Experimental study on thermal and chemical stability of pentaerythritol blended with low melting alloy as possible PCM for latent heat storage

Publication date: November 2017
Source:Experimental Thermal and Fluid Science, Volume 88
Author(s): K.P. Venkitaraj, S. Suresh
This paper presents the experimental investigation on the performance of a novel organic Solid-Solid/Low Melting Alloy composite PCM for thermal energy storage applications. Poly alcohols are solid-solid organic PCMs having low heat transfer characteristics due to their poor thermal conductivity. So additives are used to improve the thermal properties of poly alcohols. Metal and its alloys with low melting point exhibit a much stronger heat transfer capacity than that of traditional organic PCMs. Therefore, low melting metals and alloys can be considered as effective additives for improving the thermal performance of organic PCMs. But the presence of additives used for enhancing the heat transfer characteristics may result in thermal and chemical degradation of the material. In this experimental work, the effect of adding the low melting alloy (LMA) of Bi, Sn, Zn and In on the thermal and chemical stability of Pentaerythritol (PE) was investigated using the characterisation methods such as TGA-DTA, DSC and FTIR. For this, thermal cycling of pure PE, and PE mixed with 0.1% & 0.5% of LMA were performed. The characterisation results of PE mixed with LMA after 100 thermal cycles were compared with pure PE samples. The thermal conductivity of the PCM samples was studied using laser flash method. It was found that thermal conductivity of PE, PE+0.1%LMA, and PE+0.5%LMA after 100 thermal cycles decreased by 3.21%, 4.55% and 10.08%. Thermogravimetric analysis of pentaerythritol added with LMA showed a noticeable change in material thermal behavior due to thermal cycling. The test results revealed that the weight loss in the pure PE was lower than the weight loss for PE samples mixed with LMA subjected to 100 thermal cycles. The FTIR results did not show the formation of any new chemical bonds in pentaerythritol and therefore PE samples with LMA additives can be considered as chemically stable during thermal cycling. DSC and DTA results showed about 6%, 8% and 15% of the decrease in enthalpy value after 100 thermal cycles for pure PE, PE+0.1%LMA and PE+0.5%LMA respectively. Thermal storage/release test conducted showed a decrease of 14.64% and 30.22% in the time taken for total energy storage and release for PE+0.1%LMA and PE+0.5%LMA compared to pure PE.

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