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A novel airfoil fin (AFF) Printed Circuit Heat Exchanger (PCHE) with a 100 kW class heat transfer capacity was experimentally tested as a cooler in a supercritical CO2 system. Numerical analysis was also conducted to have an insight into the flow and heat transfer mechanism in the AFF channels. The results showed that the novel AFF structure has superior hydraulic performance as the pressure drop in the AFF PCHE is only about 1/6 of that in the zigzag channel PCHE with a comparative heat transfer rate. In comparison with the mass flow rate and operating pressure, the inlet temperature has relatively insignificant effect on the heat transfer rate and pressure drop in the AFF heat exchanger. The broadening of the fin has no obvious improvement in heat transfer coefficient but increases the friction factor massively, and thereby resulting in worse comprehensive performance in the fin channel. At smaller temperature and mass flow rate, the periodic fluctuations of the heat transfer coefficient and comprehensive performance criterion could be weakened significantly. In addition, the determinant effect of the effective thermal conductivity in the viscous sublayer and buffer layer on local heat transfer coefficient is also validated in AFF channels.

To improve the performance of waste heat recovery, a novel airfoil fins heat exchanger was applied to flue gas waste heat recovery. Two groups of experimental conditions were installed to test the heat effectiveness of the novel airfoil fins heat exchanger. The results showed that the heat effectiveness of the novel airfoil fins heat exchanger could reach more than 96%, which is higher than the conventional heat exchanger. The thermal–hydraulic performances of the novel airfoil channel, NACA 0020 airfoil channel and zigzag channel were investigated with the first and second laws of thermodynamics, which showed that the novel airfoil channel has the best comprehensive thermal–hydraulic performance among the three channels. The correlations of Nusselt number and friction factor of the novel airfoil fins heat exchanger were proposed for flue gas, whose maximum deviations were within ±5.0% and ±7.1%, respectively. The present work could provide guidance for the application of the novel airfoil fins heat exchanger in waste heat recovery.

A novel heat exchanger unit structure was adopted to improve the thermal–hydraulic performance of compressed humid air and high-temperature flue-gas in a megawatt (MW) grade humid air turbine (HAT) cycle. Staggered airfoil fin channels and rectangular straight fin channels were projected for the compressed humid air and flue-gas, respectively. A three-dimensional model of the heat exchanger unit structure was built to simulate the heat transfer and flow of flue-gas and compressed humid air under different moisture content, mass flow-rate, and inlet temperature of humid air. The thermal–hydraulic performances of staggered airfoil channels were contrasted with that of straight and zigzag channels. The results showed that the airfoil channel has the best comprehensive thermal–hydraulic performance. Heat transfer and friction factor correlations were proposed to predict thermal–hydraulic performances of the compressed humid air flowing in the airfoil channel. The effects of moisture content on the heat transfer and flow characteristics were quantitatively described using correlations. The moisture content of the humid air is the main influence factor on heat transfer performance. In present study, the results and correlations can provide guidance for the design and application of recuperator structures with airfoil fins for the MW grade HAT cycle.