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1
Claesson, Joachim. "Thermal and hydraulic performance of compact brazed plate heat exchangers operating as evaporators in domestic heat pumps." Doctoral thesis, KTH, Energiteknik, 2005. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-110.
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This thesis investigates the performance of compact brazed plate heat exchangers (CBE) operating as evaporator in heat pump applications. The thesis, and the performances investigated, has been divided into three main sections; One zone evaporator performance; Two zone evaporator performance; and finally Local performance. The 'One zone evaporator performance' section considers the evaporator as one "black box". It was found that "approaching terminal temperatures" were obtained as low overall heat flux is employed. It was also found that the total area averaged film heat transfer coefficient was affected by changes of the brine mass flow rate. This indicates that the widespread Wilson plot method may not be used to determine flow boiling heat transfer coefficients. Further, it seems that co- and counter-current flow configuration performs equally well if the superheat is kept low. A numerical simulation of the above investigations indicates that a nucleate boiling model better predicts the performance compared to a convective evaporation model. Finally, the significant impact of the refrigerant inlet distributor design was illustrated using several CBEs with different inlet geometries but with identical heat transfer surfaces. The 'Two zone evaporator performance section' considers the evaporator as two "black boxes", i.e. the boiling and superheating boxes. Thermochromic liquid crystals (TLC) was used to determine the boiling heat transfer area. The resulting flow boiling heat transfer coefficient was found to correlate with heat flux. The superheated heat transfer area was then estimated using single phase correlations. It was observed that the TLC measurements and the predicted superheating area did not agree. Possible causes for this deviation were discussed. The most likely explanation found was the presence of mist flow at the higher vapor quality range in the boiling section of the evaporator. The 'Local Performance' section considers local pressure drop and flow boiling heat transfer. The Chisholm parameter was found not to be a constant and was found to correlate well with the kinetic energy per volume. The resulting predictions of the pressure drop were better than ± 10%. The resulting local flow boiling heat transfer coefficient, at different vapor quality, mass flux and heat flux, was compared to flow boiling correlations available in the literature. It was found that the saturated nucleate pool boiling correlation by Cooper (1984) and narrow channel flow boiling correlations (Tran 1999, Lazarek and Black 1982) predicted the experimental data better than several traditional flow boiling correlations, developed for larger tubes.QC 20100524
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Björk, Erik. "Energy Efficiency Improvements in Household Refrigeration Cooling Systems." Doctoral thesis, KTH, Tillämpad termodynamik och kylteknik, 2012. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-93061.
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This thesis is based on eight articles all related to the characteristics of the cooling system and plate evaporator of a household refrigerator. Through these articles, knowledge is provided that can be used to increase the operational efficiency in household refrigeration. Papers A, B and C focus on heat transfer and pressure drop in a commonly used free convection evaporator – the plate evaporator. Applicable correlations are suggested on how to estimate the air side heat transfer, the refrigerant side pressure drop and the refrigerant side heat transfer. Papers D, E and F hold a unique experimental study of the refrigerant charge distribution in the cooling system at transient and steady state conditions. From this cyclic losses are identified and estimated and ways to overcome them are suggested. In paper G the topic “charging and throttling” is investigated in an unparalleled experimental study based on more than 600 data points at different quantities of charge and expansions device capacities. It results in recommendations on how to optimize the capillary tube length and the quantity of refrigerant charge. Finally, Paper H holds a thermographic study of the overall cooling system operating at transient conditions. Overall, a potential to lower the energy use by as much as 25 % was identified in the refrigerator studied. About 10 % was found on the evaporator’s air side. 1-2 % was identified as losses related to the edge effect of the evaporator plate. About 8 % was estimated to be cyclic losses. About 5 % was found in cycle length optimization. It is believed that most of these findings are of general interest for the whole field of household refrigeration even though the results come from one type of refrigerator. Suggestions of simple means to reduce the losses without increasing the unit price are provided within the thesisQC 20120411
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SOTOMAYOR, PAUL ORTEGA. "MODELING OF EVAPORATORS TYPE LAMINATED PLATE FOR AUTOMOTIVE AIR CONDITIONING SYSTEMS." PONTIFÍCIA UNIVERSIDADE CATÓLICA DO RIO DE JANEIRO, 2008. http://www.maxwell.vrac.puc-rio.br/Busca_etds.php?strSecao=resultado&nrSeq=12431@1.
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CONSELHO NACIONAL DE DESENVOLVIMENTO CIENTÍFICO E TECNOLÓGICOÉ desenvolvido um modelo de simulação de evaporadores automotivos tipo placa (Brazed Laminated Plate), para o resfriamento de ar úmido. O modelo estudado adota o método de análise local, onde o trocador de calor é dividido em um número de elementos de troca de calor, para os quais as equações de troca de calor e de conservação de energia são aplicadas. Para efeito da determinação do coeficiente local de troca de calor e do fator de atrito, o modelo considera duas regiões na troca de calor. Pelo lado do refrigerante foi considerada uma região bifásica (líquido - vapor) e outra, de superaquecimento (vapor). No lado do ar têm-se duas condições: com a superfície do evaporador seca ou molhada. Para cada zona foram levados em conta diferentes mecanismos de transferência de calor. Também foi estudada a queda de pressão do lado do refrigerante e do lado do ar, utilizando, para tal, as respectivas correlações de queda de pressão. Para a simulação foram consideradas definidas as condições de entrada dos fluídos e a geometria do evaporador. Um programa foi desenvolvido em FORTRAN para calcular os estados termodinâmicos de saída dos dois fluidos. As propriedades do refrigerante foram calculadas utilizando o software REFPROP versão 7.0, desenvolvido no NIST, EUA, o que permitiu a modelagem do trocador de calor operando com uma vasta gama de refrigerantes. Novos refrigerantes, H e 1234yf, ainda não constantes da biblioteca REFPROP v07, foram também testados. Os resultados da simulação foram comparados com dados experimentais disponíveis.
