Heat Transfer in Rotating Serpentine Passages With Smooth Walls

TLDR

The study experimentally investigated how buoyancy and Coriolis forces affect heat transfer in turbine blade coolant passages. A large‑scale, smooth‑wall, multi‑pass model with radially inward and outward flow was used, revealing that coolant‑to‑wall temperature ratio, Rossby number, Reynolds number, and radius‑to‑hydraulic diameter ratio govern heat transfer, which was varied over typical turbine ranges and correlated with dimensionless parameters. Results showed that Coriolis and buoyancy effects must be considered, with rotation altering heat transfer coefficients by up to −60 % or +250 % depending on flow direction, and the data agreed reasonably with a stationary vertical tube buoyancy experiment.

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, multi–pass, 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 which 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.