Numerical Study On Thermal Performance Of Trombe Wall System With Phase Change Material In Lanzhou

With the social and economical development of our country, the building energy consumption has attracted extensive attention as the urbanization rate increases gradually.Solar energy, as one of the most abundant renewable energy sources on the earth, is widely used in various fields with the characteristics of safety, economy and pollution-free. Trombe wall system is an effective combination of solar energy utilization technology and building integration technology, and it plays an important role in building energy conservation. In the present study, in order to improve the heat collecting efficiency of Trombe wall system,Trombe wall system with phase change material(PCM) is constructed based on ordinary Trombe wall system. Then numerical study of Trombe wall system with PCM is performed using Fluent software. Based on the computation results, the application feasibility and comfort of Trombe wall system with PCM in Lanzhou are discussed. The research contents and results are as follows:(1) In the actual process, due to the variation of outdoor ambient temperature with time,solar radiation intensity and other parameters, the heat transfer process of Trombe wall system with PCM is a kind of unsteady periodic process. In order to ensure the accuracy of the data,the numerical study on thermal performance of Trombe wall system with PCM should be carried out under the unsteady condition. By using the theory of phase change heat transfer, a2-D model is developed for Trombe wall system with PCM. By computation, the variations of temperature field, velocity field and other fields with time are obtained and discussed under different ambient conditions. The results show that the average temperature of the simulated room is about 27 K higher than the outdoor minimum temperature and it is about 17 K higher than the ambient mean temperature. The application feasibility of Trombe wall system with PCM in Lanzhou is proved. At the same time, the optimization analysis is performed for 2-D Trombe wall system with PCM with different width of air passages. Considering mean temperature difference between inlet and outlet of air passage and air flow rate of air passage,it is found that the best width of air passage is 15 cm.(2) A 3-D model is developed for Trombe wall system with PCM. The usage mode of phase change materials in 3-D Trombe wall system model with PCM is different from that in2-D Trombe wall system model. In 3-D system model, the phase change materials are added into the heavy wall to form the phase change wall in the system.In order to verify the thermal storage effect of phase change wall in the system, a 3-D ordinary Trombe wall system model for comparison is also established. By computation, the variation trend of air supply speed and the temperature gradient in the room of the system are obtained and analyzed. The application feasibility and comfort of Trombe wall system with PCM in Lanzhou is verified. It is found that there is a close relationship among the variations of flow fields of Trombe wall system with PCM, solar radiation intensity and the outdoor ambient temperature. By comparing the variation trends of flow and heat transfer of systems at different time, the theoretical basis for the promotion and use of thermal-storage-style passive solar house are provided.