5mm小管径内R290流动沸腾换热特性
low Boiling Heat Transfer Characteristics of R290 in 5mm Small-diameter Tubes

本文对R290制冷剂在5mm小管径内的流动沸腾换热特性进行实验研究，重点研究热流密度、质量流率及饱和温度对沸腾换热表面传热系数的影响。实验工况为：热流密度10～60 kW/m2、饱和温度15～25 ℃、质量流率50～200 kg/（m2?s）、干度0.1～0.9。研究结果表明：增加热流密度可以极大的强化换热，提高表面传热系数，同时使干涸现象提前发生，并加剧干涸；质量流率在低干度区间对表面传热系数的影响较小，在中干度和高干度区间表面传热系数与质量流率分别呈正相关；当热流密度较低时，在0.4～0.75中干度区间，增大饱和温度会使表面传热系数降低；而在较高的热流密度下，增大饱和温度明显引起表面传热系数的上升。
The characteristics of heat transfer for R290 flow boiling in 5 mm small diameter tubes were investigated experimentally with a focus on the effects of heat flux, mass flow rate, and saturation temperature on the surface coefficient of boiling heat transfer. The experimental conditions are as follows: heat flux=10–60 kW/m2; saturation temperature=15–25 ℃; mass flow rate=50–200 kg/(m2?s); and vapor quality=0.1–0.9. Results showed that an increase in heat flux can significantly enhance heat transfer and raise its surface coefficient, speeding up the dryout process and decreasing the starting vapor quality of dryout. Mass flow rate has slight influence on the surface coefficient of heat transfer at low vapor quality, whereas surface coefficient of heat transfer was positively correlated with mass flow rate at middle and high vapor quality. Moreover, the surface coefficient of heat transfer decreased with an enhancement in the saturation temperature with low heat flux at vapor quality range of 0.4–0.75, whereas it increased with an enhancement in the saturation temperature with higher heat flux