Using mixtures of fatty acid methyl esters as phase change materials for concrete
Phase change materials (PCMs) are an effective way of storing/releasing thermal energy via phase transformations. Incorporating PCMs into concrete pavements at airports has been suggested as a means to reduce the accumulation of snow and ice on runways. This thesis reports on the development of two phase change materials composed of binary mixtures of fatty acid methyl esters (FAME) which provide a solid-liquid transition slightly above 0°C with a high enthalpy of fusion. Current findings of this study indicate that these mixtures have the necessary properties to be a high performance PCM with the potential to reduce the levels of icing on concrete pavements. Additionally, possible methods to incorporate this PCM into concrete were examined specifically ambient and vacuum absorption into concrete aggregate and encapsulation in a SiO2 shell. Mixtures plant triacylglycerols and mixtures of saturated and unsaturated FAMEs of different carbon chain lengths (C8-C18) were investigated for targeted thermal properties, including a phase transition temperature slightly above 0°C, high latent enthalpy of fusion, high heat capacity and high thermal conductivity. Two binary mixtures were identified with suitable thermal properties to be used as a PCM: (1) methyl laurate + methyl myristate, xlaurate =0.77 ± 0.01, and (2) methyl laurate + methyl palmitate, x laurate=0.86 ± 0.01. Using differential scanning calorimetry, Tammann plots and phase diagrams were created; indicating that the phase behavior of these binary mixtures at their eutectic compositions demonstrated useful properties as PCMs. Overall, the maximal amount of methyl esters that can be absorbed into lightweight aggregate was achieved through vacuum absorption at room temperature (approximately 24% m/m). However, this may not be practical in industrial scales, hence an alternative method, such as embedding a tube filled with a methyl ester mixture into the concrete system, should be investigated
Tao, Purdue University.
Alternative Energy|Chemical engineering
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