Suitable Phase Change Temperature Research Articles

Synthesis and thermal energy storage properties of xylitol pentastearate and xylitol pentapalmitate as novel solid–liquid PCMs

In this study, xylitol pentastearate and xylitol pentapalmitate were synthesized as novel solid–liquid PCMs by an esterification reaction in order to eliminate the unfavorable thermal properties of xylitol (such as high melting point) and stearic and palmitic acids (such as high melting point, low corrosivity, bad odor, and sublimating property). The synthesized ester compounds were characterized chemically by using Fourier transform infrared (FT-IR) and proton nuclear magnetic resonance (1H NMR) spectroscopy methods. By using the differential scanning calorimetry (DSC) method, the melting temperatures of xylitol pentastearate and xylitol pentapalmitate were measured as 32.35°C and 18.75°C, respectively, while their latent heats of melting were determined as 205.65Jg−1 and 170.05Jg−1 respectively. These results indicate that the synthesized PCMs have high latent heat values and suitable phase change temperatures for thermal energy storage applications. The thermal cycling test shows that the synthesized PCMs have good thermal reliability after 1000 thermal cycles. Thermogravimetric (TG) analysis results also reveal that the PCMs have good thermal stability over their working temperatures.

SSynthesis and Characterization of Chitosan/paraffin Phase Change Microcapsules

Phase change microcapsules were synthesized using chitosan as the shell material and paraffin as the core material via multi-emulsionization and cross-linking method.During the phase change of the paraffin,the microcapsules can store and release energy.The enthalpy value of the phase change of the microcapsules is higher than 110 J/g.The suitable phase change temperature can be obtained by changing the core material.The resultant microcapsules show excellent thermal stability,and remain stable below 150 ℃ as demonstrated by TGA measurement.The microcapsules also exhibit good solvent-resistance because of the cross-linking between chitosan and glutaraldehyde.

Fatty acid esters-based composite phase change materials for thermal energy storage in buildings

Abstract In this study, fatty acid esters-based composite phase change materials (PCMs) for thermal energy storage were prepared by blending erythritol tetrapalmitate (ETP) and erythritol tetrastearate (ETS) with diatomite and expanded perlite (EP). The maximum incorporation percentage for ETP and ETS into diatomite and EP was found to be 57 wt% and 62 wt%, respectively without melted PCM seepage from the composites. The morphologies and compatibilities of the composite PCMs were structurally characterized using scanning electron microscope (SEM) and Fourier transformation infrared (FT–IR) analysis techniques. Thermal energy storage properties of the composite PCMs were determined by differential scanning calorimetry (DSC) analysis. The DSC analyses results indicated that the composite PCMs were good candidates for building applications in terms of their large latent heat values and suitable phase change temperatures. The thermal cycling test including 1000 melting and freezing cycling showed that composite PCMs had good thermal reliability and chemical stability. TG analysis revealed that the composite PCMs had good thermal durability above their working temperature ranges. Moreover, in order to improve the thermal conductivity of the composite PCMs, the expanded graphite (EG) was added to them at different mass fractions (2%, 5%, and 10%). The best results were obtained for the composite PCMs including 5wt% EG content in terms of the increase in thermal conductivity values and the decrease amount in latent heat capacity. The improvement in thermal conductivity values of ETP/Diatomite, ETS/Diatomite, ETP/EP and ETS/EP were found to be about 68%, 57%, 73% and 75%, respectively.

Research on the Thermal Storage Performance of Solid-Solid Phase-Change Material Used in the Wall

Solid-solid phase change material can increase the thermal storage capacity of the wall, decrease the indoor temperature fluctuation and building energy consumption when it was used in the phase change material (PCM) wall. This paper investigated experimentally the phase change temperature and latent heat of polyalcohols binary system with different component, and analyzed the feasibility of phase change wall. The results show that binary systems have suitable phase change temperature and bigger phase change latent. They are ideal phase change materials used in the wall.

Synthesis and thermal energy storage properties of ethylene dilauroyl, dimyristoyl, and dipalmitoyl amides as novel solid–liquid phase change materials

Ethylene dilauroyl, dimyristoyl, and dipalmitoyl amides were synthesized as novel solid–liquid phase change materials (PCMs) via condensation of ethylene diamine with the respective carboxyl chlorides (lauroyl chloride, myristoyl chloride, and palmytoyl chloride). The synthesized ethylene dilauroyl amide (EDLA), ethylene dimyristoyl amide (EDMA), and ethylene dipalmytoyl amide (EDPA) were characterized structurally by FT-IR and 1H NMR spectroscopy techniques. Latent heats of melting and freezing determined using DSC technique were found to be 127.83 and −118.30 J/g for EDLA, 129.95 and −132.40 J/g for EDMA, and 150.66 and −145.22 J/g for EDPA, respectively. Phase change temperatures of these PCMs were ranged between 38.5 and 52.5 °C. The synthesized PCMs were tested for durability by accelerated thermal cyclings including 1000 melting/freezing cycles. Besides the thermal endurance of the PCMs were determined by TG analysis. Based on the results it was concluded that EDLA, EDMA, and EDPA compounds synthesized as novel solid–liquid PCMs have considerable amount of thermal energy storage potential in terms of suitable phase change temperatures, high latent heats, thermal reliability, and thermal stability. Moreover, the other advantages of the synthesized PCMs over the fatty acids used are better odor, low corrosivity, and low sublimation rates.

