Academic literature on the topic 'Flow boiling enhancement'
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Journal articles on the topic "Flow boiling enhancement"
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Chernica, I. M., M. K. Bologa, O. V. Motorin, and I. V. Kozhevnikov. "Enhancement of heat transfer at boiling in electrohydrodynamic flow." Journal of Physics: Conference Series 2088, no. 1 (November 1, 2021): 012005. http://dx.doi.org/10.1088/1742-6596/2088/1/012005.
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Abstract The influence of the electric field strength and interelectrode spacing on the heat transfer intensity at boiling in an electrohydrodynamic flow was studied. It was stated that the heat transfer coefficient increases with the increasing of the field strength. The influence of the interelectrode spacing is ambiguous. The efficiency of the action of a electrohydrodynamic flow on the heat transfer intensity at boiling was evaluated using the ratio of the heat transfer coefficient at boiling in the field to the heat transfer coefficient at boiling without the field. The relationships for calculation were obtained that satisfactorily agree with the experimental data.
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Liu, Dong, and Suresh V. Garimella. "Flow Boiling Heat Transfer in Microchannels." Journal of Heat Transfer 129, no. 10 (December 14, 2006): 1321–32. http://dx.doi.org/10.1115/1.2754944.
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Flow boiling heat transfer to water in microchannels is experimentally investigated. The dimensions of the microchannels considered are 275×636 and 406×1063μm2. The experiments are conducted at inlet water temperatures in the range of 67–95°C and mass fluxes of 221–1283kg∕m2s. The maximum heat flux investigated in the tests is 129W∕cm2 and the maximum exit quality is 0.2. Convective boiling heat transfer coefficients are measured and compared to predictions from existing correlations for larger channels. While an existing correlation was found to provide satisfactory prediction of the heat transfer coefficient in subcooled boiling in microchannels, saturated boiling was not well predicted by the correlations for macrochannels. A new superposition model is developed to correlate the heat transfer data in the saturated boiling regime in microchannel flows. In this model, specific features of flow boiling in microchannels are incorporated while deriving analytical solutions for the convection enhancement factor and nucleate boiling suppression factor. Good agreement with the experimental measurements indicates that this model is suitable for use in analyzing boiling heat transfer in microchannel flows.
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Pranoto, I., C. Yang, L. X. Zheng, K. C. Leong, and P. K. Chan. "Flow Boiling Heat Transfer Enhancement from Carbon Nanotube-Enhanced Surfaces." Defect and Diffusion Forum 348 (January 2014): 20–26. http://dx.doi.org/10.4028/www.scientific.net/ddf.348.20.
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This paper presents an experimental study of flow boiling heat transfer from carbon nanotube (CNT) structures in a two-phase cooling facility. Multi-walled CNT (MWCNT) structures of dimensions 80 mm × 60 mm were applied to a horizontal flow boiling channel. Two CNT structures with different properties viz. NC-3100 and MERCSD were tested with a dielectric liquid FC-72. The height of the CNT structures was fixed at 37.5 μm and tests were conducted at coolant mass fluxes of 35, 50, and 65 kg/m2·s under saturated flow boiling conditions. The experimental results show that the CNT structures enhance the boiling heat transfer coefficients by up to 1.6 times compared to the smooth aluminum surface. The results also show that the CNT structures increase significantly the Critical Heat Flux (CHF) of the smooth aluminum surface from 66.7 W/cm2 to 100 W/cm2.
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Bryan, J. E., and J. Seyed-Yagoobi. "Influence of Flow Regime, Heat Flux, and Mass Flux on Electrohydrodynamically Enhanced Convective Boiling." Journal of Heat Transfer 123, no. 2 (May 15, 2000): 355–67. http://dx.doi.org/10.1115/1.1316782.
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The influence of quality, flow regime, heat flux, and mass flux on the electrohydrodynamic (EHD) enhancement of convective boiling of R-134a in a horizontal smooth tube was investigated in detail. The EHD forces generated significant enhancements in the heat transfer coefficient, but the enhancements were highly dependent on the quality, flow regime, heat flux, and mass flux. The experimental data provided evidence that an optimum EHD enhancement exists for a given set of these variables with a specific electrode design. However, experimental data also provided evidence that the EHD forces can drastically reduce the rate of heat transfer at certain conditions
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Qiu, Yun-ren, Wei-ping Chen, and Qin Si. "Enhancement of flow boiling heat transfer with surfactant." Journal of Central South University of Technology 7, no. 4 (December 2000): 219–22. http://dx.doi.org/10.1007/s11771-000-0058-0.
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Ali, Md Osman, Mohammad Zoynal Abedin, Md Dulal Ali, and Mohammad Rasel Rasel. "Effect of Nanofluids on the Enhancement of Boiling Heat Transfer: A Review." International Journal of Engineering Materials and Manufacture 6, no. 4 (October 1, 2021): 259–83. http://dx.doi.org/10.26776/ijemm.06.04.2021.03.
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Boiling heat transfer can play a vital role in the two-phase flow applications. The analysis of the boiling hat transfer enhancement is of importance in such applications and the enhancement can be mostly conducted by using various active and passive techniques. One type of passive techniques is the enhancement of heat transfer by nanofluids. This article presents an extensive review on the effect of different nanofluids on the enhancement of heat transfer coefficient (HTC) and critical heat flux (CHF) for both pool as well as flow boiling. Nanoparticles addition to a working fluid is done arbitrarily to improve the thermophysical properties which in turn improves heat transfer rate. Numerous works have been done in the studies on nanofluid boiling. Among various nanoparticles, the most frequently used nanoparticles are Al2O3 and TiO2. In the case of binary nanoparticles, the most commonly used combination is Al2O3 and TiO2. After reviewing the relevant literatures, it is found that for pool boiling, the maximum HTC is increased to 138% for TiO2 nanoparticles and the maximum CHF is increased to 274.2% for MWCNTs. Conversely, in flow boiling the maximum HTC is increased to 126% for ZnO nanoparticles and the maximum CHF increased to as 100% for GO nanoparticles. In addition, when two or more nanoparticles in succession or binary nanofluids are used the CHF in pool boiling increased up to 100% for Al2O3 and TiO2 as well as the CHF in flow boiling increased up to 100% for Al2O3, ZnO, and Diamond. Though the information of the coefficient of heat transfer and the critical heat flux varied for different nanofluids and vary from experiment to experiment for each of the nanofluids. This variation happens because the coefficient of heat transfer and the critical heat flux in boiling is dependent upon several factors.
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Fu, Ben-Ran, Shan-Yu Chung, Wei-Jen Lin, Lei Wang, and Chin Pan. "Critical heat flux enhancement of HFE-7100 flow boiling in a minichannel heat sink with saw-tooth structures." Advances in Mechanical Engineering 9, no. 2 (February 2017): 168781401668902. http://dx.doi.org/10.1177/1687814016689022.
