CFD Modeling of End Effects of Gas Cooler Heat Exchanger for sCO2 Power Blocks

Supercritical Carbon dioxide (sCO2) Brayton cycle power blocks provide unique advantages for power generation through flexible operation and highly compact power plants. Gas cooler heat exchangers for sCO2 power blocks are crucial to help maintain ideal conditions at the compressor inlet to maximize net power output and cycle efficiencies. Design, modeling and optimization of these heat exchangers is a challenging task given the proximity of operating conditions to the critical point. Microchannel heat exchanger configurations with repeating unit cell architecture are preferred to attain compact form factors while maximizing the heat transfer rates at reasonably low-pressure drop penalties. The current work investigates the end effects of surface heat loss and bounding walls of heat exchanger stack on thermo-hydraulic performance. A hybrid approach of unit cell CFD modeling coupled with a Thermal Resistance Network (TRN) for estimating complete stack performance is presented under end effects. A compensation strategy to mitigate the variations in pinch temperature is studied under different stack configurations. The findings from the current work indicate that the presence of end effects manifests as variations of channel pinch temperatures leading to flow maldistribution across the heat exchanger stack.