带有周期性扰流结构的微通道内流动与传热特性

设计了一种周期性扰流微结构，由布置在微通道侧壁的凹穴和微通道中心的针肋组成。研究了该热沉内流动和传热特性，分析了扰流结构几何参数对热沉不可逆损失和散热效率的影响，利用热阻和强化传热因子评价综合性能。研究表明，等腰梯形凹穴的底边相对长度（RL）对热沉性能具有显著影响。雷诺数（Re）较大时，减小RL能够明显减小凹穴内部的旋涡，从而减小流动摩擦损失，降低通道压降和流动不可逆性。同时，减小RL有利于增强流体对凹穴收缩段的冲刷，减小凹穴内的层流滞止区，将凹穴处的热量及时带走，从而提高热沉的散热效率。与传统光滑微通道（SM）相比，周期性扰流结构能够显著减小热沉的总熵产和热阻，增大强化传热因子，提高热沉的综合性能。综合考虑传热和流动阻力，较低泵功条件下，RL=0.3的热沉综合性能最优；较高泵功条件下，RL=0的热沉综合性能最佳。周期性扰流结构能够提高微冷却系统的效率和经济性，在微型器件冷却领域具有广阔的应用前景。

Flow and heat transfer characteristics in microchannels with periodic fluid disturbance structures

A periodic fluid disturbance microstructure was designed, which consisted of cavities arranged on the sidewall of the microchannel and pin fins in the center of the microchannel. The flow and heat transfer characteristics in the heat sink were studied, and the effects of geometric parameters of the fluid disturbance structure on the irreversible loss and heat dissipation efficiency of the heat sink were analyzed. The overall performance of the heat sink was evaluated by the thermal resistance and heat transfer enhancement factor. Results showed that relative length of the bottom of the isosceles trapezoidal cavities (RL) had a significant effect on the heat sink performance. When Reynolds number (Re) was large, decreasing RL could reduce the vortex in the cavities significantly, thus the flow friction loss, pressure drop and flow irreversibility of the microchannel were decreased. At the same time, reducing RL was beneficial to enhance the scours effect on the cavity contraction section, reduce the laminar flow stagnation zone in the cavity, take away the heat at the cavity timely, thereby the heat dissipation efficiency of the heat sink was improved. Compared with the traditional smooth microchannel (SM), the periodic fluid disturbance structure was able to reduce total entropy generation and thermal resistance of the heat sink, increase heat transfer enhancement factor, and improve overall performance of the heat sink markedly. Considering heat transfer and flow resistance synthetically, the heat sink with RL=0.3 had the best overall performance under the condition of low pump power. For the high pump power, the overall performance of the heat sink with RL=0 was the best. The periodic fluid disturbance structure can make the micro cooling system more efficient and economical, hence it has a broad application prospect in the field of micro device cooling.