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Erythritol Tetra Myristate and Erythritol Tetra Laurate as Novel Phase Change Materials for Low Temperature Thermal Energy Storage

In this study, erythritol tetra myristate and erythritol tetra laurate, as novel phase change materials (PCM) for latent heat thermal energy storage, were synthesized by the direct esterification reaction of the erythritol with myristic and lauric acids. The esterification reactions were proven by using Fourier transform infrared and nuclear magnetic resonance (1H NMR) spectroscopy techniques. The melting and freezing temperatures and latent heats of the esters were measured using differential scanning calorimetry analysis. The melting temperatures and latent heats of the erythritol tetra myristate and erythritol tetra laurate esters were determined as 10.82 and −9.03°C and 180.90 and 161.39 J/g, respectively. The thermal cycling test indicated that the synthesized esters had good thermal reliability in terms of the changes in thermal properties after 1,000 thermal cycling. Thermal stability of the PCM was also investigated by using thermal gravimetric analysis. Moreover, the thermal conductivities of the synthesized esters were increased by about 28% for erythritol tetra myristate and 25% for erythritol tetra laurate by addition of 5 wt% expanded graphite. Based on all these results, it can be concluded that the synthesized esters as novel solid-liquid PCM have great potential for low temperature applications, such as transport of blood, operating tables, hot-cold therapies, and refrigerators.

Thermal energy storage characteristics of micro-nanoencapsulated heneicosane and octacosane with poly(methylmethacrylate) shell

Abstract In this study, PMMA/heneicosane (C21) and PMMA/octacosane (C28) micro-nano capsules were fabricated via emulsion polymerisation method. The chemical structures of the fabricated capsules were verified with the FT-IR spectroscopy analysis. The results of POM, SEM and PSD analysis indicated that most of the capsules were consisted of micro/nano-sized spheres with compact surface. The DSC measurements showed that the capsules had melting temperature in the range of about 39–60 °C and latent heat energy storage capacity in the range of about 138–152 J/g. The results of TGA showed that sublimit temperature values regarding the first degradation steps of both capsules were quite over the phase change or working temperatures of encapsulated paraffins. The thermal cycling test exhibited that the capsules had good thermal reliability and chemical stability. Additionally, the prepared capsules had reasonably high thermal conductivity.

Thermal Energy Storage Properties of Xylitol Penta Myristate and Xylitol Penta Laurate as Novel Solid-liquid Phase Change Materials

In this study, xylitol penta myristate and xylitol penta laurate were prepared as novel solid-liquid phase change material by means of esterification reaction. These esters were characterized chemically using a Fourier transform infrared spectroscopy method. By using a differential scanning calorimetry method, the melting temperatures of xylitol penta myristate and xylitol penta laurate were measured as 50.28 and 43.53°C, respectively, while their latent heat values were determined as 199.50 and 184.71 J/g, respectively. These results indicated that the synthesized esters had high latent heat of melting and suitable phase change temperatures for thermal energy storage applications. A thermal cycling test showed that the synthesized phase change materials had good thermal reliability after thermal 100 melting-freezing cycles. Thermogravimetric analysis results also revealed that the phase change materials have good thermal stability over their working temperatures.

Effects of carbon nanotubes additive on thermal conductivity and thermal energy storage properties of a novel composite phase change material

Fatty acids are commonly preferred as phase change materials for passive solar thermoregulation due to their several advantageous latent heat thermal energy storage (LHTES) properties. However, further storage container requirement of fatty acids against leakage problem during heating period and also low thermal conductivity significantly limit their application fields. To overcome these drawbacks of capric acid–stearic acid eutectic mixture as phase change material, it was first impregnated with expanded vermiculite clay by melting/blending method and then doped with carbon nanotubes. The effects of carbon nanotubes additive on the chemical/morphological structures and LHTES properties of the composite phase change material and thermal enhanced change phase change materials were investigated by scanning electron microscope, Fourier transform infrared spectroscopy, X-ray diffraction, differential scanning calorimetry and thermogravimetric analysis analysis techniques. The differential scanning calorimetry results showed that the form-stable composite phase change materials and thermal enhanced composite phase change materials have melting temperatures in the range of 24.35–24.64℃ and latent heat capacities between 76.32 and 73.13 J/g. Thermal conductivity of the composite phase change materials was increased as 83.3, 125.0 and 258.3% by carbon nanotubes doping 1, 3 and 5 wt%. The heat charging and discharging times of the thermal enhanced -composite phase change materials were reduced appreciably due to the enhanced thermal conductivity without notably influencing their LHTES properties. Furthermore, the thermal cycling test and thermogravimetric analysis findings proved that all fabricated composites had admirable thermal durability, cycling LHTES performance and chemical stability.