NUMERICAL-CALCULATION OF THE EFFECT OF DEPOSIT FORMATION ON HEAT-EXCHANGER EFFICIENCY

A numerically calculated deposit was used to identify the shape of a f ouled tube and an orthogonal curvilinear grid was constructed in and a round the deposit. The flow and temperature field was calculated and a n implicit boundary condition, accounting for the effects of turbulenc e, was introduced at the solid-fluid interface for the simultaneous ca lculation of the temperature held in the fluid and the solid. Validati on is presented against experimental and numerical calculations. Final ly, a reduction of 8-17% in the heat transfer rate was found to occur for a deposit corresponding to 8 h of operation in a staggered tube bu ndle heat-exchanger of a lignite utility boiler. Thermal resistance of the deposit was also calculated. (C) 1997 Elsevier Science Ltd.