Heat transfer characteristics of subcooled water in a hypervapotron under high mass fluxes and high heat fluxes

2019 ◽  
Vol 129 ◽  
pp. 580-590 ◽  
Author(s):  
Ge Zhu ◽  
Qincheng Bi ◽  
Jianguo Yan ◽  
Teng Wang ◽  
Jinle Zhao
Keyword(s):  
Heat Transfer ◽  
High Heat ◽  
Heat Fluxes ◽  
High Mass ◽  
Heat Transfer Characteristics ◽  
Subcooled Water ◽  
Transfer Characteristics ◽  
Mass Fluxes

Heat Transfer Characteristics of Subcooled Water Flow Boiling in Circular Channels With Non-Uniform Heating Fluxes

2016 ◽  
Author(s):  
Ge Zhu ◽  
Qincheng Bi ◽  
Jianguo Yan ◽  
Qizheng Yuan ◽  
Haicai Lv ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Mass Flow ◽  
High Heat ◽  
Heat Fluxes ◽  
Dominant Factor ◽  
Uniform Heating ◽  
Heat Transfer Characteristics ◽  
Subcooled Water ◽  
Transfer Characteristics ◽  
Twisted Tapes

Experiments of heat transfer characteristics of subcooled water flowing in vertical circular channels, which were off-center in rectangular blocks, were carried out under high heat fluxes up to the ITER requirements. The heating flux distributions of the channels were non-uniform in the circumferential direction, which were obtained by electrically heating the blocks directly. Two types of channels were used: smooth channel and twisted tapes channel. The surface temperature of the rectangular blocks was measured by infrared camera and thermocouples. Effect of the system pressure, mass flow rate, inlet subcooling, and equivalent heat fluxes on heat transfer were all investigated. The main attention was paid to the subcooled water heat transfer under non-uniform heating flux, and the effect of twisted tapes. Results show that subcooled boiling is more likely to become the dominant factor under the conditions of lower mass flow rates, higher heat fluxes and lower system pressures. Twisted tapes can enhance the heat transfer, which is more evident in high heat fluxes. The temperature fields in the block were calculated with a Computational Fluid Dynamics (CFD) method to obtain, which were consistent with the experimental results.

Heat Transfer Characteristics of a Train of Droplets Impinging Over a Hot Surface: From Film Evaporation to Leidenfrost Point

2019 ◽  
Author(s):  
Ganesh Guggilla ◽  
Arvind Pattamatta ◽  
Ramesh Narayanaswamy
Keyword(s):  
Heat Transfer ◽  
High Performance ◽  
Heated Surface ◽  
Electronics Cooling ◽  
Spray Cooling ◽  
High Heat ◽  
Heat Fluxes ◽  
Air Cooling ◽  
Heat Transfer Characteristics ◽  
Transfer Characteristics

Abstract Due to the advancements in computing services such as machine learning and artificial intelligence, high-performance computing systems are needed. Consequently, the increase in electron chip density results in high heat fluxes and required sufficient thermal management to maintain the servers. In recent times, the liquid cooling techniques become prominent over air cooling as it has significant advantages. Spray cooling is one such efficient cooling process which can be implemented in electronics cooling. To enhance the knowledge of the process, detailed studies of fundamental mechanisms involved in spray cooling such as single droplet and multiple droplet interactions are required. The present work focuses on the study of a train of droplets impinging over a heated surface using FC-72 liquid. The surface temperature is chosen as a parameter, and the Dynamic Leidenfrost point (DLP) for the present impact conditions is identified. Spread hydrodynamics and heat transfer characteristics of these consecutively impinging droplets till the Leidenfrost temperature, are studied and compared.

Pool Boiling Characteristics of Metallic Nanofluids

2011 ◽  
Vol 133 (11) ◽  
Author(s):  
K. Hari Krishna ◽  
Harish Ganapathy ◽  
G. Sateesh ◽  
Sarit K. Das
Keyword(s):  
Heat Transfer ◽  
Thermal Conductivity ◽  
Boiling Heat Transfer ◽  
Volume Fraction ◽  
Pool Boiling ◽  
Heat Fluxes ◽  
Solid Particles ◽  
Heater Surface ◽  
Heat Transfer Characteristics ◽  
Transfer Characteristics

Nanofluids, solid-liquid suspensions with solid particles of size of the order of few nanometers, have created interest in many researchers because of their enhancement in thermal conductivity and convective heat transfer characteristics. Many studies have been done on the pool boiling characteristics of nanofluids, most of which have been with nanofluids containing oxide nanoparticles owing to the ease in their preparation. Deterioration in boiling heat transfer was observed in some studies. Metallic nanofluids having metal nanoparticles, which are known for their good heat transfer characteristics in bulk regime, reported drastic enhancement in thermal conductivity. The present paper investigates into the pool boiling characteristics of metallic nanofluids, in particular of Cu-H2O nanofluids, on flat copper heater surface. The results indicate that at comparatively low heat fluxes, there is deterioration in boiling heat transfer with very low particle volume fraction of 0.01%, and it increases with volume fraction and shows enhancement with 0.1%. However, the behavior is the other way around at high heat fluxes. The enhancement at low heat fluxes is due to the fact that the effect of formation of thin sorption layer of nanoparticles on heater surface, which causes deterioration by trapping the nucleation sites, is overshadowed by the increase in microlayer evaporation, which is due to enhancement in thermal conductivity. Same trend has been observed with variation in the surface roughness of the heater as well.

