A model for calculating condensation heat transfer of natural refrigerant R290 inside a tube is selected by analyzing and comparing the available correlations. The flow pattern of two-phase flow of natural refrigerant R290 condensation process inside the tube is obtained. The transition of mass velocity from stratified flow to stratified-wavy flow, from stratified-wavy flow to annular and intermittent flow, from annular and intermittent flow to mist flow, and from mist flow to bubbly flow as vapor quality changes are determined. Under the same condition, the experimental and predicted values of R290 condensation heat transfer coefficients increase with the increase of vapor quality, and their difference is not significant. The condensation heat transfer coefficients of R290 and R22 increase gradually with the increase of vapor quality, the condensation heat transfer coefficient of R290 is higher than that of R22, and their difference increases with the increase of vapor quality, so it is concluded that natural refrigerant R290 has good condensation heat transfer characteristic.%对现有的管内凝结传热系数关联式分析比较,选择出合适的自然工质R290管内凝结换热计算模型,并计算得到R290管内凝结过程两相流动的流型图.通过计算并与实验值比较得到,相同工况下,预测与实验的R290凝结传热系数值相差不大.R290的凝结传热系数较R22的凝结传热系数大,并随着蒸气干度的增加差值加大,R290表现出良好的凝结换热特性.
展开▼
