Master's Thesis Christian Grozescu

 

Extension of Thermal Storage Models for Energy System Simulations

Temperature distribution Copyright: EBC Temperature distribution in a hot water storage tank during de-charging (CFD simulation)

For the usage of hot water storage tanks (HWST) in energy systems, it is important to know not only the gross energy content, but also the temperature at which hot water is available. To simulate the temperature distribution inside a HWST in large systems, 1D finite volume models are used. This thesis presents an adaptable 3D CFD model, that can be used to simulate the operation of HWST accurately, in order to have a validation basis for such low-order models over a wide range of parameters, without the need for experiments. Therefore, a parametric geometry with the features of most common HWST is implemented. It is adapted to setups used in previous experiments,

including a 150 l HWST for electric heating experiments, the same HWST modified for discharging experiments and a 500 l HWST for a charging experiment. Simulations are carried out using the same conditions as in the experiments. Comparison against experimental data shows, that the CFD simulations accurately predict most phenomena in HWST and are therefore suitable for future parameter variations.

A parametric study is then performed using a CFD model, to investigate the behavior of water rising due to buoyancy inside a HWST. From the simulation results, parameters for an empiric buoyancy model for HWST are derived. The newly developed buoyancy model is used to simulate the effects of buoyant water flows on the temperature profile of a HWST. It is integrated in the low-order HWST model and validated against experimental data.