| 摘要: |
| 本文对水平细通道内CO2流动沸腾换热过程中流态及其转变特性进行理论分析和可视化实验研究。根据可视化实验结果，更新了CO2在低蒸发温度下的理论流动状态预测模型。实验工况为：热流密度（7.5~30 kW/m2）、质量流率（50~600 kg/(m2?s)）、饱和温度（﹣40~0 ℃）、干度（0~1）、内径（1.5 mm）。理论分析表明：质量流率对换热过程中经历的流态形式有决定性作用，热流密度对环状流-干涸区域、干涸区域-雾状流边界转变曲线影响较大，饱和温度对流态转变有重要影响。可视化研究表明：基于理论流态图对于CO2在细通道内流动沸腾换热的流态能够较好的预测，也能反映不同工况下流态的变化趋势，但理论流态图对干涸区域和雾状流区域预测偏差较大；在实验数据的基础上，增加了液气粘度比的无量纲因子，并提出一种新的临界热流密度预测模型。在考虑质量流量和热通量影响的情况下，根据更新后临界热流密度预测模型和实验数据，引入沸腾数Bo值对理论流态图中环状流-干涸区域、干涸区域-雾状流及间歇流/弹状流-环状流边界转变曲线进行了更新，可视化研究获得的流态数据89.4%符合更新后的CO2理论流态预测模型。 |
| 关键词: CO2 细通道 流动沸腾 流态图 |
| DOI： |
| Received:August 24, 2018Revised:March 02, 2019 |
| 基金项目:上海市部分地方院校能力建设专项计划（16060502600）资助。 |
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| Experimental Study on Flow Pattern Characteristics of CO2 during Flow Boiling Heat Transfer Process in a Horizontal Tubule |
|
Zhang Liang1, Liu Jianhua1, Wu Qingqing1, Jiang Linlin1, Zhao Yue2
|
| (1.Refrigeration Technology Institute University of Shanghai for Science and Technology;2.Shanghai Institute of Metrology and Measurement Technology) |
| Abstract: |
| In this paper, theoretical analysis and visual experimental research are reported on the flow-state characteristics during the heat transfer of CO2 flow boiling in a horizontal tubule. A CO2 theoretical flow-state prediction model under low evaporation temperature is updated based on visual experimental results. Experimental conditions are as follows: heat flux (7.5–30 kW/m2), mass flow rate (50–600 kg/(m2?s)), saturation temperature (?40 to 0 °C), vapor quality (0–1), and inner diameter (1.5 mm). Theoretical analysis indicates that the mass flow rate determines the flow pattern experienced during the boiling process. The form of annular-dryout and the dryout-mist flow areas in the theoretical flow pattern diagram mainly depends on the heat flux of boiling, while the flow-state transition depends on the saturated temperature. Visual research shows that the flow pattern prediction of CO2 during boiling in the horizontal tubule was satisfactory based on the theoretical flow pattern chart, as well as the trend under different conditions. However, there was a large deviation between the dry region and the mist flow region under experiment conditions. Thus, an updated critical heat flux prediction model was proposed based on experimental data by adding dimensionless factors of the liquid-gas viscosity ratio. Based on the updated model and experimental data, the transition curves of the annular flow-dry region, dry region-mist flow, and intermittent flow/slug flow-annular flow in the primary theoretical flow pattern chart were updated by introducing the boiling number Bo, considering the effect of mass flow rate and heat flux. ,89.4% of the flow pattern data obtained from the visualization study is consistent with the updated model. |
| Key words: CO2 tubule flow boiling flow pattern diagram |
