Thermophysical characterization of a by-product from the non-metallic industry as inorganic PCM

Physical characterization and thermal properties of bischofite, a by-product from the non-metallic industry, were determined and compared with those to MgCl2 center dot 6H(2)O with the idea of using it as phase change material in thermal energy storage applications. The melting point and heat of fusion were measured in the temperature range from 30 degrees C to 150 degrees C, where T-fus and Delta H-fus were 100 degrees C and 115 kJ/kg for bischofite, and 114.5 degrees C and 135 kJ/kg for MgCl2 center dot 6H(2)O. The solid heat capacity was determined from 25 degrees C to 60 degrees C, being 2.1 kJ/(kg K) at 60 degrees C for both samples. The measurements of the liquid heat capacity of bischofite were done from 115 degrees C to 125 degrees C and the Cp showed linear increase from 1.71 kJ/(kg K) to 3.01 kJ/(kg K). The thermal stability test (30 heating/cooling cycles) of bischofite and MgCl2 center dot 6H(2)O shows subcooling of about 37 K and 29 K, respectively. The solid and liquid densities were determined using the Pycnometrically method; for bischofite, rho(solid) decrease from 1686 (at 30 degrees C) to 1513 kg/m(3) (at 50 degrees C) and rho(liq) was 1481 kg/m(3) (at 115 degrees C). Based on the thermophysical properties evaluated, the energy storage density was evaluated for both materials, being 170 J/cm(3) for bischofite and 192 J/cm(3) for MgCl2 center dot 6H(2)O. This study established that bishofite is a promissory PCM with similar thermophysical characteristics to magnesium chloride hydrate, but With a lower cost. Nevertheless, further work is needed to overcome the two main problems found, subcooling and segregation of the material. (C) 2014 Elsevier B.V. All rights reserved.