Performance analysis of a solar wall integrated with latent heat storage and microencapsulated phase change material slurry

Abstract

As renewable energy deployment accelerates, efficient strategies for thermal energy storage and transport are increasingly required. This study experimentally investigates a flat-plate solar wall collector integrated with a latent heat storage tank, employing a microencapsulated phase change slurry (MPCS) as the working fluid. The collector, featuring vacuum glazing and embedded copper pipes, was evaluated under winter conditions at a 60 degrees incidence angle and an average solar irradiance of 650 W/m2. Operating parameters included flow rates of 1-8 L/min, pipe diameters of 6-12 mm, and slurry concentrations of 0-30 wt%. Through these experiments, MPCS slurry viscosity and flow rate were found to strongly influence thermal transport. Based on this analysis of viscosity and flow rate effects, distinct regimes were identified. In laminar conditions (Re <= 2300), the Nusselt number (Nu) showed weak dependence on Reynolds number but increased with PCM mass fraction (MF), reaching up to 27 at 30 wt% due to particle-induced mixing. In contrast, turbulent conditions (Re >= 4000) exhibited a strong monotonic rise of Nu with Re, with higher MF further amplifying heat transfer through turbulence intensification and particle-flow interactions. From these observations, Nu-Re-MF correlation was developed, which can serve as practical tool for predicting heat transfer in slurry-based systems. In practical operation, the system demonstrated strong thermal storage performance. Optimal operation at 5-6 L/min achieved a maximum charging efficiency of 61.8 % and a peak heat transfer coefficient of 4370 W/m2 & sdot;K. For a 5-h run at 5 L/min, the total stored energy reached 120,315 kJ (33.4 kWh). As a result, compared with water, MPCS improved efficiency by up to 33.6 %, confirming its potential to significantly enhance solar thermal storage in building-integrated applications.