Effect of sidepins on the thermohydraulic characteristics of an array of internal pin fins

Abstract

Few of the investigations on the thermohydraulic performance of the arrays of short pin fins in channels have addressed and quantified the impact of the pins located on the sidewalls. In the confined space of a channel, the pins on the sidewalls are placed sometimes to justify the flow periodicity and flow-area uniformity in the channel with multiple pin rows. The present investigation measures the influences of the sidewall pins on the flow field in a pin-fin channel employing arrays of circular pin fins in 13 staggered rows. The flow measurements are also obtained in the same pin-fin channel without the presence of the sidewall pins for comparisons. Reynolds number (Re) based on the channel hydraulic diameter and mean flow velocity for the measurements varies between 5000 and 50,000. The pin-fin array employs a spacing of two pin diameters between the pins in the streamwise and transverse directions. The results of pressure distributions, pressure losses, heat transfer coefficients, and flow temperature distributions along the pin-fin rows indicate that the sidewall pins have little influence generally on the local secondary flow structures. The differences in the measured data are primarily caused by the redistributions of local mass flux and flow acceleration as the pins on the sidewalls are employed. Because of the extra flow blockage imposed by the sidewall pins in the sidewall gap, the friction factor is 15−30% higher and the overall total pressure loss coefficient is 1−6% higher over the Reynolds number range with the sidewall pins than without the sidewall pins. The average Nusselt on the endwall differs by less than 4% between the cases of sidewall pins and no sidewalls pins irrespective of the Reynolds numbers tested.