Simulation of thermal stratification in the heat storage for CHP plant

Abstract

Thermal stratification phenomenon is successfully used to store and retrieve thermal energy from heat storages. The aim of this study is to compare two simulation models for describing thermal stratification in the heat storage tank used in the cogeneration (CHP) plant at any time. In this paper analytical and numerical analyses have been carried out to show temperature fields inside the heat storage. The first analytical model is done using an energy balance which is created and solved for each layer of the stratified heat storage. This model shows a simple onedimensional approach to theoretical analysis of thermal stratification. The other numerical model is implemented using a multi-purpose computation fluid dynamics (CFD) software PHOENICS. Two-dimensional transient model was created and solved numerically. The validation of simulated results is made successfully by the comparison against the actual data gathered from Hvide Sande CHP plant in Denmark. A good agreement with actual data is observed. The average relative discrepancy varied from 0.22 % to 5.00 % in analytical modelling and from 0.21 % to 3.66 % in numerical simulation, when the duration of simulated processes lasts from 15 min to 6 hours.