S-CO_2 heat transfer characteristics analysis in PCHE and vertical channel

摘要

Numerical simulations are applied to investigate supercritical carbon dioxide (S-CO_2) 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-CO_2 heat transfer correlation agrees well with the experimental values. Results show that high heat flux let S-CO_2 heat transfer deterioration likely to occur. Heat transfer deterioration effect will be enhanced as S-CO_2 is in area of the gas-like region. Heat transfer enhancement effect will be more significant when S-CO_2 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/m~2 heat flux; the affected length is 85-125 times of the equivalent diameter in the case of 300 kW/m~2 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.