Study of the thermal field of a mixture of soil and PCM materials with simulation of the warming effect during a phase change

Abstract Phase-change materials (PCM) possess an ability to accumulate and generate a lot of heat during the substance change from one phase to another. Such materials can be used with soil as an alternative type of thermal regulation of the subgrade during construction in cold regions. This paper reviews the impact of two types of PCM (PCMf-hybrid liquid and PCMm- microencapsulated paraffin) on the soil temperature. An experiment was conducted with three groups of samples: (1) samples with PCMm or PCMf added at a ratio of 2% and 4% of the dry weight of the soil; (2) samples reinforced with 4% of cement with an addition of PCMm or PCMf; and (3) samples with PCMf added after drying and re-adding water up to the optimal amount. PCMf and PCMm have been tested in DSC at various scanning speed levels. The results showed that, compared to that of the PCMm sample, PCMf has a greater enthalpy both during freezing and thawing, as well as the temperature peak during freezing is closer to zero. The study of temperature changes in soil samples with PCMm, PCMf, and cement added at the change of the ambient temperature T 0 = 10 ° C → ( - 10 ° C ) → ( 10 ° C ) showed that the soil samples with various PCM additions have a lower temperature change rate than the soil samples without PCM additions. The results of the Scanning Electron Microscope (SEM) microfilming confirmed satisfactory components concentration in the soil mixture. There is also a noticeable number of craters and less porosity in the samples containing liquid PCMf and cement. A two-dimensional model of PCMm microcapsule per unit volume of soil was analyzed with the help of Comsol Multiphysics software (a powerful software product for modeling heat transfer and phase change in porous medium). It was determined that, during the phase change, the PCMm microcapsule has a thawing effect on the soil. During the examination of a three-dimensional model of eight PCMm capsules per unit volume of soil, it was noted that the thawing effect extends to 18.2% of the calculated area.