A simulation model for automotive brazed laminate plate evaporators, for humid air cooling, was developed. The model adopts the local analysis method, where the heat exchanger is divided into a number of elemental control volumes, for which the equations of heat transfer and conservation of energy are applied. In order to determine the local heat transfer coefficient and friction factor, the model considers different regions in the heat exchanger. In the refrigerant side, two-phase or superheated flows were considered. In the air side, dry or wet surface conditions were modeled. For each zone different mechanisms of heat transfer and pressure drop were taken in account. The simulation model assumed prescribed evaporator geometry and inlet conditions for both fluids. A computer program was developed in FORTRAN to calculate overall thermodynamic outlet states of both fluids. Refrigerant properties were calculated using the software REFPROP version 7.0, developed by the NIST, U.S.A.. It allowed the modeling of the evaporator, operating with a vast range of refrigerants. New refrigerants, fluids H and 1234yf, (still not available in REFPROP v07 libraries) also were tested. The results of the simulation were compared with available experimental data.
4
Bedřich, Miroslav. "Plynová tepelná čerpadla se spalovacím motorem." Master's thesis, Vysoké učení technické v Brně. Fakulta strojního inženýrství, 2014. http://www.nusl.cz/ntk/nusl-231284.
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The aim of this Diploma thesis is a description of gas heat pump (GHP) technology and the possibility of their usage in real life. Also units from the major manufactures of GHP units in the Czech Republic and abroad are evaluated from technical and economical point of view. The thesis as well includes a part where is decided if it is better to further develop GHP units with higher or lower performance. In the last part of thesis are cooling circuits designed for both lower and higher performance, than performance of existing GHP unit Polo 100. As a result, the units with higher performance are more perspective. Therefore heat plate exchangers, which serve as a condenser and an evaporator, are designed for unit with higher performance.
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Down, Edward M. "Enhancement of plate heat exchanger performance using electric fields." Thesis, City University London, 2000. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.339994.
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Claesson, Joachim. "Thermal and hydraulic performance of compact brazed plate heat exchangers operating as evaporators in domestic heat pumps /." Stockholm : Division of Applied Thermodynamics and Refrigeration, Royal Institute of Technology, 2004. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-110.
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Baummer, Thomas Buchanan. "A self-contained cold plate utilizing force-fed evaporation for cooling of high-flux electronics." College Park, Md.: University of Maryland, 2007. http://hdl.handle.net/1903/7795.
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Thesis (M.S.) -- University of Maryland, College Park, 2007.Thesis research directed by: Dept. of Mechanical Engineering. Title from t.p. of PDF. Includes bibliographical references. Published by UMI Dissertation Services, Ann Arbor, Mich. Also available in paper.
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Chalidapongse, Prasai. "Steady-state and dynamic behaviour of plate-fin-tube direct expansion evaporators when using a zeotropic refrigerant mixture." Thesis, University College London (University of London), 2008. http://discovery.ucl.ac.uk/1444141/.
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Both steady-state and dynamic simulations of the operation of plate-fin-tube air coolers, under dry and wet conditions, and also of themostatic expansion valve (TEV) controlled coils under dry condition, were carried out. The investigation aimed at improving our understanding as how the operation behaviour of the cooler coils, under various coil conditions, was influenced by the use of a ternary refrigerant mixture (R407C) when compared to a pure refrigerant (R134a). Based on practical coil configurations, a distributive computer model was implemented, with governing equations for air and refrigerant sides and for tube walls set up for individual coil elements. For the TEV, equipped with an external equalizer, energy and force equations were set up. To compare the two refrigerants, a reference scheme, obtained based on the steady state simulation, was set up: the same air coil-inlet conditions, the same refrigerant mass flow rates and vapour qualities at the coil inlets, and the same refrigerant temperatures at the coil outlet. The dynamic simulation was based on having a step change in the coil inlet dry-bulb (DB) temperature. The analysis and discussion focussed on the temperature gliding and many other inter-related parameters/factors, e.g. the heat transfer coefficient (HTC), the coil arrangement, the refrigerant superheat and the refrigerant type. It was observed that for steady-state, the temperature gliding affected the spatial gradient of the temperature and humidity ratio of the tube-wall, the outlet dry-bulb temperature of the coil-face row, and the row outlet humidity ratio (HR). The temperature glide, when combined with the refrigerant HTC and the coil arrangement, had a strong influence on the sensible and latent heat fluxes, i.e. suppressing the influence of other parameters such as the effective air-side heat transfer and mass transfer coefficients. For the coil dynamics, the refrigerant temperature gliding influenced the gradients of the time profiles of the DB temperature and HR at the coil-outlet tubes that were unaffected by the superheat. For the TEV-controllcd coils, only the temperature gliding-up of R407C, not the temperature drop associated with R134a, was shown to have an impact upon the rate of change of the superheat-initiation location. The combined effect of the temperature gliding and the HTC influenced the transit times between steady states of both the superheat-initiation location and external-equalizer pressure.
