Abstract:

"Liquid-vapor separation" was applied in plate condenser with zeotropic mixtures R134a/R245fa. The impact of refrigerant mass flows, bubble point temperatures and the compositions of mixtures (mass fractions) on the heat transfer performance of the liquid-vapor separation plate condenser were examined. A comparison with experimental data from a conventional plate condenser was conducted to highlight the thermodynamic performance of zeotropic mixtures. The results showed that a high proportion of low-boiling-point refrigerant improved liquid-vapor separation, achieving a maximum liquid separation efficiency of 99.74%."Liquid-vapor separation" effectively adjusted the compositions of the zeotropic mixtures, increasing the proportion of low-boiling-point refrigerant after separation. Compared with conventional plate condenser, the liquid-vapor separation plate condenser exhibited a 5.6%—46.9% increase in heat transfer coefficient. It was inversely proportional to refrigerant mass flows and directly proportional to bubble point temperatures. The pressure drop decreased by 12.6%—44.3%, less affected by refrigerant mass flows and bubble point temperatures, a higher proportion of low-boiling-point refrigerant in the zeotropic mixtures resulted in a smaller pressure drop.

Key words: zeotropic mixtures, liquid-separation condensation, two-phase flow, heat transfer, pressure drop

摘要：

将“分液冷凝”应用于板式冷凝器中，并采用非共沸工质R134a/R245fa作为制冷剂，分别研究了工质流量、泡点温度以及工质组分（质量比）对分液板式冷凝器换热性能的影响，并与普通板式冷凝器进行对比，揭示非共沸工质在分液板式冷凝器中的热力性能。研究结果表明：低沸点工质在非共沸工质中的占比越高，气液分离的效果越好，分液效率最高可达到99.74%；“气液分离”可有效调节非共沸工质的组分，经过“气液分离”后低沸点工质在非共沸工质中的占比会提高；与普通板式冷凝器相比，分液板式冷凝器传热系数提高了5.6%~46.9%，并且与工质流量成反比，与泡点温度成正比；压降降低了12.6%~44.3%，且受工质流量、泡点温度的影响较小，低沸点工质在非共沸工质中的占比越高，压降越小。

关键词: 非共沸工质, 分液冷凝, 两相流, 传热, 压降