Experimental Study on Small Scale Printed Circuit Heat Exchanger with Zigzag Channels

Printed circuit heat exchanger (PCHE) is a promising candidate of coolers used for SCO2 Brayton cycle. The thermal-hydraulic performance of SCO2 in a PCHE depends on the PCHE structure as well as the operating conditions of SCO2 due to its dramatic variation of thermal physical properties near the pseudo-critical point. This work experimentally investigated the thermal-hydraulic characteristics of zigzag-channel PCHEs between SCO2 and water at pressures that ranged from 8.0 to 11.0 MPa. Results showed that increasing the flow rate of SCO2 might affect the PCHE more pronouncedly in comparison with changing the flow rate of water, indicating that the major convective thermal resistance is on the SCO2 side. When increasing the operating pressure from 8.0 MPa to 11.0 MPa, the Nusselt numbers of PCHEs with zigzag angles of 0 degrees, 15 degrees, and 25 degrees averagely decrease by 63.3%, 62.1%, and 54.0%, and the friction factors averagely decrease by 28.6%, 27.4%, and 21.0% respectively. Meanwhile, it is found that the buoyancy force is non-negligible during SCO2 cooling process in PCHEs. In this regard, Nusselt number and friction factor correlations considering the buoyancy effect are proposed with applicable ranges.