EFFECT OF HEIGHT AND GEOMETRY ON LOCAL HEAT-TRANSFER AND PRESSURE-DROP IN A CHANNEL WITH CORRUGATED WALLS

Local heat transfer and pressure drop were measured from the corrugated portion of the bottom wall of a rectangular channel where the opposite top wall took one of the three following constructions: (1) plane; (2) covered with corrugations making an in-phase arrangement with the bottom wall; (3) covered with corrugations making an out-of-phase arrangement with the bottom wall. There were a total of seven corrugations, and the corrugation geometry was sinusoidal. Measurements were performed for three different aspect ratios (corrugation height/channel height), and Reynolds numbers ranged from 22,000 to 52,000 in the turbulent region. Heated-coating liquid crystal technique was used for temperature measurements. The highest local Nusselt number was detected on the second corrugation regardless of Reynolds number, aspect ratio, or geometry. Higher Reynolds numbers and higher aspect ratios had similar effects, increasing local heat transfer coefficient. At the higher Reynolds numbers and with higher aspect ratios, two local minima were detected for the Nusselt numbers on each corrugation. Heat transfer results turned out almost the same weather the channel was covered with in-phase or our-of-phase corrugations; pressure drop was higher for the out-of-phase arrangements.