Development of the Instrumentation and Modeling for Heat Transfer Characteristics in CFBC

This technical report summarizes the research conducted and results obtained during the period beginning October 1, 1999 to March 31, 2000. Heat transfer characteristics study and experimental work were continued using the bench-scale CFB system with the heat transfer probe. A copper tube with thermocouples was used as the heat transfer probe which was convenient to measure the temperature changes at different locations of the bed. The heat transfer coefficient at different locations of the heat transferring surface decreases along the slides down the heat transfer surface; its temperature increase, which reducing the temperature difference between the surface of the tube and the bulk of the bed. The radial variation of heat transfer coefficients showed little increase in heat transfer coefficient near the wall. It is believed that a long heat-transferring surface is located in the core region; a boundary layer develops near the wall of the surface. This may cause clusters or streamers to form which slides down the surface. According to the results, heat transfer coefficients in the core region are not affected significantly by the location of the probe. The wall conduction resistance was eliminated and heat transfer coefficients were measured and calculated at different locations along the bed height. Heat transfer coefficients near the wall area of the bed are decreased along with the length of the probe. Heat transfer coefficient was slightly dropped when the probe was moved from the wall area to the central area of the bed.