Enhancement of Fluid Flow and Heat Transfer in Tunnel Kilns
The improper size of channels cause non-uniform flow in tunnel kilns and unequal convective heat transfer coefficients of longitudinal and transverse bricks in the lattice setting arrangement. This paper reports an approach used to optimize the dimensions of the kiln channels using a 3D-CFD model with a grid size of 4.78M cells and incorporated k- turbulence model. The CFD model was validated against experimental data for pressure drop and temperature in tunnel kilns. The effects of kiln channels on flow uniformity were thoroughly investigated and uniform flow and equal convective heat transfer coefficients of longitudinal and transverse bricks were achieved by optimizing the dimensions of wall, column, ceiling, and external channels. The optimum dimensions of the kiln channels are related to the column width of the lattice brick setting as follows: width of column channel is 0.5; width of wall channel is 0.25; ceiling channel height is 0.2; and extension channel spacing is 0.36. The pressure drop in the optimum case was larger than that in the case of non-uiform flow, however, the advantages of quality improvement and quantity enhancement of the produced bricks would surpass the increase in pumping power considerably.
Index Terms - Tunnel kilns, fluid flow, flow uniformity, heat transfer