This paper studies numerically the influence of the louver's fin thickness on heat transfer and flow performance of a parallel flow evaporator, a comprehensive evaluation and analysis of the five structures at different Reynolds numbers are systematically carried out. Comparison of the numerical results with the experimental data shows good agreement with maximal errors of 12.16% and 5.29% for the heat transfer factor and the resistance factor, respectively. The results show that the heat transfer coefficient and the pressure drop increase with the increase of the thickness of the louver fins when the Reynolds number is a constant. The analysis of the comprehensive evaluation factor shows that the A-type fin is the best, and it can effectively strengthen the heat exchange on the air side and improve the heat transfer capacity of the system. The research results can provide reference for the structural optimization of the louver fins.

When the exhaust temperature of heat pump air conditioning system of pure electric bus is too high, the performance of the system is attenuated. In order to solve the problem, an alternative system with low pressure air supply is developed. The experimental platform is set up to reveal the main factors affecting the refrigeration and heating performance of the system. The results show that the low-pressure air-supply technology can significantly reduce the exhaust temperature of the compressor.

In view of the current test methods and evaluation indicators for the performance of cold storage freezing systems, a cold storage experimental platform with a micro-channel heat exchanger is designed using the inject technology, and the power consumption and cooling performance are tested under different conditions of the internal and external environment temperatures, vapor injecting flux, compressor speed, and vapor inject pattern. The experimental results provide us with a useful source for the optimization or improvement of cold storage freezing systems.

In this paper, based on the regulation characteristics of electronic expansion valve, an experimental platform is built for studying a vehicle heat pump system. Under an ultra-low temperature condition of -10?C, the influence of the super-heat setting value of the electronic expansion valve on the main heating performance parameters of the system is analyzed. The results show that when the superheat setting value of the main valve increases from 2 K to 8 K, the discharge temperature of the compressor increases, the heating capacity of the system decreases by 12.6%, and the compressor power decreases by 15.9%. When the superheat setting value of make-up valve increases from 15 K to 30 K, the discharge temperature of the compressor increases, the heating capacity of the system decreases by 17.7%, and the compressor power decreases by 22.0%.

In order to solve the problems of a heat pump air conditioner for an electric bus under extreme conditions, such as the large compression ratio, the high discharge temperature, the reduced system performance, the frequent shutdown of the compressor due to the overheat protection, this paper proposes a vapor injection technology with an economizer, and carries out a theoretical analysis of the process to reveal the effect of the vapor injection technology on the performance of the air conditioner. The results show that at ultra-low temperature heating operating conditions, when the compressor speed increases from 2000 rpm to 5000 rpm, the heating capacity of the vapor injection system increases from 16.2% to 22.7%, and the heating performance coefficient increases from 2.8% to 14.2%.