Uniform Wall Temperature Boundary Condition Research Articles

Analysis of Heat Transfer in the Entrance Region with Fully Developed Turbulent Flow between Parallel Plates

The equation describing the turbulent Graetz problem (heat transfer to a fluid between parallel plates) is solved numerically for first ten eigenvalues and eigenfunctions in the range of both 104≤Re≤5×105 and 0.01≤Pr ≤10.In the calculation, we used the new correlations of turbulent fluid velocity, eddy diffusivity and turbulent Prandtl number from a reconsideration of the available experimental work. Heat transfer rates are predicted for both the entrance and fully developed regions of parallel plates. The effect of the uniform wall temperature boundary condition on heat transfer rate is discussed. Calculations of Nusselt numbers in the entrance region are in good agreement with experimental data.

Natural convection effects on graetz problem in horizontal rectangular channels with uniform wall temperature for large Pr

The effect of buoyancy forces on laminar forced convective heat transfer in the thermal entrance region of horizontal rectangular channels with uniform wall temperature is studied by a numerical method for the case of large Prandtl number fluids. The numerical results are presented for the aspect ratios (width/height) 0·5, 1, 2 and Rayleigh numbers 0 ~ 5 × 10 5. The correlation equations for the prediction on the onset of significant free convection effect are developed. The asymptotic behavior of local Nusselt number is compared against the known asymptote for the uniform wall temperature boundary condition. The entrance region where the free convection effect is significant is clearly established and the classical Graetz problem is shown to be a limiting case and is applicable only when Ra ⩽ 10 3.

Effectiveness and Heat Transfer With Full-Coverage Film Cooling

The paper presents experimental results for performance of full-coverage film cooled surfaces. Effectiveness and heat transfer are measured on plane surfaces with discrete injection through the surface at an array of points into a turbulent mainstream boundary layer. The injection is normal to the surface, through circular holes arranged in both in-line and staggered patterns with 4.8 hole diameters used for both the row-to-row spacing and the hole-to-hole spacing within a single row. Both the film and mainstream fluids are air, and property differences are kept small throughout the study. Uniform injection over the entire array at film-to-mainstream velocity ratios of 0.1 and 0.2 with a uniform wall temperature boundary condition are covered. Results are compared with predictions using superposition of available single hole local effectiveness values.