A new heat pipe-type natural convective heat dissipation terminal with a thermal energy storage material is proposed. A sleeve is added to the heat exchange tube at the end of the heat pipe, and the thermal energy storage material is placed between the tubes. Through condensation heat exchange, the steam in the tube transfers heat to the thermal energy storage material and then to the outer sleeve, which features natural convective heat exchange and radiative heat exchange against indoor air, thereby constructing a new household air source heat pump system. A heat transfer model of the heat pipe heat dissipation terminal with the solid-state thermal energy storage material is established, and the start-stop process of the heat pump system and the influence of the type and thickness of the thermal energy storage material on the temperature distribution and its variation with time are studied. The variation laws of the macro-performance metrics, such as the heating capacity and compressor power of the heat pump system, are analyzed. The results show that magnesium brick as the solid-state thermal energy storage material is the best. The operating time of the heat pump and the external surface temperature of the thermal energy storage material are affected by the thickness of the thermal energy storage material, and a critical thickness exists. When a magnesium brick with a thickness of 12 mm is selected as a thermal energy storage material, the domestic air-source heat pump with the thermal energy storage terminal runs for 12 minutes, leading to 26 minutes of heating time, while the surface temperature changes within the range of 35-50 ℃.

With increasing environmental awareness, natural refrigerants have regained prominence. An air-cycle refrigeration system is an effective alternative because air is harmless and environmentally friendly. The expander-compressor system is the core component of an air-cycle refrigeration system, where the compressor input power varies with the expander performance curve. To design a centrifugal compressor that can operate efficiently with an expander, modifications to traditional design methods are required. By combining the conservation of mass, momentum, and energy with the jet wake flow pattern and extending the relevant parameters of the traditional centrifugal compressor to a lower pressure range, a design method for matching the geometric parameters of a centrifugal compressor with an expander is proposed. This method was applied to design a centrifugal compressor corresponding to an existing expander, which was validated using a centrifugal compressor model previously analyzed by other researchers. Computational fluid dynamics (CFD) was employed to simulate and assess the operational performance of the expander-compressor under variable operating conditions, including the utilization efficiency of the expansion power. A centrifugal compressor designed using this method achieved more than 92% and 88% utilization efficiency under the nominal operating condition and variable operating condition, respectively. The expander functioned smoothly within the designed mass flow rate range.