复杂微通道内对流传热的场协同及熵产

利用场协同和熵产原理研究了针肋宽度、凹穴宽度及雷诺数(Re)对凹穴和针肋组合式微通道内对流传热特性的影响,分析了微结构强化传热的本质原因,并对微通道的综合性能进行了评价。结果表明,增大针肋和凹穴宽度能够显著减小传热协同角,提高流场和温度场的协同程度,有利于强化对流传热,但局部漩涡会使流动协同角减小,增大微通道压降;增大针肋宽度能够提高能量利用效率,从而强化传热,但同时导致流动熵产率增大;适当增大凹穴宽度能够减小传热熵产率,但凹穴宽度过大会导致传热不可逆性和流动摩擦均增大;综合考虑泵功、相对针肋宽度和相对凹穴宽度,提出了预测热阻的经验关联式;当相对针肋宽度为0.2,相对凹穴宽度为2时,微通道的热阻最小,综合性能最好。 

Field synergy and entropy generation of convective heat transfer in microchannels with complex structure

The effects of fin width, cavity width and Reynolds number (Re) on the convective heat transfer characteristics in the microchannels with cavities and fins were studied by field synergy and entropy generation principle. The heat transfer enhancement mechanism of micro structures was analyzed, and the comprehensive performance of the microchannel was assessed. The results showed that the increase of fin width and cavity width was able to reduce the heat transfer synergy angle, improve the synergy relationship between flow field and temperature field obviously and enhance the convective heat transfer. However, the local vortexes caused the decrease of flow synergy angle and increased the pressure drop of the microchannels; the increase of fin width was helpful to improve the energy utilization efficiency and enhance heat transfer associated with the increase of the entropy generation rate of fluid friction; increasing the cavity width properly was able to reduce the entropy generation rate of heat transfer, but the extremely large cavity width led to the increase of the heat transfer irreversibility and flow friction; considering the pump power, relative fin width and relative cavity width, new correlation of the thermal resistance was proposed; the microchannel heat sink with relative fin width 0.2 and relative cavity width 2 yielded the lowest thermal resistance and the best overall performance.