低压蒸汽滴状冷凝传热性能的实验研究

EXPERIMENTAL INVESTIGATION OF CHARACTERISTICS OF STEAM DROPWISE CONDENSATION HEAT TRANSFER AT LOW PRESSURE

实验研究了不同水蒸气压力条件下的滴状冷凝传热特性。10 kPa、40 kPa和70 kPa时的传热系数分别是常压下的56%,68%和81%。随着水蒸气压力的下降,液滴脱落直径变大,液滴生长周期延长,冷凝传热系数下降。通过液滴的动力学特性分析和基于界面效应的滴状冷凝传热模型,分析了低压对水蒸气冷凝传热的主要影响因素,压力变化主要影响了分子扩散率和气-液相际传热热阻,导致总冷凝传热系数随压力下降。

The effect of steam pressure on dropwise condensation heat transfer was investigated experimentally. The heat transfer coefficients at the steam pressures of 10 kPa, 40 kPa and 70 kPa are 56%, 68% and 81% of that at 101 kPa, respectively. The departure diameter of droplet becomes increasing, the growth cycle of droplet longer, and hence the condensation heat transfer coefficient decreases with the steam pressure decreasing. The dynamic characteristics of condensate droplets were investigated and the dropwise condensation heat transfer model was applied to analyze the variations of the steam condensation heat transfer at low pressure. It was found that the decrease of heat transfer coefficients at low pressures is attributed to the increase of the interfacial thermal resistance due to the lower molecular diffusion rate through the interface.