Relevant bibliographies by topics / Heat transfer coefficient U

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Academic literature on the topic 'Heat transfer coefficient U'

Author: Grafiati
Published: 4 June 2021
Last updated: 6 February 2022

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Journal articles on the topic "Heat transfer coefficient U"

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Sablani, S. S., and H. S. Ramaswamy. "Note. End-over-end agitation processing of cans containing liquid particle mixtures. Influence of continuous versus oscillatory rotation / Nota. Agitación por volteo de latas con una mezcla de líquido y partículas en suspensión. Influencia de la agitación en continuo y oscilatoria." Food Science and Technology International 5, no. 5 (October 1999): 385–89. http://dx.doi.org/10.1177/108201329900500503.

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Convective heat transfer coefficients were evaluated during end-over-end rotation processing of cans filled with liquid and particle mixtures in a pilot-scale, overpressure water-immersion, rotary retort. Two modes of end-over-end agitation were employed, one involving a continuous and the other involving an oscillatory rotation of the cage containing cans. Nylon spheres of diameter 0.025 m were used as test particles and a high temperature bath oil was used as the test liquid. A lumped capacity approach was employed to determine the overall heat transfer coefficient, U, and an inverse heat transfer approach was used to determined the fluid to particle heat transfer coefficient, hfp. Effects of the two modes of rotation (continuous and oscillation) on the associated heat transfer coefficients were evaluated at three speeds (8, 16 and 24 rpm) and three radii of rotation (0,13 and 26 cm). An analysis of variance showed that the effects of rotation speed and mode of rotation on both U and htp were significant ( p < 0.05). However, the effect of radius of rotation was significant only with U. These factors also affected the calculated process times for achieving an accumulated lethality ( Fo) of 10 min at the particle center and in the can liquid in a similar fashion. In general, U and hfp values associated with continuous rotation were 10-40% higher than those associated with oscillatory rotation.
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Wang, Longfei, Songtao Wang, Xun Zhou, Fengbo Wen, and Zhongqi Wang. "Numerical Prediction of 45° Angled Ribs Effects on U-shaped Channels Heat Transfer and Flow under Multi Conditions." International Journal of Turbo & Jet-Engines 37, no. 1 (March 26, 2020): 41–59. http://dx.doi.org/10.1515/tjj-2017-0008.

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AbstractRibs effects on the heat transfer performance and cooling air flow characteristics in various aspect ratios (AR) U-shaped channels under different working conditions are numerically investigated. The ribs angle and channel orientation are 45° and 90°, respectively, and the aspect ratios are 1:2, 1:1, 2:1. The inlet Reynolds number changes from 1e4 to 4e4 and rotational speeds include 0, 550 rpm, 1,100 rpm. Local heat transfer coefficient, endwall surface heat transfer coefficient ratio and augmentation factor are the three primary criteria to measure channel heat transfer. Ribs increase the heat transfer area and improve heat transfer coefficient of ribbed surfaces significantly, especially in the 1st pass, while the endwall surface contributes more to channel heat transfer because of the larger area and relatively smaller heat transfer coefficient. The wide channel (AR =2:1) owns the better augmentation factor than the narrow channel (AR =1:2) and ribs heat transfer weight increases with an increase of the inlet Reynolds number. Rotating slightly reduces the ribs heat transfer weight in channel and the trailing surface in 1st pass is the main influence object of rotating.
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Dai, Chuan Shan, Shuai Wang, and Wei Xing Qin. "U-Tube Diameter Dependence of Heat Output for Borehole Heat Exchangers." Applied Mechanics and Materials 170-173 (May 2012): 2613–16. http://dx.doi.org/10.4028/www.scientific.net/amm.170-173.2613.

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The heat output for borehole heat exchangers due to the variation of U-tube diameter was theoretically analyzed using the steady heat conduction model of a hollow cylinder. In the present model, except of the U-tube diameter, the other influencing factors on the heat output, such as the heat transfer coefficient inside U-tube, tube thickness and thermal conductivity, have been taken into account.
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Cui, Yu Zhou. "Analysis on Heat Transfer Energy Efficiency of U-Tube Buried Pipe under Variable Entering Water Temperature Conditions." Advanced Materials Research 960-961 (June 2014): 603–8. http://dx.doi.org/10.4028/www.scientific.net/amr.960-961.603.

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Taken as the carrier of heat extraction between rock-soil body and ground source heat pump systems, U-tubed pipe heat transfer efficiency was the key for ensuring the long-term and high-performance operation of ground source heat pump systems by means of improving the heat transfer effect. The efficiency coefficient, E, is defined as the ratio of the actual heat transfer capacity to the theoretically maximal heat transfer capacity from the U-tube into rock-soil body, which illustrated the effect of heat transfer ability and the variable heating or cooling loads. Aim at Variation characteristics of heat transfer coefficient of energy efficiency under the variable temperature inflow condition, decomposed into the product of the ratio of biggest buried tube heat transfer temperature difference φ and heat pump outlet water temperature difference σ. Use of u-shaped buried pipe three-dimensional heat transfer model which based on the multipole theory, the influence law of its change which caused by the construction load, buried pipe flow and the unit performance were analyzed, it can provide technical support to optimize the design of ground source heat pump system.
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Garrote, R. L., E. R. Silva, R. D. Roa, and R. A. Bertone. "Note. Overall Heat Transfer Coefficient to Canned Liquid During End-over-end Sterilisation." Food Science and Technology International 12, no. 6 (December 2006): 515–20. http://dx.doi.org/10.1177/1082013206072940.

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The overall heat transfer coefficient as a function of rotation speed (5–20rpm) was calculated for cans containing a 2% NaCl and 1.5% sucrose aqueous solution during end-over-end heat sterilisation at 120°C. The values obtained for the overall heat transfer coefficient, U (W/m2 °C), were: 544.4±85.3 at 5rpm, 710.7±24.5 at 10rpm, 760.5±17.7 at 15rpm and 941.6±22.1 at 20rpm. A correlation was developed in terms of Nusselt, rotational Reynolds and Prandtl numbers to predict U(Nu = 1.866Re0.379 Pr0.38). The characteristic dimension in Nu and Re was the diameter of the can. This correlation (R2 = 0.88) was valid for Re within the range of 3,012–14,820 and Pr within 2.02–2.63 values.
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Krasoń, Joanna, Przemysław Miąsik, Lech Lichołai, Bernardeta Dębska, and Aleksander Starakiewicz. "Analysis of the Thermal Characteristics of a Composite Ceramic Product Filled with Phase Change Material." Buildings 9, no. 10 (October 12, 2019): 217. http://dx.doi.org/10.3390/buildings9100217.

