Experimental and numerical investigations on convective heat transfer characteristics of sCO2 in a 10 mm horizontal pipe

Abstract

This study examines heat transfer characteristics of sCO₂ in horizontal tubes with an inner diameter of 10 mm on a self-built experimental system. The effects of operating parameters on heat transfer were investigated. The results indicate that elevating the mass flow rate significantly improves sCO₂ heat transfer efficiency and mitigates heat transfer deterioration (HTD). Conversely, higher inlet temperatures, pressures, and heat flow densities intensify wall temperatures, exacerbating HTD. Moreover, a novel parameter have been mentioned for sCO₂ in the horizontal tube, as the critical heat-to-mass ratio ((q/G)_max).The overall heat transfer performance of sCO₂ will be optimized when the q/G is adjusted to 0.17. Deviation from this value (0.17) may result in HTD. The mechanism of HTD in the horizontal tube was investigated through analysis of thermophysical properties velocity, distribution and turbulent kinetic energy of sCO₂. Finally, new convective heat transfer correlations were proposed by considering the effect of buoyancy force, with more than 90 % of heat transfer coefficient predictions falling within ±20 % relative error. This model can provide insights for the design and operational safety of heat exchange equipment in Brayton cycle coal-fired power generation systems.