Forced Convection Heat Transfer Outside Enhanced Tubes with Different Surface Structures

Abstract

To promote the development of enhanced tubes in heat exchangers, forced convection experiments were carried out using R410A in the annular region outside enhanced tubes. Three enhanced tubes were investigated by experiments to evaluate the heat transfer performance; with different surface structures of novel fin arrays (C-enhanced tube), newly-developed combined dimples (L-enhanced tube) and sandblasted surface (P-enhanced tube); with the 19.05 mm outer diameter; with mass flow rate range of 40-110 kg/m²s. For single-phase and condensation experiments at various saturation temperatures, the C-enhanced tube showed the best heat transfer performance and produced heat transfer coefficients of 4.25 and 3.8 times that of the smooth tube. The results of changing outlet vapor quality (0.3-0.8) of flow boiling experiments indicated that the L-enhanced tube showed the best evaporation characteristics and yielded heat transfer coefficients 2.1-3.9 times that of the smooth tube. Surprisingly, instead of showing the heat transfer performance advantage of the P-enhanced tube, heat transfer deterioration occurred despite numerous micro dimples on the surface. In addition, the pressure drop characteristics were also discussed, and the experimental results were evaluated by empirical correlations.

Disclosure statement

No potential conflict of interest was reported by the authors.

Additional information

Funding

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

Notes on contributors

Zeguan Dong

Zeguan Dong is a master student at Eletromechanical Engineering College, Qingdao University of Science and Technology, Shandong, China. He received his Bachelor’s degree from the same university in 2018. Currently, he is working on the experimental and theoretical analysis of forced convection heat transfer inside and outside enhanced tubes with different surface structures.

Jianghui Zhang

Jianghui Zhang received his master’s and Ph.D. degrees from 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.

Zhen Li

Zhen Li is a master 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 and got a master's degree in 2020. Currently, he is working on the experimental and theoretical analysis of flow boiling and condensation heat transfer in annular space outside heat transfer tubes.

Jiacheng Wang

Jiacheng Wang is a master student at Eletromechanical Engineering College, Qingdao University of Science and Technology, Shandong, China. He received his Bachelor’s degree from the same university in 2019. Currently, he is working on the experimental and theoretical analysis of two-phase flow and enhanced heat transfer.

Shangqing Liu

Shangqing Liu is a master 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 and got a master's degree from Qingdao University of Science and Technology in 2020. 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.

Yan He

Yan He is currently the dean of The School of Mechanical and Electrical Engineering and the Dean of the School of Intelligent Manufacturing, Qingdao University of Science and Technology. She is also a professor, doctoral supervisor and Taishan Scholar of Shandong Province (NO. ts20190937). Her focus is on the cross-fields of engineering thermophysics and materials, chemical industry, and carry out research work around major national needs and the main economic battlefield. The main research directions include: the preparation of carbon nanomaterials and the research and development of processes and equipment involved in the application field; research and development of micro-channel and micro-reaction equipment and technology; research and development of 3D printing technology and equipment.