Numerical Simulation And Experimental Study On The Frosting/Defrosting Characteristics Of The Heat Pump Using Alternative Refrigerant R410A

In this paper, the research work was carried out focusing on the simulation and experiment of the air source heat pump(ASHP) using alternative refrigerant R410A. The problem about the frosting and defrosting was also investigated. First of all, the mathematic model describing refrigerants' thermodynamic properties and transport properties is established using universal equations incorporated with experience equations. In this paper, based on steady distributed parameter model for ASHP, a dynamic distributed parameter model is presented by regarding the frost accumulation as the quasi-dynamic process. The split two-phase flow model was used in the heat exchange models. In the capillary tube model the homogeneous assumption was employed and the delay of the flash point and the choked flow were included. At the same time, the decrease of the air mass flow in the system model and the arrangement of the heat exchange tubes are considered. A simulation program, which is programmed with matlab, has been developed by using finite difference method to predict the dynamic performance of the (ASHP) using alternative refrigerant R410A under frosting conditions.In addition, the experimental study of the defrosting and frosting process of the ASHP using alternative refrigerant R410A and the effects of the frost on the performance and the process of defrost is disscused. A test set-up was established in the psychrometric rooms to investigate the dynamic performance under frosting conditions and defrosting characteristics of an ASHP unit. With the vary of the relative humidity and temperature outdoor air, the transient heating capacity, COP, frosting quality and wall temperature distribution along the tubes of the evaporator are measured. And what's more, the technology of micrography is adopted in order to gain the frost thickness. The numerical and experimental results, to most degree, are in good agreement, which demonstrates that the simulation model and calculation method are feasible. It is of immense importance to the defrosting control and the heat pump system optimization.