In this paper, a solar-assisted enhanced vapor injection air-source heat pump (SC-EVIHP) system was built to investigate its heating performance in cold regions. A typical-weather day in Harbin was selected for the experiment, and the heating characteristics of the SC-EVIHP system were explored under variable working conditions. The experimental results showed that the system was greatly affected by solar radiation intensity. On typical-weather days in winter, the maximum values for the heating capacity and COP of the system appeared at the time of maximum radiation intensity. Compared with conventional enhanced vapor injection air-source heat pump systems (EVI-ASHPs), the heating capacity and COP were increased by 24.9% and 12.5% at most, respectively. The COP of the system increased by at most 11.1% under conditions where the outdoor temperature was −12 °C and the outlet hot air temperature of the solar air collector was 40 °C. The SC-EVIHP system works well in a low-temperature environment and can be widely applied in cold regions.

This article proposes an effective thermal management solution for electric vehicles by incorporating a low global warming potential (GWP) hybrid refrigerant R1234ze(E)/R134a/R32 (with a mass percentage of 85/10/5). By integrating R1234ze(E), the potential of substituting R134a with this mixed refrigerant in electric vehicle air conditioning for thermal analysis was analyzed. The findings are that R1234ze(E) exhibits a COP reduction of 0.51% compared to R134a, while R1234ze(E)/R134a/R32 showcases a coefficient of performance (COP) enhancement of 1.53% over R134a. The compressor exhaust temperatures of R1234ze(E) and R1234ze(E)/R134a/R32 are, respectively, 7.4°C and 5.2°C lower than those of R134a. R1234ze(E) demonstrates a volumetric cooling capacity ~26.3% smaller than that of R134a. However, the volumetric cooling capacity of R1234ze(E)/R134a/R32 aligns closely with R134a, facilitating convenient direct charging. R1234ze(E)/R134a/R32 proves to be an excellent refrigerant for applications in the thermal management of electric vehicles.

The performance of an enhanced vapor-injection heat-pump drying system was designed and theoretically studied in cold areas. According to the simulation findings, the ideal vapor-injection charge of the system ranges from 12.3 to 13.9%, and its ideal intermediate pressure is between 1.278 and 1.498 MPa when the evaporation temperature is above 0 °C. The ideal vapor-injection charge of the system ranges from 13 to 20%, and its optimal intermediate pressure ranges from 1.078 to 1.278 MPa when the evaporation temperature is −15–0 °C. The ideal vapor-injection charge of the system ranges from 20 to 24%, and the intermediate pressure ranges from 0.898 to 1.078 MPa when the evaporation temperature is below −15 °C. The heat and humidity exhausted air source heat-pump drying (HHE–ASHPD) system has higher dehumidification efficiency than the closed heat-pump drying (CHPD) system under the same air temperature, humidity, and volume parameters.

In order to improve the operation efficiency of air-source heat pump with enhanced vapor injection (EVI), a hot air–EVI air-source composite heat pump test bench was built. Rear air supply mode and a more uniform hood air supply mode were employed. The experimental results demonstrate that, compared to the rear air supply mode, the compressor power consumption in the hood air supply mode can be reduced by 1.6%–4.6%. Simultaneously, the heating capacity experiences an increase of 1.2%–4.6%, and the coefficient of performance is elevated by 3.1–8.7%. The exhaust temperature decreased by 1.74%. Moreover, the exhaust pressure in the hood air supply mode is decreased to a certain extent. These experimental findings not only offer a dependable air supply mode transformation scheme but also furnish essential data support for solar energy–EVI air-source composite heat pumps, showcasing promising applications in cold regions.