Simulation of Heat Exchangers in Fossil Fired Power Plants: A Method to Avoid Gibbs' Phenomena

Abstract

Heat exchangers are the most important processes in fossil fired power plants. In order to account for the non-trivial spatial distribution of relevant process variables (e.g. fluid entropy and mass flow) along the fluid flow direction, mass, energy and momentum conservation laws should be written with distributed parameters. If the typical lumped parameter approach is adopted, for long exchangers, then it happens that the dynamic phenomena associated with the transport of thermal properties along the fluid flow are misrepresented, typically because parasitic effects superimpose significant non-physical oscillations to the time solution. As a consequence, it is quite common that process delays are misinterpretated, leading to incorrect understanding of basic process dynamics relevant to design. In the paper, a method is proposed to integrate the said conservation laws based on the characteristic line approach: this avoids parasitic effects and permits high accuracy.