部分互溶的R32-润滑油混合物核态沸腾中分层与换热特性
Stratification and heat transfer characteristics of partially miscible R32-lubricating oil mixtures during nucleate boiling
摘要：
在空调器中采用与制冷剂部分互溶的润滑油代替现有完全互溶的润滑油，能避免制冷剂循环量不足的问题，前提是掌握部分互溶的润滑油对沸腾换热的影响。本文针对空调器中广泛使用的制冷剂R32，搭建可视化的沸腾换热特性测试实验台，观测混合物分层现象并测定换热系数。实验结果表明：部分互溶混合物随润滑油质量分数增大先后经历均一混合、分层、均一混合状态；换热系数随时间先不变后减小，减小时刻随热流密度和初始润滑油质量分数增大、初始液相高度减小而提前；平均换热系数随热流密度增大而增大，受初始润滑油质量分数和液相高度的影响可忽略不计；热流密度从5 kW/m2增大至15 kW/m2，平均换热系数增大118.3%。
Abstract：
Applying partially miscible lubricating oil instead of completely miscible lubricating oil in room air conditioners is a promising way to avoid refrigerant insufficiency. The application of partially miscible lubricating oil to air conditioners requires the clarity of the effect of partially miscible lubricating oil on the nucleate boiling characteristics. In the study, an experiment rig for R32 with a visualization feature is built to test the heat transfer performance of the mixture, including the observation of stratified layers and the measurement of heat transfer coefficients. The test results indicate that, with the increase of oil mass fraction, partially miscible mixtures firstly are homogeneous, then stratify into two layers, finally become homogeneous. The heat transfer coefficients firstly keep steady and then decrease sharply. The moment of decreasing is advanced with the increase of heat flux and initial oil mass fraction, or the decrease of the initial height. The average heat transfer coefficient increases with the increase of the heat flux, and the effects of the initial oil mass fraction and the initial height on the average heat transfer coefficient can be ignored. The average heat transfer coefficient increases by 118.3% as the heat flux increases from 5 kW/m2 to 15 kW/m2.
Keywords:R32; partially miscible; lubricating oil; nucleate boiling; stratification; heat transfer characteristic