Experimental and analytical work was performed to determine the influence of rod surface roughening on the thermal-hydraulic behavior of rod array type, nuclear fuel elements. Experimental data was obtained using a grid-spaced, 37-rod hexagonal test section with both a smooth and a rough rod array. The rods were 0.331 inch (8.41 mm) diameter with a pitch/diameter of 1.30. The roughened surface used trapezoidal ribs 6-mils (0.15 mm) high with a rib pitch/height of 12. Velocity profiles taken at the flow exit plane indicated that when comparing the rough array results with the smooth, the gap velocities were lower, the peak-to-average velocities were higher: and the peripheral subchannel velocities were higher. Axial static pressure profiles. were used to determine rod array friction factors and grid loss coefficients. The friction factor results were in agreement with predictions using tube data.
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