Download or read book Flow Boiling Pressure Drop and Heat Transfer of Refrigerants in Multi microchannel Evaporators Under Steady and Transient States written by Houxue Huang and published by . This book was released on 2016 with total page 162 pages. Available in PDF, EPUB and Kindle. Book excerpt: Mots-clés de l'auteur: flow boiling ; multi-microchannel evaporators ; pressure drop ; heat transfer ; steady and transient states.

Download or read book Encyclopedia Of Two phase Heat Transfer And Flow Iv Modeling Methodologies Boiling Of Co2 And Micro two phase Cooling A 4 volume Set written by John R Thome and published by World Scientific Publishing. This book was released on 2018-05-15 with total page 1353 pages. Available in PDF, EPUB and Kindle. Book excerpt: Set IV is a new addition to the previous Sets I, II and III. It contains 23 invited chapters from international specialists on the topics of numerical modeling of pulsating heat pipes and of slug flows with evaporation; lattice Boltzmann modeling of pool boiling; fundamentals of boiling in microchannels and microfin tubes, CO2 and nanofluids; testing and modeling of micro-two-phase cooling systems for electronics; and various special topics (flow separation in microfluidics, two-phase sensors, wetting of anisotropic surfaces, ultra-compact heat exchangers, etc.). The invited authors are leading university researchers and well-known engineers from leading corporate research laboratories (ABB, IBM, Nokia Bell Labs). Numerous 'must read' chapters are also included here for the two-phase community. Set IV constitutes a 'must have' engineering and research reference together with previous Sets I, II and III for thermal engineering researchers and practitioners.

Download or read book Encyclopedia Of Two phase Heat Transfer And Flow Iii Macro And Micro Flow Boiling And Numerical Modeling Fundamentals A 4 volume Set written by John R Thome and published by World Scientific. This book was released on 2018-03-13 with total page 1460 pages. Available in PDF, EPUB and Kindle. Book excerpt: Set III of this encyclopedia is a new addition to the previous Sets I and II. It contains 26 invited chapters from international specialists on the topics of numerical modeling of two-phase flows and evaporation, fundamentals of evaporation and condensation in microchannels and macrochannels, development and testing of micro two-phase cooling systems for electronics, and various special topics (surface wetting effects, microfin tubes, two-phase flow vibration across tube bundles). The chapters are written both by renowned university researchers and by well-known engineers from leading corporate research laboratories. Numerous 'must read' chapters cover the fundamentals of research and engineering practice on boiling, condensation and two-phase flows, two-phase heat transfer equipment, electronics cooling systems, case studies and so forth. Set III constitutes a 'must have' reference together with Sets I and II for thermal engineering researchers and practitioners.

Download or read book Numerical Simulation of the Steady state Thermal hydraulic Performance of Microchannel and Minichannel Evaporators with Headers and Louvered Fins written by Justin J. Gossard and published by . This book was released on 2011 with total page 107 pages. Available in PDF, EPUB and Kindle. Book excerpt: In this study, a finite volume, steady-state evaporator model that includes rectangular minichannel and microchannel tubes with louvered fins and headers was developed and validated. The model provides the user with the option of selecting from several published correlations when calculating the air-side and refrigerant-side heat transfer and pressure drop within the control volume. The model was then used to compare the thermal-hydraulic performance of experimental ternary refrigerant mixtures to more traditional refrigerants -- namely, R-125/R-32/R-161 (34%/15%/51%) versus R-22 and R-125/R-143a/R-161(45%/40%/15%) versus R-404a. The numerical model was also used to study the effects of header-induced maldistribution on evaporator performance by comparing the predicted cooling capacity and refrigerant-side pressure drop to a distribution rating parameter ([phi]) defined by Bowers et al. (2010). It was shown that as the distribution of quality between tubes becomes more uniform (i.e. [phi]-> 1), the cooling capacity and refrigerant-side pressure drop both approach their maximum values.

