Thermo-Hydraulic Performance of a Roughened Square Duct Having Inclined Ribs with a Gap on Two Opposite Walls

Experimentation has been carried out to find the influence of a gap provided in ribs on thermohydraulic performance of a square duct roughened with discrete inclined ribs. The two opposite walls of the square duct are roughened with ribs having attack angle (α) of 45 and a gap on its length. The investigation has been performed for relative roughness pitch (p/e) of 10, relative roughness height (e/Dh) of 0.060 and Reynolds number is varied in the range of 5000-40,000. The other rib parameters; relative gap position (d/W) and relative gap width (g/e) is varied in the range of 1/4 – 2/3(4 steps) and 0.5 – 1.5 (3 steps) respectively. The comparative study of various cases shows that the ribs with a gap considerably enhance the value of thermohydraulic performance for the range of parameters taken for the present investigation. Presence of inclined ribs with a gap yields about 2.1-fold enhancements in thermo-hydraulic performance as compared to smooth duct. The maximum value of thermo-hydraulic performance parameter has been observed for relative gap width of 1.0 and the relative gap position of 1/3.