采用CFD方法对液氮冷却结构进行流体和热分析

低温应用的大功率器件需要设计高冷却效率的液冷室结构。采用计算流体动力学（CFD）方法模拟了以液氮-氮气两相流为制冷剂的空腔结构、微通道结构和扰流柱结构的流动与传热过程。结果表明，相比于空腔结构和微槽道结构，扰流柱结构具有较好的换热能力。圆形扰流柱易发展45°方向支流，而方形扰流柱结构有利于垂直方向流速均匀化。相较于平行排布，扰流柱交错排列时圆形和方形扰流柱结构中流速分布更为均匀。对比对流换热系数发现，交错排布优于平行排布，方形扰流柱优于圆形扰流柱。换热效果最好的结构为交错排布的2 mm方形扰流柱，对流换热系数为4223 W/(m2·K)，较空腔结构提高125.83%。采用上述结构进行测试验证，在107.6 W加热功率工况下冷头测温点温度与相同功率下仿真结果有较好的对应性。

Flow and heat analysis of liquid nitrogen cooling structure by CFD method

High-power devices for low-temperature applications require a liquid-cooled chamber structure with high cooling efficiency. The Computational Fluid Dynamics (CFD) method was used to simulate the flow and heat transfer process of the cavity structure, the microchannel structure, and the pin-fins structure under the condition of the liquid nitrogen-nitrogen two-phase flow as the refrigerant. The results show that the pin-fins structure has the best heat exchange effect among the three above structures. The circular pin-fins structure is easy to develop a branch in the direction of 45°, and the square pin-fins structure is conducive to the uniform flow velocity in the vertical direction. Compared with the parallel pin-fins structure, the flow velocity distribution in the circular and square pin-fins is more uniform when the pin-fins are staggered. Comparing the convective heat transfer coefficients in different liquid cooling chambers with pin-fin structures, under the same other parameters, the staggered arrangement is better than the parallel arrangement, and the square pin-fin is better than the circular pin-fin. The structure with the best heat transfer effect is the staggered 2 mm square pin-fin structure, and the convective heat transfer coefficient is 4223 W/(m2·K), which is 125.83% higher than cavity structure. The above structure is manufactured for physical verification. The temperature of the cold head under the 107.6 W heating power corresponds well with the simulation result under the same condition.