Study on Heat Transfer Performance of PCHE Adapted to Physical Property Variation of SCO₂

In view of the problems, such as the near-critical state of CO₂ working fluid in the cold end of the supercritical CO₂ Brayton cycle, the physical properties change drastically with temperature, and the difficulties in design and operation control of the cold end heat exchanger, the straight channel printed circuit heat exchanger (PCHE) and the variable section channel PCHE applied to supercritical CO₂ power cycle cold end heat transfer were designed, and the flow and heat transfer characteristics of SCO₂ in PCHE of variable-section flow channel were analyzed, based on the method of segmented design of heat exchanger. SIMULINK was used to establish a simulation model of the heat exchanger, the influences of the inlet parameters on the SCO₂ outlet parameters of heat exchangers with different flow channel forms were studied when the inlet parameters deviated from the design working conditions. Results show that the designed flow channel section of gradual expansion in SCO₂ side can increase the heat transfer performance of PCHE, but the pressure loss will be increased. PCHE with flow channel cross-section of progressive expansion can better stabilize the outlet temperature of SCO₂ while the inlet parameters of the cold side and hot side deviate from the design working conditions, and the operating range of the cold end parameters can be broadened.