Simulation for the thermal performance of super-hydrophilic fabric evaporative cooling roof based on experimental results

Abstract

With characteristics of lightweight and simple construction, wet fabric roofs can achieve preferable cooling effects for top floor spaces of buildings leading to reductions of building air conditioning. However, the potentials of applying them to real projects are not well recognised, because we lack simulation models to precisely predict the thermal performance of the fabric roof. This paper aims to investigate the dynamic performance of a super-hydrophilic fabric roof for a single-storey building under the climates of Beijing based on an empirical model. Initially, a dedicated experimental system was built to measure the fabric's actual evaporation rate under a wide range of parameters including inlet air dry-bulb temperature, humidity, velocity, and imposed radiation intensity. The test data were used to develop an empirical model of evaporation rate by the symbolic regression method. The discrepancy between prediction and measurement was found to be within 90%, representing the model's accuracy was satisfactory. Furthermore, by incorporating the empirical model, an EnergyPlus program with an Energy Management System module was developed to predict the thermal performance of a single-storey building. The results showed that internal and external surface temperatures of the fabric roof can be reduced by up to 15.7 °C and 11.8 °C respectively. We concluded that the proposed fabric roof has great potential of cutting cooling load by 34%–44% in average compared to traditional roofs. This paper develops an empirical model for estimating the wet fabric's evaporation rate and paths a way for evaluating the cooling potential of fabric roofs for buildings in various climates.