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The article presents a comparative analysis carried out using three methods, determining the heat transfer coefficient U for a ceramic product modified with a phase change material (PCM). The purpose of the article is to determine the convergence of the resulting thermal characteristics, obtained using the experimental method, numerical simulation, and standard calculation method according to the requirements of PN-EN ISO 6946. The heat transfer coefficient is one of the basic parameters characterizing the thermal insulation of a building partition. Most often, for the thermal characteristics of the partition, we obtain from the manufacturer the value of the thermal conductivity coefficient λ for individual homogeneous materials or the heat transfer coefficient U for the finished (prefabricated) partition. In the case of a designed composite element modified with a phase change material or other material, it is not possible to obtain direct information on the above parameter. In such a case, one of the methods presented in this article should be used to determine the U factor. The U factor in all analyses was determined in stationary conditions. Research has shown a significant convergence of the resulting value of the heat transfer coefficient obtained by the assumed methods. Thanks to obtaining similar values, it is possible to continue tests of thermal characteristics of partitions by means of numerical simulation, limiting the number of experimental tests (due to the longer test time required) in assumed different partition configurations, in stationary and dynamic conditions.
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Alagha, Mohamed Sobhi, Botond Szucs, and Pal Szentannai. "Numerical study of mixing and heat transfer of SRF particles in a bubbling fluidized bed." Journal of Thermal Analysis and Calorimetry 142, no. 2 (December 13, 2019): 1087–96. http://dx.doi.org/10.1007/s10973-019-09135-2.

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AbstractIn this article, numerical investigations on mixing and heat transfer of solid refused fuel (SRF) particles in a bubbling fluidized bed are carried out. The numerical model is based on the Eulerian–Eulerian approach with empirical submodels representing gas–solid and solid–solid interactions. The model is verified by experimental data from the literature. The experimental data include SRF vertical distribution in SRF–sand mixtures of different sand particle sizes ($$d_{\mathrm{pm}} = 654,810$$ d pm = 654 , 810 and 1110 $$\upmu$$ μ m) at different fluidization velocities ($$u/u_{\mathrm{mf}} = 1.2$$ u / u mf = 1.2 –2.0). We proposed magnification of drag force exerted by the gas on SRF particles based on Haider and Levenspiel (Powder Technol 58(1):63–70, 1989) drag coefficient. The proposed model shows good agreement with the experimental data at high fluidization velocities ( $$u/u_{\mathrm{mf}} = 1.5$$ u / u mf = 1.5 –2.0) and poor predictions at low fluidization velocities ($$u/u_{\mathrm{mf}} = 1.2$$ u / u mf = 1.2 –1.5). Heat transfer results showed that the present model is valid and gives good agreement with the experimental data of wall–bed heat transfer coefficient.
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Yu, Guo Qing, Gang Feng Gao, and Xin Feng Lin. "Identification of Building Envelope Overall Coefficient of Heat Transfer Using Recursive Least Squares Algorithm." Advanced Materials Research 250-253 (May 2011): 3239–44. http://dx.doi.org/10.4028/www.scientific.net/amr.250-253.3239.

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This paper introduces the methodology and procedures of identification of overall coefficient of heat transfer (U-factor) of building envelopes using recursive least squares algorithm and dynamic heat transfer data. Application this method to three types of typical to examine the correctness and feasibility of this method. The following conclusions can be obtained: 1) Identification of U-factor of building envelopes using recursive least squares algorithm is feasible for engineering purpose, the identified U-factor can be near to its real value; 2)The testing periods can be much shorter than the steady testing; 3)The identification error is associated with the thermal inertia. The error is larger as the thermal inertia of building envelope is large within the same testing circumstances.
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Andrzejczyk, Rafal, Tomasz Muszynski, and Przemysław Kozak. "Experimental investigation on straight and u-bend double tube heat exchanger with active and passive enhancement methods." MATEC Web of Conferences 240 (2018): 02001. http://dx.doi.org/10.1051/matecconf/201824002001.

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Authors in this work want to demonstrate the possibility to increase the heat transfer efficiency by using simple wire coil inserts to create turbulent flow in the boundary layer as well as air blowing into the annulus of the pipe. In the study, Wilson plot approach was applied in order to estimate heat transfer coefficients for all heat exchanger (HX) configurations. The study focuses on experimental values of heat transfer coefficient (HTC) and pressure drops. The primary objectives of the work are to: I. Provide an experimental comprehensive database for HTC and pressure drops; II. Analysis effect of different flow conditions e.g. water mass flow rate, the void fraction on heat transfer and hydraulic performance of tested elements. III. Compare influences of both passive and active methods at the efficiency of simple heat exchangers constructions; IV. Validation experimental results with selected experimental models from the open literature.
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Rasheed, Adnan, Jong W. Lee, and Hyun W. Lee. "Development of a model to calculate the overall heat transfer coefficient of greenhouse covers." Spanish Journal of Agricultural Research 15, no. 4 (February 7, 2018): e0208. http://dx.doi.org/10.5424/sjar/2017154-10777.

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A Building Energy Simulation (BES) model based on TRNSYS, was developed to investigate the overall heat transfer coefficient (U-value) of greenhouse covers including polyethylene (PE), polycarbonate (PC), polyvinyl chloride (PVC), and horticultural glass (HG). This was used to determine the influences of inside-to-outside temperature difference, wind speed, and night sky radiation on the U-values of these materials. The model was calibrated using published values of the inside and outside convective heat transfer coefficients. Validation of the model was demonstrated by the agreement between the computed and experimental results for a single-layer PE film. The results from the BES model showed significant changes in U-value in response to variations in weather parameters and the use of single or double layer greenhouse covers. It was found that the U-value of PC, PVC, and HG was 9%, 4%, and 15% lower, respectively, than that for PE. In addition, by using double glazing a 34% reduction in heat loss was noted. For the given temperature U-value increases as wind speed increases. The slopes at the temperature differences of 20, 30, 40, and 50 °C, were approximately 0.3, 0.5, 0.7, and 0.9, respectively. The results agree with those put forward by other researchers. Hence, the presented model is reliable and can play a valuable role in future work on greenhouse energy modelling.
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Dissertations / Theses on the topic "Heat transfer coefficient U"

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Lazar, Kovačević. "Primena metoda inverznog inženjerstva u cilju pronalaženja graničnih uslova pri livenju u peščanim kalupima." Phd thesis, Univerzitet u Novom Sadu, Fakultet tehničkih nauka u Novom Sadu, 2015. http://www.cris.uns.ac.rs/record.jsf?recordId=95359&source=NDLTD&language=en.

