| Summary: | Latent heat storage in phase change material (PCM) is an efficient technology that can be applied in building envelopes. Installing PCM in building roof has been effective in altering space cooling loads. However, the heat absorbed by the PCM during the daytime will be released at night; the cooling load is shifted to the night. So, this study proposed a new ventilated roof with form-stable PCM (VRFP). The night cool air is used for ventilation during summer to remove the solidification heat of PCM and to store the cooling energy in the roof. Form-stable PCM is placed in the upper layer and ventilation duct is placed in the middle layer. The inner surface temperature of this roof is reduced sharply compared with the conventional PCM roof. The thermal performance of this PCM roof with night ventilation in Wuhan, a city in southern China, was studied by through Computation Fluid Dynamics (CFD) simulation. A three-dimensional dynamic numerical model of this roof was built. The effects of melting temperature range, thickness of Form-stable PCM layer and ventilation strategy on the thermal performance were analyzed. Results show that, in Wuhan city, the optimal melting temperature range is 35~38 °C, the appropriate thickness of PCM layer is 30~40 mm and the optimal ventilation speed is 2.4~2.5 m/s. This structure can effectively prevent the stored heat of PCM transferring from the exterior to the interior during the summer and reduce cooling energy consumption.
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