A Parametric Study of the Heat Transfer in the Convection Chamber of a Utility Boiler

摘要

A mathermatical mdoel of the physical phenomena taking place in the convection chamber of a utility boiler is paplied to quantify the influence of several parameters on the heat transfer. The flow field calcuation is based on the numerical solution of the equations goverming mass, momentum and energy conservation and transport equations for the turbulent quantites. Th 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 exchenagers in sdetermined by means of energy balances performed along each exchanger. The flow and the heat transfer calucations are performed in sequence in an interative fashio. It is found that the fouljg resistance on the inner side of the tubes has only a marginal influence on the results, contrary to the outer, fouling resistance which strogly 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 onthe heat transfer rate is quantfied. The influence of the emissivity of the walls is found to be small, while tyhe infl,uence of the emissivity of the tube bundles is larger, but still marginal.