Thermophysical Characterization and Response Surface Modeling of Aqueous Glycerol-NaCl Phase Change Materials

Abstract:

Developing effective low-temperature thermal storage requires precise control over phase change material (PCM) properties. This study engineered a multi-component PCM system by blending glycerol, sodium chloride (NaCl), and water, evaluating them via a Design of Experiments (DOE) strategy built on Response Surface Methodology (RSM). Solute concentrations for both glycerol and NaCl ranged from 0-5%. Batches were prepared using ultrasonic agitation to determine how these variables dictate freezing thresholds, viscosity variations, specific heat, latent heat capacity, and thermal conductivity. Our laboratory data prove that salt content controls the freezing threshold. Adding 5% NaCl depressed the freezing point to -5.85°C because ions physically disrupt the water crystallization lattice, which also triggered a distinct supercooling pocket down to -6.5 °C. Meanwhile, glycerol drives internal fluid friction and thermal transport. It pushes viscosity along a parabolic curve to a 3.86 cP peak via hydrogen bonding networks and forces a linear decline in thermal conductivity to 0.5976 W/mK. Combined, these solutes lowered specific heat to 3.926 J/g°C and latent heat to 300.6 J/g. Strong model accuracy (R² = 0.9642) provides a highly dependable optimization framework for cold-chain logistics engineering.