Analysis of Optimal Injection Ratio of Vapor Injection Heat Pump for Electric Railway Vehicles

Sa？etak Air-source heat pump with vapour injection is a prospective efficient heating method for electric railway vehicles in cold regions. A heating performance analysis modelling for air source heat pump with vapour injection is set up for performance optimization in this paper. The maximum errors of the program are within 15%. Heating performance, as well as the optimal injection ratio is analysed. The optimal injection ratio varies mainly from 0.12 to 0.3 under the typical working condition of railway vehicles in winter. It goes up with increasing inlet air temperature of condenser and goes down with increasing ambient temperature. The ambient temperature has very little effect on the optimal injection temperature of the internal heat exchanger. The results indicate that the expander valve opening of the injection branch can be controlled by its outlet temperature to get the optimal heating performance