Local heat (mass) transfer in a diagonally-oriented rotating two-pass channel with rib-roughened walls
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This experimental investigation examined the effects of channel orientation, rotational Coriolis force, and a sharp turn, on the local heat (mass) transfer distributions in a two-pass square channel with ribroughened walls, rotating about a perpendicular axis. The test channel was oriented so that the direction of rotation was perpendicular to or at a 45 angle to the leading and trailing walls. In the two straight passes of the test channel, there were 90 or 60 ribs on the leading and trailing walls. The height of the ribs was equal to one-tenth of the channel hydraulic diameter, and the spacing between two ribs was equal to ten times the rib height. The test channel modeled serpentine cooling passages in modern gas turbine blades. The Reynolds number and the rotation number were kept at 5,500 and 0.24, respectively. The results of the investigation show that, in the straight passes of a diagonally-oriented channel with transverse or angled ribs, the local heat (mass) transfer is higher along the outer edges of both the leading and trailing walls than along the inner edges of the walls. The heat (mass) transfer is the lowest on the leading wall in the first straight pass of a normally-oriented channel with transverse or angled ribs. The diagonal orientation of a channel with transverse or angled ribs causes the heat (mass) transfer on both the smooth leading and trailing walls at the sharp turn to be lower than in the case of a normally-oriented channel. For radial outward flow in a diagonally-oriented channel, angled ribs enhance less heat (mass) transfer on both the leading and trailing walls than transverse ribs. The trends are reversed for radial outward flow in a normally-oriented channel.