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U disertaciji je razvijena nova eksperimentalna postavka za merenjegraničnih uslova pri livenju u peščanim kalupima. Utvrđeno je da seuvođenjem pojma prividne toplotne difuzivnosti materijala kalupamože poništiti greška pozicioniranja termoparova i time smanjitigreška procene graničnih uslova. Dodatno, pokazano je da procesizdvajanja intermetalnih jedinjenja tokom procesa očvršćavanjakalupa može uticati na vrednosti graničnih uslova. Razvijena je inova empirijska korelaciona funkcija kojom se može opisati promenavrednosti koeficijenta prenosa toplote između kalupa i odlivka.
In this study a new experimental technique and apparatus for estimation ofboundary conditions in sand casting process were developed. It is shownthat thermocouple positioning errors can be nullified by introducing a conceptof apparent heat diffusivity of the mold material. In this way, total error of theheat transfer estimation can be reduced. Additionally, it was found that theprocess of precipitation of intermetallic compounds can influence the value ofachieved metal-mold heat transfer. A novel empirical correlation function isproposed. This function has the ability to accurately describe the change ininterfacial heat transfer with the casting surface temperature.
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Soukupová, Veronika. "Vliv provedení zateplení rodinného domu v Brodku u Prostějova na výdaje spojené s jeho provozem." Master's thesis, Vysoké učení technické v Brně. Ústav soudního inženýrství, 2018. http://www.nusl.cz/ntk/nusl-390157.

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This diploma thesis evaluates the influence of a thermal insulation of a structure on expenses related to its operation. It addresses the issues of a thermal insulation, energy loss, energy consumption, and evaluates the recovery of investments considering the insulation costs. It also monitors the insulation price projection on the total cost of the property.
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Bergh, Jonas, and Oscar Klockars. "Mall för jämförelse av ytterväggar i byggprojekt : Examensarbete i jämförande av ytterväggar för byggprojekt av flerbostadshus med en Excelmall." Thesis, KTH, Byggteknik och design, 2017. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-213506.

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Byggbranschen har många olika ytterväggar i projekt. Det är ofta svårt och tidskrävande att ta reda på vilket av ytterväggsalternativen som är bäst för ett specifikt projekt. I examensarbetet har det tagits fram en mall för att kunna jämföra prefabricerade ytterväggars; värmegenomgångskoefficient (U-värde), arbetstider, kostnader för material och arbete, avfall i produktion, skillnader i bruksarea och skillnad i intäkter beroende på väggens tjocklek. Genom tester med hjälp av kalkylering- och U-värdesberäkningsprogram har mallen kontrollerats för att få värden som stämmer överens med dessa. Det resulterade i att totalkostnaderna skiljer sig med 0,002-2,395 %, tidsåtgången 0-0,007 % och U-värdet 2,4 %. Jämförelse mellan två olika väggtyper har gjorts åt Järntorgets begäran. Ena väggen är en prefabricerad utfackningsvägg bestående av mineralullsisolering med stålreglar och den andra en bärande betongvägg med PIR-isolering. Resultatet av jämförelsen visade att utfackningsväggen var det mest lönsamma alternativet. En tredje yttervägg lades även till i jämförelsen för att hitta ett bättre alternativ. Det är en utfackningsvägg med PIR-isolering innehållande låg andel genomgående stålreglar. Resultatet visade att utfackningsväggen med PIR-isolering är det bättre alternativet.
The construction industry has many different exterior walls in projects. It is often difficult and time consuming to find out which of the exterior wall options is best for a specific project. In the bachelor thesis a template has been developed to compare prefabricated outer walls; Heat transfer coefficient (U value), working hours, materials and labor costs, waste in production, differences in usage area and difference in revenue depending on the thickness of the wall. Through tests using programs for cost calculation and U-value calculation, the template has been examined to match those values. As a result, total costs differed 0.002-2.395%, duration of the project 0-0.007% and U-value 2.4%. Comparison between two different wall types has been made to Järntorget's request. The single wall is a prefabricated infill wall consisting of mineral wool insulation with steel bars and the other a load-bearing concrete wall with PIR insulation. The result of the comparison showed that the prefabricated infill wall was the most profitable option. A third exterior wall was also added to the comparison to find a better alternative. It is a prefabricated infill wall with PIR insulation with low proportion of continuous steel studs. The result showed that the prefabricated infill wall with PIR insulation is the better option
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Skarin, Erik, and Andreas Carlsson. "ANVÄNDNING AV VAKUUMISOLERING I EN NÄRA-NOLLENERGIVILLA; MÖJLIGHETER OCH BEGRÄNSNINGAR." Thesis, Tekniska Högskolan, Högskolan i Jönköping, JTH, Byggnadsteknik, 2016. http://urn.kb.se/resolve?urn=urn:nbn:se:hj:diva-29695.

