Study on Inorganic Phase Change Materials Encapsulated by Rice Straws

Abstract

Na2SO4 solution was impregnated into rice straws, then the straws impregnated with Na2SO4 was cemented using water glass and molded to shaped phase change plate. The plate was subsequently inserted into the concrete bricks with rectangular holes, assembled as phase change bricks. The latent heat of phase change of the plate was measured by DSC, the microstructure of the plate was observed by SEM, and the heat insulating property of the brick was investigated. The results are as follows. The rice straws can encapsulate 2 times Na2SO4•10H2O in mass and the phase change heat of the plate is 121 J/g. The microstructure shows that the rice straws and hardened water glass play an encapsulating action for the package of Na2SO4•10H2O. The weight loss of the plate was 0.9% after 30 times of phase change cycles. For the concrete bricks (size: 240×240×115 mm) inserted with phase change plates, when the heated surface temperature was 80 oC and the initial cold surface temperature was 14.5 oC, the needed time that the cold surface temperature rose to 25 oC was 17 h, which was 6.5 h and 9 h longer than the concrete bricks inserted with rice straw plates and the original concrete bricks, respectively. When the heating was maintained for 5 h and 8 h, the cold surface temperature increased by only 1.4 oC and 3.9 oC and the temperature difference between the cold surface and hot surface was 64.1 oC and 61.6 oC. This study provides a new way for the encapsulation of phase change materials and its application in construction.