竖直细管中超临界二氧化碳传热数值研究

Numerical Study of Convection Heat Transfer of Supercritical CO_2 in a Vertical Mini-tube

采用Realizable k-ε湍流模型对冷却条件下超临界二氧化碳竖直向上流过内径为0.4 mm的细圆管的对流换热进行了数值研究,分析了二氧化碳进口温度、质量流量、压力以及冷却水量等对二氧化碳对流换热的影响.研究表明,二氧化碳进口温度和冷却水量对于其换热过程的影响比较小;二氧化碳质量流量和压力的影响较为显著,质量流量越高,传热系数提高就越明显;压力越接近二氧化碳的临界压力,传热系数在临界点附近的变化越剧烈,峰值越大.

Convection heat transfer of CO2 at supercritical pressures during cooling in vertical circular mini-tube with inner diameter of 0.4 mm was studied numerically using Realizable turbulent model.The effects of pressure,cooling water mass flux,CO2 mass flow rate and CO2 inlet temperature on the heat transfer coefficient were investigated.The simulated results indicate that cooling water mass flow rate and CO2 inlet temperature have little influence on convection heat transfer of supercritical CO2,but CO2 inlet mass flow rate and inlet pressure affect significantly.With the increasing of CO2 mass flow rate,coefficient of heat transfer improves dramatically.The inlet pressure is closer to the critical pressure,the change of coefficient of heat transfer near critical point is more drastically,and the peak value is higher.