Heat Transfer in Rotating Serpentine Passages With Smooth Walls

Abstract

Experiments were conducted to determine the effects of buoyancy and Coriolis forces on heat transfer in turbine blade internal coolant passages. The experiments were conducted with a large-scale, multipass, smooth-wall heat transfer model with both radially inward and outward flow. An analysis of the governing flow equations showed that four parameters influence the heat transfer in rotating passages: coolant-to-wall temperature ratio, Rossby number, Reynolds number, and radius-to-passage hydraulic diameter ratio. These four parameters were varied over ranges that are typical of advanced gas turbine engine operating conditions. It was found that both Coriolis and buoyancy effects must be considered in turbine blade cooling designs and that the effect of rotation on the heat transfer coefficients was markedly different depending on the flow direction. Local heat transfer coefficients were found to decrease by as much as 60 percent and increase by 250 percent from no-rotation levels. Comparisons with a pioneering stationary vertical tube buoyancy experiment showed reasonably good agreement. Correlation of the data is achieved employing dimensionless parameters derived from the governing flow equations.

Effect of rib spacing on heat transfer and friction in a rotating two-pass square channel with asymmetrical 90-deg rib turbulators

“…Thus, heat transfer is enhanced on the leading side and the average Nu ratio begins to rise with Buo. For the smooth square channel, this turning point is about 0.15[17].In the second passage with radially inward flow, the observed behavior is qualitatively similar to the first passage. The average Nu ratios on the leading surface increase slightly withBuo through the entire operating range investigated.…”

“…Wagner et al ( , 1992 [16][17][18] provide a set of data in a square multi-passage channel with smooth and 90-deg ribs. They concluded that the local heat transfer coefficients increase over 200% on the trailing surface and decrease up to 60% on the leading surface compared to non-rotating results in the first pass.…”

Experimental study of thermal development in a rotating square-ended U-bend

“…1, the passage also rotates orthogonally [1][2][3][4][5][6]. Experimental investigations focus entirely on the effects of rotation in straight ducts have also appeared [7,8].…”

Heat transfer study in a rotating ribbed two-pass channel with engine-similar cross section at high rotation number

“…So experiments with rotation have been conducted to model engine cooling environments more closely. Wagner et al [5,6] systematically conducted experimental investigations on heat transfer in a four-pass rotating smooth channel. They found that the Coriolis force had a positive effect on heat transfer of trailing wall but negative effect on leading wall in the first radial outward passage.…”