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Objectives set by the EU means that all buildings after 2020 has to be nearly zero energy buildings. This means that thicker layers of insulation have to be added in the wall construction which makes the wall thicker. It means that the living area will be reduced. Vacuum insulation is a highly effective type of insulation and because of its low thermal conductivity it has the ability to reduce the thickness in wall structures. This project investigates a proposal to apply vacuum insulation in one-storey buildings. In order to achieve the goals of the project, a proposal for a one-storey building was developed. Calculations have been made and the proposal was developed as an alternative to show how to construct a family home containing vacuum insulation. The empirical data was collected through interviews, document analysis and literature studies. The collected data was analyzed together with the theoretical framework that has been developed through literature studies and document analysis. Creating a wall construction containing vacuum insulation as a primary insulation usually means that the wall will be considerably thinner than a wall construction with traditional insulation. This means that living area can be saved. Vacuum insulation has to be protected properly as it is easily punctured where upon it loses the most of its insulation capacity. Vacuum insulation is not common on the Swedish construction market today, this is due to many factors, including its high price. Vacuum insulation is a good problem solver which can be used in bay windows to gain extra space. One can also make use for it in tight spaces. From an economic point of view vacuum insulation offers the greatest advantages in cities where living space is considerably higher than in rural areas. To take part of the work there is no need for prior knowledge about vacuum insulation. The project focuses only on wall structures in the single-storey villas, therefor, no indentations has been made on the floor- and roof structures or other building types. The project only focuses on newly constructed buildings. No calculations are made for moisture or production costs.
Mål uppsatta av EU innebär att samtliga byggnader som uppförs vid år 2020 måste vara nära-nollenergihus. För väggarna i konstruktionen innebär det att tjockare lager av isolering måste adderas vilket ger bredare väggkonstruktioner. Bredare väggkonstruktioner innebär även att boarean minskas. Vakuumisolering är ett högeffektivt isoleringsmaterial som genom sin låga värmeledningsförmåga har möjligheten att minska tjockleken vid väggkonstruktioner på grund av dess tunna skikt. Arbetet utreder ett förslag att applicera vakuumisolering i enplansvillor. För att uppnå arbetets mål har ett förslag på enplansvilla tagits fram. Beräkningar har gjorts och förslaget är framtaget som ett alternativ för att visa hur en villa innehållande vakuumisolering kan utformas. Det empiriska materialet har samlats in genom intervjuer, dokumentanalyser samt litteraturstudier. Empirin analyseras sedan tillsammans med det framtagna teoretiska ramverket genom litteraturstudier och dokumentanalyser. Att skapa en väggkonstruktion med vakuumisolering som primär isolering betyder oftast att väggen blir avsevärt mycket tunnare än en väggkonstruktion av traditionell isolering, vilket betyder att boarea kan sparas. Vakuumisolering måste skyddas på rätt sätt i väggkonstruktioner eftersom materialet lätt punkteras varpå det förlorar den största delen av sin isoleringsförmåga. Idag är inte vakuumisolering utbrett på den svenska byggmarknaden vilket beror på många faktorer, bland annat dess höga pris. Vakuumisolering är en väldigt bra problemlösare som med fördel kan användas i burspråk för att vinna extra utrymme. Det kan även användas i trånga utrymmen som elnischar. Ur ekonomisk synpunkt ger vakuumisolering störst fördel i städer där boarea per kvadratmeter är högre än motsvarande på landsbygden. För att ta del av arbetet krävs inga förkunskaper om vakuumisolering. Arbetet fokuserar endast på väggkonstruktioner i enplansvillor, därför har inga fördjupningar skett på golv- och takkonstruktioner eller andra byggnadstyper. Enbart nybyggnationer av trästommar är utrett. Beräkningar är inte gjorda för fukt och produktionskostnader.
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Stromecký, Jiří. "Vliv provedení zateplení objektu rodinného domu v obci Újezd u Rosic na výdaje spojené s provozem této nemovitosti." Master's thesis, Vysoké učení technické v Brně. Ústav soudního inženýrství, 2016. http://www.nusl.cz/ntk/nusl-254198.

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The influence of the thermal insulation of a family house in the village of Újezd u Rosic and the expenses related with the operation of this property. Brief characteristics of the task and its challenges: The task will be to work on a proposal to insulate the chosen property. Based on this proposal, then evaluate the difference in cost for the operation of the property before and after insulation. The work will also evaluate the economic return on the investments made.
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Sartori, Ana Paola. "Desenvolvimento e caracterização de compósitos sanduíche para isolamento térmico." reponame:Repositório Institucional da UCS, 2009. https://repositorio.ucs.br/handle/11338/453.

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Um painel sanduíche consiste essencialmente em duas faces, podendo inclusive possuir reforços metálicos e um núcleo formado normalmente por um polímero celular. As faces deste tipo de painel podem estar unidas por um adesivo estrutural, ou por espuma rígida de poliuretano (PU) injetado diretamente sobre os substratos, quando a união ocorrerá naturalmente. A propriedade de maior relevância que o painel sanduíche deve ter para o transporte de cargas congeladas (0ºC a -30ºC) ou refrigeradas (7ºC a 1ºC) é a condutividade térmica (k). Dentro deste contexto o objetivo deste trabalho foi propor e caracterizar painéis sanduíches que possam ser utilizados em câmaras frigoríficas. Este trabalho apresenta as seguintes alternativas para compósito sanduíche: amostra 1 (PRFV/PU/PRFV); amostra 2 (AG/PU/AG); amostra 3 (Frisado/PU/PRFV); e amostra 4 (Al/PU/Al), onde PRFV é poliéster reforçado com fibra de vidro, PU é espuma rígida de poliuretano, AG é aço galvanizado, Frisado é alumínio frisado, e Al é alumínio. Estes painéis foram caracterizados quanto às propriedades físico-mecânicas, térmicas, morfológicas e custo. Foi possível concluir que o sistema (AG/PU/AG) mostrou o melhor custo versus desempenho dentre os compósitos propostos.
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A sandwich panel consists essentially of two face sheets and may even have metal reinforcements and a core formed, usually by a cellular polymer. The faces of this type of panel may be joined by a structural adhesive or in cases where the core is a rigid polyurethane foam injected directly on the substrates the union will occur naturally. The most relevant property of the sandwich panels for the transport of frozen (0ºC a -30ºC) or chilled (7ºC a 1ºC) cargo is thermal conductivity (k). Within this context the objective of this work is to obtain and characterize sandwich panels which can be used in refrigerated chambers. This work presents four alternatives for composite sandwich, sample 1 (PRFV/PU/PRFV), sample 2 (AG/PU/AG), sample 3 (Al Crimpy/PU/PRFV) and sample 4 (Al /PU/Al), were PRFV is a glass fibre reinforced plastics, PU is a rigid polyurethane, AG is galvanized steel, Al Crimpy is crimpy aluminum and Al is aluminum. These composites were characterized by physicalmechanical, thermal, morphologic and cost. It could be concluded that the AG/PU/AG showed the best cost versus performance.
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Palkovič, Peter. "Možnosti snížení nákladů za energie pro RD." Master's thesis, Vysoké učení technické v Brně. Fakulta strojního inženýrství, 2015. http://www.nusl.cz/ntk/nusl-231826.

