微通道内超临界氮气三维热流场实验与数值模拟

利用实验与数值模拟相结合的方法研究了超临界氮气（SCN₂）三维热流场特性，在用实验数据验证数值方法可靠性基础上，分析了压力（3.6~7 MPa）和质量流速［800~1200 kg/（m²?s）］对SCN₂对流传热特性的影响，揭示了微通道圆管不同圆周方向上SCN₂热流场规律。结果表明：在低压力和高质量流速下，同一轴向位置处，径向内壁温最大值出现在圆管90°处；质量流速越大，内壁温最大值和对流传热系数最小值由圆管180°向90°处发生了转移；当浮升力系数Gr*/Re²>1时，浮升力有利于强化圆管底部区域流体传热能力；基于获得的数据，提出了一个新的适合预测微通道圆管内SCN₂对流传热特性的无量纲换热关联式，预测误差小于20%。研究结果为微通道换热器优化设计提供了参考。

Experimental and numerical simulation on three-dimensional heat flow field of supercritical nitrogen in micro-channel

Three-dimensional heat flow field characteristics of supercritical nitrogen (SCN₂) in the micro-channel was studied by combining experimental and numerical simulation methods. Based on the reliability of numerical method verified by experimental data, the effects of pressure (3.6—7 MPa) and mass flux (800—1200 kg/(m²?s)) on the convective heat transfer characteristics of SCN₂ were analyzed. The heat flux field of SCN₂ in different circumferential directions of the tube was revealed. The results show that under low pressure and high mass flux, the maximum radial inner wall temperature appears at 90° of the circular tube at the same axial position. With the increase of mass flux, the maximum inner wall temperature and the minimum heat transfer coefficient gradually shifted from 180° to 90° of tube. When buoyancy coefficient Gr*/Re²>1, the buoyancy force was conducive to enhance the fluid heat transfer capacity at the bottom of the circular tube. Based on the obtained data, a new dimensionless correlation is proposed to predict the convective heat transfer characteristics of SCN₂ in micro-channel, and the prediction error is less than 20%. The results provide a reference for the optimal design of micro-channel heat exchanger.