Heat transfer characteristics on the inner surface of a converging duct with ribs are investigated by conducting transient heat transfer experiments using thermochromic liquid crystals. In particular, features associated with the smooth duct are addressed as reference. The parameters studied are: the non-dimensional rib pitch (p/w = 10, 20, 50, p is the rib pitch, w is the rib width), the rib blockage ratio (e/H = 10%, 20%, e is the rib height, H is the channel height) and the inlet Reynolds number Re (Re = 6000∼20000). The results are presented on the top wall and its center line. Due to the converging shape of channel, the value of Nu/Nu0 increases downstream the channel, especially near the side wall. The effects of these parameters are: Firstly, the heat transfer improves with the increasing rib height whose influence decreases with the rise of Re number. Secondly, the value of Nu/Nu0 rises firstly, reaching its maximum at p/w = 20, and then declines with an increasing rib pitch. Thirdly, the value of Nu/Nu0 rises firstly and decreases afterwards with the Re number, as the Re number is within the range of Re≤12000.

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