Heat transfer and pressure drop for a staggered wall-attached array of cylinders with tip clearance

Experiments have been performed to determine the detailed row-by-row heat-transfer characteristics of a staggered array of circular cylinders situated in a crossflow of air in a flat rectangular duct. The cylinders were attached perpendicular to one of the principle walls of the duct, with a clearance space between the free ends of the cylinders and the other principle wall. The heat-transfer coefficients were obtained by applying the analogy between heat and mass transfer to mass-transfer coefficients measured via the napthalene sublimation technique. Pressure measurements were also made to determine the incremental pressure drop due to the presence of the cylinder array. The row-by-row transfer coefficients were found to vary only in the initial rows and to attain a constant fully developed value for the fourth and all subsequent rows. The fully developed transfer coefficients are quite insensitive to cylinder height (i.e. to the extent of the tip clearance), increasing moderately as the height increases (and the clearance decreases). On the other hand, the array pressure drop increases markedly with increasing cylinder height.