Abstract

This paper presents critical analysis of process modeling and mechanisms of CO₂ evaporation inside macro- and micro-channels. First, some existing experimental results of CO₂ evaporation heat transfer in macro-channels and micro-channels are compared and discussed. Then, the comprehensive two-phase flow pattern map of Cheng et al. for CO₂ evaporation inside channels is presented. The flow pattern map has widely been used to predict flow patterns of CO₂ evaporation processes and favorably agrees with observed CO₂ two phase flow patterns in various channels. Next, the Cheng et al. generalized CO₂ evaporation heat transfer model based on flow patterns is compared to the experimental data. It has been proved that the heat transfer model favorably agrees with the experimental data by many researchers over the past decade. Simulation results of evaporation heat transfer in both macro- and micro-channels using the model are also presented. Furthermore, evaporation heat transfer mechanisms are analyzed from the flow regime variations and unstable evaporation heat transfer characteristics in both macro- and micro-channels. Finally, applications of the Cheng et al. CO₂ evaporation heat transfer model in evaporator design for various thermal systems are reviewed. Future research needs are identified according to this comprehensive analysis and review.

摘要

本文对宏观和微通道内的 CO _{2蒸发过程建模和机制进行了批判性分析。}首先对已有的大通道和微通道中CO ₂蒸发传热的一些实验结果进行了比较和讨论。然后，Cheng 等人的综合两相流模式图。介绍了通道内的 CO ₂蒸发。流动模式图已广泛用于预测CO ₂蒸发过程的流动模式，并且与观察到的各种通道中的CO ₂两相流动模式一致。接下来，Cheng 等人。广义CO ₂基于流动模式的蒸发传热模型与实验数据进行了比较。过去十年来，许多研究人员已经证明，传热模型与实验数据吻合得很好。还给出了使用该模型对宏通道和微通道中的蒸发传热进行的模拟结果。此外，还从宏观和微通道中的流态变化和不稳定的蒸发传热特性分析了蒸发传热机理。最后，Cheng 等人的应用。综述了各种热力系统蒸发器设计中的CO ₂蒸发传热模型。根据这一综合分析和审查确定未来的研究需求。