Study On The Methods Of Modeling And Simulating For Heat Exchanger In Refrigeration System

Refrigeration air-condition system now is one of the most energy-consuming systems in the world. Its simulation is not only an important tool for refrigeration system to design, control optimally and match, but also the developing direction of modern method of designing refrigeration air-condition products. Evaporator and condenser (called as refrigeration system's heat exchanger in the paper) are the crucial parts in vapor compression refrigeration system, whose methods of simulating and modeling are important contexts and hard questions about the thermodynamics and simulation of refrigeration system.Based on the existed research achievements, the main problems on simulating and modeling for the dynamic process of heat exchanger in refrigeration system are presented and studied in the paper. The investigations and results contain the following five parts.The calculation model of thermodynamics parameters for the refrigerant is established, meanwhile, the corresponding simulation module is developed, according to Martin-Hou's state equation. The calculation results of R12, R22, R502, and R134a show that the module has high precision and can meet the requirements of refrigeration system's simulation. Furthermore, in order to enhance the operation speed of thermal parameters, the Levenberg—Marquardt optimization method is adopted to improve BP neural network and the new refrigerant state parameters'model based on the improved neural network is established. A uniform distributing parameter model of heat exchanger in refrigeration system is proposed, so that the thermodynamic parameters and transient distribution properties of heat exchanger and refrigerant's various phase areas could be described in a uniform way by the model, which may avoid the repeat switch of the different phase area's former models. In addition to simulate the dynamic process, the model can be utilized to analyze the steady properties of heat exchanger in refrigeration system.According to the tracing view of material point, a general numerical simulation algorithm is established in order to apply for refrigerant's various phase areas. The algorithm has effectively overcome the numerical stability problems which existed in the former algorithm and calculate successfully the instantaneous position of phase transient points. The spatial discretization is automatically finished in the flow process...