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A heat sink with convective boiling in micro- or mini-channels is with great potential to meet the requirement of the high heat dissipation of the electronic devices. This study investigates the flow boiling of HFE-7100, having a suitable boiling temperature at atmospheric pressure and dielectric property, in the minichannel heat sink with the modified surface (namely, the saw-tooth structure). The effect of the system pressure on the boiling characteristics was also studied. The results reveal that the critical heat flux can be significantly improved by introducing the saw-tooth structures on the channel surface or boosting the system pressure as well as by increasing the mass flux. Compared to the non-modified channel, the enhancements of the critical heat flux for the parallel and counter saw-tooth channels are 44% and 36%, respectively, at the small mass flux. The boiling visualization further indicates that the minichannels with the saw-tooth structures interrupt the boundary layer and restrain the coalescence of the bubble, which may be the reason for the critical heat flux enhancement. Moreover, the degree of the critical heat flux enhancement, contributed by the saw-tooth modification of the channel, decreases with an increase in the mass flux.
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Azadbakhti, Reza, Farzad Pourfattah, Abolfazl Ahmadi, Omid Ali Akbari, and Davood Toghraie. "Eulerian–Eulerian multi-phase RPI modeling of turbulent forced convective of boiling flow inside the tube with porous medium." International Journal of Numerical Methods for Heat & Fluid Flow 30, no. 5 (July 17, 2019): 2739–57. http://dx.doi.org/10.1108/hff-03-2019-0194.
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Purpose The purpose of this study is simulation the flow boiling inside a tube in the turbulent flow regime for investigating the effect of using a porous medium in the boiling procedure. Design/methodology/approach To ensure the accuracy of the obtained numerical results, the presented results have been compared with the experimental results, and proper coincidence has been achieved. In this study, the phase change phenomenon of boiling has been modeled by using the Eulerian–Eulerian multi-phase Rensselaer Polytechnic Institute (RPI) wall boiling model. Findings The obtained results indicate using a porous medium in boiling process is very effective in a way that by using a porous medium inside the tub, the location of changing the liquid to the vapor and the creation of bubbles, changes. By increasing the thermal conductivity of porous medium, the onset of phase changing postpones, which causes the enhancement of heat transfer from the wall to the fluid. Generally, it can be said that using a porous medium in boiling flows, especially in flow with high Reynolds numbers, has a positive effect on heat transfer enhancement. Also, the obtained results revealed that by increasing Reynolds number, the created vapor phase along the tube decreases and by increasing Reynolds number, the Nusselt number enhances. Originality/value In present research, by using the computational fluid dynamics, the effect of using a porous medium in the forced boiling of water flow inside a tube has been investigated. The fluid boiling inside the tube has been simulated by using the multi-phase Eulerian RPI wall boiling model, and the effect of thermal conductivity of a porous medium and the Reynolds number on the flow properties, heat transfer and boiling procedure have been investigated.
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Fujita, Yasunobu, and Satoru Uchida. "Enhancement of nucleate boiling on composite surfaces." Heat Transfer - Japanese Research 27, no. 3 (1998): 216–28. http://dx.doi.org/10.1002/(sici)1520-6556(1998)27:3<216::aid-htj4>3.0.co;2-y.
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Ammerman, C. N., and S. M. You. "Determination of the Boiling Enhancement Mechanism Caused by Surfactant Addition to Water." Journal of Heat Transfer 118, no. 2 (May 1, 1996): 429–35. http://dx.doi.org/10.1115/1.2825862.
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In the present investigation, boiling heat transfer coefficients are measured for an electrically heated 390-μm-dia, platinum wire immersed in saturated water, and in water mixed with three different concentrations of sodium dodecyl sulfate (an anionic surfactant). The addition of a surfactant to water is known to enhance boiling heat transfer. A recently developed photographic/laser-Doppler anemometry measurement technique is used to quantify the vapor volumetric flow rate departing from the wire during the boiling process. The volumetric flow rate data are used to calculate the latent heat and, indirectly, the convection heat transfer mechanisms that constitute the nucleate boiling heat flux. Comparisons are made to determine how the heat transfer mechanisms are affected by the surfactant addition, and thus, which mechanism promotes boiling enhancement. The present data are also compared with similar data taken for a 75-μm-dia wire immersed in saturated FC-72 (a highly wetting liquid) to provide increased insight into the nature of the boiling heat transfer mechanisms.
Dissertations / Theses on the topic "Flow boiling enhancement"
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Mogaji, Taye Stephen. "Theoretical and experimental study on convective boiling inside tubes containing twisted-tape inserts." Universidade de São Paulo, 2014. http://www.teses.usp.br/teses/disponiveis/18/18147/tde-21102014-103453/.
