Thermal properties and performance of glycerol-water-NaCl phase change material for cold chain applications
Zakaria Ouaouja, Michel Havet, Olivier Rouaud, Cyril Toublanc, A. Ousegui
Abstract
This study investigates the thermal properties of glycerol-water mixtures and their potential as P hase C hange M aterials ( PCM s) for C old T hermal E nergy S torage ( CTES ) in cold chain applications. The study characterizes key thermal properties, including P hase C hange T emperature ( PCT ), latent heat, density, thermal conductivity, and specific heat. Results indicated that increasing glycerol concentration decreased the PCT of the mixture, reaching −7.76 °C to −21.82 °C, at glycerol concentrations ranging between 25 wt% to 45 wt%, respectively. However, this decrease in PCT is accompanied by a reduction in latent heat, 147.5 kJ·kg −1 to 73.6 kJ·kg −1 for the respective concentrations. To enhance the PCM properties and achieve optimal thermal performance, NaCl was added as an additive to the glycerol-water mixture. The R esponse S urface M ethodology ( RSM ) was employed to optimize the concentrations of PCM components, aiming to achieve a desired PCT of −20 °C and maximize latent heat capacity. The developed model demonstrated high predictability, with an R 2 of 99.20 %, and good statistical significance, as indicated by an overall model F-value of 98.68 and a P-value of 0.0003. Based on this optimization, three mixtures were selected for further characterization, exhibiting suitable PCT values of around −20 °C to −18 °C and latent heat capacities ranging from 97 kJ·kg −1 ( PCM-M1 ) to 280 kJ·kg −1 ( PCM-M3 ). A one-dimensional model was developed to assess the impact of optimized PCM-M3 on the temperature stability of frozen food products. Incorporating the PCM layers significantly improved the thermal control of the perishable product. During standard freezer operation, the product temperature was maintained at −20 °C ± 0.065 °C compared to the reference case (without PCM) at −20 ± 0.81 °C. During defrost cycles, and using PCM-M3 , the maximum product temperature reached −19.42 °C, compared to −16.98 °C without PCM.