S–CO2 heat transfer characteristics analysis in PCHE and vertical channel

Abstract

Numerical simulations are applied to investigate supercritical carbon dioxide (S–CO2) and heat transfer characteristics in the case of uniform/nonuniform heating conditions in the straight vertical channel and printed circuit heat exchanger (PCHE). The proposed S–CO2 heat transfer correlation agrees well with the experimental values. Results show that high heat flux let S–CO2 heat transfer deterioration likely to occur. Heat transfer deterioration effect will be enhanced as S–CO2 is in area of the gas-like region. Heat transfer enhancement effect will be more significant when S–CO2 is in the area of the liquid-like region. The concept of total length is proposed which is the channel length affected by heat transfer deterioration and entrance effect together. The affected length is 55–70 times of the equivalent diameter in the case of 140 kW/m2 heat flux; the affected length is 85–125 times of the equivalent diameter in the case of 300 kW/m2 heat flux. Changes in dominance of h and λ of PCHE suggest that the convective heat transfer and heat conduction resistance strength of the fluid layer is changing. This study provides guidance for PCHE design and heat transfer enhancement.