Download or read book Two phase Pressure Drop of Refrigerants During Flow Boiling in Small Channels written by and published by . This book was released on 1999 with total page 19 pages. Available in PDF, EPUB and Kindle. Book excerpt: Two-phase flow pressure drop measurements were made during a phase-change heat transfer process with three refrigerants (R-134a, R-12, and R-113) at six different pressures ranging from 138 kPa to 856 kPa, and in two sizes of round tubes (2.46 mm and 2.92 mm inside diameters) and one rectangular channel (4.06 x 1.7 mm). State-of-the-art large-tube correlations failed to satisfactorily predict the experimental data. The data were used to develop a new correlation for two-phase pressure drop during flow boiling in small channels. The correlation was then tested against the experimental data for the three refrigerants; the error was "20%.

Download or read book Flow boiling and condensation in microscale channels written by Fabio Kanizawa and published by Springer. This book was released on 2021-04-23 with total page 277 pages. Available in PDF, EPUB and Kindle. Book excerpt: This book covers aspects of multiphase flow and heat transfer during phase change processes, focusing on boiling and condensation in microscale channels. The authors present up-to-date predictive methods for flow pattern, void fraction, pressure drop, heat transfer coefficient and critical heat flux, pointing out the range of operational conditions that each method is valid. The first four chapters are dedicated on the motivation to study multiphase flow and heat transfer during phase change process, and the three last chapters are focused on the analysis of heat transfer process during boiling and condensation. During the description of the models and predictive methods, the trends are discussed and compared with experimental findings.

Download or read book Influence of fully miscible lubrication oil on flow boiling of CO inside horizontal evaporator tubes written by Wetzel, Markus and published by KIT Scientific Publishing. This book was released on 2017-12-27 with total page 452 pages. Available in PDF, EPUB and Kindle. Book excerpt: Flow boiling heat transfer, pressure drop and flow pattern of CO?-POE oil mixtures were experimentally investigated in smooth and micro-fin tubes. The POE oil used features full miscibility in the range of operation investigated. The experimental data was evaluated based on mixture properties, used to evaluate and improve established predictive methods. The knowledge obtained contributes to understanding the influence of oil, which is essential for achieving an efficient evaporator design.

Download or read book Microchannel Heat Exchangers with Carbon Dioxide written by and published by . This book was released on 2001 with total page 117 pages. Available in PDF, EPUB and Kindle. Book excerpt: The objective of the present study was to determine the performance of CO2 microchannel evaporators and gas coolers in operational conditions representing those of residential heat pumps. A set of breadboard prototype microchannel evaporators and gas coolers was developed and tested. The refrigerant in the heat exchangers followed a counter cross-flow path with respect to the airflow direction. The test conditions corresponded to the typical operating conditions of residential heat pumps. In addition, a second set of commercial microchannel evaporators and gas coolers was tested for a less comprehensive range of operating conditions. The test results were reduced and a comprehensive data analysis, including comparison with the previous studies in this field, was performed. Capacity and pressure drop of the evaporator and gas cooler for the range of parameters studied were analyzed and are documented in this report. A gas cooler performance prediction model based on non-dimensional parameters was also developed and results are discussed as well. In addition, in the present study, experiments were conducted to evaluate capacities and pressure drops for sub-critical CO2 flow boiling and transcritical CO2 gas cooling in microchannel heat exchangers. An extensive review of the literature failed to indicate any previous systematic study in this area, suggesting a lack of fundamental understanding of the phenomena and a lack of comprehensive data that would quantify the performance potential of CO2 microchannel heat exchangers for the application at hand. All experimental tests were successfully conducted with an energy balance within "3%. The only exceptions to this were experiments at very low saturation temperatures ( -23 C), where energy balances were as high as 10%. In the case of evaporators, it was found that a lower saturation temperature (especially when moisture condensation occurs) improves the overall heat transfer coefficient significantly. However, under such conditions, air side pressure drop also increases when moisture condensation occurs. An increase in airflow rate also increases the overall heat transfer coefficient. Air side pressure drop mainly depends on airflow rate. For the gas cooler, a significant portion of the heat transfer occurred in the first heat exchanger module on the refrigerant inlet side. The temperature and pressure of CO2 significantly affect the heat transfer and fluid flow characteristics due to some important properties (such as specific heat, density, and viscosity). In the transcritical region, performance of CO2 strongly depends on the operating temperature and pressure. Semi-empirical models were developed for predictions of CO2 evaporator and gas cooler system capacities. The evaporator model introduced two new factors to account for the effects of air-side moisture condensate and refrigerant outlet superheat. The model agreed with the experimental results within "13%. The gas cooler model, based on non-dimensional parameters, successfully predicted the experimental results within "20%. Recommendations for future work on this project include redesigning headers and/or introducing flow mixers to avoid flow mal-distribution problems, devising new defrosting techniques, and improving numerical models. These recommendations are described in more detail at the end of this report.

