Evaporation Heat Transfer of R134a on outside of Smooth and Enhanced Tubes

Abstract

Increasing attention has been paid to the flow and heat transfer in annular channels since their intensive applications in engineering. In this study, evaporation of the outer surface of two enhanced heat transfer tubes (2EHT) was compared to the performance of a smooth surface copper tube through experimental research. The refrigerant flowed in an annular space between the outer tube and the test tube. The outside and inside diameters of tubes used in this study were 19.05 and 17.10 mm, respectively. Tests were performed using refrigerant R134a as the working fluid, over the saturation temperature of 6 °C for evaporation, the quality range of 0.1–0.8 and the mass fluxes is from 30 to 58 kg/m²s. It is observed that through different surface structures, the heat transfer area increased, while both the nucleate boiling and convective boiling were improved, leading to the heat transfer coefficient of 2EHT being significantly enhanced. According to the evaluation, the evaporation enhanced tube had better enhancement effect. Finally, correlation analysis was conducted based on experimental data. The results from correlation analysis can be implemented to predict the experimental heat transfer coefficients within a deviation of ±10%.

Additional information

Funding

This work was supported by the national key research and development projects under Grant 2017YFB0602901-4.

Notes on contributors

Zhen Li

Zhen Li is a M.E. student at Eletromechanical Engineering College, Qingdao University of Science and Technology, Shandong, China. He received his Bachelor’s degree from the same university in 2016. Currently, he is working on the experimental and theoretical analysis of flow boiling and condensation heat transfer in annular space outside heat transfer tubes.

Shangqing Liu

Shangqing Liu is a M.E. student at Eletromechanical Engineering College, Qingdao University of Science and Technology, Shandong, China. He received his Bachelor’s degree from Qilu University of Technology in 2017. He is currently working on enhanced heat transfer in evaporation and condensation heat exchange tubes under experimental aspect. At present, several Chinese and English papers have been published on this aspect.

Jianghui Zhang

Jianghui Zhang received his master’s and Ph.D. degrees in Qingdao University of Science and Technology, Shandong, China. He received his Bachelor’s degree from the same university in 2009. In recent years, he has presided over four research projects on energy conservation and emission reduction, and published more than eight papers. He presided or participated in more than 50 consultation projects on energy audit in enterprises, which has achieved remarkable environmental and social benefits.

Lan Zhang

Lan Zhang is a M.E. student at Eletromechanical Engineering College, Qingdao University of Science and Technology, Shandong, China. She received her Bachelor’s degree from University of Science and Technology Liaoning in 2016. Currently, she is working on theoretical research and analysis of numerical simulation of evaporation and condensation heat and mass transfer in enhanced heat exchange tubes.