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This research comprises an experimental and theoretical study on convective boiling inside tubes containing twisted-tape inserts. The demand for more compact and efficient thermal systems, in which the heat exchangers plays an important role, has led to the development and use of various heat transfer enhancement techniques. Among them twisted-tape insert as a swirl flow device is one of the most used. Twisted-tape inserts have been used for over more than one century ago as a technique of heat transfer enhancement applied to heat exchangers. However, the heat transfer augmentation comes together with pressure drop increment, impacting the pumping power and, consequently, the system efficiency. Moreover, until now it is not clear, the operational conditions under which the heat transfer coefficient augmentation by the use of twisted-tape inserts overcomes pressure drop penalty. In the present study, initially, extensive investigations of the literature concerning convective boiling inside plain tubes with and without twisted-tape inserts were performed. This literature review covers pressure drop, heat transfer coefficient and the leading frictional pressure drop gradient and heat transfer coefficient predictive methods during convective boiling inside tubes with and without twisted-tape inserts. Then, pressure drop and heat transfer coefficient results acquired in the present study were obtained in an experimental apparatus of 12.7 and 15.9 mm ID tubes during flow boiling of R134a for twisted-tape ratios of 3, 4, 9, 14 and tubes without inserts, mass velocities ranging from 75 to 200 kg/m2 s, saturation temperatures of 5 and 15°C and heat fluxes of 5 and 10 kW/m2. The experimental results were parametrically analyzed and compared against the predictive methods from literature. An analysis of the enhancement of the heat transfer coefficient and the pressure drop penalty is presented. Heat transfer coefficient increments up to 45% keeping the same pumping power and pressure drop penalty of about 35% were obtained by using twisted-tape relative to tubes without inserts. Additionally, through comparison of the present study experimental results with the predictive methods from the literature for heat transfer coefficient during two-phase flow inside tube containing twisted-tape inserts, it was verified that non of these methods predict satisfactory well the experimental results. However, a new method was develop for predicting the heat transfer coefficient during flow boiling inside tubes containing twisted-tape inserts based on the experimental results obtained in the present study. The predictive method takes into account the physical picture of the swirl flow phenomenon by including swirl flow effects promoted by the twisted-tape inserts. The proposed method predicts satisfactorily well the data obtained in the present study, predicting 89.1% of the experimental data within an error band of ± 30% and absolute mean deviation of 15.7%.A presente pesquisa trata-se de um estudo teórico e experimental sobre a ebulição convectiva no interior de tubos com fitas retorcidas. A crescente demanda por sistemas térmicos mais compactos e eficientes, nos quais os trocadores de calor apresentam elevada relevância, tem motivado o desenvolvimento de inúmeras técnicas de intensificação de troca de calor, sendo que a utilização de fitas retorcidas é uma das técnicas mais adotadas. Fitas retorcidas são utilizadas como técnicas de intensificação de troca de calor há mais de um século. Entretanto o incremento da transferência de calor é acompanhado do aumento da perda de pressão, que por sua vez implica em aumento da potência de bombeamento, e consequentemente afeta a eficiência global do sistema. Adicionalmente, até os dias de hoje não há consenso sobre as condições operacionais em que o ganho com o incremento do coeficiente de transferência de calor é superior à perda devido ao aumento da perda de pressão. Neste estudo, inicialmente foi realizada uma extensa revisão da literatura sobre a ebulição convectiva no interior de tubos com e sem fitas retorcidas. Esta revisão aborda aspectos relacionados à perda de pressão e ao coeficiente de transferência de calor, juntamente com os métodos de previsão destes parâmetros. Foram realizados experimentos para determinação experimental de perda de pressão e coeficiente de transferência de calor, em aparato experimental contando com tubos horizontais com diâmetros internos iguais a 12,7 e 15,9 mm, para escoamento bifásico de R134a, razões de retorcimento iguais a 3, 4, 9, 14 e tubo sem fita, velocidades mássicas entre 75 e 200 kg/m²s, temperaturas de saturação iguais a 5 e 15°C, e fluxo de calor iguais a 5 e 10 kW/m². Os resultados experimentais foram analisados e comparados com estimativas segundo métodos disponíveis na literatura. Uma análise do aumento do coeficiente de transferência de calor e da perda de pressão friccional é apresentada. Foram verificados incrementos do coeficiente de transferência de calor de até 45% para a mesma potência de bombeamento, e aumento de perda de pressão de aproximadamente 35% para tubos com fitas retorcidas em relação aos tubos sem fita. Adicionalmente, através da comparação dos resultados experimentais com os métodos de previsão para coeficiente de transferência de calor, foi verificado que nenhuma metodologia apresentava previsões satisfatórias dos resultados. Portanto um novo método para previsão do coeficiente de transferência de calor durante ebulição convectiva no interior de tubos com fitas retorcidas foi desenvolvido com base nos resultados experimentais obtidos durante o presente estudo. O método proposto é função de parâmetros geométricos e do escoamento, e também de parâmetros físicos do escoamento rotacional induzido pela fita. A metodologia desenvolvida apresenta previsões satisfatórias dos resultados experimentais, prevendo 89,1% dos resultados experimentais com erro inferior a ± 30% e erro médio absoluto igual a 15,7%.
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Filho, Enio Pedone Bandarra. "Um estudo experimental da ebulição convectiva de refrigerantes no interior de tubos lisos e internamente ranhurados." Universidade de São Paulo, 2002. http://www.teses.usp.br/teses/disponiveis/18/18135/tde-25072016-152106/.
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A presente pesquisa trata de um estudo experimental da transferência de calor e da perda de carga de fluidos refrigerantes puros e suas misturas em mudança de fase convectiva no interior de tubos lisos e aqueles dotados de ranhuras internas. Para tanto, foi desenvolvido um equipamento experimental cujo componente básico é composto por um tubo horizontal, aquecido por intermédio de uma resistência elétrica do tipo fita, aderida à superfície externa do tubo. As condições de ensaio variaram numa ampla faixa, permitindo cobrir as condições verificadas na maioria das instalações frigoríficas. Os resultados experimentais foram agrupados em duas faixas de velocidades mássicas: elevadas (G > ou = 200 kg/s.m2), onde prepondera o padrão anular de escoamento, e reduzidas (G < 200 kg/s.m2), predominando o padrão estratificado. Os principais parâmetros que afetam o coeficiente de transferência de calor, tais como, velocidade mássica, fluxo de calor, tipo de refrigerante, temperatura de evaporação e diâmetro do tubo foram analisados. O desempenho termo-hidráulico, relativo ao efeito combinado da transferência de calor e da perda de carga dos tubos ranhurados, foi sensivelmente superior quando comparados aos tubos lisos. A análise dos resultados experimentais permitiu a proposição de correlações para a perda da carga, avaliada através do multiplicador bifásico, φL, e para coeficiente de transferência de calor, em tubos lisos e ranhurados. As correlações propostas se mostraram adequadas para aplicações práticas, proporcionando desvios reduzidos em relação aos resultados experimentais. Destacam-se as correlações obtidas para o multiplicador bifásico para tubos microaletados e para o coeficiente de transferência de calor para vazões reduzidas em tubos lisos. Diversos registros fotográficos dos principais padrões de escoamento foram levantados, tendo sido importante na análise e entendimento da mudança de fase.Present research deals with an experimental study of the heat transfer and pressure drop of pure and mixtures of refrigerants undergoing convective boiling inside horizontal smooth and microfin tubes. An experimental apparatus has been developed and constructed whose main component is a horizontal tube electrically heated. Experimental results have been grouped into two mass velocity ranges: the one corresponding to mass velocities lower than 200 kg/s.m2, where the stratified flow pattern is dominant, and that for mass velocities higher than 200 kg/s.m2, where typically the annular flow pattern can be found. Effects over the heat transfer coefficient of physical parameters such as mass velocity, heat flux, diameter, saturation temperature, and refrigerant have been investigated and analyzed. It has been found out that the thermo-hydraulic performance of microfin tubes is better than that of the smooth ones. Empirical correlations have been proposed for both the two-phase flow multiplier and the heat transfer coefficient for different ranges of operating conditions as well as for smooth and microfin tubes. Results from the proposed correlations can be deemed adequate for practical applications given the limited dispersion obtained with respect to their experimental counterpart. Noteworthy are the results obtained from correlations for both the two phase flow multiplier for microfin tubes and the heat transfer coefficient for the lower range of mass velocities in smooth tubes. Finally, worth mentioning is the photographic essay developed in present research involving the flow patterns that occur under convective boiling of refrigerants in horizontal tubes.
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"Microchannel Flow Boiling Enhancement via Cross-Sectional Expansion." Doctoral diss., 2013. http://hdl.handle.net/2286/R.I.16463.
