In this paper, a comprehensive transient three-dimensional model for heat transfer performance and flow resistance is applied to investigate the characteristics of a fin-and-tube heat exchanger with an H-typed fin. The overall and local dynamic response performance of Nu number and Eu number under volatile flow conditions are analyzed in detail. The results indicate that for the H-typed fin-and-tube heat exchanger, both the heat transfer and the fluid flow are influenced by volatile flow, which consists of three key parameters, time-averaged velocity, volatile amplitude, and the cycle time. Correlations of Nu number and Eu number for each case of volatile flow conditions are presented.

The comprehensive performance of heat exchangers is represented by the maximum thermal transfer, the minimum pressure loss, and the smallest pumping power. In recent years, the application of longitudinal vortex generators is developed as an effective technique and important research topic, which could increase the heat transfer enhancement of compact heat exchangers. A 3-D CFD numerical simulation is successfully carried out on thermohydraulic characteristics of the fin-and-tube compact heat exchanger with new types of vortex generators. The effects of six different arrangement of delta winglets are studied, which are front-up-rear-down, front-down-rear-up, common-flow-up, and common-flow-down. In addition, there are also different direction of hole position in the same delta winglets arrangement. The investigation of thermal-hydraulic performance is conducted for Reynolds number in the range of 204-2034. The overall and local performance comparisons among the fin with delta winglets and the wavy fin are performed. Then, the comprehensive performance evaluation diagram was adopted to analyze the combined index point of thermal and flow. This study shows that the flow distinction between different fins has a profound influence on the thermal-hydrodynamic performance. The results reveal that the fin with delta winglets can considerably strengthen the thermal efficiency with a moderate pressure loss penalty. The computational results indicate that the average j-factor for the fin with delta wing-lets can be increased up to 41.9% over the baseline case and the corresponding f-factor decreased up to 19.5%. The combination property of front-up-rear-down are better the others at lower Reynolds number, and that of front-down-rear-up are better at higher Reynolds number. Compare with the traditional arrangement (common-flow-up and common-flow-down), The newly designed fin has great effectiveness and uniform performance in the local region.

In many applications, such as the miniaturization and cooling of high-power electronics in aerospace, a new thermal management solution is needed, and metal foam radiators may be a valuable solution. In this work, X-ray scanning was applied to obtain the original structure of the metal foam. The real structure calculation model of the metal foam was obtained through a series of modeling, and high-precision numerical simulation was built to study heat and mass transfer in the original structure and homogeneous substitution model for three-dimensional porous metal foam. The distribution of velocity, pressure and temperature field is investigated. The results show that the heat transfer characteristics increase and flow resistance decreases with an increase in the Reynolds number. The heat transfer performance and flow resistance increase with the decrease of porosity. The porous media homogenization model can be consistent with the original real calculation results of metal foam by using appropriate values of resistance coefficient and porosity. The variation of resistance coefficient and porosity with the working condition in the porous homogenization model is identified.

Porous adsorbent material is promising to be used to regeneratively remove CO₂ from space shuttles. In this work, the amount and isosteric heat of CO₂ adsorption in solid amine are experimentally studied at pressures ranging from 0 to 6 bar and temperatures ranging from 20 °C to 60 °C. The amount and isosteric heat of water adsorption in the solid amine is tested at different humidities (relative humidity 30–80%). The effective thermal conductivity of the solid amine at different atmospheres (air, N₂, CO₂ and water), pressures and temperatures is also investigated. The results show that the best temperature for CO₂ adsorption in the solid amine is 45 °C under dry conditions. The amount of water adsorption increases with enhanced humidity, while the isosteric heat of water adsorption remains a constant value. The effective thermal conductivity of the solid amine increases with an increase in pressure. The adsorbed phase (CO₂ and water) in the solid amine makes a contribution to improving the effective thermal conductivity of solid amine particles. The above findings can help design a better adsorption system in space.