Thermal performance evaluation of silica dip-coated phase change material beads for thermal energy storage in cement-based composites

Abstract

The present study proposed a simple manufacturing method of silica dip-coated PCM beads based on the phase transition characteristics of PCM without using complex processes (e.g., centrifugal extrusion, interfacial polymerization, and suspension cross-link), reagent-grade chemicals (e.g., urea (CH4N2O), formaldehyde (CH2O), etc.), or any porous medium. In addition, the technique in this study incorporated markedly more PCM into the same volume of mixture than other existing PCM integration techniques. Mechanical properties and thermal performance of cementitious composites were tested in the presence of silica dip-coating and the substitutions of PCM beads and fly ash cenosphere (FAC). In the results, the silica dip-coating improved the strength (by pozzolanic reaction) and the latent heat by 10.9% and also reduced the thermal conductivity by 8.4% (by reducing PCM leakage). The silica dip-coated PCM beads in samples decreased the cooling rate and converged the temperature to similar to 29.4 degrees C. In particular, the cementitious composite containing 20% silica dip-coated PCM effectively reduced indoor temperature fluctuation by lowering the internal peak temperature by up to 7.5 degrees C; it also delayed the peak time in an outdoor cyclic temperature change environment. The added FAC reduced thermal conductivity by 34% due to its hollow structure and accelerated the initial cooling rate of the sample containing PCM beads.