Experimental Investigation of Heat Transfer Characteristics on PCHE Precooler in the Brayton Cycle for Supercritical CO2 Waste Heat Recovery

Energy saving and emission reduction is the main theme of the development of present shipbuilding industry, and the recovery of flue gas waste heat is a promising direction. The supercritical CO2 (SCO2) Brayton cycle power generation system is used to realize waste heat recovery based on its high efficiency and compact characteristics. Compared with the traditional heat exchanger, the printed circuit heat exchanger (PC HE) has the advantages of high efficiency, high temperature resistance and high pressure resistance, so it is used in SCO2 Brayton cycle power generation system. In this paper, a SCO2 Brayton cycle test platform was built, and a large number of heat transfer characteristic tests were done to verify the reliability of the PCHE test piece of this platform. The study found that within the range of working conditions studied, the friction coefficient of SCO2 decreases with the increase of its Re, and the Nu of SCO2 increases with the increase of its Re. By comparing the experimental values with the traditional friction coefficient correlation and heat transfer correlation, it is found that these empirical formulas cannot accurately predict the thermal-hydraulic characteristics of SCO2 in PCHE; in addition, studies have shown that the increase in the temperature difference on the hot side can increase the minimum heat exchanger effectiveness. This research provides support for the subsequent experimental research of SCO2 in the Brayton cycle power generation system.