Simulation model for complex refrigeration systems based on two-phase fluid network – Part I: Model development

Some complex refrigeration and heat pump systems with several condensers and evaporators have been developed for different kinds of application. Traditional simulation models were developed for systems in certain operating modes and they failed in modeling the complex refrigeration systems with uncertainties of heat exchangers function and refrigerant flowing direction. In order to predict the performance of complex refrigeration systems, a simulation model is presented based on the two-phase fluid network. The model is consisted of distributed-parameter model of heat exchangers and connecting tubes, map-based model of inverter compressor and electronic expansion valve (EEV). Based on the characteristic of refrigeration system and fluid network, the three conservation equations, i.e. energy, momentum and mass equations, are solved iteratively. This model can deal with the uncertainty of refrigerant flow direction by separating the solving process of the components and the fluid network model, and therefore can simulate different kinds of complex refrigeration systems in different operating modes and conditions. The model is validated by the experimental data of an inverter air conditioner in heating/cooling operating modes and it shows the error of the model is mainly determined by the error of submodels of components in calculating heat transfer and pressure loss. The model is applied for performance analysis of three kinds of complex refrigeration systems in the accompanying article [Shi W.X., Shao, S.Q., Li, X.T., Yan, Q.S., 2008. Simulation model for complex heat pump systems based on two-phase fluid network: part II – model applications, International Journal of Refrigeration 31 (3), 500–509.].