Experimental Investigation of Performances of Microcapsule Phase Change Material for Thermal Energy Storage

AbstractPerformances of microcapsule phase change material (MPCM) for thermal energy storage are investigated. The MPCM for thermal energy storage is prepared by a complex coacervation method with gelatin and acacia as wall materials and paraffin as core material in an emulsion system. A scanning electron microscope (SEM) was used to study the microstructure of the MPCM. In thermal analysis, a differential scanning calorimeter (DSC) was employed to determine the melting temperature, melting latent heat, solidification temperature, and solidification latent heat of the MPCM for thermal energy storage. The SEM micrograph indicates that the MPCM has been successfully synthesized and that the particle size of the MPCM is about 81 μm. The DSC output results show that the melting temperature of the MPCM is 52.05 °C, the melting latent heat is 141.03 kJ/kg, the solidification temperature is 59.68 °C, and the solidification latent heat is 121.59 kJ/kg. The results prove that the MPCM for thermal energy storage has a larger phase change latent heat and suitable phase change temperature, so it can be considered as an efficient thermal energy storage material for heat utilizing systems.

Thermal Characteristics of Paraffin/Expanded Perlite Composite for Latent Heat Thermal Energy Storage

This study focuses on the preparation and thermal properties of paraffin/expanded perlite composite as novel form-stable phase change material for latent heat thermal energy storage by vacuum impregnation method. The paraffin could be absorbed in pores of expanded perlite as much as 55 wt% without melted phase change material seepage from the composite and this mixture was described as form-stable composite phase change material. The melting and freezing temperatures and latent heats of form-stable composite phase change material were measured using differential scanning calorimetry analysis. The thermal cycling test indicated that the form-stable composite phase change material had good thermal reliability in terms of the changes in thermal properties after 5,000 thermal cycling. Thermal conductivity of the form-stable composite phase change material was increased by about 46% by adding 5 wt% expanded graphite. The results indicated that the prepared form-stable paraffin/expanded perlite/expanded graphite composite phase change material has a great potential for latent heat thermal energy storage systems solar passive heating purposes due to suitable phase change temperature, high latent heat capacity, good thermal reliability, and thermal conductivity.

Capric–myristic acid/expanded perlite composite as form-stable phase change material for latent heat thermal energy storage

The aim of this study is to prepare a novel form-stable phase change material (PCM) for latent heat thermal energy storage (LHTES) in buildings. A eutectic mixture of capric acid (CA) and myristic acid (MA) is incorporated with expanded perlite (EP). Thermal properties, thermal reliability, and thermal conductivity of the form-stable composite PCM are determined. The maximum CA–MA absorption of EP was found to be 55 wt% without melted PCM seepage from the composite, and therefore this mixture was described as a form-stable composite. The form-stable composite PCM was characterized using the FT-IR spectroscopy method. The melting and freezing temperatures and latent heats of form-stable composite PCM were measured using DSC analysis. Thermal cycling test of the form-stable composite PCM indicated good thermal reliability in terms of changes in thermal properties after 5000 thermal cycling. The thermal conductivity of the form-stable CA–MA/EP composite PCM was increased about 58% by adding 10 wt% expanded graphite (EG). The form-stable CA–MA/EP/EG composite PCM was considered as an effective LHTES material in the building energy conservation due to suitable phase change temperatures, high latent capacities, good thermal reliability, and good thermal conductivity.

Study on preparation of montmorillonite-based composite phase change materials and their applications in thermal storage building materials

Three composite phase change materials (PCMs) were prepared by blending butyl stearate, dodecanol and RT20 with an organically modified montmorillonite (MMT), respectively. After the three composite PCMs were characterized by DSC, it was indicated that the RT20/MMT composite PCM was a good candidate for building applications due to its large latent heat, suitable phase change temperature and good performance stability. Compared with RT20, the RT20/MMT composite PCM exhibited higher heat transfer efficiency and had good compatibility with gypsum due to the combination with MMT. The composite gypsum boards containing RT20/MMT composite PCM had the function of reducing building energy consumption by reducing the indoor temperature variation, and the function was enhanced with the increase in the mass ratio of the RT20/MMT composite PCM.

Preparation and thermal properties of ethylene glycole distearate as a novel phase change material for energy storage

The latent heat thermal energy storage (LHTES) capacity of phase change materials (PCMs) increases with molecular weight and secondary interactions as their efficiency depends on the energy storage capacity per unit mass during its melting and freezing. In this study, ethylene glycole distearate (EGDS) as a novel PCM having high energy storage capacity (215.80 J/g) and suitable phase change temperature for LHTES was synthesized by esterification of stearic acid with ethylene glycol. The esterification reaction was proven by Fourier Transform Infrared (FT-IR) Spectroscopy. Thermal stability of the novel PCM was investigated by thermal cycling (1000 melting/freezing cycles). Latent heats of melting and freezing of EGDS were found 215.43 J/g–216.45 J/g by Differential Scanning Calorimetry (DSC) method, respectively after thermal cycling as melting and freezing temperatures were 65.35 and 65.83 °C, respectively. Thermal gravimetric analysis (TGA) was used to determine endurance of EGDS.