Dynamic Simulation Model of a Two-Fluids Heat Exchanger Based on a Numerical Discretization Method

The present paper deals with both the steady-state and dynamic simulation of a double-pipe heat exchanger, in parallel-flow or counterflow arrangement. In particular, the article describes the thermodynamic model that has been implemented in the Matlab/Simulink environment; the main hypotheses and physical parameters, which characterize the simulation model, are listed. The paper is focused on the discretization of the heat exchanger which has been divided into N cells, each modeled by means of the energy balance equation. It’s important to point out that the model considers the storage of thermal energy in the metal parts and the method of discretization, that has been adopted, gives just acceptable results dividing the heat exchanger in a small number of cells. The paper shows some results of the steady-state simulation of a counterflow heat exchanger, as a function of the number of cells, and the effects of some typical transient operating conditions are described.