Heat transfer enhancement due to a staggered element using liquid crystal thermography in an inclined discrete rib roughened solar air heater

In the present work, flow topology and heat transfer characteristics have been studied experimentally to visualize the Nusselt number distribution of inclined discrete rib with staggered elements inside a rectangular duct using liquid crystal thermography technique. Thermo-chromic liquid crystals act as a thermal imaging tool and used for visualizing the surface temperature distributions throughout the specified zone of a roughened surface. The experiment has been carried out with an applicable range of waft parameters, Reynolds number varied from 4000 to 12,500. The roughness pitch to rib height ratio assorted from 8 to 14, the ratio of length of staggered element to gap width as 2, relative staggered position as 0.6 and ratio of width of gap to roughness height as 1. The comparison of Nusselt number, flow friction, and thermal performance of the rectangular channel having inclined rib staggered arrangement with inclined rib without a staggered element has done. The staggered element helps to strengthen the flow by increasing the turbulence intensity in its nearby region and resulting in more heat transfer. The maximum increment in the Nusselt number and friction factor is 3.29 & 4.04, respectively, at a pitch of 10. The maximum thermo-hydraulic performance obtained as 2.06 at Reynolds number of 12,438.