Approximation of Fundamental Equations for Finite-Dimensional Modeling of Thermo-Fluid Processes

Abstract

Finite-dimensional lumped models of thermo-fluid processes are usually formulated from fundamental conservation equations. In dynamic modeling and system simulation, internal energy is often replaced by enthalpy in the energy conservation equation without considering the work term (p/ρ). For compressible fluids, this leads to a significant dynamic error, although the steady-state results are unchanged. A more exact formulation, presented here, can be easily implemented. A numerical example is given for a typical case.