Numerical study of the flow and heat transfer of supercritical CO2 flowing in various vertical serpentine tubes
HUANG Teng1, LI Xuefang1, CHRISTOPHER D M2, BA Qingxin1, CHENG Lin1
1. Institute of Thermal Science and Technology, Shandong University, Jinan 250061, China; 2. Key Laboratory of Thermal Science and Power Engineering of Ministry of Education, Department of Energy and Power Engineering, Tsinghua University, Beijing 100084, China
Abstract：As an environmentally friendly natural refrigerant, CO2 has been increasingly used as the working fluid in heat pumps. The flow and heat transfer of supercritical CO2 flowing in various serpentine tubes were modeled here to investigate the influence of the tube geometry on the heat transfer and to investigate the heat transfer enhancement mechanisms. Twelve full-size three-dimensional geometries were generated with different inner diameters and bend diameters to investigate the effects of the tube inner diameter and bend diameter on the flow and heat transfer of supercritical CO2 for a given flow flux. The results show that the heat transfer coefficient decreases as both the bend diameter and the inner diameter decrease. Thus, the outer wall temperature increases more rapidly and is higher with larger inner diameters and tube bend diameters. Finally, the effects of flow direction on the heat transfer were also studied to show that upward flow results in a higher heat transfer coefficient than downward flow for inner diameters larger than 1 mm. The present results are useful for enhanced heat exchanger designs to improve system efficiencies.
黄腾, 李雪芳, 柯道友, 巴清心, 程林. 不同几何参数竖直蛇形管内超临界压力CO2流动与换热数值模拟[J]. 清华大学学报（自然科学版）, 2020, 60(3): 263-270.
HUANG Teng, LI Xuefang, CHRISTOPHER D M, BA Qingxin, CHENG Lin. Numerical study of the flow and heat transfer of supercritical CO2 flowing in various vertical serpentine tubes. Journal of Tsinghua University(Science and Technology), 2020, 60(3): 263-270.
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2020, Vol. 60 