9
Carlsson, Matthias. "Development and Characterization of Parallel-Plate Avalanche Counters for Nuclear Physics Experiments." Thesis, Uppsala universitet, Tillämpad kärnfysik, 2018. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-354818.
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Parallel-plate avalanche counters, PPACs, are commonly used to detect fission fragments. The PPAC detects them and mark (very accurately) the time of detection. Such measurements can be used to measure the neutron energy (via time-of-flight) to study neutron-induced fission.This project report provides a method that, together with the discussed improvements, allows the fabrication of good quality PPAC detectors. Several PPACs are manufactured and the electrodes are built from 0.9 µm thick mylar foils which are evaporated with a 40-80 nm thin layer of aluminum.The developed PPACs are characterized with well known radioactive Cf and Am sources (the source characterization also found in this report), and compared against each other. Additionally, the PPAC signal amplitude spectrum are found to follow theoretical expectations with regards to angular dependence, gas pressure and an applied electrode voltage.At a specific applied electrode voltage and range of gas pressures (3-9 mbar), the measured time resolutions are 2.24-1.38 ns. A trend is observed for finer time resolutions at higher gas pressures.Parallel-plate avalanche counters, PPACs, används ofta för att detektera fissionsfragment. PPAC:en detekterar fragmenten med väldigt god tidsupplösning och således kan PPAC detektorer användas till att mäta neutron energier (mha. flygtidsmetoden), vilka uppmätts för att studera neutroninducerad fission.Det här projektet och den här rapporten beskriver en metod, med föreslagna förbättringar, som möjliggör tillverkning av PPAC detektorer av bra kvalitet. Under projektet har flera PPACs byggts med elektroder gjorda av 0.9 µm tunn mylar förångade med 40-80 nm aluminium. De tillverkade PPAC detektorerna är karaktäriserade med väl kända radioaktiva Cf- och Am-källor (dessa karaktäriseras även i den här rapporten). Detektorerna är sedan jämförda mot varandra och är funna att följa teoretiska förväntningar med avseende på vinkel-, gastryck- och pålagd elektrodspänningsberoende.Resultaten av projektet, som besvarar flera tidigare frågeställningar och bekräftar vissa antaganden, flyttar utsikten och förståelsen framåt för hur PPACs fungerar och vad forskarna kan uppnå med dem.
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Bakri, Zohra. "Contribution a l'etude du sechage par rayonnement infrarouge d'un film de peinture sur un substrat plat en verre." Paris, ENMP, 1988. http://www.theses.fr/1988ENMP0081.
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On determine la composition, la densite, les proprietes thermodynamiques (pression de saturation en fonction de la temperature, coefficient de diffusion, chaleur latente de vaporisation) et les proprietes radiatives de la peinture (spectre d'absorption, spectre de reflexion diffuse, coefficient d'emissivite globale). On etablit une correlation donnant la quantite de solvant a evaporer en fonction de la temperature du substrat. Par ailleurs, l'evolution des profils experimentaux de temperature a ete obtenue par resolution numerique des equations de transfert de chaleur, sous l'hypothese que, pour ce produit quasi homogene, la puissance d'evaporation est infime. Enfin, dans une approche simplifiee, on propose une equation permettant de decrire les profils de perte de masse en fonction de la temperature du substrat
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Ferragh, Omar. "Etude du transfert de chaleur et de masse dans un écoulement d'air entre deux plaques parallèles en présence d'un ruissellement d'eau : Application aux réfrigérants industriels." Valenciennes, 1995. https://ged.uphf.fr/nuxeo/site/esupversions/4aad8950-0f32-46d7-9276-1f08fd498651.
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L'étude consiste a analyser les échanges thermiques et massiques découlant d'une évaporation par convection forcée, entre deux plaques parallèles en présence d'un ruissellement d'eau. L'étude est entreprise sous ses deux aspects: théorique et expérimental. La modélisation est basée sur les théories des couches limites dynamique et thermique couplées avec les concepts de transport de masse, au sein du fluide en écoulement, pour un régime de couches limites laminaires. Le couplage des deux problèmes thermique et massique est réalisé par l'intermédiaire des conditions à l'interface eau-air. Suite à ce modèle théorique, un programme de calcul et de simulation a été développé. Pour une géométrie de dispositif et une puissance de chauffe donnée, et pour des caractéristiques d'entrée données, le programme de simulation détermine toutes les performances dynamiques et thermiques. Les résultats issus de celui-ci ont été comparés aux mesures expérimentales. Enfin, une étude expérimentale menée sur les réfrigérants industriels, en fonctionnement humide, a permis de montrer une certaine analogie entre les phénomènes mis en évidence par ces essais et par le modèle théorique, qui a été développé, pour le cas du transfert de chaleur et de masse entre deux plaques parallèles. Cette approche a montrée l'importance des phénomènes d'évaporation en convection forcée dans l'industrie.
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Rothfuss, Youri. "Partition de l'évapotranspiration réelle en évaporation du sol et transpiration des couverts végétaux à partir du traçage naturel en milieu contrôlé : expérimentation et modélisation SiSPAT_Isotopes." Paris 6, 2009. http://www.theses.fr/2009PA066682.
