Numerical modeling of the thermal performance of soil containing microencapsulated PCM

Abstract Phase change material (PCM) can be used with soil as an alternative type of thermal regulation of the subgrade, since it has an ability to accumulate and generate heat during the phase change. This paper evaluates the position of PCM microcapsules in the soil by means of scanning electron microscopy (SEM) and X-ray photoelectron spectroscopy (XPS) analysis. The SEM image processing method includes an integrated approach to transferring a color pixel image into a numerical matrix, followed by noise removal and precise determination of the position and size of microcapsules. Based on these data, a macroscale model of the soil volumetric unit with the inclusion of the microencapsulated phase change material (mPCM) was created, which made it possible to estimate the temperature of the mixture at a changing external temperature, as well as the nature of the effect of mPCM on the soil temperature regime. Through the analysis of many points in the model, the following results were obtained: 1) mPCM not only reduces the peak temperatures of its own volume, but it also softens the peak temperatures of the surrounding soil, 2) with a decrease in the external temperature, there is a tendency to a decrease in the temperature change rate as the model temperature approaches the phase change temperature range, 3) in the second cycle of changing the outside temperature, the effect of mPCM on peak temperatures is greater than in the first cycle due to the cumulative effect of decreasing the temperature change from cycle to cycle. PCM materials release/absorb a large amount of latent heat during hardening/melting, which can be useful in solving problems associated with seasonal freezing and thawing of pavements.