A Simplified Dynamic Model of Roof Integrated with Shape-Stabilized Phase Change Material

Abstract

Roof integrated with shape-stabilized phase change material (SSPCM) is composed of the PCM layer and the precast concrete hollow slab, the PCM layer is placed on the outer layer of which. During daytime in summer, the PCM absorbs and stores the solar radiation heat and releases the heat by convection and long-wave radiation at night. This can effectively reduce roof heat transfer and inner surface peak temperature. In order to study the thermal performance of the structure, a simplified dynamic thermal network model (RC model) of the roof is established. The resistances and capacitances of the PCM layer and hollow slab layer are identified by using genetic algorithm (GA). Firstly, the parameter identification of the hollow slab layer’s RC model can be obtained by matching the frequency response characteristics of the simplified model with its frequency-domain finite difference model. Another GA program is then used to find out the optimal resistances and capacitances of the PCM layer’s RC model (together with the parameters identified of the hollow slab layer) which gives the best fitting with the heat performance by using CFD numerical simulation in time domain. Further, the thermal performance of the roof integrated with shape-stabilized was investigated under a typical summer day in Wuhan. The simulation results showed that the use of PCM has helped to increase the thermal insulation of the roof, compared with the roof without PCM layer, the decrement factor is decreased by 0.31, and peak internal surface temperature is decreased by 7.02 °C when the PCM is 30 mm.