NUMERICAL STUDIES ON THERMAL-HYDRAULIC PERFORMANCE AND CORRELATIONS OF PRINTED CIRCUIT HEAT EXCHANGER WITH ZIGZAG CHANNEL FOR SUPERCRITICAL CO2 POWER CYCLE

The supercritical carbon dioxide Brayton cycle is a key technology in VHTR (Very High Temperature Reactor). The compact heat exchanger, PCHE (printed circuit heat exchanger) is one of the most important devices in supercritical CO2 power cycle. In this research, 3D PCHE unit model with semicircle zigzag channel with diameter of 1.9 mm is established and computed using CFD methods. The numerical methods and geometric model are firstly verified by comparison with previous experimental results. Numerical simulation is performed with inlet pressure of 7.5 MPa/8.1 MPa, inlet temperature varied from 313.15 K to 373.15 K, and mass flux varied from 400 kg/(m2 •s) to 800 kg/(m2 •s) in the side of supercritical CO2. Thermal-hydraulic characteristics of the zigzag PCHE were investigated in this paper. The pitch average local heat transfer coefficient is defined. The relationship between the pitch averaged local heat transfer coefficient and total average heat transfer coefficient is analyzed and discussed based on the numerical results. The effects of the thermo-physical property variations of supercritical CO2 and the channel structure on the heat transfer and flow are discussed. Visual analysis is applied to show the velocity profile, pressure profile and temperature profile, which are of great help for performance analysis of PCHE. A new correlation is developed based on the numerical results in the present study considering the effects of thermo-physical property variations and channel structures, which is of great significance for the design and optimization of zigzag PCHE.