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Thesis deals with the possibility of reducing the energy costs of a typical family house located in Brno. In the first part is a detailed calculation of heat loss of the building, considering heat gain and subsequent quantification of costs for heating, hot water and total annual costs. In other sections provide specific calculation of the economics for the partial implementations of planned procedures leading to a reduction in heating costs (replacing windows, doors, facades and floor ceiling). A calculation for changing the heating method and compared to the existing boiler. A possible reduction in the energy required when using energy from the Sun. In the penultimate section briefly review the options for what you get a subsidy from the grant program "New Green Savings Programme" and reduce the initial investment. Finally the comprehensive proposals of different options exchanges boiler insulation, replacing windows and doors, and the subsequent evaluation of the best solution when investing 350 000 CZK.
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Webber, Helen. "Compact heat exchanger heat transfer coefficient enhancement." Thesis, University of Bristol, 2011. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.540881.

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Macbeth, Tyler James. "Conjugate Heat Transfer and Average Versus Variable Heat Transfer Coefficients." BYU ScholarsArchive, 2016. https://scholarsarchive.byu.edu/etd/5801.

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An average heat transfer coefficient, h_bar, is often used to solve heat transfer problems. It should be understood that this is an approximation and may provide inaccurate results, especially when the temperature field is of interest. The proper method to solve heat transfer problems is with a conjugate approach. However, there seems to be a lack of clear explanations of conjugate heat transfer in literature. The objective of this work is to provide a clear explanation of conjugate heat transfer and to determine the discrepancy in the temperature field when the interface boundary condition is approximated using h_bar compared to a local, or variable, heat transfer coefficient, h(x). Simple one-dimensional problems are presented and solved analytically using both h(x) and h_bar. Due to the one-dimensional assumption, h(x) appears in the governing equation for which the common methods to solve the differential equations with an average coefficient are no longer valid. Two methods, the integral equation and generalized Bessel methods are presented to handle the variable coefficient. The generalized Bessel method has previously only been used with homogeneous governing equations. This work extends the use of the generalized Bessel method to non-homogeneous problems by developing a relation for the Wronskian of the general solution to the generalized Bessel equation. The solution methods are applied to three problems: an external flow past a flat plate, a conjugate interface between two solids and a conjugate interface between a fluid and a solid. The main parameter that is varied is a combination of the Biot number and a geometric aspect ratio, A_1^2 = Bi*L^2/d_1^2. The Biot number is assumed small since the problems are one-dimensional and thus variation in A_1^2 is mostly due to a change in the aspect ratio. A large A_1^2 represents a long and thin solid whereas a small A_1^2 represents a short and thick solid. It is found that a larger A_1^2 leads to less problem conjugation. This means that use of h_bar has a lesser effect on the temperature field for a long and thin solid. Also, use of ¯ over h(x) tends to generally under predict the solid temperature. In addition is was found that A_2^2, the A^2 value for the second subdomain, tends to have more effect on the shape of the temperature profile of solid 1 and A_1^2 has a greater effect on the magnitude of the difference in temperature profiles between the use of h(x) and h_bar. In general increasing the A^2 values reduced conjugation.
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Hussein, Mohammed Sabah. "Coefficient identification problems in heat transfer." Thesis, University of Leeds, 2016. http://etheses.whiterose.ac.uk/12291/.

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The aim of this thesis is to find the numerical solution for various coefficient identification problems in heat transfer and extend the possibility of simultaneous determination of several physical properties. In particular, the problems of coefficient identification in a fixed or moving domain for one and multiple unknowns are investigated. These inverse problems are solved subject to various types of overdetermination conditions such as non-local, heat flux, Cauchy data, mass/energy specification, general integral type overdetermination, time-average condition, time-average of heat flux, Stefan condition and heat momentum of the first and second order. The difficulty associated with these problems is that they are ill-posed, as their solutions are unstable to inclusion of random noise in input data, therefore traditional techniques fail to provide accurate and stable solutions. Throughout this thesis, the Crank-Nicolson finite-difference method (FDM) is mainly used as a direct solver except in Chapter 7 where a three-level scheme is employed in order to deal with the nonlinear heat equation. An explicit FDM scheme is also employed in Chapter 10 for the two-dimensional case. The inverse problems investigated are discretised using the FDM and recast as nonlinear least-squares minimization problems with simple bounds on the unknown coefficients. The resulting problem is efficiently solved using the \emph{fmincon} or \emph{lsqnonlin} routines from MATLAB optimization toolbox. The Tikhonov regularization method is included where necessary. The choice of the regularization parameter(s) is thoroughly discussed. The stability of the numerical solution is investigated by introducing Gaussian random noise into the input data. The numerical solutions are compared with their known analytical solution, where available, and with the corresponding direct problem numerical solution where no analytical solution is available.
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Books on the topic "Heat transfer coefficient U"

1

Al-Ahmadi, Adel Bin Musaed Sulaiman. Electrohydrodynamic (EHD) enhancement of condensation heat transfer - development of correlation for heat transfer coefficient for tubular systems. Birmingham: University of Birmingham, 2003.

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Nazeri, Habib. The measurement of the heat transfer coefficient between cryolite and ledge. Ottawa: National Library of Canada, 1994.

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Solar technologies for buildings. Chichester: Wiley, 2003.

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Eicker, Ursula. Solar Technologies for Buildings. New York: John Wiley & Sons, Ltd., 2006.

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Impact of the heat transfer coefficient on pressurized thermal shock. Washington, DC: Division of Systems Technology, Office of Nuclear Regulatory Research, U.S. Nuclear Regulatory Commission, 1999.

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T, Dickson, U.S. Nuclear Regulatory Commission. Office of Nuclear Regulatory Research. Division of Systems Technology, and Oak Ridge National Laboratory, eds. Impact of the heat transfer coefficient on pressurized thermal shock. Washington, DC: Division of Systems Technology, Office of Nuclear Regulatory Research, U.S. Nuclear Regulatory Commission, 1999.

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Carletti, Horazio G. Determination of metal-mold heat transfer coefficient for aluminum alloys. 2006.

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Lester, Donald J. Jr. Indirect measurement of local condensing heat-transfer coefficient around horizontal finned tubes. 1987.

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Transient liquid-crystal technique used to produce high-resolution convective heat-transfer-coefficient maps. [Washington, DC: National Aeronautics and Space Administration, 1993.

