Thermal-Hydraulic Performance of a Printed Circuit Heat Exchanger in a CO2-H2O Heat Exchange Process under Different Mass Flow Rates
A printed circuit heat exchanger based on the technologies of chemical etching and diffusion bonding has advantages of compactness and efficiency in high pressure or high temperature applications. Considering efficiency and safety, it is very important to evaluate this new type heat exchanger under unstable working condition, especially in high pressure or high temperature systems. In this article, a numerical study is carried out to investigate the heat transfer and pressure drop characteristics in a CO2-H2O heat exchange process just like CO2 cooling or H2O heating. The results show that the heat transfer coefficient in the CO2 side has a parabolic distribution along the flow direction and moves or backward when changing the CO2 mass flow rate, which plays a major role in constituting the heat exchanger’s main thermal resistance in the entrance and exit region. In a CO2 cooling process, the heat transfer coefficient in CO2 side will gradually increase when the temperature of CO2 decreases to approach the pseudo-critical point, which may be caused by the increasing specific heat. However, the heat transfer coefficient will gradually decrease when the temperature is away from the pseudo-critical point, which will be unfavorable for further reduction in heat exchanger size. Unlike in water side, the pressure drop per length of CO2 gradually decreases in the flow direction. The Filonenko equation overestimates the total pressure drop.