A parametric study of the heat transfer in the convection chamber of a utility boiler

A mathematical model of the physical phenomena taking place in the convection chamber of a utility boiler is applied to quantify the influence of several parameters on the heat transfer. The flow field calculation is based on the numerical solution of the equations governing mass, momentum and energy conservation and transport equations for the turbulent quantities. The distributed resistance concept is used to deal with the drag force caused by the heat exchangers. The heat transfer from the combustion products to the steam flowing in the heat exchangers is determined by means of energy balances performed along each exchanger. The flow and the heat transfer calculations are performed in sequence in an iterative fashion. It is found that the fouling resistance on the inner side of the tubes has only a marginal influence on the results, contrary to the outer fouling resistance which strongly affects the steam temperature at the exit from the final superheater and reheater. The influence of the opening angles of the plates of the control dampers on the heat transfer rate is quantified. The influence of the emissivity of the walls is found to be small, while the influence of the emissivity of the tube bundles is larger, but still marginal.