PCM in Water Emulsions: Supercooling Reduction Effects of Nano‐Additives, Viscosity Effects of Surfactants and Stability

Abstract

This study aims to develop a paraffin‐based phase change material (PCM) for water emulsions with a low degree of supercooling, high fluidity and stability, which can be applied in thermal energy storage (TES) systems to improve the cooling efficiency. A hexadecane/water emulsion was prepared and chemically modified multi‐wall carbon nano‐tube (MWCNT) particles were dispersed in the emulsion as a nucleating agent to reduce supercooling. Three surfactants were also tested on the properties of the hexadecane/water emulsions. Thermal analysis by differential scanning calorimeter (DSC) indicated that the degree of supercooling of the emulsion was significantly decreased by the nucleating agent. The effective nucleating agent concentrations required for the PCM liquid were found to be low, which agrees with the previous finding, but for the emulsion there appeared to be a minimum effective concentration to reduce the supercooling. The rheology characters and the stability of the emulsions were also observed and discussed.

Graphite nanoparticles-dispersed paraffin/water emulsion with enhanced thermal-physical property and photo-thermal performance

“…Comparatively, PCM emulsions have several advantages such as simple process for emulsifying [18], negligible thermal resistance of the protective surfactant layer, and good operation stability [8]. Consequently, PCM emulsions have attracted an increasingly interest in recent years, which researches mainly focus on preparing stable PCM emulsions by selecting suitable emulsifiers [8,[19][20][21], reducing the supercooling of the PCM emulsions with low phase change temperatures by adding higher melting temperature PCM [22,23], suitable surfactants [24] as well as nanoparticles [25,26], together with investigations on the rheological properties of PCM emulsions [27,28]. It has been found that the viscosity of a PCM emulsion increases with the mass fraction of the PCM, and the PCM emulsions with a mass fraction of the PCM lower than 50 wt% is more suitable for practical application [27].…”

Preparation of Stable Phase Change Material Emulsions for Thermal Energy Storage and Thermal Management Applications: A Review

“…It is easier for the larger droplets to form nuclei, and also for the containment of nucleating agents (NAs). Nanoparticles such as graphite [ 76 ], graphene [ 77 ], multi-wall carbon nanotubes (MWCNTs) [ 78 ] and nano-SiO 2 [ 72 , 74 ] and organic materials with higher melting points (paraffin [ 79 ] and fatty acids [ 71 , 80 ]) have been applied as nucleating agents to lower the supercooling. However, the introduction of NAs usually negatively affects stability.…”

Preparation and Experimental Evaluation of Phase-Change Characteristics in Carbon-Based Suspensions

“…The T cp during the charging process is higher than the starting temperature ( T cs ), which means that subcooling (or supercooled) occurs. The difference between T dp and T cp was defined as the SD of the sample [ 19 , 33 , 34 ]. The area of the charging and discharging peaks was calculated using DSC test software (Universal Analysis 2000, TA, New Castle, DE, USA) to obtain the phase-change heat for solidification (Δ H s ) and for melting (Δ H m ).…”