A numerical study of heat transfer of a porous block with the random porosity model in a channel flow

2002 ◽  
Vol 38 (7-8) ◽  
pp. 695-704 ◽  
Author(s):  
W. S. Fu ◽  
S. F. Chen
Keyword(s):  
Heat Transfer ◽  
Channel Flow ◽  
Numerical Study ◽  
Porous Block ◽  
Porosity Model ◽  
Random Porosity

Numerical Study of Heat Transfer of a Porous-Block-Mounted Heat Source Subjected to Pulsating Channel Flow

2008 ◽  
Vol 54 (4) ◽  
pp. 426-449 ◽  
Author(s):  
Yueh-Liang Yen ◽  
Po-Chuan Huang ◽  
Chao-Fu Yang ◽  
Yen-Jen Chen
Keyword(s):  
Heat Transfer ◽  
Heat Source ◽  
Channel Flow ◽  
Numerical Study ◽  
Porous Block

scholarly journals Numerical Study of Heat Transfer Mechanism in Turbulent Supercritical CO2 Channel Flow

2008 ◽  
Vol 3 (1) ◽  
pp. 112-123 ◽  
Author(s):  
Xinliang LI ◽  
Katsumi HASHIMOTO ◽  
Yasuhiro TOMINAGA ◽  
Mamoru TANAHASHI ◽  
Toshio MIYAUCHI
Keyword(s):  
Heat Transfer ◽  
Channel Flow ◽  
Supercritical Co2 ◽  
Numerical Study ◽  
Transfer Mechanism ◽  
Heat Transfer Mechanism

Experimental and Numerical Study of Heat Transfer and Flow Friction in Channels With Dimples of Different Shapes

2015 ◽  
Vol 137 (3) ◽  
Author(s):  
Yu Rao ◽  
Yan Feng ◽  
Bo Li ◽  
Bernhard Weigand
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Enhancement ◽  
Flow Structure ◽  
Channel Flow ◽  
Numerical Study ◽  
Rectangular Channel ◽  
Transfer Enhancement ◽  
Number Range ◽  
Flow Friction ◽  
Different Shapes

An experimental and numerical study was conducted to investigate the effects of dimple shapes on the heat transfer and flow friction of a turbulent flow over dimpled surfaces with different dimple shapes: spherical, teardrop, elliptical, and inclined elliptical. These dimples all have the same depth. The heat transfer, friction factor, and flow structure characteristics in the cooling channels with dimples of different shapes have been obtained and compared with each other for a Reynolds number range of 8500–60,000. The study showed that the dimple shape can have distinctive effects on the heat transfer and flow structure in the dimpled channels. The teardrop dimples show the highest heat transfer, which is about 18% higher than the conventional spherical dimples; and the elliptical dimples have the lowest heat transfer, which is about 10% lower than the spherical dimples; and however the inclined elliptical dimples have comparable heat transfer and pressure loss performance with the spherical dimples. The experiments still showed the realistic heat transfer enhancement capabilities of the dimpled channels relative to a smooth rectangular channel flow under the same flow and thermal boundary conditions, even after considering the thermal entrance effects in the channel flow and the enlarged heat transfer (wetted) area due to the dimpled surface. The three-dimensional numerical computations showed different vortex flow structures and detailed heat transfer characteristics of the dimples with different shapes, which revealed the influential mechanisms of differently shaped dimples on the convective heat transfer enhancement.

Cooling Enhancement of a Heat Source Through Flow Pulsation and Porous Block

Volume 4 ◽  
2004 ◽  
Author(s):  
Po-Chuan Huang ◽  
Shy-Her Nian ◽  
Chao-Fu Yang
Keyword(s):  
Heat Transfer ◽  
Heat Source ◽  
High Speed ◽  
Numerical Study ◽  
Particle Diameter ◽  
Pulsating Flow ◽  
Flow Pulsation ◽  
Cycle Space ◽  
Porous Block ◽  
Cooling Enhancement

A numerical study of forced pulsating flow in a parallel-plate channel with a porous-block-attached strip heat source at the bottom wall is presented. Comprehensive time-dependent flow and temperature data are calculated and averaged over a pulsation cycle in a periodic steady state. The results show that the cycle-space averaged Nusselt number for pulsating flow is higher than that for steady flow. The heat transfer enhancement factor increases with particle diameter, and pulsation frequent, but decreases with pulsation amplitude. The method combining flow pulsation with particle-porous heat sink can be considered as an augment heat transfer tool for cooling high-speed electronic devices.

Variant Porosity Pebble Bed Reactor Core Thermal Hydraulic Simulation

2010 ◽  
Author(s):  
Gang Zhao ◽  
Ping Ye ◽  
Toru Obala
Keyword(s):  
Heat Transfer ◽  
Cooling System ◽  
Reactor Core ◽  
Maximum Temperature ◽  
Porous Media Flow ◽  
Pebble Bed ◽  
Pebble Bed Reactor ◽  
Passive Cooling System ◽  
Porosity Model ◽  
Random Porosity

Spherical fuel elements are distributed randomly in the pebble bed reactor core and helium flow through the pebble bed to remove nuclear reaction heat. Pebble bed reactor core is usually treated as a uniform porous media flow in thermal hydraulic research. However the porosity distribution is nonuniform and the porosity near the wall increase sharply. A new random model is developed in this paper to investigate thermal hydraulic characteristics of pebble bed reactor core. Porosity assumption is based on porosity measurement of other research. Porosity simulation is divided into three parts according to the distance from wall. In the center of core, porosity is assumed to obey normal distribution, where average porosity is from the experimental relation based on statistical results. The mean and standard deviation of porosity distribution near the wall will increase because of the wall effect, where the distance from the wall is about three times of fuel ball’s diameter. The third part is zone from three times to five times of ball’s diameter departed from the wall. The wall effect of this zone is between center and the wall zone. Based on above assumption, a random porosity simulation is completed to apply in this research. COMSOL Multiphysics 3.5a software is used in this research. COMSOL Multiphysics are a calculation platform using proven Finite Elements Methods (FEM). In this research, Brinkman equation for porous media flow is applied in the simulation. Non-thermal Balance model is used in local heat transfer research between gas and pebble bed. A geometry model is built to simulate HTR-10. Temperature profile of variant porosity is gained from stationary analysis and comparison with uniform porosity is also discussed in the paper. For transient analysis, four cases simulation is carried out in the research. Case 1 and 2 simulate heat transfer phenomena with forced cooling system and with passive cooling system after reactor shut down. Way-Wigner-curve is used in Case 1 and Case 2 to simulate decay heat in the calculation. Case 3 and Case 4 simulate ATWS phenomena with natural convection and without natural convection system when blower is trip off in normal operation. Simulation results also are compared with some ATWS experiments and some discussion is done in the paper. From the results, it can be seen that random porosity will affect temperature distribution near the wall and make outlet temperature non-uniform greatly. The maximum temperature of variant porosity is much greater than the maximum temperature of uniform porosity at the same condition. Transient analyses of variant model show that passive cooling system can remove residual heat even in accident conditions when the blower trip off whether reactor shut down or not and the analyses results correspond substantially with experimental results. In general, variant porosity should be considered in the thermal hydraulic research of pebble bed reactor core. Variant porosity model can provide good prediction of heat transfer phenomena than uniform porosity model. Especially it can explain some transient analysis results.

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