Numerical Investigation of Thermohydraulic Characteristics in Supercritical CO₂ Natural Circulation Loop with Spatially Varying Temperature

Abstract

Investigation of thermohydraulic characteristics is highly significant for any natural circulation loop (NCL) applications. The physical properties of supercritical fluids are highly sensitive to temperature when they cross pseudo-critical points. In the current study, steady state thermohydraulic characteristics of NCL with a spatially varying temperature distribution on the source along with different orientations of the source and sink are numerically investigated. A three-dimensional rectangular NCL with a uniform diameter and constant length of source and sink is modeled. The temperature of the sink is held constant, while the temperature of the source varies spatially with local maximum and minimum temperatures. The system performance is investigated for four different operating pressures ranging from 8 to 12 MPa. The mass flow rate is observed to increase with increasing operating pressure for all orientations and heat load distribution at the source. The results also indicate that heat transfer degrades when the fluid crosses the pseudo-critical point. It has been noticed that spatially varying temperature distribution has a maximum of 48% heat transfer variation compared to the constant temperature distribution. Furthermore, a source or sink located in the horizontal leg performs better than the vertical leg.

Acknowledgment

The authors acknowledge the support and computational facilities provided by the Vellore Institute of Technology–Vellore and CO₂ Research and Green Technologies Centre, for carrying out this research work.

Disclosure statement

No potential conflict of interest was reported by the authors.

Additional information

Notes on contributors

Vignesh Boopalan

Vignesh Boopalan is a Ph.D. research scholar at Vellore Institute of Technology in Vellore, India. He received his master’s degree from the Kingston University London, United Kingdom in 2019 in Aerospace Engineering. His research interests are in the field of fluid dynamics and heat transfer. He is currently developing a supercritical CO₂ natural circulation flow system for a various sustainable energy application.

Parthasarathy Rajesh Kanna

Parthasarathy Rajesh Kanna is a Professor in the CO₂ Research and Green Technologies Research Center, Vellore Institute of Technology Vellore, India. He received his Ph.D. from Indian Institute of Technology Guwahati, India in 2006 and master’s from Bharathiar University, India (2000). He has coauthored more than 90 international publications including refereed journals and conferences. He received his D.Sc. degree from Cracow University of Technology, Poland (2015). His research interests include fluid dynamics, heat transfer, CO₂ refrigeration and green energy technologies.

Senthil Kumar Arumugam

Senthil Kumar Arumugam obtained his doctoral degree from Indian Institute of Science, Bangalore in the field of cryogenics. He carried out his post-doctoral research in the field of sub-millimeter gravitational force at Washington University in St. Louis, USA. He has more than 30 years of experience in teaching and research. His research interests include cryogenic heat pipes, CFD analysis of steam turbine exhaust-hood, transcritical CO₂ refrigeration, and solid hydrogen extrusion. He has successfully handled three funded research projects and six consultancy projects. He has published over fifty research papers in international Journals and conferences. He is a fellow of Institution of Engineers, India.