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E, Poinsatte Philip, and United States. National Aeronautics and Space Administration., eds. Transient liquid-crystal technique used to produce high-resolution convective heat-transfer-coefficient maps. [Washington, DC: National Aeronautics and Space Administration, 1993.

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Book chapters on the topic "Heat transfer coefficient U"

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Herwig, Heinz. "Wärmedurchgangskoeffizient k* (overall heat transfer coefficient U*)." In Wärmeübertragung A-Z, 320–22. Berlin, Heidelberg: Springer Berlin Heidelberg, 2000. http://dx.doi.org/10.1007/978-3-642-56940-1_72.

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Shang, De-Yi, and Liang-Cai Zhong. "Skin-Friction Coefficient." In Heat and Mass Transfer, 81–90. Cham: Springer International Publishing, 2018. http://dx.doi.org/10.1007/978-3-319-94403-6_7.

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Venkateshan, S. P. "Heat Flux and Heat Transfer Coefficient." In Mechanical Measurements, 205–40. Chichester, UK: John Wiley & Sons, Ltd, 2015. http://dx.doi.org/10.1002/9781119115571.ch6.

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Venkateshan, S. P. "Heat Flux and Heat Transfer Coefficient." In Mechanical Measurements, 221–57. Cham: Springer International Publishing, 2021. http://dx.doi.org/10.1007/978-3-030-73620-0_6.

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Herwig, Heinz. "Wärmeübergangskoeffizient α* (heat transfer coefficient h*)." In Wärmeübertragung A-Z, 377–80. Berlin, Heidelberg: Springer Berlin Heidelberg, 2000. http://dx.doi.org/10.1007/978-3-642-56940-1_83.

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Dixon, John M., and Francis A. Kulacki. "Measurement of the Heat Transfer Coefficient." In Mixed Convection in Fluid Superposed Porous Layers, 47–60. Cham: Springer International Publishing, 2017. http://dx.doi.org/10.1007/978-3-319-50787-3_4.

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Pham, Q. Tuan. "Heat Transfer Coefficient and Physical Properties." In Food Freezing and Thawing Calculations, 5–24. New York, NY: Springer New York, 2014. http://dx.doi.org/10.1007/978-1-4939-0557-7_2.

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Fujikawa, Shigeo, Takeru Yano, and Masao Watanabe. "Vapor Pressure, Surface Tension, and Evaporation Coefficient for Nanodroplets." In Heat and Mass Transfer, 111–41. Berlin, Heidelberg: Springer Berlin Heidelberg, 2011. http://dx.doi.org/10.1007/978-3-642-18038-5_4.

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Shang, De-Yi, and Liang-Cai Zhong. "Skin-Friction Coefficient." In Heat Transfer of Laminar Mixed Convection of Liquid, 129–38. Cham: Springer International Publishing, 2016. http://dx.doi.org/10.1007/978-3-319-27959-6_9.

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Kumar, Ramanuj, Amlana Panda, Ashok Kumar Sahoo, and Deepak Singhal. "Analysis of Heat Transfer Coefficient in Turning Process." In Lecture Notes in Mechanical Engineering, 655–63. Singapore: Springer Singapore, 2020. http://dx.doi.org/10.1007/978-981-15-7831-1_61.

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Conference papers on the topic "Heat transfer coefficient U"

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Hu, Yang, and David H. Archer. "Steady State Heat Transfer Models of CO2 Condensing in a Vertical U-Tube." In ASME 2010 International Mechanical Engineering Congress and Exposition. ASMEDC, 2010. http://dx.doi.org/10.1115/imece2010-39112.

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Two distinct steady state models have been programmed to calculate heat transfer and pressure loss from a saturated CO2 vapor in a vertical U-tube to the surrounding grout and earth. The work began with calculations of the individual heat transfer coefficients from vapor, from the condensing vapor, and from the liquid to the tube, and then from the U-tube to the surrounding grout and earth. According to computations for the tube to the earth reviewed in the ASHARE Handbook and relevant literature on the coefficients inside the tube, all reviewed in the paper, the internal heat transfer coefficient area products, hA, for CO2 condensing in a 3/4 inch tube diameter are much higher than the ground heat transfer coefficient; the ground heat transfer coefficient limits the heat transfer in the U-tube. A homogeneous model assumed that the vapor-liquid mixture in the tube is represented by a fluid whose properties and heat transfer coefficients are a weighted average between those of the vapor and the liquid present at the point. The homogeneous model has been developed by the mass balance, momentum balance, energy balance, enthalpy property, equation of state, and phase equilibrium of liquid and vapor CO2. The equations of the model have been numerically calculated in Matlab by solver ODE4 (Runge-Kutta). Measured values of heat transfer were closed to values calculated by the model. Measurements of the pressure loss over the U-tube were significantly higher than those predicted by the model. Based on the assumption that the pressure differences in the U-tube between the inlet and outlet are mainly due to the presence of liquid CO2 in the up and down legs, a new simplified model has been created and the simulation results have been compared with the experimental results. Greater agreement between measured and predicted pressure losses was achieved. This study is useful in understanding heat transfer and pressure loss of CO2 condensing in a vertical U-tube transferring heat to the earth.
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Helmns, Andrea, and Van P. Carey. "Modeling of Intramatrix Heat Transfer in Thermal Energy Storage for Asynchronous Cooling." In ASME 2017 Heat Transfer Summer Conference. American Society of Mechanical Engineers, 2017. http://dx.doi.org/10.1115/ht2017-4870.

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In this paper, we investigate sensible and latent heat transfer through heat exchanger matrix structures containing phase change material (PCM) in the interstitial spacing. The heat transfer is driven by a temperature difference between fluid flow passages and the phase change material matrix which experiences sensible heat transfer until it reaches the phase change material fusion point; then it undergoes melting or solidification in order to store, or reject, energy. In prior work, a dimensionless framework was established to model heat transfer in a thermal energy storage (TES) device much like effectiveness-NTU analysis methods for compact heat exchangers. A key difference, however, is that in TES units, the overall heat transfer coefficient, U, within the phase change material matrix varies spatially in the unit and with time during storage or extraction. Determination of a mean U for these processes is a key challenge to applying the effectiveness-NTU analysis to design of a TES unit. This paper assesses and identifies strategies for determining the matrix overall heat transfer coefficient in a TES unit from model predictions or experiments. The sensitivity of the TES energy efficiency to the matrix overall heat transfer coefficient is also explored, and the implications for some typical applications are discussed.
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Alkhalidi, Ammar, Suhil Kiwan, and Haya Hamasha. "A Comparative Study Between Jordanian Overall Heat Transfer Coefficient (U-Value) and International Building Codes." In 2019 10th International Renewable Energy Congress (IREC). IEEE, 2019. http://dx.doi.org/10.1109/irec.2019.8754639.

