小管径强化管内R410A-油混合物流动沸腾阻力特性

实验研究了环保制冷工质R410A-润滑油混合物在5 mm小管径内螺纹强化管内流动沸腾的摩擦压降特性.实验结果表明,对于纯制冷剂R410A,摩擦压降随着干度的增大先增大后减小,峰值出现在干度为0.7~0.8左右;R410A-油混合物的摩擦压降随油平均质量分数、干度和质流密度的增大而增大,当油平均质量分数从0增长到5%时,在干度为0.9的高干度工况下,摩擦压降最大可增加120%.R410A-油混合物在5 mm强化管内流动沸腾的摩擦压降与7 mm强化管的相比约增大10%~30%;用已有的7 mm强化管的压降关联式预测5 mm强化管的压降时,误差为±40%.以R410A-油混合物在7和5 mm强化管内摩擦压降的实验值为基础,建立了基于混合物物性的R410A-油混合物在不同管径强化管内的摩擦压降关联式.该关联式的预测值与95%的实验值误差在±20%以内.

Flow Resistance Characteristics of R410A-oil Mixture during Evaporation in a Small Diameter Enhanced Tube

An experimental study of flow resistance characteristics of R410A oil mixture during evaporation inside a 5 mm internally spiral grooved enhanced tube was performed. The test results show that the frictional pressured drop of R410A initially increases with vapor quality and then decreases, presenting a local maximum in the vapor quality range between 0.7 and 0.8; the frictional pressure drop of R410A oil mixture increases with increasing nominal oil concentration, vapor quality and mass flux; the presence of oil enhances frictional pressure drop maximum by 120% as the oil concentration increases from 0 to 5% at a vapor quality of 0.9. The frictional pressure drop of R410A oil mixture in 5 mm enhanced tube is about 10% to 30% higher than that in 7 mm enhanced tube. The deviations of the prediction of existing correlation for 7 mm enhanced tube to the pressure drop characteristics of R410A oil mixture in 5 mm enhanced tube are within ±40%. Based on the experimental data of R410A oil mixture in 7 mm and 5 mm enhanced tubes, a new correlation of frictional pressure drop was developed by considering the mixture properties, which agreed with 95% of the experimental data within the deviation of ±20%.