Effect of key parameters on the transient thermal performance of a building envelope with Trombe wall containing phase change material

The thermal behavior of a building envelope having a Trombe wall incorporating phase change material (PCM) is investigated during heating season, using experimentally validated 3D computational fluid dynamics (CFD) simulations. The effects of transient versus steady-state ambient irradiation and temperature, presence of PCM and different solar irradiation intensities on the spatial and temporal variation of temperature and airflow rate in the conditioned room are investigated. The results show that the flow transition and temperature rise mainly happen in the near-wall regions close to the room ceiling and in the air channel. They also indicate that the Trombe wall with PCM tends to prevent large fluctuations in room temperature and airflow rate. More importantly, it is determined that under constant radiation flux and ambient temperature, the PCM significantly improves the thermal performance of the envelope and effectively shifts the heating load, but under diurnally transient solar radiation flux and ambient temperature, these benefits seem less evident. Accordingly, caution must be exercised in extrapolating results obtained under constant ambient conditions to situations involving transient ambient conditions.