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L’utilisation des isotopes stables et lourds de l’eau lors d’une série d’études réalisées sur monolithes de sol en milieu contrôlé nous a permis de déterminer l’évolution de la partition de l’évapotranspiration en évaporation du sol et transpiration des plantes au cours du développement d’un couvert de fétuque élevée. La contribution de l’évaporation du sol à l’évapotranspiration réelle a diminué durant l’expérience de 100% (sol nu) pour finalement atteindre 1% (43 jours après le semis). Le recours au milieu contrôlé nous a permis d’associer à chaque valeur de partition une description détaillée du couvert végétal ainsi que des conditions climatiques dans l’atmosphère et hydriques dans le sol. Les données collectées permettent l’évaluation du fonctionnement d’un modèle de flux de chaleur, d’eau et d’isotopes à travers le continuum sol-plante-atmosphère SiSPAT_Isotopes (Simple Soil Plant Atmosphere Transfer model). Ce travail a tout particulièrement permis l’évaluation du module de transport des isotopes dans le sol et la plante : on a pu modéliser les profils ainsi que les flux d’isotopes dans le sol et déterminer les profondeurs d’extraction racinaire.
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Chen, Chung-Wei, and 陳仲威. "Visualization and Evaporation Resistance Measurement for Groove-Wick Evaporator of Operating Flat-Plate Heat Pipes." Thesis, 2010. http://ndltd.ncl.edu.tw/handle/56864342489570572865.
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陳志嘉. "The Thermal Performance Investigation of Loop Heat Pipe with Plate Evaporator." Thesis, 2007. http://ndltd.ncl.edu.tw/handle/03375147476485247961.
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碩士國立清華大學
動力機械工程學系
95
Loop Heat Pipes (LHPs), which are generally and widely used with cylindrical evaporators, have a great potential for applications on spacecrafts and electronic cooling due to the advantages of high transfer capacity and long transport distances. However, the cylindrical evaporators of loop heat pipes cannot work on a flat thermo-contact surface without saddle. The saddle creates an extra thermal resistance. To avoid the above disadvantages, we utilize the flat evaporators of loop heat pipes. According to the literature, however, the heat leak problem is more serious in the flat evaporators than in the cylindrical evaporators. This problem also makes more difficult start-up and higher thermal resistance of flat evaporators. Hence this study uses stainless steel mesh and compares the affect of one or two primary wick structure. The results show that that method can ease heat leak problem, when flat evaporators of loop heat pipes have stainless steel mesh and two primary wick structures. Then loop heat pipes can start-up and work more easily at low load. Vapor flow resistance drops by four times and increases heat transfer when diameter of vapor line increases from 3mm to 4mm. When the temperature of the heater is less than 100 oC and the sink temperature is at 30oC, the maximum heat capacity reaches 140W for horizontal orientation and 170W for vertical orientation.
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張烔堡. "Heat transfer performances of a spray shell-and-tube-evaporator and a plate condenser." Thesis, 1997. http://ndltd.ncl.edu.tw/handle/12983588000805416878.
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Chang, Chia-Wei, and 張家瑋. "Visualization and Measurement for Sintered-Wick Evaporator in an Operating Flat-Plate Heat Pipe." Thesis, 2008. http://ndltd.ncl.edu.tw/handle/48869875797606783280.
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Wu, Wei-Ting, and 吳韋廷. "Heat Transfer Enhancement of Loop Heat Pipe with Flat Plate Evaporator using 2-Butanol Aqueous Solution." Thesis, 2018. http://ndltd.ncl.edu.tw/handle/r7gj95.
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碩士中華科技大學
飛機系統工程研究所
106
Under the rapid development of the electronics, consumer electronic product, the demand of cooling increases with the raises of power density. Loop Heat Pipe (LHP) system often characterized by high heat transfer capacity and long transport distancing. It shows great potential for electronic cooling. The objective of this study is the application of self-rewetting fluid as the working fluid on Loop Heat Pipe with flat evaporators (FLHP) to increases the heat transfer performance. Use the 2-butanol aqueous solution as the working fluid on FLHP, with nickel as the capillary structure material. Self-rewetting fluid shows better wettability compared with pure water. At a certain temperature, a self-rewetting fluid, contrary to common fluids, has the ability to reverse its surface tension’s trend, inducing colder fluid to flow to the heated surface and delaying the occurrence of dry-out in FLHP, it is advantageous to use self-rewetting fluid as working fluid on heat-transfer devices. Heat transfer performance test results shows that water and 2-Butanol(20wt%) aqueous solution in nickel wick FLHP, the maximum heat load from 150W to 425W, can improve heat transfer performance about 180%, the thermal resistance decreased from 1.2℃/W to 0.61℃/W, the heating area is 961mm2 and the maximum heat flux from 15W/cm2 to 41W/cm2.
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林宇中. "Visualization and Measurement for Evaporator in Operating Flat-Plate Heat Pipes－Different Working Fluids and Wettabilities." Thesis, 2010. http://ndltd.ncl.edu.tw/handle/56220279196942776357.
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Liou, Jhan-Hong, and 劉展宏. "Visualization and Measurement for Evaporator of Different Sintered-Wicks and Working Fluids in Operating Flat-Plate Heat Pipes." Thesis, 2009. http://ndltd.ncl.edu.tw/handle/50107468376505893258.