High heat flux flow boiling in silicon multi-microchannels – Part I: Heat transfer characteristics of refrigerant R236fa

2008 ◽  
Vol 51 (21-22) ◽  
pp. 5400-5414 ◽  
Author(s):  
Bruno Agostini ◽  
John Richard Thome ◽  
Matteo Fabbri ◽  
Bruno Michel ◽  
Daniele Calmi ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Heat Flux ◽  
Flow Boiling ◽  
High Heat ◽  
High Heat Flux ◽  
Heat Transfer Characteristics ◽  
Flux Flow ◽  
Transfer Characteristics

scholarly journals Enhanced Heat Transfer Characteristics of Graphite Concrete and Its Application in Energy Piles

2018 ◽  
Vol 2018 ◽  
pp. 1-12 ◽  
Author(s):  
Qingwen Li ◽  
Lu Chen ◽  
Haotian Ma ◽  
Chung-Ho Huang
Keyword(s):  
Heat Transfer ◽  
High Heat ◽  
Transfer Efficiency ◽  
Heat Transfer Characteristics ◽  
Enhanced Heat Transfer ◽  
Energy Pile ◽  
Transfer Characteristics ◽  
Heat Transfer Efficiency ◽  
High Heat Transfer ◽  
Energy Piles

The latest research on energy piles demonstrates that most scholars are focusing their attention on optimization by designing more efficient heat exchanger coils, analyzing the heat pump matching parameters, and so on. However, after more than 20 years of development, these traditional methods for improving the heat transfer efficiency of energy piles have reached a bottleneck, and a new approach for the continued enhancement of this technology must be investigated. In this study, powdered graphite with high heat transfer characteristics was included in a concrete mix to create graphite concrete piles with enhanced heat transfer characteristics. The results from theoretical analysis, laboratory testing, and numerical simulation indicate that using graphite to improve the heat transfer efficiency of a concrete material is an effective method for enhancing the thermal efficiency of an energy pile system. The research results also show that the heat transfer coefficient of the concrete exhibits greater improvement when the graphite content is greater than 15% under the same environmental temperature. After studying the performance of the proposed graphite concrete energy pile under different environmental temperatures (10°C, 20°C, 30°C, and 40°C), the results indicate that the working efficiency of the energy pile is better in the summer than in the winter. Finally, parameters such as the cast-in pipe configuration and pile spacing are optimized.

scholarly journals Numerical Study on the Fluid Flow and Heat Transfer Characteristics of Al2O3-water Nanofluids in Microchannels of Different Aspect Ratio

2021 ◽  
Author(s):  
Huajie Wu ◽  
Shanwen Zhang
Keyword(s):  
Heat Transfer ◽  
Aspect Ratio ◽  
Volume Fraction ◽  
High Heat ◽  
High Heat Flux ◽  
Nanoparticle Volume Fraction ◽  
Heat Transfer Characteristics ◽  
Transfer Characteristics ◽  
Flow And Heat Transfer ◽  
Heat Transfer Capacity

The study of the influence of the nanoparticle volume fraction and aspect ratio of microchannels on the fluid flow and heat transfer characteristics of nanofluids in microchannels is important in the optimal design of heat dissipation systems with high heat flux. In this work, the computational fluid dynamics method was adopted to simulate the flow and heat transfer characteristics of two types of water–Al2O3 nanofluids with two different volume fractions and five types of microchannel heat sinks with different aspect ratios. Results showed that increasing the nanoparticle volume fraction reduced the average temperature of the liquid–solid heat transfer surface and thereby improved the heat transfer capacity of the nanofluids. Meanwhile, the increase of the nanoparticle volume fraction led to a considerable increase in the pumping power of the system. Changing the aspect ratio of the microchannel effectively improved the heat transfer capacity of the heat sink. Moreover, increasing the aspect ratio effectively reduced the average temperature of the heating surface of the heat sink without significantly increasing the flow resistance loss. When the aspect ratio exceeded 30, the heat transfer coefficient did not increase with the increase of the aspect ratio. The results of this work may offer guiding significance for the optimal design of high heat flux microchannel heat sinks.

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