Augmented heat transfer in rectangular duct with angled Z-shaped ribs

An experiment is focused on the design of the suitable ribs used for enhancing heat transfer in a rectangular duct heat exchanger by using wall heat transfer (Nusselt number), friction loss (friction factor) and thermal performance (thermal enhancement factor) data. The Z-shaped ribs were set on the rectangular duct at 30°, 45° and 60° and flat rib was set at 90° relative to the air flow direction. Reynolds numbers studied ranging from 5000 to 25,000 in the test section. The rectangular duct has aspect ratio, AR = 10 and height, H = 30 mm with the Z-rib height (e), e/H = 0.2 and the rib pitch (P), P/H = 3. The ribs were fitted in Z-shape (Z-rib) aligned in series on the whole area of the upper plate. The results of the Z-ribs show the significant increase in heat transfer rate and friction loss over the smooth channel. The 45° Z-rib provides the highest increase in the heat transfer rate and the best thermal performance.