DETERMINATION OF HEAT CAPACITY AND HEAT CONDUCTIVITY COEFFICIENT OF PHASE TRANSITION MATERIALS USING THE T-HISTORY METHOD UDC: 662.997

Abstract

It is known that the demand for energy in the world is increasing, traditional fuel resources are not evenly distributed on the globe, and the negative impact of carbon dioxide gases on the environment is high when using them. Today, determining the relative heat capacity of substances that increase the possibilities of using solar energy and accumulate the obtained energy, as well as the use of phase change materials for solar devices is an effective way to prevent energy shortages.
In this article, the specific heat capacity and heat transfer coefficient of paraffin, which is one of the phase change materials, in liquid and solid state, is determined by the results obtained during experiments in laboratory conditions, as well as theoretical calculations.
In this article, as a result of experimental research conducted by the authors in laboratory conditions, the thermal properties of phase change material (PCM) were determined using the T-history method. In this case, methods of experimental research of heat capacities of substances, determination and calculation of heat-technical parameters were used.
Based on the results obtained by the authors from the experiment, the relative heat capacity of paraffin in liquid (cp,l) and solid (cp,s) state, heat of synthesis (Hm) and heat transfer coefficient (ks) were determined. According to the calculations, specific heat capacity of paraffin in liquid state cp,l=3545 J/(kg∙K), specific heat capacity during solidification cp,s=5288 J/(kg∙K), fusion heat Hm= 256 103 J/kg and the coefficient of thermal conductivity was found to be equal to ks=0.168 W/(m∙K).
The specific heat capacity and heat transfer coefficient ks of paraffin in liquid cp,l and solid cp,s states were determined. It was determined that during the solidification process (phase change process) of PCMs, the specific heat capacity increases up to 60 kJ/(kg∙K). It is shown that the temperature at the highest point of relative heat capacity is the melting and solidification temperature for this material. In order to ensure the continuous operation of solar devices, the thermal technical parameters of paraffin as a heat collecting material were studied.