Experimental Study of Flow Boiling and Condensation in Tubes with Pin-Fin and Metallic Foam Structures

Abstract

Appropriate arrangement of the fin structures in the evaporator and condenser not only enhances the heat transfer coefficient but also suppresses the increase of pressure drop. Due to this reason, a new method of using large-scale pin fins is explored to increase the heat transfer area and to modify the liquid film flow characteristics in the enhanced tubes. In the present study, four enhanced tubes and one plain tube were manufactured by selective laser melting. The working fluid is R407C and the enhanced tubes are eight short pin fins tube, five long pin fins tube, twisted pin fins tube and a tube filled with metallic foam. The results show that the shorter fin tube has the largest heat transfer coefficient for condensation at 3967 W/m²⋅K and the metallic foam tube demonstrates the largest heat transfer coefficient for boiling at 10606 W/m²⋅K. However, the shorter fins have the highest efficiency indices based on the heat transfer coefficient-pressure drop evaluation criterion and the heat transfer coefficient-area evaluation criterion. For condensation, the indices are 1.28 and 1.35, respectively. For boiling, the indices are 2.55 and 1.62, respectively.

Additional information

Funding

The SLM 250 equipment used in this research is supported by the National Research Foundation, Prime Minister’s Office, Singapore under its Medium-Sized Centre funding scheme.

Notes on contributors

Xu Wen Wang

Xu Wen Wang is an Assistant Professor in the School of Mechanical and Electrical Engineering of Guilin University of Electronic Technology, China. He received the Ph.D. degree from University of Chinese Academy of Sciences, China in 2016. His main research interests are in boiling and condensation heat transfer and thermal energy storage.

Jin Yao Ho

Jin Yao Ho is an International Postdoctoral Scholar in the School of Mechanical and Aerospace Engineering at Nanyang Technological University (NTU), Singapore. He received the Ph.D. degree from NTU, Singapore in 2019. He is currently a Visiting Scholar in the Mechanical Science and Engineering Department of the Grainger College of Engineering at the University of Illinois at Urbana-Champaign, USA. His main research interests are in condensation heat transfer and additive manufacturing. He is a Registered Professional Mechanical Engineer in Singapore.

Kai Choong Leong

Kai Choong Leong is an Associate Professor in the School of Mechanical and Aerospace Engineering and Fellow of the Renaissance Engineering Programme at Nanyang Technological University (NTU), Singapore. He received the Ph.D. degree from the University of Queensland, Australia in 1999. His research interests are in single- and two-phase heat transfer (boiling, condensation, solidification/melting), additive manufacturing (3-D Printing) of heat transfer devices, adsorption refrigeration and potable water generation. He has been principal investigator for many research projects funded by NTU and external funding agencies and is the author or coauthor of more than 100 papers in refereed international journals, 79 papers in conference proceedings and 5 book chapters. He is a past President of the American Society of Heating, Refrigerating, and Air-Conditioning Engineers (ASHRAE), Singapore Chapter, a Senior Member of the Institution of Engineers, Singapore and a Registered Professional Mechanical Engineer in Singapore.

Teck Neng Wong

Teck Neng Wong is an Associate Professor in the School of Mechanical and Aerospace Engineering at Nanyang Technological University (NTU), Singapore. He received the Ph.D. degree in Mechanical Engineering from the University of Strathclyde, UK in 1990. His research interests focus on two-phase flow and heat transfer in microchannels. He has published numerous top quality international journal papers, conference papers, and book chapters and holds several patents.