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Lin, Zun-Bin, and 林子斌. "Application of Inverse Method to Estimate the Heat Transfer Coefficient on the Plate Finned-Tube Evaporator under Frosting Conditions." Thesis, 1999. http://ndltd.ncl.edu.tw/handle/96091195538166827847.
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碩士國立成功大學
機械工程學系
87
Application of the Inverse Method to Estimate the Heat Transfer Coefficient on the Plate Finned-Tube Evaporator under Frosting Conditions Zun-Bin Lin* Han-Taw Chen** Department of Mechanical Engineering National Cheng Kung University Tainan, Taiwan, R.O.C ABSTRACT This thesis presents the relationship between the heat transfer rate and the frost on the Plate Finned-Tube Evaporator. This thesis is studied in two ways. One is using numerical method to estimate the relationship between the thickness of frost and the heat transfer coefficient , another is to estimate the heat transfer coefficients with experimental data by experiment. According to the numerical method, the hybrid scheme of the Laplace transfer method and central different method in conjunction with the leate-sqrares scheme is used to solve the two-dimensional inverse heat conduction problems for evaluating heat transfer coefficient. To evidence the accuracy of the present scheme, the comparison of the present estimations and exact results is made. In the estimation of unknown heat transfer coefficient, several cases are illustrated to show the applicability and efficiency of the present numerical inverse method. We set up a plate finned-tube evaporator in conjunction with the other experimental equipment for measuring the frost thickness and tube temperature. The heat transfer coefficient and heat flux on the tune under frosting condition can be determined using the present numerical method and these temperature measurements. In addition, the effect of relative humidity of the air and refrigerant temperature on the frost growth, heat transfer coefficient and overall heat transfer rate is investigated. *：Author **：Advisor
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Huang, Yao-Chun, and 黃耀俊. "Application of the Inverse Method to Estimate the Heat Transfer Coefficient of the Forced Convection on the Plate Finned-Tube Evaporator." Thesis, 2000. http://ndltd.ncl.edu.tw/handle/85203437747501908557.
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碩士國立成功大學
機械工程學系
88
The main task of the project is to estimate the convection coefficient on the plate finned-tube evaporator under frosting condition. Researches will include numerical and experimental work; the numerical work is to present the relationship between the thickness of frost and the convection coefficient, and the experimental work is to obtain the convection coefficients by experiment. The numerical method based on the hybrid scheme of the Laplace transfer method and central different method in conjunction with the least-squares scheme is used to solve the two-dimensional inverse heat conduction problems for evaluating coefficient. The least-squares minimization technique is applied to minimize the sum of the squares of the deviations between the calculated and curve-fitted temperature measurements. In the inverse heat conduction problem, slight inaccuracies in the measured interior temperatures can affect the accuracy of estimated the thermal properties. Thus the effect of measurement errors on the estimation of heat transfer coefficient will be investigated in the present analysis. A plate finned-tube evaporator is set up in conjunction with the other experimental equipment for measuring the frost thickness and tube temperature. The convection coefficient and heat flux on the tune under frosting condition can be determined by using the present numerical method and the temperature measurements.
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Hsu, Yung-Yi, and 許永毅. "Estimation of the Heat Transfer Coefficient on the Fin of the Double Plate Finned-Tube Evaporator under Frosting Conditions with Experimental Data." Thesis, 2002. http://ndltd.ncl.edu.tw/handle/gyqk74.
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碩士國立成功大學
機械工程學系碩博士班
90
The main task of the thesis is to estimate the heat transfer coefficient on the double plate finned-tube evaporator under frosting condition. Researches will include numerical and experimental works; the numerical work is to present the relationship between the thickness of frost and the heat transfer coefficient, and the experimental work is to obtain the temperature data. The numerical method based on the hybrid scheme of the Laplace transform method and central different method in conjunction with the least-squares scheme is used to solve the two-dimensional inverse heat conduction problems for evaluating heat transfer coefficient. The least-squares minimization technique is applied to minimize the sum of the squares of the deviations between the calculated and curve-fitted temperature measurements. In the inverse heat conduction problem, slight inaccuracies in the measured interior temperatures can affect the accuracy of estimated the thermal properties. Thus the effect of measurement errors on the estimation of heat transfer coefficient will be investigated in the present analysis. A plate finned-tube evaporator is set up in conjunction with the other experimental equipment for measuring the frost thickness and tube temperature. The heat transfer coefficient and heat flux on the fin under frosting condition can be determined by using the present numerical method and the temperature measurements.
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Shiu, Shu-cheng, and 許書誠. "Estimation of Heat Transfer Coefficient on the Fin of Plate Finned-Two Elliptical Tubes Evaporator under Frosting Condition with Experimental Temperature Data." Thesis, 2005. http://ndltd.ncl.edu.tw/handle/55736451420778353813.
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碩士國立成功大學
機械工程學系碩博士班
93
The purpose of the thesis is to investigate the effects of the fin spacing on the frosted heat transfer coefficient of the plate fin inside plate finned-tube evaporator with two-tube elliptical tube under natural and force convection. The thesis includes the numerical and experimental parts. The present inverse scheme in conjunction with the fin temperature measurement at various measurement locations is applied to predict the frosted heat transfer coefficient on the plate fin. The hybrid numerical method involving the Laplace transform technique and the finite-difference method is applied to solve the 2-D inverse heat conduction problem in order to predict the frosted heat transfer coefficient on the fin. The least-squares scheme is applied to minimize the sum of the squares of the deviations between the calculated and measured temperatures in order to correct the estimated values. In general, slight inaccuracies of the interior measured temperatures can affect the accuracy of the estimated results for most of the previous inverse scheme. Thus the effect of the measurement error on the estimation of the frosted heat transfer coefficient will be investigated in the present analysis. A plate finned-tube evaporator is set up in conjunction with its relative experimental equipments for measuring the fin temperature. The frosted heat transfer coefficient can be predicted by using the present inverse scheme in conjunction with the fin temperature measurements.
