The calculation of the external boundary layer and associated heat transfer to turbine blading is described. Three separate Two-Dimensional Boundary Layer programs were utilised in this study. The programs incorporated the k-epsilon turbulence model with several different formulations. The test case chosen for this study was the von Karman Institute blade VKI Tech. Note-174, Sept-1990. It is shown that in most cases all programs tend to predict the correct behaviour of the onset of transition. However, the transition length between the laminar and turbulent values is predicted too abruptly on the blade suction side. It was found that the magnitude of the predicted heat transfer coefficient was most consistent with experimental values for exit Mach numbers between 0.7 -0.9, and for all inlet turbulence levels and Reynolds numbers. For higher blade exit Mach numbers in the transonic region (M > 0.95) it was difficult to correctly predict the heat transfer in comparison with experimental data. The predicted values were all higher than the measurement. For this blade, the pressure side is quite well predicted for most of the operating conditions.

No abstract

No abstract

This paper describes a computational and analytical study to investigate the effect of the table boundary condition on the thermal Performance of a generic electronics box. The box, a simplified model of a typical laptop computer configuration, has been used to examine the effect of varying: e table conductivity; e air gap thickness; and radiative heat transfer.over the limits that would be likely to be found in practical situations.It is shown that, far from being an adiabatic boundary condition, typical tables are much closer to being isothermal heat sinks than one might imagine. It is also shown that, within a practical range, the thickness of the air gap has relatively little effect on the temperature of components within the box. Finally, advice is offered to designers faced with analyzing products in this configuration.

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.