CIESC Journal ›› 2019, Vol. 70 ›› Issue (5): 1779-1787.DOI: 10.11949/j.issn.0438-1157.20181440

• Fluid dynamics and transport phenomena • Previous Articles     Next Articles

Convective heat transfer of supercritical CO2 flowing a mini circular tube under high heat flux and low mass flux conditions

Jianguo YAN(),Fengling ZHU,Pengcheng GUO(),Xingqi LUO   

  1. State Key Laboratory of Eco-hydraulics in Northwest Arid Region, Xi’an University of Technology, Xi’an 710048, Shaanxi,China
  • Received:2018-12-05 Revised:2019-02-22 Online:2019-05-05 Published:2019-05-05
  • Contact: Pengcheng GUO

高热流低流速条件下超临界CO2在小圆管内的对流传热特性

颜建国(),朱凤岭,郭鹏程(),罗兴锜   

  1. 西安理工大学省部共建西北旱区生态水利国家重点实验室,陕西 西安 710048
  • 通讯作者: 郭鹏程
  • 作者简介:<named-content content-type="corresp-name">颜建国</named-content>(1987—),男,博士,讲师,<email>jgyan@ xaut.edu.cn</email>|郭鹏程(1975—),男,博士,教授,<email>guoyicheng@xaut.edu.cn</email>
  • 基金资助:
    中国博士后科学基金项目(2018M633546);国家自然科学基金项目(51479166);陕西省教育厅科学研究计划专项项目(17JK0560)

Abstract:

To obtain the heat transfer law of supercritical CO2 under high heat flow and low flow rate, the experimental study on convective heat transfer of supercritical CO2 in a small circular tube with an inner diameter of 2 mm was carried out, and the effects of variable properties, buoyancy and thermal acceleration were discussed. The operating parameters were as follows: system pressure p = 7.6—8.4 MPa, mass flux G = 400—500 kg/(m2?s), heat flux q = 0—200 kW/m2, fluid temperature T b = 20—62℃, and Reynolds number Re = 1.23×104—4.3×104. The dimensionless parameters of Gr/Re 2 and Kv were adopted to represent the buoyancy effect and thermal acceleration, respectively. The results show that the buoyancy effect is significant (Gr/Re 2 > 10-3) under high heat flux and low mass flux conditions, and the heat transfer coefficients at top wall are always lower than those at bottom wall for a certain section. The buoyancy effect is the main factor that cause heat transfer deteriorate, while the thermal acceleration criterion is insignificant (Kv < 8.5×10-7) and thus can be neglected. The experimental data were compared with typical heat transfer empirical correlations, in which the Liao-Zhao correlation fit well with the experimental data.

Key words: supercritical CO2, heat transfer, flow, buoyancy, empirical correlation

摘要:

为获取高热流、低流速条件下超临界CO2的传热规律,开展了超临界CO2在内径2 mm水平小圆管内对流传热试验研究,并重点探讨了变物性、浮升力和热加速等效应对传热过程的影响。试验参数范围:系统压力7.6~8.4 MPa,质量流速400~500 kg/(m2?s),热通量0~200 kW/m2,流体温度20~60℃,Reynolds数1.2×104~4.3×104。分别采用Gr/Re 2Kv作为浮升力效应和热加速效应的判别因子。结果显示,在高热流低流速工况下,浮升力效应显著(Gr/Re 2 > 10-3),同一个截面处的上壁面传热系数始终小于下壁面传热系数。浮升力效应是高热流低流速工况下传热恶化的主要诱发因素。试验中热加速因子较小(Kv < 8.5×10-7),其效应可以忽略。将试验数据与典型的传热经验关联式作对比,结果表明Liao-Zhao关联式的计算结果与试验结果最吻合。

关键词: 超临界二氧化碳, 传热, 流动, 浮升力, 关联式

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