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Lin, Lung-Chang, and 林倫慶. "Estimation of the Heat Transfer Coefficient on the Fin of the Plate Finned-Tube Evaporator with Experimental Data under Frosting and Various Operational Conditions." Thesis, 2001. http://ndltd.ncl.edu.tw/handle/59595178596396748637.
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碩士國立成功大學
機械工程學系
89
The main task of the project is to estimate the heat transfer coefficient on the fin of the plate finned-tube evaporator under frosting condition in forced convection. This project includes numerical and experimental works. The numerical work is to present the relationship between the frost thickness and the heat transfer coefficient. The numerical method based on the hybrid scheme of the Laplace Transform Method and Finite-Difference Method in conjunction with the least-squares scheme is used to solve the two-dimensional inverse heat conduction problems for evaluating the heat transfer coefficient on the fin. The least-squares technique is applied to modify the predicted values. The effect of measurement errors on the estimation of the heat transfer coefficient will be investigated in the present analysis. A plate finned-tube evaporator is set up in conjunction with the other experimental equipment for measuring the frost thickness, fin temperature and tube temperature. The heat transfer coefficient and heat flux on the fin under frosting condition can be determined by using the present numerical method and the temperature measurements.
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Lee, Chi-Shien, and 李啟賢. "Application of the inverse heat conduction technique to estimate the heat transfer coefficient and fin efficiency on the plate finned-tube evaporator under frosting conditions." Thesis, 1998. http://ndltd.ncl.edu.tw/handle/24707067152045235523.
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碩士國立成功大學
機械工程學系
86
This thesis presents a hybrid numerical scheme for the inverse heat conductionproblem and an experimental equipment to estimate the heat transfer coefficient and fin efficiency on the Plate Finned-Tube Evaporator under frosting conditions. Thus, the comparison of the heat transfer rate and fin efficiency obtained by the assumption of the constant heat transfer coefficient and the exact values is made. Afterward, the scheme of the inverse heat conduction in conjunction with temperature measurements at various times and various sensor locations is presented to estimate the heat transfer coefficient on the fin.To evidence the accuracy of the present scheme,the comparison of the present estimations and exact values is made.In addition, the effect of the measurement error and sensor location on the estimated results is also be studied. We set up a plate finned-tube evaporator in conjunction with the other experimental equipments for measuring the frost thickness and fin temperature. The heat transfer coefficient, heat transfer rate and fin efficiency on the fin under frosting conditions can be determined using the present method and these temperature measurements. In addition, the effect of relative humidity of the air, refrigerant temperature and air temperature on the frost growth, heat transfer coefficient,overall heat transfer rate and fin efficiency is also investigated. This tesis can present some information for the relation between the frosting phenomenon and performance of the evaporator under various operation conditions. We hope that its results are useful for the design of the refrigeration and air condition system.
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Huang, Jianchang. "Performance analysis of plate heat exchangers used as refrigerant evaporators." Thesis, 2011. http://hdl.handle.net/10539/9779.
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PhD, Faculty of Engineering and the Built Environment, University of the WitwatersrandIn this study the heat transfer and frictional pressure drop performance characteristics of plate heat exchangers (PHE’s) used as refrigerant liquid overfeed evaporators were investigated. PHE’s have been gaining new applications in the refrigeration industry, especially as evaporators, during the last few decades, but the available information in the open literature for operation in this mode is rather limited. This study aims to extend the knowledge of PHE evaporator performance and to develop a model for use in evaluating heat transfer and pressure drop over as wide a range of operating conditions as possible. A laboratory experimental facility was constructed and the thermal-hydraulic characteristics of three middle-size industrial PHE’s were measured. The exchangers all had 24 plates of the same size but with different chevron angle combinations of 28°/28°, 28°/60°, and 60°/60°. Two sets of tests were carried out with the three units: single-phase performance tests with water, and evaporator performance tests with R134a and R507A, for which the exchangers operated as refrigerant liquid over-feed evaporators. The tests with water served to provide accurate water-side heat transfer information for the evaporator performance analysis which is the primary purpose of this study. In the evaporator performance tests, refrigerant flow boiling heat transfer and two-phase pressure drop data were obtained under steady conditions, over a range of heat flux from 1.9 to 6.9 kW/m2, refrigerant mass flux from 5.6 to 31.4 kg/(m2s), outlet vapour quality from 0.2 to 0/95, and saturation temperatures from 5.9 to 13.0 °C. Additional field data of thermal performance were collected on an ammonia and a R12 PHE water chiller, operating as thermo-siphon evaporators at their design working conditions. All experimental data were reduced and analyzed to obtain the refrigerant-side heat transfer coefficients and frictional pressure drops in the PHE evaporators. The heat transfer results showed a strong dependence on heat flux and a weak dependence on mass flux, vapour fraction and the chevron angle. Along with the ii observations from the ammonia and R12 evaporators, it is concluded that the dominating heat transfer mechanism in this type of evaporator is