A Numerical Investigation of X-Shaped Transverse Rib Roughened Solar Air Heater

A numerical investigation has been performed to study the effects of different rib shapes on heat transfer and fluid flow characteristics through transversely roughened rectangular channels for Reynolds number ranging from 3800 to 15,000 and subjected to uniform heat flux of 1000 W/m2. Considering single-phase approach, the three-dimensional continuity, Navier-Stokes, and energy equations developed for the physical model have been solved by using the finite volume method (FVM). The optimization was carried out by using various Rib shapes (X-section rib channel & Square section rib channel) in in-line and different aspect ratios (Dh=33.33, Aspect ratio of duct W/H=5, Relative roughness pitch P/e=7.14, Relative roughness height e/D=0.042) to reach the optimal geometry of the rib with maximum Performance Evaluation Criterion (PEC). The highest PEC was obtained for the X-section rib at Re =3800 is 1.703. For the X-section rib channel, the increase in average Nusselt number value is about 162.48% more than the smooth channel and the use of the X-section rib channel compare with Square section rib channel shows a higher average Nusselt number around 17.70%.