Experimental and numerical research of thermal processes in the ТST Tanks with thermal oil and a phase change medium

Abstract

This paper surveys a part of the activities (performed during the realization of the third year of project III 42011 financed by the Ministry of education and science of the Republic of Serbia) on the development of TST whose storage medium melts at the atmospheric pressure, enabling on that way the use of the energy of phase change for energy storage. The original experimental setup adapted for use of paraffin as a phase change media (volume 77 dm3, heating power 2.4 kW) was modified by inserting four vertically positioned tubes (inner diameter 120 mm) filled by paraffin into the tank. The rest of the tank was filled with thermal oil. Storage media was cooled by the air which circulates around the tank. The research was realized in two phases: a) with thermal oil as the only storage media; b) with the combination of paraffin and thermal oil. Inside the main body of the tank the temperature measurements were performed by 12 thermocouples, 4 along the tanks height and 3 along the tank radius, and inside the cylinder filled with paraffin with 4 vertically positioned thermocouples. For the development of the numerical model of heat transfer and fluid flow processes in TST a commercial numerical package Fluent 12.1 was used, since it possesses its own routine for computation a temperature and flow fields in TST with the change of phases, but also it allows to user to implement the package with its own model by using the user define functions. Measurements and the numerical computation were performed for nonstationary as well as for stationary working regimes. A good agreement between the numerical and experimental results was achieved.