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Article
Publication date: 1 January 2004

Bengt Sundén, Rongguang Jia and Andreas Abdon

Impingement and forced convection are preferable methods for cooling gas turbine components. However, influences of various design parameters like crossflow and surface…

937

Abstract

Impingement and forced convection are preferable methods for cooling gas turbine components. However, influences of various design parameters like crossflow and surface enlargements (like ribs) are not well understood. Thus there is a request for reliable and cost‐effective computational prediction methods, due to the experimental difficulties. Such methods could be based on the numerical solution of the Reynolds‐averaged Navier‐Stokes equations, the energy equation and models for the turbulence field. This paper describes some recent advances and efforts to develop and validate computational methods for simulation of impingement and forced convection cooling in generic geometries of relevance in gas turbine cooling. Single unconfined round air jets, confined jets with crossflow, and three‐dimensional ribbed ducts are considered. The numerical approach is based on the finite volume method and uses a co‐located computational grid. The considered turbulence models are all the so‐called low Reynolds number models. Our recent investigations show that linear and non‐linear two‐equation turbulence models can be used for impinging jet heat transfer predictions with reasonable success. However, the computational results also suggest that an application of a realizability constraint is necessary to avoid over‐prediction of the stagnation point heat transfer coefficients. For situations with combined forced convection and impingement cooling it was revealed that as the crossflow is squeezed under the jet, the heat transfer coefficient is reduced. In addition, inline V‐shaped 45° ribs pointing upstream performed superior compared to those pointing downstream and transverse ribs.

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International Journal of Numerical Methods for Heat & Fluid Flow, vol. 14 no. 1
Type: Research Article
ISSN: 0961-5539

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Article
Publication date: 1 November 2001

Rongguang Jia, Masoud Rokni and Bengt Sundén

A numerical investigation to determine the velocity and heat transfer characteristics of multiple impinging slot jets in rib‐roughened channels in the presence of cross‐flow has…

915

Abstract

A numerical investigation to determine the velocity and heat transfer characteristics of multiple impinging slot jets in rib‐roughened channels in the presence of cross‐flow has been carried out. Fluid flow is modeled using an explicit algebraic stress model. A simple eddy diffusivity and a generalized gradient diffusion hypothesis are applied for the modeling of turbulent heat fluxes. The computations are validated against available experimental fluid flow and heat transfer data. Different size and arrangement of jets and ribs are considered in detail, while the Reynolds numbers of a jet and the channel inlet are fixed at 6,000 and 14,000, respectively. Results show that the ratio (B/W) between the size of the jets and ribs is most important. An explanation is that the ribs inhibit the motion of eddies by preventing them from coming very close to the surface when B/W is low, e.g. B/W = 1, although the ribs will increase the turbulence intensity. This blockage limited the heat transfer enhancement effect of the ribs and impinging jets.

Details

International Journal of Numerical Methods for Heat & Fluid Flow, vol. 11 no. 7
Type: Research Article
ISSN: 0961-5539

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