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abstract: The heat transfer enhancements available from expanding the cross-section of a boiling microchannel are explored analytically and experimentally. Evaluation of the literature on critical heat flux in flow boiling and associated pressure drop behavior is presented with predictive critical heat flux (CHF) and pressure drop correlations. An optimum channel configuration allowing maximum CHF while reducing pressure drop is sought. A perturbation of the channel diameter is employed to examine CHF and pressure drop relationships from the literature with the aim of identifying those adequately general and suitable for use in a scenario with an expanding channel. Several CHF criteria are identified which predict an optimizable channel expansion, though many do not. Pressure drop relationships admit improvement with expansion, and no optimum presents itself. The relevant physical phenomena surrounding flow boiling pressure drop are considered, and a balance of dimensionless numbers is presented that may be of qualitative use. The design, fabrication, inspection, and experimental evaluation of four copper microchannel arrays of different channel expansion rates with R-134a refrigerant is presented. Optimum rates of expansion which maximize the critical heat flux are considered at multiple flow rates, and experimental results are presented demonstrating optima. The effect of expansion on the boiling number is considered, and experiments demonstrate that expansion produces a notable increase in the boiling number in the region explored, though no optima are observed. Significant decrease in the pressure drop across the evaporator is observed with the expanding channels, and no optima appear. Discussion of the significance of this finding is presented, along with possible avenues for future work.Dissertation/Thesis
Ph.D. Mechanical Engineering 2013
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Chou, Chi-Sheng, and 周記生. "Flow boiling Heat Transfer Enhancement in Porous Microchannel Evaporator." Thesis, 2012. http://ndltd.ncl.edu.tw/handle/38925659236684849096.
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碩士國立臺灣大學
機械工程學研究所
100
The microchannel evaporator,which possesses the advantage of high heat transfer coefficient,good temperature uniformity,and small requirement for coolant flow rates,is considered as a potential cooling technology.The porous structure with a large number of nucleation site density as well as the reentrant grooves is to enhance the heat transfer performance in the microchannels evaporator. In present study,the flow boiling experiments were conducted with a plane and porous microchannels evaporator on one square inch copper substrates. Using water as working fluid,the mass flux from103~207 kg/m^2 s and the saturated pressure of 140kpa. Both microchannels have 62 channels(225μm in width；and 660μm in depth).The effects of powder size,thickness of structure upon heat transfer performance are investigated.The comparsions of heat transfer characteristics,pressure drop, pressure instability,and heat transfer enhanced effects between the plane and the porous microchannels evaporator are made.Finally,the comparisons of heat transfer performance,pressure drop,pressure instability between two different working fluid water and R-134a in microchannels. The experiment results were substituted into the heat transfer correlations in which the surface tension force was taken into consideration.The mean average error was16.5%. Pressure drop raised by increasing heat fluxes,but did not vary with increasing mass flux.The experiment results were substituted into the separation model incorporating surface tension force. The mean average error was 21.3%. The pressure drop oscillation suggested that the presence of instability inside plane microchannels as well as the maximum amplitude of oscillation were found near the onset of nucleation. The porous microchannel evaporators were sintered under the following parameters: the powder diameter dp ranged from 1~100μm, thickness of porous structure δ ranged from 225~375μm, and δ/dp ranged from 3~20, respectively. The investigation on the effect of particle size dp as well as thickness δ indicated that the ratio of the thickness to the particle size δ/dp had a significance in the heat transfer performance. This ratio must be properly chosen in order to reach a better heat transfer performance. The better ratio of δ/dp was between 3~4 in our work,withδ 225μm and dp 53μm.The average heat transfer coefficient enhanced about 3 times larger than the plane microchannels. For the porous microchannels evaporator,the heat transfer results different from the plane microchannels evaporator,heat transfer coefficient varied with varing mass flux.Pressure drop in porous microchannel evaporator was raised by increasing heat fluxes.The pressure drop was higher than plane microchannels；however,the maximum pressure drop was not over 50%. The maximum amplitude of oscillation was 66% lower than plane microchannels.This result presented that the porous microchannels evaporator provided a stable boiling behavior when nucleation began. For the porous microchannels： Working fluid water,the better ratio ofδ/dp was between 3~4；however, the better ratio ofδ/dp was between 8~12 when R-134a as working fluid.Surface tension force was probably the different choose between the better ratio ofδ/dp .The comparisons between two different working fluid water and R-134a in microchannels： The pressure results showed that water in the plane microchannels,its maximum amplitude of oscillation was larger than R-134a.The maximum amplitude of oscillation was obviously lower than the plane microchannels in two different working fluids. To conclude the present study, the porous microchannel evaporator is highly potential for the industrial applications
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"A Theoretical Analysis of Microchannel Flow Boiling Enhancement via Cross-Sectional Expansion." Master's thesis, 2011. http://hdl.handle.net/2286/R.I.9081.
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abstract: Microchannel heat sinks can possess heat transfer characteristics unavailable in conventional heat exchangers; such sinks offer compact solutions to otherwise intractable thermal management problems, notably in small-scale electronics cooling. Flow boiling in microchannels allows a very high heat transfer rate, but is bounded by the critical heat flux (CHF). This thesis presents a theoretical-numerical study of a method to improve the heat rejection capability of a microchannel heat sink via expansion of the channel cross-section along the flow direction. The thermodynamic quality of the refrigerant increases during flow boiling, decreasing the density of the bulk coolant as it flows. This may effect pressure fluctuations in the channels, leading to nonuniform heat transfer and local dryout in regions exceeding CHF. This undesirable phenomenon is counteracted by permitting the cross-section of the microchannel to increase along the direction of flow, allowing more volume for the vapor. Governing equations are derived from a control-volume analysis of a single heated rectangular microchannel; the cross-section is allowed to expand in width and height. The resulting differential equations are solved numerically for a variety of channel expansion profiles and numbers of channels. The refrigerant is R-134a and channel parameters are based on a physical test bed in a related experiment. Significant improvement in CHF is possible with moderate area expansion. Minimal additional manufacturing costs could yield major gains in the utility of microchannel heat sinks. An optimum expansion rate occurred in certain cases, and alterations in the channel width are, in general, more effective at improving CHF than alterations in the channel height. Modest expansion in height enables small width expansions to be very effective.Dissertation/Thesis
M.S. Mechanical Engineering 2011
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Wang, Hailei. "An experimental study of flow boiling heat transfer enhancement in minichannels with porous mesh heating wall." Thesis, 2006. http://hdl.handle.net/1957/28962.