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Madani, Hatef, Jose Acun˜a, Joachim Claesson, Per Lundqvist, and Bjo¨rn Palm. "The Ground Source Heat Pump: A System Analysis With a Particular Focus on The U-Pipe Borehole Heat Exchanger." In 2010 14th International Heat Transfer Conference. ASMEDC, 2010. http://dx.doi.org/10.1115/ihtc14-22395.

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The mass flow rate of the secondary refrigerant flowing in the borehole heat exchanger of a ground source heat pump is an influential system parameter whose variation can influence the pumping power, efficiency of the pump, heat distribution in the borehole, heat pump heat capacity, and above all, the system Overall Coefficient Of Performance (COP). The present paper uses both in-situ field measurements and modeling to evaluate these effects. From the field measurements, it can be concluded that the thermal contact between U-pipe channels increases as the brine mass flow rate decreases. Furthermore, the modeling results show that there is a certain optimum brine mass flow rate which gives a maximum overall system COP. Different optimum mass flow rates are obtained for different compressor speed and it is shown that their relation is almost linear. However, concerning system COP maximization, it can be concluded that a constant but carefully-selected brine mass flow rate can still be an appropriate option for the variable capacity heat pump unit studied in the present paper where the compressor frequency changes between 30Hz and 75Hz. Concerning the heat capacity maximization in the system, a variable speed brine pump can be used to help the insufficiently-sized compressor to cover the peak heat demand of the building.
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Bashar, Mohammad, and Kamran Siddiqui. "Effect of Heat Source Geometry on the Transient Heat Transfer During Melting Process of a PCM." In ASME 2016 Heat Transfer Summer Conference collocated with the ASME 2016 Fluids Engineering Division Summer Meeting and the ASME 2016 14th International Conference on Nanochannels, Microchannels, and Minichannels. American Society of Mechanical Engineers, 2016. http://dx.doi.org/10.1115/ht2016-7232.

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Thermal energy storage (TES) systems using phase change materials (PCMs) are used in various engineering applications. TES is a means by which heat is ‘hold’ for a certain period of time for use at a later time. We report an experimental study which was conducted to investigate the melting process and associated heat transfer in a rectangular chamber with a cylindrical u-shaped heat source imbedded inside the PCM. The results showed that geometry and orientation of the heat source immensely influenced the heat transfer behavior during solid-liquid phase transition. The heat transfer behavior, interface movement and the heat transfer coefficients differed both axially and vertically inside the chamber as well as with the melting rate. The local convective heat transfer coefficient, hlocal in the inner region, enclosed by the U-tube, was observed to increase at a higher rate than the outer region. Stronger convective flow and a lower viscosity owing to higher temperature in the inner region is believed to have caused faster melting in this region. The melting rate was also found comparatively higher until approximately two-third of the PCM volume was melted before the rate declined.
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Ammari, H. D., N. Hay, and D. Lampard. "Effect of Acceleration on the Heat Transfer Coefficient on a Film Cooled Surface." In ASME 1990 International Gas Turbine and Aeroengine Congress and Exposition. American Society of Mechanical Engineers, 1990. http://dx.doi.org/10.1115/90-gt-008.

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Results are presented of an experimental investigation into the influence of mainstream acceleration on the heat transfer coefficient downstream of injection through a row of 35° holes in a flat plate. A mass transfer analogue technique was used, with two uniform acceleration parameters, K (=ν(du∞/dx)/u∞2), of 1.9 × 10−6 and 5.0 × 10−6 in addition to the zero acceleration base-line case. Two injectants, air and carbon dioxide, were employed to give coolant to mainstream density ratios of 1.0 and 1.52 respectively. The blowing rate varied from 0.5 to 2.0. The heat transfer coefficient beneath the film reduced progressively as the acceleration increased, with maximum reductions from the zero acceleration datum case of about 27%. In the presence of acceleration, the heat transfer coefficient at a given blowing rate was dependent on the density ratio, an increase in the density ratio leading to a decrease in the heat transfer coefficient. An empirical correlation of the data over most of the range of densities and blowing rates of the experiments has been developed.
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Shiau, Chao-Cheng, Andrew F. Chen, Je-Chin Han, and Robert Krewinkel. "Detailed Heat Transfer Coefficient Measurements on a Scaled Realistic Turbine Blade Internal Cooling System." In ASME Turbo Expo 2019: Turbomachinery Technical Conference and Exposition. American Society of Mechanical Engineers, 2019. http://dx.doi.org/10.1115/gt2019-90097.

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Abstract A realistic internal cooling system of a turbine blade includes both ribs and pin-fins inside the passages to enhance the heat transfer. However, the majority studies in the open literature assessing the heat transfer characteristics on a simplified cooling model by examining ribbed-roughen passages and pin-finned passage separately. This work presents the high-resolution heat transfer coefficients of a scaled realistic turbine blade internal cooling design. The cooling system, using a 3D-printed plastic material, consists of an S-shaped inlet, four serpentine passages (three U-bends) of variable aspect ratio, and the trailing edge ejection. Angled ribs are implemented inside the passages and the elongated fins and pins are used near the trailing edge. Two dust holes are realized on the blade tip, the injections are individually controlled to reflect the realistic coolant flow rate variation inside the entire internal cooling system. The tests are conducted at two Reynolds number, 45,000 and 60,000 based on the hydraulic diameter of the inlet passage. Transient heat transfer technique using thermochromic liquid crystal is applied to obtain the detailed heat transfer characteristic inside the cooling channel. The local and averaged Nusselt numbers are also compared with the correlations in the open literature. This paper provides gas turbine designers the difference of local heat transfer distributions between the realistic and simplified internal cooling designs.
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Sourbron, Maarten G., and Nesrin Ozalp. "Determination of Heat Transfer Characteristics of Solar Thermal Collectors as Heat Source for a Residential Heat Pump." In ASME 2015 International Mechanical Engineering Congress and Exposition. American Society of Mechanical Engineers, 2015. http://dx.doi.org/10.1115/imece2015-51461.

