Experimental determination of temperature-dependent thermal conductivity of solid eicosane-based nanostructure-enhanced phase change materials

The effective thermal conductivity of composites of eicosane and copper oxide nanoparticles in the solid state was measured experimentally by using the transient plane source technique. Utilizing a controllable temperature bath, measurements were conducted at various temperatures between 10 and 35 °C for the solid samples. In the course of preparation of the solid specimen, liquid samples with eight different mass fractions (0, 1, 2, 3.5, 5, 6.5, 8 and 10 wt%) of nanoparticles were poured into small diameter molds and were degassed within a vacuum oven. The molds were then subjected to one of the three solidification procedures, i.e. ambient solidification, ice-water bath solidification or oven solidification method. Measured thermal conductivity data of the composites were found to be nearly independent of the measurement temperature for a given loading of CuO nanoparticles regardless of the solidification procedure. Irrespective of the solidification method, as the melting temperature was approached, thermal conductivity data of the solid disks rose sharply for the three sets of samples. The ice-water bath solidification route for the eicosane–CuO samples consistently exhibited the lowest values of thermal conductivity, whereas the samples of oven solidification scheme exhibited to the highest values. This behavior is assumed to be due to the greater void percentage of ice-water bath samples and/or crystal structure variations due to the adopted phase transition method.