Experimental and Numerical Investigations of Subcooled Boiling Heat Transfer in a Small-Diameter Tube

2020 ◽  
Vol 12 (6) ◽  
Author(s):  
Makoto Shibahara ◽  
Qiusheng Liu ◽  
Koichi Hata ◽  
Katsuya Fukuda
Keyword(s):  
Heat Transfer ◽  
Numerical Simulation ◽  
Heat Flux ◽  
Boiling Heat Transfer ◽  
Fluid Model ◽  
Three Dimensional ◽  
Small Diameter ◽  
Inlet Temperature ◽  
Simple Method ◽  
Subcooled Water

Abstract The boiling heat transfer for subcooled water flowing in a small-diameter tube was investigated experimentally and numerically. In the experiment, a platinum tube was used as an experimental tube (d = 1.0–2.0 mm) to conduct joule heating by direct current. The heat generation rate of the tube was controlled with an exponential function. The numerical simulation of boiling heat transfer for subcooled water flowing in the small-diameter tube was conducted using the commercial computational fluid dynamics (CFD) code, phoenics ver. 2013. The small-diameter tube was modeled in the simulation. As the boundary condition, the measured heat flux was given at the inner wall. The inlet temperature ranged from 302 to 312 K. The flow velocities of d = 1.0 mm and d = 2.0 mm were 9.29 m/s and 2.34 m/s, respectively. The three-dimensional analysis was carried out from non-boiling to the critical heat flux (CHF). Governing equations were discretized using the finite volume method in the phoenics. The semi-implicit method for pressure linked equation (SIMPLE) method was applied in the numerical simulation. For modeling boiling phenomena in the tube, the Eulerian–Eulerian two-fluid model was adopted using the interphase slip algorithm of phoenics. The surface temperature difference increased as the heat flux increased in the experiment. The numerical simulation predicted the experimental data well. When the heat flux of the experiment reached the CHF point, the predicted value of the heat transfer coefficient was approximately 3.5% lower than that of the experiment.

Numerical and Experimental Investigation of Boiling Heat Transfer for Subcooled Water Flowing in a Small-Diameter Tube

2019 ◽  
Author(s):  
Makoto Shibahara ◽  
Qiusheng Liu ◽  
Koichi Hata ◽  
Katsuya Fukuda
Keyword(s):  
Heat Transfer ◽  
Numerical Simulation ◽  
Heat Flux ◽  
Exponential Function ◽  
Boiling Heat Transfer ◽  
Small Diameter ◽  
Uniform Heat Flux ◽  
Inlet Temperature ◽  
Simple Method ◽  
Subcooled Water

Abstract Numerical simulation of boiling heat transfer for subcooled water flowing in a small-diameter tube was conducted using the commercial computational fluid dynamics (CFD) code, PHOENICS ver. 2013. A small-diameter tube (d = 1.0–2.0 mm) was modeled in the simulation. A uniform heat flux with an exponential function was given at the inner tube wall as the boundary conditions. The inner wall boundary condition was set to a non-slip. The inlet temperature ranged from 302 to 312 K. The flow velocities of d = 1.0 mm and d = 2.0 mm are 9.29 m/s and 2.34 m/s, respectively. The transient analysis was carried out from the non-boiling region since the heat flux increased with time in the author’s experiments. The governing equations including the energy equation were discretized using the finite volume method in the PHOENICS code. The SIMPLE method was applied for the numerical simulation. For modeling boiling phenomena in the tube, the Eulerian-Eulerian two-fluid model was adopted using the interphase slip algorithm of PHOENICS code. In the experiment, a platinum tube was used as the experimental tube (d = 1.0–2.0 mm) to conduct joule heating by direct current. The distilled and deionized water was pressured by the pressurizer. The heat generation rate of the tube was controlled with the exponential function to obtain the transient heat transfer characteristics from the non-boiling region. The surface superheat increased as the heat flux increased in the experiment. The numerical simulation predicted the experimental data well. When the heat flux of the experiment was reached to the CHF point, the predicted value of heat transfer coefficient was approximately 3.5 % lower than that of the experiment.

Numerical Simulation Of A Microchannel For Microelectronic Cooling

2012 ◽  
Author(s):  
Wai Hing Wong ◽  
Normah Mohd. Ghazali
Keyword(s):  
Heat Transfer ◽  
Numerical Simulation ◽  
Heat Flux ◽  
Aspect Ratio ◽  
Three Dimensional ◽  
Large Temperature ◽  
Rectangular Microchannel ◽  
Numerical Work ◽  
Solid Region ◽  
Wall Interaction

