微通道内超临界氮气三维热流场实验与数值模拟

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.