Download or read book Horizontal Convective Boiling of R134a R1234yf R134a and R1234ze e Within Micro Fin Tube with Extensive Measurement and Analysis Details written by U.s. Department of Commerce and published by CreateSpace. This book was released on 2014-06-24 with total page 56 pages. Available in PDF, EPUB and Kindle. Book excerpt: Internally enhanced tubes, like the micro-fin tube, are used by most manufacturers in the construction of evaporators and condensers for new unitary refrigeration and air-conditioning equipment. The reason for the micro-fin tube's hold on unitary equipment is that it provides the highest heat transfer with the lowest pressure drop of the commercially available internal enhancements (Webb and Kim, 2005). Most of the experimental measurements for evaporative heat transfer coefficients in the micro-fin tube have been done for traditional refrigerants like R134a. Pressure from the policies set by the Montreal Protocol (1987), the Kyoto Protocol (1997) and the European Mobile Directive (2006) have caused a recent shift to refrigerants with both zero ozone depletion potential (ODP) and low global warming potential (GWP). Johnson et al. (2012) reports that azeotropic R1234yf/ R134a (56/44) (i.e., XP10) 1 and R1234ze(E) are among the low-GWP refrigerants identified for evaluation by the Air-Conditioning, Heating, and Refrigeration Institute (AHRI) Low-GWP Alternative Refrigerants Evaluation Program as potential replacement refrigerants for R134a. The reason for this is that both R1234yf/ R134a (56/44) and R1234ze(E) have zero ODP and 100 year GWPs of approximately 600 and 6, respectively (Hickman, 2012 and Bitzer, 2012). Consequently, flow boiling heat transfer data for the micro-fin tube with R1234yf/ R134a (56/44) and R1234ze(E) are essential for the evaluation of their use for unitary applications.

Download or read book Microchannel Phase Change Transport Phenomena written by Sujoy Kumar Saha and published by Butterworth-Heinemann. This book was released on 2015-09-27 with total page 358 pages. Available in PDF, EPUB and Kindle. Book excerpt: Microchannel Heat transfer is the cooling application of high power density microchips in the CPU system, micropower systems and many other large scale thermal systems requiring effective cooling capacity. This book offers the latest research and recommended models on the microsize cooling system which not only significantly reduces the weight load, but also enhances the capability to remove much greater amount of heat than any of large scale cooling systems. A detailed reference in microchannel phase change (boiling and condensation) including recommended models and correlations for various requirements such as pressure loss, and heat transfer coefficient. Researchers, engineers, designers and students will benefit from the collated, state-of-the-art of the research put together in this book and its systematic, addressing all the relevant issues and providing a good reference for solving problems of critical analysis. - Up-to-date information will help delineate further research direction in the microchannel heat transfer - The latest modeling information and recommendations will help in design method and purpose

