Dynamic model for multi-compartment indirect cooling household refrigerator using Z-transfer function based cabinet model

Multi-compartment indirect cooling household refrigerator is widely used and the prediction of the dynamic performance based on dynamic model is useful for improving refrigerator performance and saving energy. The dynamic model to be developed should be accurate, fast and robust, especially considering the computation in dynamic simulation increases dramatically with the compartment numbers. This paper presents a dynamic model for multi-compartment indirect cooling household refrigerator, in which a Z-transfer function based cabinet sub-model, a semi-dynamic compressor sub-model, an approximate analytic capillary sub-model integrated with effective enthalpy method, a multi-zone heat exchanger sub-model, and an implicit curve-fitting method for refrigerant thermodynamic properties are integrated. The model is carried out with the predictor–corrector method as well as the adaptive time step algorithm and the time step interpolation method to match the adaptive time step for dynamic model and the fixed time step for cabinet model. A case study shows that the calculation speed of the Z-transfer function based cabinet sub-model is about 40,000 times faster than that based on direct differential equation solving with a difference of less than 0.06 °C in predicting air temperature with these two methods. Simulation of 24-h running process of a refrigerator by the dynamic model on a personal computer costs 178.3 s; and the differences between the predictions and the experimental data are within 2 °C for compartment air temperature, within 2 °C for evaporating/condensing temperature, and within 10% for compressor input power.