A variable resistance variable capacitance simplified thermal model for pipe-encapsulated PCM

In recent years, PCMs as the thermal energy storage media have been widely used in building envelope to improve the thermal and energy performance of buildings. Pipe-encapsulated PCM is a new type of thermal storage and insulation structure. It can be incorporated into walls, floors and ceilings simply without leakage of PCM. The recycle of PCM can be achieved by actively removing heat by the circulating fluid in the inner pipe. Numerical models are widely used for predicting the thermal characteristics of the pipe-encapsulated PCM accurately. However, all those models are computationally intensive and too complicated to be integrated with conventional building thermal and energy calculation package for simulation. Fast and feasible simplified model is essential for the simulation and application of pipe-encapsulated PCM. In this paper, a simplified thermal model composed of the PCM model and pipe model for the pipe-encapsulated PCM is developed. The PCM model is composed of four variable resistances and two variable capacitances (4R2C) and the parameters are identified using GA. An experimental setup is established, and the thermal characteristics of the pipe-encapsulated PCM with dynamic boundary condition are tested. The simplified model is validated by comparing the results of simulation and that of experiment. The mean error of internal surface temperature of PCM is 0.45℃, and the mean error of heat flow through the internal of surface inner pipe is 14.4%. It indicates that the simplified model has good accuracy for thermal performance prediction for practical applications of pipe-encapsulated PCM.