Cold storage condensation heat recovery system with a novel composite phase change material

Abstract

Cold storage systems release huge amount of condensation heat into the ambient leading to severe environmental pollution and significant energy waste. On the other hand, research into phase change materials appropriate to heat recovery in cold storages has not yet been well reported. The paper presented a dedicated study into a novel phase change composite material appropriate to this kind of application, which has relatively larger latent heat and thermal conductivity, and appropriate phase change temperature (i.e. 80 o C). Taking Carnauba Wax (CW) as the Phase Change Material (PCM) and the highly thermal conductive porous expanded graphite (EG) as the additive, a composite was thus developed at the mass ratio of 10:1 that was recognized as the optimal mixing rate. Thermal & physical properties and interior structure of the composite were then investigated by using the scanning electron microscope (SEM), thermal constants analyzer (Hot Disk), differential scanning calorimeter (DSC), and Fourier transform infrared spectrometer (FT-IR). Furthermore, experiments on the melting & solidification and the accelerated cooling & heating cycling were also undertaken. It is found that at the optimal mass ratio, temperatures of the CW/EG composite in the melting and solidification processes were 81.98 o C and 80.43 o C respectively, while the corresponding latent heats were 150.9J/g and 142.6J/g. During both processes, the CW could retain its original vermiform structure after being completely adsorbed by the EG. Compared to the CW alone, the melting and solidification timings of the CW/EG composite were reduced by 81.7% and 55.3% respectively; while its thermal conductivity became 17.4 times higher. After undertaking around 1000 runs of accelerated cooling & heating cycling, the endothermic/exothermic phase change temperatures of the CW and CW/EG composite were increased by only 0.42%/0.42% and 0.23%/0.27% respectively; while their endothermic/exothermic latent heats were reduced by 4.96%/4.78% and 2.05%/3.

Preparation and Properties of Stearic Acid–Acetanilide Eutectic Mixture/Expanded Graphite Composite Phase‐Change Material for Thermal Energy Storage

“…We compared the thermal properties of SA–AA/EG CPCM with those of some CPCM reported previously (Table ). The as‐prepared SA–AA/EG CPCM has a higher enthalpy value than other organic EG‐based CPCM . Therefore, SA–AA/EG CPCM is an excellent potential thermal energy material.…”

Heat transfer evaluation of metal oxides based nano-PCMs for latent heat storage system application

“…Xia et al [18] conducted experimental investigations on expanded graphite (EG) based PCM composite in heat recovery condenser. In case of optimum mass ratio of 10:1, the charging and discharging rates were increased by 81.7% and 55.3%, respectively.…”

Amplified charge and discharge rates in phase change materials for energy storage using spatially-enhanced thermal conductivity

“…Thermal energy can be stored in the form of sensible heat and latent heat [1]. Thermal energy storage in the form of sensible heat occurs primarily through the activation of vibrations, realized as heat capacity within the stor- PCMs to increase their thermal conductivities [14][15][16][17][18][19].…”

“…High radius ratios improve the average charge rate over that of uniform enhancement by more than 100%. The range of B and H result from Eq (19). and Eq.…”