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A unique channel surface enhancement technique via diffusion-bonding a layer of
conductive fine wire mesh onto the heating wall was developed and used to
experimentally study flow boiling enhancement in parallel microchannels. Each
channel was 1000 μm wide and 510 μm high. A dielectric working fluid, HFE
7000, was used during the study. Two fine meshes as well as two mesh materials
were investigated and compared. According to the flow boiling curves for each
channel, the amount of wall superheat was greatly reduced for all the mesh
channels at four stream-wise locations; and the critical heat fluxes (CHF) for
mesh channels were significantly higher than that for a bare channel in the low
vapor quality region. According to the plots of local flow boiling heat transfer
coefficient h versus vapor quality, a consistent increasing trend for h with vapor
quality was observed for all the tested channels until the vapor quality reached
approximately 0.4. However, the three mesh channels showed much higher values
of h than the bare channel, with the 100 mesh copper performing the best.
Visualization using a high-speed camera was performed thereafter to provide
some insights to this enhancement mechanism. A significant increase in
nucleation sites and bubble generation was observed, and departure rates inside
the mesh channels were attributed to the flow boiling enhancement. A sudden
increase of h for mesh channels can also be attributed to the characteristics of
nucleate boiling and indicates that nucleate boiling was the dominant heat transfer
mode. Another interesting point observed was that the 100 mesh bronze outperformed
the 200 mesh bronze for most of the studies. This suggests that
nucleations happened inside the mesh openings, instead of on the mesh openings.
In addition, an optimal mesh size should exist for HFE 7000 flow boiling.Graduation date: 2006
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Wang, Shu-Lei, and 汪書磊. "Enhancement of FC-72 Flow Boiling Heat Transfer over Heated Plate by Installing Fine Copper Strings, Light Beads and Liquid Superheating." Thesis, 2015. http://ndltd.ncl.edu.tw/handle/52892229164071585638.
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博士國立交通大學
機械工程系所
104
An experimental study is carried out here to explore possible enhancement of FC-72 flow boiling heat transfer over a small horizontal heated copper plate by two different active-like passive augmentation methods and by slight inlet liquid superheating. In the first part of the study, movable fine copper strings are installed above the plate. Specifically, parallel strings of uniform size and pitch with their ends only fixed at the plate edges are placed normal to the upstream flow direction. In this part of the experiment, the imposed heat flux is varied from 0.1 to 11 W/cm2, the diameter of strings from 79 to 254 μm, string-heated surface separation distance from 0 to 1.0 mm, and the length of the strings from 10 to 12 mm with the pitch of the strings fixed at 1.0 mm for the FC-72 mass flux maintained at 300 kg/m2s. In the second part of the study, small plastic beads like thick circular rings are mounted additionally on the fine copper strings, in addition. The beads can be irregularly rotated by the shear force from the boiling flow and by the buoyancy of the bubbles. In the test, the chosen reference beads have average outer and inner diameters of 1.45 and 0.65 mm, respectively, and thickness of 1.0 mm. The average weight of a bead is 0.0038 g. Straight parallel strings of the beads at selected pitch and height are placed above the heated plate normal to the incoming upstream flow with their ends fixed at the rig installed near the plate edges. The effects of the relevant parameters on the saturated and subcooled FC-72 flow boiling heat transfer enhancement, including the imposed heat flux, string pitch, number of beads on each wire, and bead-plate separation distance, are examined in detail. In the third and final part of this study, the inlet liquid superheating is controlled by the auxiliary heater which is installed at the upstream diverging portion of the channel. Meanwhile, the pressure in test section is maintained at saturated state. Besides, combination of the installation of copper strings and beads with the inlet liquid superheating to enhance boiling heat transfer is also examined. The experimental data obtained from the first part of the study for the installation of the copper strings show that installing the fine copper strings above the heating surface can enhance the FC-72 flow boiling heat transfer coefficient up to about 30% over that for a bare surface for a well selected set of the experimental parameters. Besides, the string size and length exhibit nonmonotonic effects on enhancing the boiling heat transfer due to complex influences of the strings on the bubble dynamics near the heating surface. Moreover, the presence of the strings is found to increase the size of nucleation bubbles and active bubble nucleation site density but meanwhile impede the bubble departure from the boiling surface. In the second part of the study, the experimental results indicate that the bubble pumping away from the heated surface from the rotating beads can effectively enhance the boiling heat transfer in the saturated and subcooled flows. Besides, the enhancement in the boiling heat transfer is more pronounced when the beads are placed closer to the plate at the medium string pitch. Moreover, there exists an optimal number of beads threaded on each wire. The best enhancement in the saturated boiling heat transfer coefficient in this study can be as high as 55 % for a suitable selection of the experimental parameters. The corresponding best subcooled boiling heat transfer enhancement is 50%. Moreover, the rotating beads can substantially reduce the wall superheat required for incipient boiling in both saturated and subcooled flows. This is particularly beneficial for electronics cooling. Finally, it is noted from third part of the present study that a slight inlet liquid superheating can be very effective in enhancing the FC-72 boiling heat transfer. The significant enhancement is found to mainly result from the increasing the bubble departure size and frequency at increasing liquid superheating. The best boiling heat transfer enhancement can be around 100% for the inlet liquid superheating of 1.2℃ and 1.5℃.
Books on the topic "Flow boiling enhancement"
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Alvin, Smith, and Lyndon B. Johnson Space Center., eds. Flow boiling with enhancement devices for cold plate coolant channel design: Semiannual report. Prairie View, TX: College of Engineering, Prairie View A&M University, 1990.
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Flow boiling with enhancement devices for cold plate coolant channel design: Final report. Prairie View, TX: Prairie View A&M University, 1991.
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Flow boiling with enhancement devices for cold plate coolant channel design: Semiannual report. Prairie View, TX: College of Engineering, Prairie View A&M University, 1989.
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United States. National Aeronautics and Space Administration., ed. Flow boiling enhancement for thermal management systems: Final report : from the Thermal Science Research Center (TSRC). [Washington, DC: National Aeronautics and Space Administration, 1998.
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United States. National Aeronautics and Space Administration., ed. Flow boiling enhancement for thermal management systems: Final report : from the Thermal Science Research Center (TSRC). [Washington, DC: National Aeronautics and Space Administration, 1998.
Find full textBook chapters on the topic "Flow boiling enhancement"
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Saha, Sujoy Kumar, Hrishiraj Ranjan, Madhu Sruthi Emani, and Anand Kumar Bharti. "Flow Boiling Enhancement Techniques." In Two-Phase Heat Transfer Enhancement, 43–77. Cham: Springer International Publishing, 2019. http://dx.doi.org/10.1007/978-3-030-20755-7_3.
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Phelan, Patrick, and Mark Miner. "Flow Boiling Enhancement via Cross-Sectional Expansion." In Handbook of Multiphase Flow Science and Technology, 1–22. Singapore: Springer Singapore, 2016. http://dx.doi.org/10.1007/978-981-4585-86-6_17-1.
