Study on the encapsulation effect and mechanism of hollow ceramsite to phase change materials (PCMs)

Abstract

In order to promote the development of phase change materials (PCMs) and make them better applied, more in-depth research on the PCMs encapsulation is needed. The hollow ceramsite prepared in this study is a new type of PCMs carrier. Due to its unique structure, the encapsulation of PCMs by hollow ceramsite differs from that of ordinary porous ceramsite. In this paper, the adsorption and sealing effect of hollow ceramsite on PCMs was studied, the key factors affecting the adsorption and sealing effect were determined, and the encapsulation mechanism was revealed. The results show that the driving force of PCMs into the cavity of hollow ceramsite is mainly from the external pressure; the pore size and PCMs properties are the key factors determining the adsorption effect of hollow ceramsite. The pressure on the pore is proportional to the square of the pore diameter; increasing pore size enhances the possibility of the PCMs entering the cavity of ceramsite. The contact angle between PCMs and pores is smaller, and the surface tension of the PCMs in the pores is greater, making it difficult for PCMs to enter the cavity of ceramsite. The sealing mechanism of the coating on infiltrating PCMs is achieved by reducing the pore diameter of the sealing coating and increasing the resistance of PCMs to break through the pore. The sealing mechanism of the coating on non-infiltrating PCMs is achieved by changing the contact property between the PCMs and pore, increasing the energy barrier. After coating, the mass loss rate of infiltrating paraffin was controlled within 5 %, and the leakage rate of non-infiltrating hydrated salt was controlled within 1 %.