Heat transfer and fluid flow behaviour of a rectangular duct roughened with V-ribs with symmetrical gaps

In the present work, artificial roughness in the form V-ribs with symmetrical gaps have been applied on the heated surface to enhance the heat transfer in the limbs of V-ribs. Symmetrical gaps on both legs were provided by varying the relative gap width from 1 to 5 and number of gaps from 1 to 5. The relative roughness pitch, relative roughness height and aspect ratio of the rectangular duct are kept constant to the value of 10, 0.0433 and 12, respectively. The Nusselt number and friction factor of the artificially roughened absorber plates has been determined experimentally and corresponding values were compared with that of the smooth duct for the range of flow Reynolds number 4000–18,000. The maximum enhancement in Nusselt number was reported for relative gap width of 4 and Number of gaps of 3. The thermohydraulic enhancement factor was found to be in order of the 1.54–2.39.