Fluid flow and heat transfer performance in a micro-reactor with non-uniform micro-pin-fin arrays for hydrogen production at low Reynolds number

2017 ◽  
Vol 42 (1) ◽  
pp. 553-561 ◽  
Author(s):  
Miao Qian ◽  
Deqing Mei ◽  
Zoudongyi Yi ◽  
Yanbing Feng ◽  
Zichen Chen
Author(s):  
X. Yu ◽  
C. Woodcock ◽  
Y. Wang ◽  
J. Plawsky ◽  
Y. Peles

In this paper we reported an advanced structure, the Piranha Pin Fin (PPF), for microchannel flow boiling. Fluid flow and heat transfer performance were evaluated in detail with HFE7000 as working fluid. Surface temperature, pressure drop, heat transfer coefficient and critical heat flux (CHF) were experimentally obtained and discussed. Furthermore, microchannels with different PPF geometrical configurations were investigated. At the same time, tests for different flow conditions were conducted and analyzed. It turned out that microchannel with PPF can realize high-heat flux dissipation with reasonable pressure drop. Both flow conditions and PPF configuration played important roles for both fluid flow and heat transfer performance. This study provided useful reference for further PPF design in microchannel for flow boiling.


2012 ◽  
Vol 134 (7) ◽  
Author(s):  
Yu Rao ◽  
Yamin Xu ◽  
Chaoyi Wan

A numerical study was conducted to investigate the effects of dimple depth on the flow and heat transfer characteristics in a pin fin-dimple channel, where dimples are located spanwisely between the pin fins. The study aimed at promoting the understanding of the underlying convective heat transfer mechanisms in the pin fin-dimple channels and improving the cooling design for the gas turbine components. The flow structure, friction factor, and heat transfer performance of the pin fin-dimple channels with various dimple depths have been obtained and compared with each other for the Reynolds number range of 8200–80,800. The study showed that, compared to the pin fin channel, the pin fin-dimple channels have further improved convective heat transfer performance, and the pin fin-dimple channel with deeper dimples shows relatively higher Nusselt number values. The study still showed a dimple depth-dependent flow friction performance for the pin fin-dimple channels compared to the pin fin channel, and the pin fin-dimple channel with shallower dimples shows relatively lower friction factors over the studied Reynolds number range. Furthermore, the computations showed the detailed characteristics in the distribution of the velocity and turbulence level in the flow, which revealed the underlying mechanisms for the heat transfer enhancement and flow friction reduction phenomenon in the pin fin-dimple channels.


Author(s):  
Yan Wang ◽  
Xiang Ling

The heat transfer performance of fluid flowing in a microchannel was experimentally studied, to meet the requirement of extremely high heat flux removal of microelectronic devices. There were 10 parallel microchannels with rectangular cross-section in the stainless steel plate, which was covered by a glass plate to observe the fluid flowing behavior, and another heating plate made of aluminum alloy was positioned behind the microchannel. Single phase heat transfer and fluid flow downstream the microchannel experiments were conducted with both deionized water and ethanol. Besides experiments, numerical models were also set up to make a comparison with experimental results. It is found that the pressure drop increases rapidly with enlarging Reynolds number (200), especially for ethanol. With comparison, the flow resistance of pure water is smaller than ethanol. Results also show that the friction factor decreases with Reynolds number smaller than the critical value, while increases the velocity, the friction factor would like to keep little changed. We also find that the water friction factors obtained by CFD simulations in parallel microchannels are much larger than experiment results. With heat flux added to the fluid, the heat transfer performance can be enhanced with larger Re number and the temperature rise could be weaken. Compared against ethanol, water performed much better for heat removal. However, with intensive heat flux, both water and ethanol couldn’t meet the requirement and the temperature at outlet would increase remarkably, extremely for ethanol. These findings would be helpful for thermal management design and optimization.


2016 ◽  
Vol 138 (10) ◽  
Author(s):  
Nasi Mou ◽  
Yong Jiun Lee ◽  
Poh Seng Lee ◽  
Pawan K. Singh ◽  
Saif A. Khan

In order to scrutinize the coolant mass distribution and its effect to the heat transfer in oblique fin microchannel array, extensive numerical studies are performed on planar oblique fin configuration. Full-domain simulations using common-flow down (CFD) approach are employed to provide better insights into the flow distribution, flow stability, and heat transfer performance at a global level. The flow field and temperature profile analysis shows that nonuniform coolant distribution and coolant migration occur in the oblique fin microchannel, and the heat transfer performance for both edges of the heat sink is affected due to changing secondary flow rate. However, the flow migration does not affect the local coolant velocity and temperature profiles significantly in the middle region (0.2 < Z′ < 0.8). Meanwhile, it is also found that Reynolds number affects the coolant migration, the stability of the fluid flow, and heat transfer performance significantly. Higher Reynolds number increases the percentage of secondary flow rate and, hence, enhances the heat transfer for fin surfaces in secondary channels.


Author(s):  
Shuichi Torii ◽  
Wen Jei Yang

A numerical study is performed to investigate unsteady, two-dimensional, incompressible laminar flow over both sides of a slot-perforated flat surface in a pulsating channel flow. Enhances is placed on the effects of the pulsating Strouhal number, the Reynolds number Re, the blockage factor, i.e., the ratio of plate thickness, d, to channel width, W, on the heat transfer performance and the velocity and thermal fields. It is found from the study that: (i) when the fluid stream is pulsated, the alternating change in the fluid flow disturbs the thermal boundary layer formed along the plate and induces mixing of the upper and lower streams of the plate downstream from the slot, resulting in an amplification of heat-transfer performance; (ii) heat transfer performance at the rear plate is induced with Re; (iii) by contrast, heat transfer performance is attenuated with an increase in the blockage factor, whose effect becomes larger in the lower region of the Reynolds number; and (iv) heat transfer performance is intensified with an increase in fSr, whose effect becomes minor in the lower region of the Reynolds number.


Author(s):  
Shuichi Torii ◽  
Wen-Jei Yang

A theoretical study is performed to investigate unsteady thermal and fluid flow transport phenomena over flat fins with heat sink, which are placed in a forced convection environment. Emphasis is placed on the effects of Reynolds number and fin pitch on heat transfer performance and velocity and thermal fields. It is found from the study that (i) in the high Reynolds number region, the alternating changes in the fluid flow take place for larger fin pitch, (ii) the alternating flow in the space area between two fins is mutually interacted by the corresponding one from the adjacent in-line plate fines, resulting in an amplification of heat transfer performance, and (iii) heat-transfer performance is intensified with a decrease in the fin pitch, whose trend becomes larger in the higher Reynolds number region considered here.


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