化工学报 ›› 2016, Vol. 67 ›› Issue (4): 1244-1250.DOI: 10.11949/j.issn.0438-1157.20151178

• 流体力学与传递现象 • 上一篇    下一篇

低质量流速下超临界CO2在管内冷却换热特性

白万金1, 徐肖肖2, 吴杨杨2   

  1. 1. 重庆交通大学机电与汽车工程学院, 重庆 400074;
    2. 重庆大学动力工程学院, 低品位能源利用技术及系统教育部重点实验室, 重庆 400044
  • 收稿日期:2015-07-22 修回日期:2015-11-15 出版日期:2016-04-05 发布日期:2016-04-05
  • 通讯作者: 白万金
  • 基金资助:

    国家自然科学基金项目(51206197)。

Heat transfer characteristics of supercritical CO2 at low mass flux in tube

BAI Wanjin1, XU Xiaoxiao2, WU Yangyang2   

  1. 1. College of Mechanical and Automotive Engineering, Chongqing Jiaotong University, Chongqing 400074, China;
    2. Key Laboratory of Low-grade Energy Utilization Technologies and Systems of Ministry of Education, College of Power Engineering, Chongqing University, Chongqing 400044, China
  • Received:2015-07-22 Revised:2015-11-15 Online:2016-04-05 Published:2016-04-05
  • Supported by:

    supported by the National Natural Science Foundation of China(51206197).

摘要:

开展了低质量流速下超临界CO2在水平直管内冷却过程的换热特性的实验研究。实验压力为p=7.5~9.0 MPa,质量流速为G=79.6~358.1 kg·m-2·s-1,流体温度为25.0~50.0℃。分析了质量流速、压力、流体温度对换热的影响,并引入Richardson数阐述浮升力对超临界CO2在水平直管内冷却换热影响。实验结果表明: 传热系数随着质量流速的增加而增大。传热系数峰值点随压力的升高向高温区偏移。当质量流速较小时,传热系数峰值点出现在准临界温度之前,且浮升力作用加大,流体处于混合对流状态。将传热系数的实验值和已有的换热关联式计算值作对比后发现在低质量流速下误差较大,拟合了低质量流速工况的超临界CO2在水平直管内冷却换热的关联式,94%的实验值和拟合关联式误差在±20%范围内。

关键词: 传热, 超临界CO2, 对流, 浮升力, 准临界温度

Abstract:

An experimental investigation on the heat transfer characteristics of CO2 during gas cooling process in a horizontal tube is conducted. The experimental data is obtained over a mass flux range of 79.6-358.1 kg·m-2·s-1, inlet pressure range of 7.5-9.0 MPa and mean bulk temperature from 25.0 to 50.0℃. The effects of mass flux, pressure and bulk temperature on the heat transfer efficiency are investigated. The combined parameter of Gr/Re2 is used to quantify the buoyancy force effect on the heat transfer. The experimental results show that the heat transfer coefficient of the CO2 increases with increasing mass flux. The peak value of the heat transfer coefficient shifts to a higher temperature region as the pressure increases. It appears that the peak value of the heat transfer coefficient occurs at bulk temperature slightly lower than the pesudo-critical temperature at low mass flux. The lower mass flux is reached, the greater influence of buoyancy force effect. The experimental heat transfer coefficients are compared with some existing correlations. The predicted results present obvious deviation compared to the experimental results at low mass flux. A new heat transfer correlation for the tube is proposed based on the experimental data. The maximum error between the predicted results of the new correlation and the experimental data is 20%.

Key words: heat transfer, supercritical CO2, convection, buoyancy, pesudo-critical temperature

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