Download or read book Pressure Drop and Heat Transfer in the Two phase Flow of Freon 12 written by José Ricardo Napadensky and published by . This book was released on 1969 with total page 84 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Carbon Dioxide and R410A Flow Boiling Heat Transfer Pressure Drop and Flow Pattern in Horizontal Tubes at Low Temperatures written by Chang Yong Park and published by . This book was released on 2006 with total page 192 pages. Available in PDF, EPUB and Kindle. Book excerpt: Carbon dioxide (CO2) has been seriously considered as an alternate refrigerant for HCFC and HFC fluids, due to the increasing interest of environmentally safe refrigerants in air-conditioning and refrigeration systems. In this study, CO2 flow boiling heat transfer coefficients and pressure drop are measured in macro-scale (6.1 and 3.5 mm) tubes at evaporation temperatures of -15 and -30°C. The measured results show that the nucleate boiling is a main heat transfer mechanism in the 6.1 mm tube and the contribution of convective boiling becomes greater with the decrease of tube diameters and the increase of mass fluxes. The surface roughness of the 6.1 and 3.5 mm tube are presented by SEM and AFM images and surface profiles, and it is shown that the rougher surface of the 6.1 mm tube can affect the flow boiling heat transfer. The CO2 heat transfer coefficients and pressure drop are measured in a mini-scale (0.89 mm) multi-ported tube at the evaporation temperature of -30°C. Also, R410A and R22 flow boiling heat transfer coefficients and pressure drop in a macro-scale (6.1 mm) tube were measured, and they are compared with CO2. This comparison presents that the CO2 flow boiling heat transfer coefficients are higher than R410A and R22 at low vapor qualities, and CO2 pressure drop is significantly lower than R410A and R22. This advantageous characteristic for CO2 could be explained by properties such as surface tension, reduced pressure, and the density ratio of liquid to vapor. The prediction of heat transfer coefficients and pressure drop was performed by general correlations and the calculation results are compared with measured values. Two-phase flow patterns were visualized for CO2 and R410A in the 6 and 3 mm glass tubes, and they are compared with the Weisman et al. and the Wojtan et al. flow pattern maps. The flow pattern maps can determine the flow patterns relatively well, except the transition from intermittent to annular flow.

Download or read book Critical Heat Flux in Flow Boiling in Microchannels written by Sujoy Kumar Saha and published by Springer. This book was released on 2015-06-25 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: This Brief concerns the important problem of critical heat flux in flow boiling in microchannels. A companion edition in the SpringerBrief Subseries on Thermal Engineering and Applied Science to “Heat Transfer and Pressure Drop in Flow Boiling in Microchannels,” by the same author team, this volume is idea for professionals, researchers, and graduate students concerned with electronic cooling.

Download or read book Flow Boiling Heat Transfer Pressure Drop and Dryout Characteristics of Low GWP Refrigerants in a Vertical Mini channel written by and published by . This book was released on 2014 with total page 99 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Heat Transfer and Pressure Drop During Condensation of Refrigerants in Microchannels written by Akhil Agarwal and published by . This book was released on 2006 with total page 373 pages. Available in PDF, EPUB and Kindle. Book excerpt: The results from the current study thus make an important contribution to the understanding of pressure drop and heat transfer mechanisms during condensation in microchannels. The proposed model may be used by engineers for analyzing condensing two-phase flow in microchannels.

Download or read book Two Phase Flow in Refrigeration Systems written by Junjie Gu and published by Springer Science & Business Media. This book was released on 2013-08-17 with total page 167 pages. Available in PDF, EPUB and Kindle. Book excerpt: Two-Phase Flow in Refrigeration Systems presents recent developments from the authors' extensive research programs on two-phase flow in refrigeration systems. This book covers advanced mass and heat transfer and vapor compression refrigeration systems and shows how the performance of an automotive air-conditioning system is affected through results obtained experimentally and theoretically, specifically with consideration of two-phase flow and oil concentration. The book is ideal for university postgraduate students as a textbook, researchers and professors as an academic reference book, and by engineers and designers as handbook.

Download or read book Heat Transfer and Fluid Flow in Minichannels and Microchannels written by Satish Kandlikar and published by Elsevier. This book was released on 2006 with total page 492 pages. Available in PDF, EPUB and Kindle. Book excerpt: &Quot;This book explores flow through passages with hydraulic diameters from about 1 [mu]m to 3 mm, covering the range of minichannels and microchannels. Design equations along with solved examples and practice problems are also included to serve the needs of practicing engineers and students in a graduate course."--BOOK JACKET.