印刷电路板式换热器Z型通道内制冷剂流动冷凝特性的数值模拟

摘要

The application of printed circuit heat exchanger (PCHE) with zigzag channels in liquefied natural gas (LNG) becomes more and more extensively. The required prerequisites for optimizing PCHE is to know the flow condensation characteristics of refrigerant flow condensation in zigzag semicircular channels. In the present study, a numerical model of two-phase flow condensation in zigzag semicircular channels was developed and validated by the existing experiment data. Based on the validated model, the flow patterns of refrigerant in zigzag channel under different conditions were obtained and compared with the existing flow map of R134a for circular tube. The comparison shows that, the annular flow region of flow condensation is expanded and the transformation from stratified flow to annular flow is promoted; the heat transfer coefficient inside tube increases with the decreasing vapor quality. The heat transfer coefficient under slug flow conditions is the largest, followed by the annular and stratified flow conditions. The results can be the theoretical foundation of zigzag channel design in PCHEs.%Z型通道印刷电路板式换热器在液化天热气等领域应用越来越广泛，了解Z型通道内流动冷凝的换热特性是该类型换热器优化设计的必要前提。本文建立了Z型半圆通道相变两相流的数值模型，借助已有的实验数据验证了模型的有效性。基于验证的数值模型，得出了 Z 型通道内制冷剂在不同工况下的流型，并与已有的圆管R134a流型图进行对比。对比结果表明，冷凝流型环状流区域较大，并且促进分层流向弹状流的转化；干度越小，管内换热系数越大；弹状流型下的换热效果最好，其次是环状流、分层流。研究结果对印刷电路板式换热器Z型通道的设计提供了理论依据。