Transient CFD simulation of charging hot water tank

Abstract

This paper presents characteristics of heat accumulation system operation in one of the Polish combined heat and power (CHP) plants. The heat source cooperating with this installation is cogeneration units consisting of gas engines with a total heat output of 8 MWt and total electrical power of 8 MWe. The total thermal capacity of the non-pressure hot water accumulator is 75 MWh. An important issue in the case of hot water tanks is thermal stratification caused by the difference in density between higher-temperature water, located at the top of the hot water storage tank and colder water at its bottom. The article presents the results of numerical analysis based on the axial-symmetric model of a hot water tank using Ansys Fluent R19.2 software. Simulations with the Computational Fluid Dynamics (CFD) method were carried out for the process of charging the heat accumulator lasting 10 h. The effect of mesh density on the results obtained was analysed. The results were compared with the measurement data from the CHP plant. Heat losses from the hot water tank were taken into account and the density characteristics of the heat flux lost to the environment were presented.