of the tested porous medium.And we
study the flow pattern, heat transfer mechanism by streamline
observation. The experimental data proves that the overall heat
transfer coefficients of the aluminum foam metal is dominated
by the flow velocity through the porous medium and the pore
structure.The overall heat transfer coefficient for item C is
about 390 Watt per square meter per Kelvin degree for velocity
through porous medium at 4.6 meter per second,higher than the
rectangular fin of the same volume,while the weight is only 0.3
of the fin.
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Vijay, Dig. "Forced convective heat transfer through open cell foams." Doctoral thesis, 2016. https://tubaf.qucosa.de/id/qucosa%3A23120.
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The purpose of this study is to investigate forced convection of air through open cell foams. It can be numerically investigated either by implementing the time efficient macroscopic models or computationally expensive microscopic models. However, during the course of this study, it was observed that the macroscopic models are not sufficient for determining the desired key parameters. Nevertheless, it is still possible that these macroscopic models can be used to design an application accurately with minimum time efforts if the concerned key parameters are already known through other means. Accordingly, in this work, a methodology is developed to determine the desired key parameters by implementing the microscopic models, which are further used into the macroscopic models for designing different applications. To validate the proposed methodology, a set of steady state and transient forced convection experiments were performed for a set of ceramic foams having different pore diameter (10−30 PPI) and porosity (0.79−0.87) for a superficial velocity in the range of 0.5−10 m/s.
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Wu, Hsin-Hsuan, and 吳欣璇. "Heat Transfer Analysis of Plate-Type Fins in Natural and Forced Convection." Thesis, 2011. http://ndltd.ncl.edu.tw/handle/30242742282517060512.
Full textAbstract:
博士<br>國立臺灣大學<br>機械工程學研究所<br>99<br>Two analytical models were used in this study to predict the performance of a plate-fin array heat sink in forced convection and natural convection cases respectively. The optimization of geometry variables for designing a plate-fin heat sink in both cases was also analyzed in this study.
While the pressure drop of heat sink was fixed at 10 mmAq, and the height was fixed at 24 mm in forced convection situations, optimal values for fin spacing, base thickness, base width and base length were found. In natural convection situation, it was found that there are lower limits for the variation of fin height, base length, base width and base thickness of heat sink. Increase of these parameters has limited benefit of performance. Considering the limits of these parameters and the cost factors, the optimal values of these design parameters were suggested in this study.
As the airflow rate through the heat sink becomes small in force convection, the effect of nature convection has to be considered. For the case of a fixed size of heat sink with a slow airflow velocity considered in this study, it’s found the overall performance of forced convection (with thermal resistance of 4.62 ℃/W) is worse than that of nature convection (with thermal resistance of 4.38 ℃/W) when airflow rate was under 0.68 cfm.
In the case of forced convection using fan as driving force, the effect of fan performance curve has to be considered in the design optimization process of heat sink’s geometry variables. The optimal operating points of airflow rate, pressure drop and sizes of heat sink, can be found with this model for a single heat sink with a fixed fan. Example of the optimal operating point was illustrated in this study.