Increasing the thermal conductivity of the phase-change material graphene nanotubes

Abstract

The paper presents the results of experimental studies of the use of graphene nanotubes to increase the thermal conductivity of a phase-changing material. Graphene nanotubes were dispersed in molten paraffin by ultrasonic treatment in an amount of 0.1–0.5 wt.%. The obtained samples of paraffin with graphene nanotubes were examined on a scanning calorimeter. All samples with different content of nanotubes during heating and cooling on the DSC curves had two peaks corresponding to the phase transitions of the main hydrocarbons that are part of the paraffin. The presence of nanotubes in paraffin did not significantly affect the shape of the DSC curves. Expe¬riments with sample heating in a thermostat in terms of the time delay in changing the temperature of the samples indicated an increase in the thermal conductivity of paraffin in the solid state when graphene nanotubes were added to it and a decrease in the liquid state. These effects increased with increasing mass content of nanotubes. The method of stationary heat flow was used to determine the coefficient of thermal conductivity of samples of a phase-changing material with nanotubes. According to the measurement results, the maximum increase in the thermal conductivity of paraffin in the solid state was 22 % at a nanotube concentration of 0.5 wt.%. The thermal conductivity coefficients of various materials with «contrasting» inclusions are compared accor¬ding to the results of calculations and experiments.