Building Mathematical Model And Simulation Of Condenser And Evaporator In Auto Mobile A/C System

The dynamitic matching character among evaporator, condenser, compressor and expansion valve have direct effect on saving power of automobile A/C system. To achieve the optimization matching character among the four parts, it is necessary to study their own structure and operating characters at first. Automobile A/C system is installed on the moving object, which requires high cooling performance, compact figure and small weight. This paper has studied and developed a dynamitic mathematical model with moving boundary, describing two-phase flowing and heat transferring process of refrigerant in the heat exchanger (Condenser and evaporator are regarded as"the heat exchanger"in this paper together), taking condenser and evaporator of core parts of automobile A/C system as studying object. This paper has its own important value at theory reference and engineering application by improving the heat exchanging efficiency of condenser and evaporator, optimizing their structure parameters and making their reasonable developing flow.This paper has paid more attention to as following contents:A dynamic general model of condenser and evaporator has built. And basing on it, linking to a program data of the refrigerant (or calling it as"the medium"), this paper has built evaporator model which can be put into engineering practice. To accurately describe the refrigerant working process and to think of the general of the mathematical model and possible operating condition, a simpler set of conservation ordinary differential equations is formulated by integrating separately over the three zones (liquid, two-phase and vapor). All the ordinary differential equations have formed the heat exchanger dynamic general mathematical model.To make the model suit to complex operating conditions of automobile A/C system, all possible operating conditions of the heat exchanger have been taken into account, using a condition control rules to deal with the operating condition, and have realized the parameters smoothly transition with the monitoring state parameters method.Basing on method and data have been described in"Thermodynamic Properties of Pure and Blended Hydro fluorocarbon (HFC) Refrigerants", which been published by JSRAE in 1998, naming it"free energy"method (The R134a equations established by it is been considered standard R134a physical equations by IEA), R134a physical computing mathematical model have been built and been composed of the heat exchanger structure equation.The paper has design different simulation test plans basing on the above work, and taking the evaporator as an example to simulate and verify, and ensuring the model has experienced all kinds of possible condition changing, that is the evaporator can moving between liquid and vapor zones. The test result curves show the parameters changing are smooth and the model conversion method is reasonable. As also show the model of evaporator can operate over a wide range of operating conditions and it is general and flexible.A full mathematical of auto A/C system can be established when the mathematical models of compressor, throttle device and drier would have been build in the future. Then as will be foundation for the system optimizing design, system components best matching and simulating operating analysis.