Experimental investigation of convective heat transfer between corrugated heated surfaces of rectangular channel

Abstract

The convective heat transfer between corrugated heat transfer surfaces in the rectangular channel have been investigated experimentally. The optical measurement technique of holographic interferometry is used to visualize the temperature fields between heat transfer surfaces. Studies were carried out for the triangular, trapezoidal and wing corrugated heat transfer surfaces, comparing them to a smooth surface. The cooling air is sucked in between heated surfaces at different flow rates of 5, 10, 15 and 20 m3/h, which corresponds to the Reynolds numbers in the 732 to 3,020 range. The wall temperature was held constant at 318.15 K. The effects of the different corrugated channels and different heights of the gaps between heated surfaces (H = 40, 50 mm) and Reynolds numbers on heat transfer characteristics are discussed. Experiments were performed to determine local and mean heat transfer coefficients, Nusselt numbers, ratio j/f and thermal performance η. The results showed that the trapezoidal offset with 40 mm gap height and the Reynolds number Re = 3,020 achieved the highest values of mean Nusselt numbers (Num´ = 26.97) in comparison with smooth and other corrugated channels. The mean Nusselt number Num´ with raising of Re increased by 102 % for trapezoidal offset with gap H = 0.04 m. When considering heat transfer and pressure drop in the channel (ratio j/f), the trapezoidal offset with gap H = 0.05 m (j/f = 0.0104) is the most optimal case.