Study On Preparation And Properties Of Paraffin/cement-base Phase Change Materials

Heating and air conditioning energy consumption are the main parts of the building heat loss. Therefore, saving energy and reducing the building energy loss is a very urgent task. Phase change energy storage technology could regulate indoor temperature effectively, improve the living comfort and reduce the energy consumption for air condition and heating equipment using phase change materials(PCM) to absorb(release) thermal energy.Based on the solid paraffin and liquid paraffin as phase change material, with expanded perlite and diatomite as matrix material, the paraffin/expande d perlite composite phase change materials(EP-PCM) and paraffin/diatomite composite phase change materials(DP-PCM) were prepared by the vacuum adsorption, respectively. Combine these composite phase change materials with cement-base materials to prepare the phase change energy storage mortar, and establish an energy storage model test room to analyze its thermal properties and thermal control effect of energy saving.The microstructure of the composite was observed by scanning electron microscopy(SEM). The chimeric relation of between composite materials was characterized using infrared spectrometer(FT-IR). Differential scanning calorimeter(DSC) results show that phase change temperature of paraffin was 24.94℃, and its phase change latent heat was 111.5 J/g. After the phase change recycling 50 times, 100 times and 150 times, the phase change temperature changes a little and the phase change latent heat just decreases slightly. The best adsorption amount of paraffin is 70.6% and 47.4% for expanded perlite and diatomite, respectively. The phase change temperature of EP-PCM composite phase change materials and DP-PCM composite phase change materials are 22.5℃, 22.46℃, respectively. The phase change latent heat of the two kinds of composite phase change materials were 75.72J/g, 49.6J/g, respectively. The phase change temperature decreases slight ly, the phase change latent heat and the calculated value of paraffin percentage are basically identical. Thermogravimetric analyzer(TG) results show that the EP-PCM composite phase change materials and the DP-PCM composite phase change materials under 150 ℃ do not decompose without weight loss, suggesting that two kinds of composite phase change materials have good thermal stability.By studying the performance of cement-base phase change mortar, it is found that with the increase of dosage of composite phase change materials, phase change energy storage mortar compress ive strength, volume density and thermal conductivity reduce gradually. The compressive strength decreases from 23.87 MPa to 23.87 MPa the volume density decreases from 2234.6 kg/m3 to 1885.9 kg/m3, and the coefficient of thermal conductivity decreases from 1.75 W/m·K to 0.32 W/m·K. The phase change mortar has large heat storage coefficient(6.87-18.7 W/m2·K).By studying the performance of phase change energy storage model test room thermal control activity, the results show that compared with ordinary mortar test room, the heating rate and the cooling rate of test room after mixing with phase change materials are lower, reaching the time at the maximum temperature is delayed. With the increasing amount of phase change materials, the indoor maximum temperature gradually decreased. When the amount of phase change materials is 15 mm, the maximum temperature difference can reached 15.5 ℃.