Heat transfer and friction of molten salt and supercritical CO₂ flowing in an airfoil channel of a printed circuit heat exchanger

Airfoil printed circuit heat exchanger (PCHE) is considered as one of the competitive candidates in the 3rd generation of concentrating solar power (CSP) plant, where the molten salt and supercritical carbon dioxide (S-CO₂) are adopted as the heat transfer fluids (HTFs). To study the flow features and heat transfer performance of the two HTFs in the airfoil channel of PCHE, a three-dimensional numerical model was firstly developed and validated by experiment. Then, the friction features and heat transfer of the two HTFs under different mass flow rate and inlet temperature conditions were numerically investigated. Then, the performance of distributed airfoil channels was compared with that of straight channels and zigzag channels. Finally, the heat transfer and friction factor correlations were fitted for the two HTFs in the airfoil channel of PCHE, which can be used in relatively wide ranges of Reynolds number and temperature. The results show that the larger inlet temperature leads to higher heat transfer performance for molten salt, but causes lower heat transfer performance for S-CO₂. The airfoil channels have the best comprehensive heat transfer performance among these three channels at the given pumping power. Moreover, the maximum deviations between the simulation results and the proposed heat transfer correlations are within ±6% for both the molten salt and S-CO₂. Finally, the maximum deviations between the proposed friction correlations and the calculated results are within ±4% and ±8% for the salt and S-CO₂, respectively. The correlations and results given in current study can contribute to the design and application of airfoil PCHEs in the 3rd generation of CSP plant.