Determination of loss coefficients for high-temperature flow devices: An entropy-based approach

Thermodynamic analysis of a high-temperature confined turbulent gas-jet is presented in this paper. The numerical model is two dimensional, steady, and includes the effect of gravity in the governing equations. Computations are carried out with a commercial CFD code and the local exergy losses are determined as post processed quantities. The analysis takes into account the second law effects of viscous dissipation, heat conduction and convection, and radiative heat transfer. The study is extended by conducting a parametric investigation to determine the effects of Reynolds number, inlet fluid temperature, optical thickness, and Planck number on the exergy loss coefficient, which is defined as the total exergy destroyed per unit mechanical energy input. The results show that exergy loss trough radiation entropy production is higher than that due to heat conduction and convection when the inlet gas temperature is high. It has also been found that in contrast to the conventional head loss coefficient, the exergy loss coefficient increases with inlet gas temperature, optical thickness, and Planck number.