R717在微通道散热器内流动沸腾特性数值研究

Numerical Study on Flow Boiling Characteristics of R717 in Microchannel Radiator

摘要: 针对空间应用的热控任务，设计了一款矩形微通道散热器(MCHS)，以R717为工质，通过数值模拟，研究了微通道中的流动沸腾过程，重点研究了气泡生长与融合过程中的关键影响因素，深入探讨微通道内流动沸腾的流型演化，在此基础上探究其对沸腾过程中压降、换热特性的影响。结果表明：微通道中发生沸腾换热时出现的流型主要可分为泡状流、段塞流、环状流、雾状流，质量流速增大、热流密度降低、提高入口过冷度均能够延缓流型的发展。在相同热流密度下，提高质量流速对于降低壁温、提高壁面均温性有显著影响，但会随着热流密度降低而衰减。较高的热流密度与质量流速之间的匹配性较差，容易产生局部干涸现象造成壁温急剧升高。

Abstract: A rectangular microchannel heat sink (MCHS) was designed for the thermal control task of space application, using R717 as the working mass. Through numerical simulation, the flow boiling process in the microchannel was investigated, focusing on the key influencing factors in the growth and fusion of bubbles, and the evolution of the flow pattern of the flow boiling in the microchannel was deeply explored, based on which its influence on the pressure drop and the heat transfer characteristics during the boiling process was investigated. The results show that the flow patterns occurring in the microchannel when boiling heat transfer occurs can be mainly categorized into vesicular flow, segmented plug flow, annular flow, and foggy flow, and that increasing the mass flow rate, decreasing the density of heat flow, and increasing the inlet subcooling degree can retard the development of the flow patterns. At the same heat flow density, increasing the mass flow rate has a significant effect on lowering the wall temperature and increasing the wall homogeneity, but it will be attenuated with the decrease of heat flow density. The match between higher heat flow density and mass flow rate is poor, and it is easy to produce local drying phenomenon resulting in a sharp increase in wall temperature.