CO_2微通道气冷器流量分配和换热特性的数值模拟及验证

Numerical Simulation and Verification of Flow Distribution and Heat Transfer Characteristics of CO_2 Micro-channel Gas Cooler

本文建立了CO_2微通道气冷器集流管和微通道扁管两部分的物理模型并进行网格划分,模拟研究了扁管插入集流管深度f分别为4、5、6 mm和入口管在集流管1/6、1/2位置处对质量流量分配的影响,实验验证了CO_2微通道气冷器扁管壁面温度分布。结果表明:当f为4 mm、入口管位于集流管1/6处时,质量流量分配最均匀,此时不均匀度为0.4×10^(-3);模拟扁管内CO_2换热特性发现随着CO_2质量流量的增加,扁管换热量增加,流量由2.3 kg/h增至2.5 kg/h,换热量提高了21.4%;当质量流量一定时,CO_2的出口温度随着CO_2入口温度的升高而升高,在不同CO_2入口温度条件下,微通道扁管壁面温度实验值与模拟值误差在10%以内,验证了模拟的准确性。

The physical model of a CO2 micro-channel air cooled tube and micro-channel flat tube was established and the grid was divided. The effects of mass flow distribution were simulated when the depth f was 4,5,and 6 mm and the inlet tube was at 1/6 and 1/2 of the length of collector tube. The predicted wall temperature distribution was verified by the experimental results of CO2 micro-channel gas cooler with flat tube. The predicted results show that when f is 4 mm and the inlet pipe is at 1/6 location of the collector tube,mass flow distribution is the best with an unevenness of 0. 4 × 10-3. The predicted heat transfer of CO2 in the flat tube shows that with the increase in mass flow of CO2,the heat exchange in the flat tube increases. When the mass flow rate is increased from 2. 3 kg/h to 2. 5 kg/h,the heat exchange rate is increased by 21. 4%. When the mass flow is kept constant,the outlet temperature of CO2 increases with the increase in CO2 inlet temperature. Besides,under the condition of different CO2 inlet temperatures,the error range of the micro-channel flat wall surface temperature between experimental and simulation values is within 10%,which verifies the accuracy of this simulation. Therefore,the results can guide the engineering design of micro-channel cooling unit.