Research On A New Passive Solar Collector-storage Wall System With Phase Change Materials

Passive solar building is widely used in engineering applications because of its simple structure and low cost. However, traditional passive solar building can not both meet heating in winter and ventilated/cooling in summer. To solve this problem, a combination of passive solar building and phase change materials (PCMs) is proposed. The feasibility of its application in the building field is characterized by the theoretical analysis, numerical simulation and experimental study. The main results obtained are as follows.By the method ofporous inorganic carrier composite, the form-stable PCMs composed of paraffin as phase change material, expanded perlite as supporting material and graphite as additive to improve the thermal conductivity of paraffin, are prepared. The structure and thermal characterizations of the form-stable PCMs are investigated by transient hot-wire method, differential scanning calorimetry, thermogravimetry, scanning electron microscopy and Fourier-transform infrared, respectively. The results show that the thermal conductivity of the form-stable PCMs increase, obviously. Paraffin is dispersed uniformly into the porous structures of expanded perlite after soaking. The form-stable PCMs have a good thermal stability in its working temperature. In addition, it is just a physical cross-linking between paraffin, expanded perlite and graphite, and no significant new peak appear.Cement mortar with the form-stable PCMs is prepared by direct mixing method for thermal energy storage in building applications. To avoild the leakage of the form-stable PCMs in practice use, epoxy resin as the second encapsulation material mixes with the form-stable PCMs, and then add into the ordinary cement mortar. The mechanical and thermal properties of cement mortar with the form-stable PCMs are investigated. The results show that the compressive strength and flexural strength decrease with increasing amount of the form-stable PCMs. The optimal content of the form-stable PCMs in cement mortar is determined as 20%. When the content of epoxy resin is more than 22%, the cement mortar with the form-stable PCMs has no leakage at 40 ℃ for 5h. The heat storage/release curves change slightly after 500 cycles, which indicates that the cement mortar with the form-stable PCMs has good thermal stability.A new type of passive solar collector-storage wall system with PCMs is designed. The heat transfer process is expressed by energy balance equations including sunlight board, air in the channel, collector mortar layer and inner surface of wall. A further analysis on air channel width, vent size, wall height and wall thickness of the passive solar collector-storage wall system with PCMs are carried out by numerical simulation method. The results show that the best air channel width range is from 100mm to 150mm; vent size of the best value is 200mm×200mm; wall height should be increased as far as the condition pertmit; wall thickness is 370mm in cold region and 240mm in other areas.Experimental studies on the new solar passive collector-storage wall system are carried out. Compared with ordinary room, the new solar passive collector-storage wall system can increase the indoor temperature 5.38 ℃ in winter and decrease the indoor temperature 5.32℃ in summer.