M10 Heat Transfer and Momentum Flux in Rarefied Gases

The distributed Yavuzkurt injection model is extended to predict the effectiveness and heat transfer coefficients for film cooling injection from a single row of holes, aligned both along the direction of the freestream and at an angle with it. The injection angles were 24° and 35°. The compound angles considered were 50.5° and 60°. The Yavuzkurt film cooling model is used in conjunction with a one-equation model to yield the effectiveness and heat transfer predictions. The density ratios considered were 1.6 and 0.95 for the effectiveness predictions and 1.0 and 0.95 for the heat transfer predictions. For the effectiveness predictions, the blowing ratios range from 0.5 to 2.5, and the momentum flux ratios from 0.16 until 3.9. The hole spacings were 3, 6, and 7.8 hole diameters. The Yavuzkurt model constants are seen to be definitely correlated with the momentum flux ratio. Correlations for the model constants are obtained in terms of the momentum flux ratio. For the heat transfer predictions, the blowing ratios ranged from 0.4 to 2.0, and the momentum flux ratios from 0.16 to 3.9. The spacing between the holes was 3, 6, and 7.8 hole diameters. The matching between the effectiveness correlations and the heat transfer predictions is done on the basis of the momentum flux ratio. Results indicate that the Yavuzkurt model predictions are best for the in-line round holes. Heat transfer predictions are close to the experimental results for lower blowing ratios, until the ratio exceeds 1. For higher blowing ratios, the predictions, though less accurate, follow the experimental trends.

Download Full-text

Effect of Slip Velocity and Heat Transfer on the Condensed Phase Momentum Flux of Supersonic Nozzle Flows

Journal of Fluids Engineering ◽

10.1115/1.483240 ◽

1999 ◽

Vol 122 (1) ◽

pp. 14-19 ◽

Cited By ~ 4

Author(s):

S. A. Sherif ◽

W. E. Lear ◽

N. S. Winowich

Keyword(s):

Heat Transfer ◽

Momentum Flux ◽

Slip Velocity ◽

Figure Of Merit ◽

Supersonic Nozzle ◽

Nozzle Design ◽

Gaseous Nitrogen ◽

Liquid Phases ◽

Nozzle Flows ◽

Phase Momentum

One of the methods used for industrial cleansing applications employs a mixture of gaseous nitrogen and liquid water injected upstream of a converging-diverging nozzle located at the end of a straight wand assembly. The idea is to get the mixture to impact the surface at the maximum momentum flux possible in order to maximize the cleansing effectiveness. This paper presents an analysis geared towards this application in which the effects of slip and heat transfer between the gas and liquid phases are present. The model describes the liquid momentum flux (considered a figure of merit for cleansing) under a host of design conditions. While it is recognized that the emulsification mechanism responsible for cleansing is far more complicated than simply being solely dependent on the liquid momentum flux, the analysis presented here should prove useful in providing sufficiently accurate results for nozzle design purposes. [S0098-2202(00)01801-0]

Download Full-text

Investigation of heat transfer in rarefied gases over a wide range of Knudsen numbers

International Journal of Heat and Mass Transfer ◽

10.1016/0017-9310(84)90161-3 ◽

1984 ◽

Vol 27 (10) ◽

pp. 1789-1799 ◽

Cited By ~ 32

Author(s):

Yu.G. Semyonov ◽

S.F. Borisov ◽

P.E. Suetin

Keyword(s):

Heat Transfer ◽

Rarefied Gases ◽

Knudsen Numbers ◽

Wide Range

Download Full-text

Effects of Free-Stream Turbulence and Surface Roughness on Film Cooling

Volume 4: Heat Transfer; Electric Power; Industrial and Cogeneration ◽

10.1115/96-gt-462 ◽

1996 ◽

Cited By ~ 21

Author(s):

Donald L. Schmidt ◽

David G. Bogard

Keyword(s):

Heat Transfer ◽

Surface Roughness ◽

Heat Transfer Coefficient ◽

Transfer Coefficient ◽

Film Cooling ◽

Momentum Flux ◽

Free Stream ◽

Cooling Performance ◽

Free Stream Turbulence ◽

Adiabatic Effectiveness

A flat plate test section was used to study how high free-stream turbulence with large turbulence length scales, representative of the turbine environment, affect the film cooling adiabatic effectiveness and heat transfer coefficient for a round hole film cooling geometry. This study also examined cooling performance with combined high free-stream turbulence and a rough surface which simulated the roughness representative of an in-service turbine. The injection was from a single row of film cooling holes with injection angle of 30°. The density ratio of the injectant to the mainstream was 2.0 for the adiabatic effectiveness tests, and 1.0 for the heat transfer coefficient tests. Streamwise and lateral distributions of adiabatic effectiveness and heat transfer coefficients were obtained at locations from 2 to 90 hole diameters downstream. At small to moderate momentum flux ratios, which would normally be considered optimum blowing conditions, high free-stream turbulence dramatically decreased adiabatic effectiveness. However, at large momentum flux ratios, conditions for which the film cooling jet would normally be detached, high free-stream turbulence caused an increase in adiabatic effectiveness. The combination of high free-stream turbulence with surface roughness resulted in an increase in adiabatic effectiveness relative to the smooth wall with high free-stream turbulence. Heat transfer rates were relatively unaffected by a film cooling injection. The key result from this study was a substantial increase in the momentum flux ratios for maximum film cooling performance which occurred for high free-stream turbulence and surface roughness conditions which are more representative of actual turbine conditions.

Download Full-text