Prof. Lixin Cheng

Department of Engineering and Mathematics, Sheffield Hallam University,

City Campus, Howard Street, Sheffield S1 1WB, UK

Bio

Lixin Cheng obtained his Ph.D. in Thermal Energy Engineering at Xi’an Jiaotong University, China in 1998. He has worked at Sheffield Hallam University, UK since 2016 and has extensive international work experience at several universities in China, UK, Netherlands, Germany, Switzerland and Denmark for more than 24 years. He has received several prestigious awards such as Alexander von Humboldt Fellowship in Germany in 2006, an ERCOFTAC Visitor Grant in Switzerland in 2010, an Oversea Talent Professorship of the City of Beijing at Beijing University of Technology, China in 2016 and the best paper awardee of the 6th World Congress on Momentum, Heat and Mass Transfer (MHMT’2021) in 2021. His research interests are multiphase flow and heat transfer, microscale and nanoscale fluid flow and heat transfer, thermal energy engineering, thermal management and high heat flux cooling, utilization of CO2 for energy systems, decarbonized heating and cooling technology and energy systems and sustainability. He has published more than 140 papers in journals and conferences, 9 book chapters and edited 10 books/ebooks. He has delivered more than 65 keynote/invited lectures worldwide. He is the congress chair of the World Congress on Momentum, Heat and Mass Transfer (MHMT) since 2017. He is one of the founders and co-chair of the International Symposium of Thermal-Fluid Dynamics (ISTFD) held in Xi’an in 2019. He is associate editor of Heat Transfer Engineering and Journal of Fluid Flow, Heat and Mass Transfer. He is on the Scientific Organizing Committee and a leading scientist of the 10th Conference on Experimental Heat Transfer, Fluid Mechanics and Thermodynamics (ExHFT-10), Greece in 2024, International Scientific Committee of the 2024 International Conference on Supercritical CO2 Power Cycle and Comprehensive Energy Systems (ICSPC2024), Shanghai, China in 2024, a member of Editorial Board of IET Smart Energy Systems and an international advisor of Thermal Power Generation (a Chinese journal).

Title

Generalized mechanistic heat transfer models for CO2 evaporation in macro- and micro-channels: perspective and latest version

Abstract

Applications of CO2 in various thermal and energy systems can improve energy efficiency and environment safe. CO2 is widely used in geothermal energy utilization, hybrid power and heat systems, solar energy utilization and recovery of industrial waste heat, electronic cooling, two-phase thermosyphon loop and evaporative carbon dioxide cooling systems. As the effects of peculiar thermophysical properties of CO2, favorable evaporation heat transfer characteristics of CO2 can be achieved. However, CO2 evaporation heat transfer behaviors and mechanisms at low reduced pressures are quite different from those at high reduced pressures. In order to design CO2 evaporators, it is essential to develop generalized mechanistic evaporation heat transfer models based on flow patterns for macro- and micro-channels. Such models intrinsically relate flow patterns to evaporation heat transfer mechanisms. They do not only predict the heat transfer coefficients but also capture the heat transfer trends such as dryout occurrence and completion. However, due to the limitation of CO2 evaporation and two phase flow database, the previous models do not work for CO2 evaporation heat transfer at low reduced pressures. Therefore, the models have been updated based on the new database including more than 6000 experimental heat transfer data for better prediction of CO2 evaporation in macro- and micro-channels. This lecture presents the perspective for developing the latest version of the mechanistic heat transfer models for CO2 evaporation at a wide range of the reduced pressures from 0.1332 to 0.9082 (the corresponding saturation temperature from -40 to 27C), the channel diameter from 0.5 to 10 mm, the heat flux from 2 to 72 kW/m2 and the mass flux from 100 to 1500 kg/m2s. First, a comprehensive diabatic flow pattern map has been developed by considering evaporation heat transfer mechanisms for various flow patterns. New criteria for dryout and mist flow regimes have been proposed. Then, generalized flow boiling heat transfer models have been proposed based on the flow pattern map. The latest developed models favorably predict the experimental database. The models are applicable to the design of carbon dioxide evaporators for various thermal and energy systems.