nucleate boiling rather than forced convection. In contrast to the heat transfer characteristics, the refrigerant two-phase frictional pressure drop was found to be strongly influenced by mass flow rate, vapour fraction and also the chevron angle. An almost linear increase of the frictional pressure drop with the homogeneous two-phase kinetic energy per unit volume was observed for both refrigerants. Based on the experimental data, correlations were developed for predicting the refrigerant boiling heat transfer coefficient and two-phase frictional pressure drop in PHE liquid over-feed evaporators. Two correlations were developed for boiling heat transfer, one of these reflecting the h-q relationship in pool boiling, the other with all constants and exponents determined by regression analysis. The mean absolute errors are respectively 7.3% and 6.8% for these correlations. For two-phase frictional pressure drop, data were correlated using two established methods, namely the homogeneous and the Lockhart-Martinelli methods, with means absolute errors of 6.7% and 4.2%, respectively. The homogeneous model showed a slightly higher discrepancy with the experimental data but is likely to be more physically sound for PHE evaporators, and is much simpler to apply. Validation of these correlations with other data has been difficult due to the shortage of published information. For other refrigerants operating at comparable conditions, these correlations should serve as a guide, while more accurate design or evaluation may need to be based on further testing. The performance analysis carried out in this study was based on systematic experimental investigations and field tests on industrial PHE units. Correlations were developed covering a rather extensive range of flow parameters, plate geometry and various refrigerants. Such correlations have not been reported previously for PHE liquid over-feed evaporators. The results simplify the performance analysis of PHE evaporators and provide a reliable thermalhydraulic model of PHE liquid over-feed evaporators, which can be used for system modeling of water-chilling machines employing this type of evaporator.
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TSENG, HUAN CHUAN, and 曾煥全. "The Measurement and Analysis of Thermal-Hydraulic Performance of Plate finned-tube Evaporators under Frosting Conditions." Thesis, 1999. http://ndltd.ncl.edu.tw/handle/98521532484222965255.
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碩士國立成功大學
機械工程學系
87
Experiments are conducted to measure and analyze the thermal-hydraulic characteristics of plate finned-tube evaporators under frosting conditions for different fin pitches (3,6 fins per inch) , different outside tube diameters (1/2,5/16 inch),and different operating conditions( i.e., different air velocity, ambient temperature, ambient relative humidity ratio and tube wall temperature). The variations of the heat transfer rate , overall heat transfer coefficient , pressure drop, frost thickness and air volume flow rate are recorded and compared. The experimental results indicated that as the ambient temperature、relative humidity ratio and air velocity are increased , or the tube wall temperature is decreased ，the frost thickness is increased. Heat transfer rate and overall heat transfer coefficient start to decrease after the frost thickness 0.4~0.6 mm. Frost formation also makes pressure drop increase, and makes air volume flow rate decrease. It is also shown that evaporator with sweat fin pitch makes heat transfer performance decrease faster than large one; small tube outside diameter makes frost formation faster then large one.
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Kuo, Hsing-Yu, and 郭星宇. "Investigating the application of nanoscale bilayers assembly on stainless steel plate to evaporation behavior." Thesis, 2015. http://ndltd.ncl.edu.tw/handle/29679744772460995341.
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Lin, Hung-Ta, and 林宏達. "Experimental Studies of Falling film Evaporation on Smooth and Finned Plates." Thesis, 2005. http://ndltd.ncl.edu.tw/handle/gnu67a.
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碩士國立臺北科技大學
冷凍空調工程系所
93
This thesis discusses the effect of surface geometries and inclination angle on the falling film evaporation performance. Falling film evaporation experiments were conducted on a smooth plate and two finned plates using refrigerant R-134a at 10.5+-0.5 oC system temperatures, and R-141b at 15.5+-0.5 oC. The fin pitch = 0.6 mm and the fin thickness = 0.3 mm for both finned surfaces. The fin height is 0.5 mm for Fin-A, and 0.3 mm for Fin-B. All plates are tested with an inclination angle between 10o and 40o, and the heat fluxes are varied between 17.9 and 45.7 kW/m2. The local heat transfer coefficients are measured at four different heights, and the falling film flow distribution is observed through a sight glass. The test results showed that the falling film evaporation heat transfer coefficient increases as the heat flux increases. For the finned surfaces, the heat transfer coefficient increases as the inclination angle increases. However, the inclination angle showed negligible effect on the smooth surfaces for both R-134a and R141b. The finned surface yields better falling film evaporation heat transfer performance than the smooth surface for R-134a an R141b. For the R-134a, the Fin-A surface, having 0.5 mm fin height, yields 2~4 times enhancement of the heat transfer coefficient over the smooth surface, and the Fin-B surface enhanced the heat transfer by 2.5~4.8 folds. For the R-141b, the Fin-B surface yields 1.5~1.8 times heat transfer coefficients of the smooth surface. The visualization observation showed that bubble nucleation is more pronounced on the finned surface than the plain surface. The enhancement of the falling film evaporation is mainly attributed to the bubble nucleation effects on the finned surfaces.
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Chou, Yin, and 鄒穎. "Heat and Mass Transfer for Liquid Film Evaporation along an Inclined Plate Covered with a Porous Layer." Thesis, 2005. http://ndltd.ncl.edu.tw/handle/75404511181857311753.