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Thome, John R. "Flow Boiling Inside Microfin Tubes: Recent Results and Design Methods." In Heat Transfer Enhancement of Heat Exchangers, 467–86. Dordrecht: Springer Netherlands, 1999. http://dx.doi.org/10.1007/978-94-015-9159-1_26.
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Thome, John R. "Flow Boiling of Refrigerant-Oil Mixtures in Plain and Enhanced Tubes." In Heat Transfer Enhancement of Heat Exchangers, 487–513. Dordrecht: Springer Netherlands, 1999. http://dx.doi.org/10.1007/978-94-015-9159-1_27.
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Hegde, Ramakrishna N., Shrikantha S. Rao, and R. P. Reddy. "Flow Visualization, Critical Heat Flux Enhancement, and Transient Characteristics in Pool Boiling Using Nanofluids." In Nanofluids, 42–63. 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959: ASTM International, 2012. http://dx.doi.org/10.1520/stp156720120003.
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Peles, Yoav. "Boiling Heat Transfer Enhancement at the Microscale." In Encyclopedia of Two-Phase Heat Transfer and Flow II, 109–36. WORLD SCIENTIFIC, 2015. http://dx.doi.org/10.1142/9789814623285_0003.
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Kumar Purohit, Bijoy, Zakir Hussain, and PVR Sai Prasad. "Boiling and Condensation." In Heat Transfer [Working Title]. IntechOpen, 2022. http://dx.doi.org/10.5772/intechopen.105882.
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This chapter contains a brief overview of both boiling and condensation heat transfer phenomena. Boiling and condensation are the two convective heat transfer phenomena that involve phase change from liquid to vapour and vapour to liquid, respectively. The chapter starts with the basis of heat transfer with an emphasis on the boiling and condensation phenomenon. Next, the overview of the boiling phenomenon and its different classifications like pool, flow, and subcooled and saturated boiling are discussed in detail. Different boiling regimes (natural convection boiling, nucleate boiling, transition boiling and film boiling) with the observed heat transfer rate in the case of pool boiling are mentioned in detail using the boiling curve. The heat transfer aspect and basics of condensation with types (drop and film-wise condensation) and application are also presented. The derivation for the calculation of the rate of heat transfer during film condensation with the correlations for heat transfer coefficient on vertical, horizontal and inclined plates is explained. Some numerical for the calculation of the rate of heat transfer and heat transfer coefficient for condensation phenomena has been also been mentioned. Apart from a basic overview, this chapter also includes information about the advanced heat transfer enhancement techniques available for boiling and condensation.
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Ramesh Korasikha, Naga, Thopudurthi Karthikeya Sharma, Gadale Amba Prasad Rao, and Kotha Madhu Murthy. "Recent Advancements in Thermal Performance Enhancement in Microchannel Heatsinks for Electronic Cooling Application." In Heat Transfer - Design, Experimentation and Applications [Working Title]. IntechOpen, 2021. http://dx.doi.org/10.5772/intechopen.97087.
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Thermal management of electronic equipment is the primary concern in the electronic industry. Miniaturization and high power density of modern electronic components in the energy systems and electronic devices with high power density demanded compact heat exchangers with large heat dissipating capacity. Microchannel heat sinks (MCHS) are the most suitable heat exchanging devices for electronic cooling applications with high compactness. The heat transfer enhancement of the microchannel heat sinks (MCHS) is the most focused research area. Huge research has been done on the thermal and hydraulic performance enhancement of the microchannel heat sinks. This chapter’s focus is on advanced heat transfer enhancement methods used in the recent studies for the MCHS. The present chapter gives information about the performance enhancement MCHS with geometry modifications, Jet impingement, Phase changing materials (PCM), Nanofluids as a working fluid, Flow boiling, slug flow, and magneto-hydrodynamics (MHD).
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Rios, Jaime, Mehdi Kabirnajafi, Takele Gameda, Raid Mohammed, and Jiajun Xu. "Convective Heat Transfer of Ethanol/Polyalphaolefin Nanoemulsion in Mini- and Microchannel Heat Exchangers for High Heat Flux Electronics Cooling." In Heat Transfer - Design, Experimentation and Applications [Working Title]. IntechOpen, 2021. http://dx.doi.org/10.5772/intechopen.96015.
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The present study experimentally and numerically investigates the flow and heat transfer characteristics of a novel nanostructured heat transfer fluid, namely, ethanol/polyalphaolefin nanoemulsion, inside a conventionally manufactured minichannel of circular cross section and a microchannel heat exchanger of rectangular cross section manufactured additively using the Direct Metal Laser Sintering (DMLS) process. The experiments were conducted for single-phase flow of pure polyalphaolefin (PAO) and ethanol/PAO nanoemulsion fluids with two ethanol concentrations of 4 wt% and 8 wt% as well as for two-phase flow boiling of nanoemulsion fluids to study the effect of ethanol nanodroplets on the convective flow and heat transfer characteristics. Furthermore, the effects of flow regime of the working fluids on the heat transfer performance for both the minichannel and microchannel heat exchangers were examined within the laminar and transitional flow regimes. It was found that the ethanol/PAO nanoemulsion fluids can improve convective heat transfer compared to that of the pure PAO base fluid under both single- and two-phase flow regimes. While the concentration of nanoemulsion fluids did not reflect a remarkable distinction in single-phase heat transfer performance within the laminar regime, a significant heat transfer enhancement was observed using the nanoemulsion fluids upon entering the transitional flow regime. The heat transfer enhancement at higher concentrations of nanoemulsion within the transitional regime is mainly attributed to the enhanced interaction and interfacial thermal transport between ethanol nanodroplets and PAO base fluid. For two-phase flow boiling, heat transfer coefficients of ethanol/PAO nanoemulsion fluids were further enhanced when the ethanol nanodroplets underwent phase change. A comparative study on the flow and heat transfer characteristics was also implemented between the traditionally fabricated minichannel and additively manufactured microchannel of similar dimensions using the same working fluid of pure PAO and the same operating conditions. The results revealed that although the DMLS fabricated microchannel posed a higher pressure loss, a substantial heat transfer enhancement was achieved as compared to the minichannel heat exchanger tested under the same conditions. The non-post processed surface of the DMLS manufactured microchannel is likely to be the main contributor to the augmented heat transfer performance. Further studies are required to fully appreciate the possible mechanisms behind this phenomenon as well as the convective heat transfer properties of nanoemulsion fluids.
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YOU, SEUNG M., KEVIN N. RAINEY, and CURTT N. AMMERMAN. "A New Microporous Surface Coating for Enhancement of Pool and Flow Boiling Heat Transfer." In Advances in Heat Transfer, 73–142. Elsevier, 2004. http://dx.doi.org/10.1016/s0065-2717(04)38002-0.
