Transient thermal behavior in brick tunnel kiln with guide vanes: Experimental study

Time-dependent measurements are essential to describe the temperature and heat transfer coefficient development lead to understanding the unsteady nature of tunnel kiln behavior during cooling. The present paper introduces experimental investigations in a brick tunnel kiln equipped with a U-shape guide vane to monitor its transient thermal behavior. The experimental test rig of scale 1:4 has been fabricated for this purpose. Three U-shape guide vanes have attack angles (theta = 120 degrees, 135 degrees, and 150 degrees) positioned in the flow direction are used to direct the flow to the confined zone among bricks columns. Two settings with a Reynolds number range from 14285 to 25480 are used. The results revealed that in absence of vanes, the average heat transfer coefficient (AHTC) has low values compared to that with vanes. The highest values of AHTC are obtained at vane angle theta = 135 degrees , over the whole time. The Longitudinal middle bricks have the highest heat transfer coefficient for all vane angles due to high flow velocity with a good air-cooling rate. The maximum augmentation reached 48% at vane angle, theta = 135 degrees, for setting 7. The guide vanes have beneficial features when used as a turbulence generator to improve the heat transfer rate from the brick setting.