Object-oriented modeling for the transient response simulation of multi-pass shell-and-tube heat exchangers as applied in active indirect thermal energy storage systems for concentrated solar power

This work focuses on the transient numerical modeling of multi-pass shell-and-tube heat exchangers that apply single-phase fluids. A one-dimensional modeling approach is used for the heat exchanger ducts. The governing partial differential equations are solved numerically by applying the finite volume method. In particular, the commonly applied cell-method is used, which is presented in a flexible, intuitive and simulation-platform-independent way. Simulation results are checked for consistency by comparing them to theoretical as well as experimental data available in the literature. Subsequently, the presented modeling approach is used for a specific case study, showing the transient behavior of a typical heat exchanger train configuration currently used at active indirect thermal energy storage systems for CSP (concentrated solar power). Typical process parameters (process gain, dead time and time constant) are given for charging as well as for discharging mode at different heat exchanger loads. Furthermore, transient response simulation results are discussed in detail, providing all used boundary conditions and assumed heat exchanger specifications, thus enabling future model comparison studies. Finally, suitable degrees of discretization are discussed for transient CSP performance simulations on system level, offering a good trade-off between simulation speed and accuracy. Modelica is used as modeling language.