Full textConference papers on the topic "Flow boiling enhancement"
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Çıkım, Taha, Efe Armağan, Gözde Özaydın İnce, and Ali Koşar. "Flow Boiling Enhancement in Microtubes With Crosslinked pHEMA Coatings." In ASME 2013 International Mechanical Engineering Congress and Exposition. American Society of Mechanical Engineers, 2013. http://dx.doi.org/10.1115/imece2013-64388.
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In this experimental study, flow boiling in mini/microtubes was investigated with surface enhancements provided by crosslinked polyhydroxyethylmethacrylate (pHEMA coatings), which is used as a crosslinker coating with different thicknesses (50 nm, 100 nm and 150 nm) on inner microtube walls. Flow boiling heat transfer experiments were conducted on microtubes (with inner diameters of 249 μm and 507 μm) with enhanced inner surfaces with crosslinked pHEMA coatings. pHEMA nanofilms were coated with initiated chemical vapor deposition (iCVD) technique. De-ionized water was utilized as the working fluid in this study. Experimental results obtained from coated microtubes were compared to their plain surface counterparts at two different mass fluxes, (5,000 kg/m2s and 30,000 kg/m2s) and significant enhancements in Critical Heat Flux and boiling heat transfer were attained. These promising results support the use of crosslinked pHEMA coated microtubes/channels as a surface enhancement technique for micro scale cooling applications.
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Jeon, Saeil, Pratanu Roy, N. K. Anand, and Debjyoti Banerjee. "Investigation of Flow Boiling on Nanostructured Surfaces." In 2010 14th International Heat Transfer Conference. ASMEDC, 2010. http://dx.doi.org/10.1115/ihtc14-22926.
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Flow boiling experiments were performed on copper, bare silicon and carbon nanotube (CNT) coated silicon wafer using water as the test fluid. Wall heat flux was measured by varying the wall superheat. The experiments were performed under pool boiling conditions (zero flow rate) as well as by varying the flow rates of water. The liquid sub-cooling was varied between 40 ∼ 60 °C. An infra–red camera was used to calibrate the surface temperature of the silicon wafers and the copper surface. Heat flux measurements were performed by using a calorimeter apparatus. High speed visualization experiments were performed to measure the bubble departure diameter, bubble departure frequency and bubble growth rate as a function of time. Heat flux values for all three surfaces were calculated from the temperature differences obtained by sheathed thermocouples inside the copper block in the calorimeter apparatus. Flow boiling curves were plotted to enumerate the enhancements in heat transfer. It was observed that MWCNT coated silicon surface enables higher heat fluxes compared to bare silicon surface. This enhancement can be ascribed to be due to the high thermal conductivity of the carbon nanotubes, micro-layer effect, enhancement of transient heat transfer due to periodic solid-liquid contact and increase in active nucleation sites on nanostructured surfaces.
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Lee, Taeseung, Jong Hyuk Lee, and Yong Hoon Jeong. "Pool Boiling and Flow Boiling CHF Enhancement at Atmospheric Pressure Using Magnetic Nanofluid." In 2012 20th International Conference on Nuclear Engineering and the ASME 2012 Power Conference. American Society of Mechanical Engineers, 2012. http://dx.doi.org/10.1115/icone20-power2012-55094.
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In this study, we suggest a new working fluid: magnetic nanofluid, or magnetite-water nanofluid, which is a colloidal suspension of magnetite nanoparticles in the pure water. By using the nanofluid, we can expect the critical heat flux (CHF) enhancement, and also for the magnetic nanofluid. Since the magnetite nanoparticles can be controlled by an external magnetic field, the magnetic nanofluid is regarded as a controllable nanofluid, and thus, we can expect the advantages of magnetic nanofluid: 1) the nanoparticle suspension in nanofluid can be maintained by applying the alternating magnetic field, 2) the nanofluid concentration can be localized by applying the magnetic field for a region of interest and 3) the magnetite nanoparticles can be removed from magnetic nanofluid easily. In this study, we focused on the CHF characteristics of magnetic nanofluid in both pool boiling and flow boiling. The first part is for the pool boiling CHF of magnetic nanofluid. At atmospheric pressure, saturated pool boiling CHF experiments were conducted using Ni-Cr wire for magnetic nanofluid and the other nanofluids. Among the various nanofluids, magnetic nanofluid has the highest value of pool boiling CHF, and the enhancement ratio (with respect to the pure water) ranges from 170 to 240 percent. To elucidate the mechanism underlying the pool boiling CHF enhancement, three approaches were introduced: 1) scanning electron microscope (SEM) images were obtained to explain the pool boiling CHF enhancement mechanism due to the deposited nanoparticles, which is related to the surface wettability of the heat transfer surface, 2) ultra-high speed movie were taken and analyzed to observe the bubble dynamics at the heat transfer surface and 3) the strength of electricity-induced magnetic field neat the heat transfer surface were calculated to examine the effect of magnetic field on the pool boiling CHF. The second part is for the flow boiling CHF of magnetic nanofluid. A series of flow boiling CHF experiments were performed at atmospheric pressure and low mass flux conditions. Based on the experimental data, we conclude that the use of magnetic nanofluid improves the flow boiling CHF characteristics: the flow boiling CHF enhanced for the magnetic nanofluid. This is mainly due to the deposition of magnetite nanoparticles on the heat transfer surface, which results in the improvement of wettability and re-wetting characteristics. And we need enough time to ensure the nanoparticle deposition and the flow boiling CHF enhancement, when a nanofluid is used as a working fluid.
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Bryan, James E., and Jamal Seyed-Yagoobi. "Influence of Flow Regime, Heat Flux, and Mass Flux on Electrohydrodynamically Enhanced Convective Boiling." In ASME 1997 International Mechanical Engineering Congress and Exposition. American Society of Mechanical Engineers, 1997. http://dx.doi.org/10.1115/imece1997-0844.
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Abstract The influence of quality, flow regime, heat flux, and mass flux on the EHD enhancement of convective boiling of R-134a in a horizontal smooth tube was fundamentally investigated. The EHD forces generated significant enhancements in the heat transfer coefficient, but the enhancements were highly dependent on the quality, flow regime, heat flux, and mass flux. The experimental data provided evidence that an optimum EHD enhancement exists for a given set of these variables for a specific electrode design. However, experimental data also provided evidence that the EHD forces can drastically reduce the rate of heat transfer at certain conditions.
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Wang, Hailei, and Richard Peterson. "Flow Boiling Enhancement in Microchannels With Diffusion Bonded Wire Mesh." In ASME/JSME 2007 Thermal Engineering Heat Transfer Summer Conference collocated with the ASME 2007 InterPACK Conference. ASMEDC, 2007. http://dx.doi.org/10.1115/ht2007-32119.
