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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。
Z-Channel Printed Circuit Heat Exchanger is widely used in the field of liquefied natural gas and other fields. Understanding the heat transfer characteristics of the flow condensation in the Z-channel is the necessary prerequisite for the optimal design of this type of heat exchanger. In this paper, a numerical model of phase-change two-phase flow in a semicircular channel of Z-shape is established. The validity of the model is verified by the available experimental data. Based on the verified numerical model, the flow pattern of refrigerant in Z-type channel under different operating conditions was obtained and compared with the existing flow pattern of circular tube R134a. The comparison results show that the condensing flow pattern annular flow area is larger and promotes the stratified flow to the slug flow conversion; the smaller the dryness, the larger the heat transfer coefficient in the tube; the heat exchange under the slug flow pattern is the best, followed by Is a circular flow, stratified flow. The results provide a theoretical basis for the design of Z-type channel of PCB heat exchanger.