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碩士國立成功大學
機械工程學系碩博士班
93
Abstract Two main topics have been studied numerically in this thesis：First is to study the co-current liquid film evaporation along an inclined plate. The second is to evaluate the heat and mass enhancement of liquid film evaporation by covering a porous layer. The present investigations include： (1) For the liquid film evaporation along an inclined plate, the parametric analyses such as the inlet water flow rate, inlet air flow rate and the angle of inclination are examined in detail. For numerical analysis, the upstream scheme is used to model the convection term in flow direction (x direction), while the second-order central difference schemes are employed for the transverse convection and diffusion terms. The discretization equations are solved by the Box method. The numerical results show that the variations of liquid film thickness and liquid velocity are significant for lower inlet liquid mass flow rate and inclination angle. And the interfacial temperature and concentration are increased for such above situations. In addition, as the liquid mass flow rate is 0.3% of the air flow, the heat transfer enhancement is about to 8%~22%. Compared with the experimental results, the error of numerical results are within 20% (2) For the liquid film evaporation covered with a porous layer, the non-Darcy inertia and boundary effects are included. The corresponding parametric analyses on features such as gas inlet conditions (Reynolds number and ambient relative humidity f) and the structural properties of the porous material (porosity e and thickness of the porous layer d) on the performance of liquid film evaporation are examined in detail. The results show that both the average Nusselt and Sherwood numbers are increased with the decrease of e, d and f. In addition, as the Lewis number increases (Le>1), a larger heat transfer rate and mass flow rate are achieved.
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LIN, SIN-JIE, and 林信介. "Investigating the Effect of Hydrophilic and Hydrophobic Surface Modification on Stainless steel plate to Evaporation and Condensation." Thesis, 2016. http://ndltd.ncl.edu.tw/handle/26604563477328010582.
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碩士中華科技大學
飛機系統工程研究所
104
This study is surface modification of stainless steel flat plates was performed using nanoscale bilayers assembly method to increase the surface’s hydrophilicity and enhance evaporation. Thin layers of SiO2 nanoparticles layered onto the stainless steel surfaces were used to modify their surface properties, and the relationship between the number of layers (0~30) and water’s hydrophilicity (surface tension) was investigated. The effects of modification on evaporation were then tested using de-ionized water. According to experimental results, surface modification was able to reduce the contact angle of water on stainless steel flat plate from the unmodified 87º to 4º at 18 layers, significantly increasing the hydrophilicity of the surface. Evaporation experiments show that the evaporation heat transfer enhancement for droplets on stainless steel plates is at 700%. Using Chemical Vapor Deposition (CVD), to modify the surface structure and thereby the wettability of the surface at 18 bilayers. Experimental results showed 18 bilayers to be the optimal number of bilayers among the samples tested, resulting in the largest contact angle of 153° (compared to 87° on unmodified surface), corresponding to the highest surface hydrophilicity; however, beyond 18 bilayers there seems to be no significant changes or improvements to hydrophobicity. Visualization of the condensation process also indicated later formation of film condensation on super-hydrophobic (18 bilayers) surface, and by tilting the condensation surfaces at 90°, the self-cleaning property of the super-hydrophobic surface allows water droplets to roll off the surface due to gravity before formation of film condensation, while large water droplets still remain stuck on unmodified surface. Therefore, by allowing the condensation process on the super-hydrophobic surface to continuously cycle back to droplet condensation, there is great potential for condensation enhancement on superhydrophobically modified surface. Condensation experiments show that the condensation enhancement for cumulants on stainless steel plates is at 500%.
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Lin, Yueh-Hung, and 林岳宏. "Effect of Flow Direction for the Heat Transfer Performance of Refrigerant R-410A Evaporation in Plate Heat Exchanger." Thesis, 2015. http://ndltd.ncl.edu.tw/handle/49931962331197860409.
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博士國立中央大學
機械工程學系
103
Plate heat exchangers have been popularly used in industrial applications and air-conditioning systems for several decades due to their high effectiveness and compactness. However, owing to its flow complexity, very few test results have been published in the literature for evaporation heat transfer of refrigerant in plate heat exchangers. This article provides an experimental investigation and Infrared Thermal Image observation on the evaporation heat transfer of refrigerant R-410A in plate heat exchanger with various flow arrangement and exit superheat conditions. Parallel flow and counter flow arrangements with 2 oC, 5 oC and 10 oC exit superheat conditions were tested. The refrigerant entered the test section at as vapor quality of 0.24 and evaporated at a saturation temperature of 1.1 oC. The experimental results were analyzed by the evaporation heat transfer coefficient and overall average heat transfer coefficient separately. The evaporation heat transfer coefficient in parallel-flow arrangement is higher than that in the case of counterflow arrangement. However, the average heat transfer coefficients are affected not only by the flow direction, but also by the exit superheat condition. The interaction of these two effects causes there to be almost no difference of the average heat transfer performance between these two flow arrangements for low exit superheat condition. While the refrigerant exit superheat is high, the overall heat transfer performance of the parallel-flow case is lower than that of the counterflow case.
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顏貽乙. "= Experimental study of evaporation and condensation heat transfer and pressure drop of R-134a in plate heat exchanger and small pipe and subcooled flow boiling of R-134a in an annular duct." Thesis, 1998. http://ndltd.ncl.edu.tw/handle/19015641460799464932.
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