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Flow boiling and heat transfer enhancement in four parallel microchannels using a dielectric working fluid, HFE 7000, was investigated. Each channel was 1000 μm wide and 510 μm high. A unique channel surface enhancement technique via diffusion bonding a layer of conductive fine wire mesh onto the heating wall was developed. According to the obtained flow boiling curves for both the bare and mesh channels, the amount of wall superheat was significantly reduced for the mesh channel at all stream-wise locations. This indicated that the nucleate boiling in the mesh channel was enhanced due to the increase of nucleation sites the mesh introduced. Both the nucleate boiling dominated and convective evaporation dominated regimes were identified. In addition, the overall trend for the flow boiling heat transfer coefficient, with respect to vapor quality, was increasing until the vapor quality reached approximately 0.4. The critical heat flux (CHF) for the mesh channel was also significantly higher than that of the bare channel in the low vapor quality region. Due to the fact of how the mesh was incorporated into the channels, no pressure drop penalty was identified for the mesh channels. Potential applications for this kind of mesh channel include high heat-flux electronic cooling systems and various energy conversion systems.
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Moreira, Debora C., Gherhardt Ribatski, and Satish G. Kandlikar. "Review of Enhancement Techniques With Vapor Extraction During Flow Boiling in Microchannels." In ASME 2020 18th International Conference on Nanochannels, Microchannels, and Minichannels collocated with the ASME 2020 Heat Transfer Summer Conference and the ASME 2020 Fluids Engineering Division Summer Meeting. American Society of Mechanical Engineers, 2020. http://dx.doi.org/10.1115/icnmm2020-1068.
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Abstract Flow boiling heat transfer in microchannels can remove high heat loads from restricted spaces with high heat transfer coefficients and minimum temperature gradients. However, many works still report problems with instabilities, high pressure drop and early critical heat flux, which hinder its possible applications as thermal management solutions. Much comprehension on the phenomena concerning flow boiling heat transfer is still missing, therefore many investigations rely on empirical methods and parametric studies to develop novel configurations of more efficient heat sinks. Nevertheless, investigations involving vapor extraction have successfully addressed all these previously reported issues while also increasing the heat transfer of heat sinks employing flow boiling in microchannels. In this sense, the objective of this review is to identify the main techniques employed for vapor extraction in microchannels-based heat sinks and analyze the physical mechanisms underneath the observed improvements during flow boiling, such that some design guidelines can be drawn. Three main strategies can be identified: passive vapor extraction, active vapor extraction, and membrane-based vapor extraction. All these strategies were able to dissipate heatfluxes higher than 1 kW/cm2, with the best performance achieved by a membrane-based heat sink, followed by active and passive designs. According to the present experimental and numerical data available in the literature, there is still room for improvement.
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Gupta, Sanjay Kumar, and Rahul Dev Misra. "Study on flow boiling critical heat flux enhancement of Al2O3/water nanofluid." In Proceedings of the 24th National and 2nd International ISHMT-ASTFE Heat and Mass Transfer Conference (IHMTC-2017). Connecticut: Begellhouse, 2018. http://dx.doi.org/10.1615/ihmtc-2017.2410.
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Kos¸ar, Ali. "Flow Boiling in Microscale at High Flowrates." In ASME 2011 9th International Conference on Nanochannels, Microchannels, and Minichannels. ASMEDC, 2011. http://dx.doi.org/10.1115/icnmm2011-58289.
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Boiling heat transfer is an important heat removal mechanism for cooling applications in micro scale and finds many applications. Many studies were conducted to shed light on boiling heat transfer in microchannels. They were concentrated on saturation boiling at low mass fluxes (G<1000 kg/m2s). With the enhancement in micro pumping capabilities, flow boiling could be performed at higher mass velocities so that high cooling rates (>1000 W/cm2) could be possibly attained. Due to the increasing trend in critical heat flux and suppression of boiling instabilities with increasing mass velocity flow boiling is becoming more and more attractive at higher mass velocities, where subcooled boiling conditions are expected at high mass velocities. With the shift from low to high flow rates, a transition in both boiling heat transfer (saturated boiling heat transfer to subcooling boiling heat transfer) and critical heat flux (dryout type critical heat flux to departure from nucleate boiling critical heat flux) from one mechanism to another is likely to occur. Few experimental studies are present in the literature related to this subject. In this paper, it is aimed at addressing to the lack of information about boiling heat transfer at high flow rates and presenting experimental data and results related to boiling heat transfer and Critical Heat Flux (CHF) at high flowrates. New emerging technologies resulting in local heating such as nano-scale plasmonic applications and near field radiative energy exchange between objects could greatly benefit from boiling heat transfer at high flow rates in micro scale.
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Choi, Young Jae, Dong Hoon Kam, and Yong Hoon Jeong. "Experiment of CHF Enhancement by Magnetite Nanoparticle Deposition in the Subcooled Flow Boiling Region." In 2017 25th International Conference on Nuclear Engineering. American Society of Mechanical Engineers, 2017. http://dx.doi.org/10.1115/icone25-67087.
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CHF experiments were conducted in subcooled flow boiling region at atmospheric pressure. Magnetite nanoparticles were deposited sufficiently on the test sections in same deposition process. Then, working fluid was changed to DI water. After the nanoparticle deposition process, the surface became very hydrophilic even after CHF experiment using DI water. The wettable surfaces were observed using static contact angle and SEM image. CHF results of bare stainless surface and nanoparticle-deposited surface were obtained in the subcooled boiling region. Experiments were conducted over a mass flux range from 1,000 kg/m2s to 5,000 kg/m2s and with inlet temperatures of 40, 60, and 80 °C. The CHF enhancement was from 0% to 40 % by the nanoparticle deposition, which is related wettability enhancement. The CHF enhancement increased as the mass flux increased, which lead to exit quality decrement.
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Cheng, Lixin, Tingkuan Chen, and Yushan Luo. "Flow Boiling Heat Transfer of Kerosene Inside Ribbed Tube." In ASME 1997 International Mechanical Engineering Congress and Exposition. American Society of Mechanical Engineers, 1997. http://dx.doi.org/10.1115/imece1997-0849.
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Abstract Results of a study on flow boiling heat transfer enhancement of kerosene with ribbed tube (rib pitch 9 mm, rib height 0.4 ∼ 0.6 mm, rib width 3.9 mm) are reported. Experiments of upward flow boiling heat transfer in smooth tube and ribbed tube at a pressure 2 bar were performed for a range of heat flux (28.5 ∼ 93.75 kW/m2), mass flux (410 ∼ 810 kg/m2 s) and equilibrium mass quality (0 ∼ 0.3) respectively. Heat transfer coefficients in the ribbed tube are improved by a factor of 1.4 ∼ 1.6 as compared with the smooth tube. A correlation of flow boiling heat transfer coefficients is proposed for the enhanced ribbed tube. Phenomenon and mechanism of flow boiling heat transfer with kerosene are discussed.