Kertas kerja ini membincangkan simulasi berangka ke atas sinki haba saluran mikro dalam penyejukan alatan mikroelektronik. Model Dinamik Bendalir Berkomputer (CFD) tiga dimensi dibina menggunakan pakej komersil, FLUENT, untuk mengkaji fenomenon aliran bendalir dan pemindahan haba konjugat di dalam suatu sinki haba segi empat yang diperbuat daripada silikon. Model ditentusahkan dengan keputusan daripada uji kaji dan pengkajian berangka yang lepas untuk lingkungan nombor Reynolds kurang daripada 400 berdasarkan diameter hidraulik 86 mm. Kajian ini mengambil kira kesan kelikatan bendalir yang bersandaran dengan suhu dan keadaan aliran pra–membangun dari segi hidrodinamik dan haba. Model memberi maklumat tentang taburan suhu dan fluks haba yang terperinci di dalam sinki haba saluran mikro. Kecerunan suhu yang tinggi dicatat pada kawasan pepejal berdekatan dengan sumber. Fluks haba paling tinggi didapati pada dinding tepi saluran mikro diikuti oleh dinding atas dan bawah. Purata pekali pemindahan haba yang lebih tinggi bagi silikon menjadikan ia bahan binaan sinki haba saluran mikro yang lebih baik berbanding dengan kuprum dan aluminium. Peningkatan nisbah aspek saluran mikro yang bersegi empat memberi kecekapan penyejukan yang lebih tinggi kerana kelebaran saluran yang berkurangan memberi kecerunan halaju yang lebih tinggi dalam saluran. Nisbah aspek yang optimum yang diperoleh adalah dalam lingkungan 3.7 – 4.1. Kata kunci: Saluran mikro, CFD, FLUENT, simulasi berangka, penyejukan mikroelektron The paper discusses the numerical simulation of a micro–channel heat sink in microelectronics cooling. A three–dimensional Computational Fluid Dynamics (CFD) model was built using the commercial package, FLUENT, to investigate the conjugate fluid flow and heat transfer phenomena in a silicon–based rectangular microchannel heatsink. The model was validated with past experimental and numerical work for Reynolds numbers less than 400 based on a hydraulic diameter of 86 mm. The investigation was conducted with consideration of temperaturedependent viscosity and developing flow, both hydrodynamically and thermally. The model provided detailed temperature and heat flux distributions in the microchannel heatsink. The results indicate a large temperature gradient in the solid region near the heat source. The highest heat flux is found at the side walls of the microchannel, followed by top wall and bottom wall due to the wall interaction effects. Silicon is proven to be a better microchannel heatsink material compared to copper and aluminum, indicated by a higher average heat transfer. A higher aspect ratio in a rectangular microchannel gives higher cooling capability due to high velocity gradient around the channel when channel width decreases. Optimum aspect ratio obtained is in the range of 3.7 – 4.1. Key words: Microchannel, CFD, FLUENT, numerical simulation, microeletronics cooling

Simple Model of Boiling Heat Transfer on Tubes in Large Pools

1997 ◽  
Vol 119 (2) ◽  
pp. 376-379 ◽  
Author(s):  
Y. Parlatan ◽  
U. S. Rohatgi
Keyword(s):  
Heat Transfer ◽  
Experimental Data ◽  
Heat Flux ◽  
Heat Exchanger ◽  
Atmospheric Pressure ◽  
Boiling Heat Transfer ◽  
Saturation Temperature ◽  
Flow Dynamics ◽  
Simple Method ◽  
Vertical Tubes

A simple method has been developed to model boiling heat transfer from a heat exchanger to pools using the experimental data available in the literature without modeling the flow dynamics of the pool. In this approach the heat flux outside vertical tubes is expressed as a function of outside wall temperature of the tubes and saturation temperature of the pool at or near atmospheric pressure.

Flow Boiling Heat Transfer of Subcooled Water on Sintered Microporous Surfaces

2017 ◽  
Vol 139 (8) ◽  
Author(s):  
Yeonghwan Kim ◽  
Junsub Kim ◽  
Seung M. You ◽  
Jungho Lee ◽  
Jeong Lak Sohn ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Heat Flux ◽  
Boiling Heat Transfer ◽  
Flow Boiling ◽  
Average Particle ◽  
Temperature Uniformity ◽  
Subcooled Water ◽  
Wall Superheat ◽  
Flow Boiling Heat Transfer ◽  
Plain Surface

Electronic devices such as battery packs in electric vehicles and LED lights require advanced control in temperature uniformity for their optimum performance and prolonged lifetime. Flow boiling heat transfer of subcooled water (∆Tsub = 20K) in a 300 mm long minichannel with the cross section of 20×10 mm2 was investigated to improve the temperature uniformity over the entire minichannel. The minichannel was uniformity heated from the bottom copper surface. A 10 mm thick Pyrex glass was used for the top plate of the channel to visualize two-phase flow during the experiment. Microporous coating was fabricated by sintering copper particles on the top surface of the copper block. The average particle size was 50 μm, the average coating thickness was 300 μm, and the porosity was 41%, respectively. At the heat flux of 100 kW/m2, more bubbles are shown on the microporous surface compared with plain surface, resulting in better boiling heat transfer performance. These bubbles were large and stationary as liquid is evaporated and condensed to transport the heat as if heat pumps. As heat flux increases, bubble nucleation becomes more intensive, however, the larger stationary bubbles observed at 100 kW/m2 started to decrease. Most of the generated bubbles flowed through the downstream and they shrank quickly upon departure from the wall due to the 20K subcooling. High speed video showed some streaks of these small bubbles, and more streaks were observed as the heat flux increased. As shown in the left graph above, at 50 kW/m2 in subcooled flow boiling, both plain and microporous surfaces show similar local wall temperature because both are placed in the single-phase regime. In contrast, the difference of wall superheat between plain and porous surface is relatively large at higher heat flux of 500 kW/m2. Sintered microporous surface showed smaller increase in wall superheat compared with plain surface at higher wall superheat. [This study was supported by National Research Council of Science and Technology (NST) grant, Korea (Grant No. KIMM-NK203B)].

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