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One of the best ways of making efficient use of energy in residential units is to use heat pump. Heat pump performance can be further enhanced by integrating a solar thermal unit to provide hot water and subsidize space heating. This paper presents numerically examined energy feasibility study of a solar driven heat pump system for a low energy residence, where a flat plate solar collector served as the sole low temperature heat source. A parametric study on the ambient-to-solar fluid heat transfer coefficient has been conducted to determine the required solar collector heat transfer characteristics in this system. Solar collector area and storage tank volume were varied to investigate their impact on the system performance. A new performance indicator availability was defined to assess the contribution of the solar collector as low temperature energy source of the heat pump. Results showed that the use of a solar collector as low temperature heat source was feasible if its heat transfer rate (UA-value) was 200 W/K or higher. Achievement of this value with a realistic solar collector area (A-value) required an increase of the overall ambient-to-solar fluid heat transfer coefficient (U-value) with a factor of 6 to 8 compared to the base case with only natural convection heat exchange between solar collector cover and ambient.
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Curbelo, Andres, Jayanta S. Kapat, Steven J. Thorpe, and Michael Maurer. "Optimization of Inserts to Minimize Cross-Flow Impact in Impingement Heat Transfer." In ASME Turbo Expo 2019: Turbomachinery Technical Conference and Exposition. American Society of Mechanical Engineers, 2019. http://dx.doi.org/10.1115/gt2019-91068.

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Abstract To increase gas turbine cycle efficiency it requires higher turbine inlet temperatures. Multiple cooling mechanisms are used in order to ensure the survival of hot-gas-path components. Impingement cooling is one of the most prevalent methods due to its ability to remove heat over a localized area with a high local heat transfer coefficient. However,, the same level of high heat transfer cannot be uniformly maintained over a large surface due to degradation of downstream jets by cross-flow created by post impingement flow from upstream jets. In order to avoid jet degradation and hence to enhance overall heat transfer, this study focuses on use of U-shaped guide vane inserts surrounding downstream impingement jets. A multi-objective numerical optimization approach is performed to perfect the U-shape guide vane insert where heat transfer and pressure ratio are maximized for a given coolant flow. Three models are obtained from the Pareto optimal front and compared through experimental testing. Temperature Sensitive Paint (TSP) is used to experimentally obtain the local Heat Transfer distributions for an average jet Reynolds number ranging from 75,000 to 150,000. Results show that utilizing U-shaped guided vane inserts can protect against cross-flow and thus enhance overall heat transfer at the target surface.
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Ding, Liang, Shuqing Tian, and Hongwu Deng. "Heat Transfer in a Rotating Rib-Roughened Wedge-Shaped U-Duct." In ASME Turbo Expo 2017: Turbomachinery Technical Conference and Exposition. American Society of Mechanical Engineers, 2017. http://dx.doi.org/10.1115/gt2017-64508.

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Heat transfer in a rotating two-pass trapezium-shaped channel, with staggered 90-deg ribs on both leading and trailing surfaces is experimentally investigated. The hydraulic diameter of the first and second pass is 24.5 mm and 16.9 mm, respectively. The inlet Reynolds number and rotational speed range from 10000 to 50000 and zero to 1000 rpm, respectively, which results in the inlet rotation number varying from zero to 1.0. The heated copper plate technique is employed to measure the regional averaged heater transfer coefficients. Pressure drops are measured by newly designed rotating pressure measurements module. Both ribbed cases and smooth cases are compared to present rib enhancement effect. For non-rotating result, the results show that the trailing surface presents much higher heat transfer than other cases due to the special wedge-shaped geometry. The ribbed wedge-shaped achieves enhanced regional heat transfer performances than the smooth case at all locations. Compared with the non-rotating results in the first pass, heat transfer on both trailing and leading surfaces is enhanced except for the position near the turn region, but weakened on outer surface in stream-wise direction. And at high rotation numbers, the highest maximum heat transfer on railing surface happens at a location of approximately X/D = 10. In the first pass, rotation always enhances heat transfer on the trailing surface as rotation number increases and the rotation-to-stationary Nusselt number ratio reaches to 2.0 at the rotation number of 0.5. The leading and outer surfaces both have a critical rotation number located at Roc = 0.05.
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Reports on the topic "Heat transfer coefficient U"

1

Leslie, P., R. Wood, F. Sigler, A. Shapiro, and A. Rendon. Heat transfer coefficient in serpentine coolant passage for CCDTL. Office of Scientific and Technical Information (OSTI), December 1998. http://dx.doi.org/10.2172/345040.

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Donovan, William F. Determination of Heat Transfer Coefficient in a Gun Barrel from Experimental Data. Fort Belvoir, VA: Defense Technical Information Center, January 1985. http://dx.doi.org/10.21236/ada151815.

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Howard, Isaac, Thomas Allard, Ashley Carey, Matthew Priddy, Alta Knizley, and Jameson Shannon. Development of CORPS-STIF 1.0 with application to ultra-high performance concrete (UHPC). Engineer Research and Development Center (U.S.), April 2021. http://dx.doi.org/10.21079/11681/40440.

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This report introduces the first release of CORPS-STIF (Concrete Observations Repository and Predictive Software – Structural and Thermodynamical Integrated Framework). CORPS-STIF is envisioned to be used as a tool to optimize material constituents and geometries of mass concrete placements specifically for ultra-high performance concretes (UHPCs). An observations repository (OR) containing results of 649 mechanical property tests and 10 thermodynamical tests were recorded to be used as inputs for current and future releases. A thermodynamical integrated framework (TIF) was developed where the heat transfer coefficient was a function of temperature and determined at each time step. A structural integrated framework (SIF) modeled strength development in cylinders that underwent isothermal curing. CORPS-STIF represents a step toward understanding and predicting strength gain of UHPC for full-scale structures and specifically in mass concrete.
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Horizontal nucleate flow boiling heat transfer coefficient measurements and visual observations for R12, R134a, and R134aEster lubricant mixtures. Gaithersburg, MD: National Institute of Standards and Technology, 1993. http://dx.doi.org/10.6028/nist.ir.5144.

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