Heat transfer and flow behavior in the mini rod bank were examined. The tube bank was simulated with 5 wires of 1 mm diameter. The wires were arranged on the center line of the flow channel of 30 mm wide, 15 mm high and 300 mm long. The pitch between wires were varied from 1.5 mm to 9 mm. Experiments were performed in the range of the rod Re = 1 ∼ 400, i.e. the flow velocity in the channel was in the range of 0.0036 m/s ∼ 0.34 m/s. The measured heat transfer coefficients of the first row were a little bit higher than, rather close to, the predicted values by the correlations. The heat transfer coefficients after the second row were lower than those of the first row. The difference between those increased as the Reynolds number was increased. Around Reynolds number = 100, the difference turned to decrease. After the occurrence of the heat transfer coefficient recovery in the rows after the second row, the deeper the row was, the larger the heat transfer coefficient was. The flow visualization results and the analytical results by the STAR-CD code indicated that when the Reynolds number was low, the wake region of the preceding rod was stagnant. This flow stagnation caused the heat transfer coefficient deterioration around the stagnation point of the rear rod. As the Reynolds number was increased, the flow state in the wake region changed from the stagnant condition to the more disturbed condition by periodical shedding of the Karman vortex from the preceding rod. This agitation of the wake region by the vortices caused the recovery of the deteriorated heat transfer coefficients. The deeper the row was, the more disturbed the wake flow state was. The measured average heat transfer coefficients of the tube bank agreed well with the analytical results by the STAR-CD code. The measured and the analyzed results were close to the predicted values by correlations.

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