Optimization Of Structures Of Phase Change Heat Storage Wall In Tianjin Region

The rapid development of facility agricultures provides a convenient for the supply of fresh vegetables in winter of north China. The greenhouse has been widely used because of its simple equipment, low cost as one of the facility agricultures. However, the greenhouse is still faced with some problems and challenges, such as low science and technology, high labor intensity, low efficiency and so on. The greenhouse is eager for transform to new energy-saving greenhouse.The greenhouse is a thermal and humid environment which is established by the covered membrane and the building envelopes. The wall carries the many functions such as load-bearing, heat storage and heat preservation as one of the building envelopes. The previous study on the choice of wall materials is much more than the thickness of the wall layer. There is not a regional thickness standard. At the same time, the traditional building materials limit the use of solar energy, which store heat through the method of sensible heat storage.Based on the two problems, the vitrified microsphere particle is selected as a phase change material(PCM) which combines with the characteristics of the greenhouse. Then a contrast experiment on the heat storage of P CM and cement mortar is conducted. The results show that the PCM has a temperature platform in the process of heat storage compared with the ordinary building materials, which suggests that there is an obvious storage or release of latent heat. Also, the higher storage temperature and the lower release temperature are more conducive to “Peak cut and valley up”. Then, the PCM wall with three layer structures is put forward, which is constituted by the PCM layer, block layer and insulation layer from the inside. The dynamic model of greenhouse is established by Sketchup, which is imported into the EnergyPlus to solve the problem of the thickness of PCM wall through the method of finite difference and the enthalpy-temperature method for PCM. Finally, the optimized combination is defined with 40 mm PCM+300mmaerated concrete +50mm EPS.On the basis of the simulation, the experiment is used to proof the influence of daub method on the PCM layer. The PCM layers are constructed with layered daub and respectively in two contractible greenhouses. The results show that the temperature in greenhouse with direct daub is higher 1.09 ℃ than that with layered daub and the highest increase is 2.69℃. So we can draw a conclusion that the direct daub layer can play PCM performance of the heat storage better, especially the environment temperature of the greenhouse is improved during the night.Finally, is compared with three kinds of common walls in Tianjin region. The results show that the optimizing wall is best in the thermal perfo rmance, environmental benefit and economic benefit, which has a high heat storage and heat preservation, energy conservation and economical efficiency. The optimizing wall increases the energy utilization and responds to the national call of energy-saving greenhouse, which has a larger prospect.