An experimental and theoretical investigation into the heat transfer of a finned water wall tube in a circulating fluidized bed boiler

Abstract

Heat transfer improvement in a water wall tube with fins was investigated in a circulating fluidized bed (CFB) boiler. Experiments were first conducted in a 6 MWth CFB boiler then a model was developed to analyse and interpolate the results. Temperatures at some discrete points within the wall cross‐section of the tube were measured by burying 0.8 mm thermocouples within a tube. Experimental data showed an increase in heat absorption up to 45 per cent. A good agreement between measured and predicted values was noted. The distribution of temperature in the metal wall and of heat flux around the outer wall of a tube with longitudinal and lateral fins was analysed by numerical solution of a two‐dimensional heat conduction equation. Effects of bed‐to‐wall heat transfer coefficient, water‐to‐tube inside heat transfer coefficient, bed temperature, water temperature and thermal conductivity of the tube material on the heat flux around the water tube are discussed. The present work also examines the influence of the length of the longitudinal fin and the water tube thickness. Heat flux was highest at the tip of the longitudinal fin. It dropped, but increased again near the root of the lateral fin. Copyright © 2000 John Wiley & Sons, Ltd.

An experimental investigation of the effect of longitudinal fin orientation on heat transfer in membrane water wall tubes in a circulating fluidized bed

“…Reddy and Nag [12] reported that the addition of a longitudinal fin to membrane tube at the tube crest leads to an increase in the heat absorption from bed to wall but results in a drop in the heat transfer coefficient. An increase in heat absorption up to 45% is found in the work of Basu and Cheng [10]. Since the fact that fin efficiency increases with a decrease in fin height, for the same surface area, heat transfer might be improved by adding shorter longitudinal fins.…”

Rapid Rise Of Heat Input Effects On The Tubes Characteristics In Boiler Of Steam Power Plant

“…The linear zed behavior can be described by the wet surface ( d A ) at the operating level. The deviation of the drum level ( l ) measured from its normal operating level is [29] To measure the drum level response with firing rate change, read drum level directly from the glass gauge (d11) with the same time when we measure the drum pressure at increasing firing rate by (10% and 20%) . Repeat the same procedure above but in opposite i.e.…”

Effect of flue gas recirculation on heat transfer in a supercritical circulating fluidized bed combustor

“…For this reason, detailed knowledge and experience about the heat transfer mechanisms inside a large-scale furnace chamber are major aspects to properly design an effective active heat transfer surface and to achieve desirable high performance in the circulating fluidized bed combustor. Recent research studies have been focused on heat transfer characteristic in the laboratory or pilot scale [14][15][16][17][18], but as far as author knows, there are not studies about how flue gas recirculation influences heat absorption from the bed material to the membrane wall in large-scale CFB unit. This fact is due to measuring difficulties and commercial reasons.…”