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Impinging fluid jets are widely used in industrial processes where high momentum and/or mass transfer have to be reached. Typical applications are jet wiping, the drying of paper and textile, the cooling of turbine blades, the anti-icing of aircraft, the tempering of glass sheets, the cooling of moving metal strips, the cooling of electronic equipment, ... Numerical simulations of these impinging jets are mainly performed solving the Reynolds Averaged Navier-Stokes equations. However, it has been shown that this approach for the simulation of turbulence overestimates the heat transfer coefficient at the impinging region (overestimates of 100% have been observed). Therefore, the Large Eddy Simulation (LES) approach, which models only the small scales of turbulence and resolves the large scales is used to compute a round impinging jet with a Reynolds number varying from 3.000 to 70.000.

The paper describes a study of convective heat transfer in a multiple-jet systems composed of round nozzles. The application concerned is the fast cooling of moving strip. The experimental approach involves the application of infrared thermography associated with the steady-state heated foil technique. The study aims to determine the effect on the average heat transfer coefficient of the jet Reynolds number in the range 40000 to 85000, the normalised nozzle to strip standoff distance Z/D from 2 to 10 and the normalised nozzle spacing W/D from 2 to 5. The geometrical nozzle arrangements tested include staggered and non-staggered configuration. The experimental findings are compared with an existing correlation; deviations, which are observed at small Z/D-values may reach 30%.

An experimental investigation of the forced convection along vertical. slender cylinders aligned in a uniform air flow is performed using quantitative infrared thermography. In the laminar regime, the heat transfer data are correlated in terms of a local dimensionless curvature parameter and validate the thermal boundary layer model for a single slender cylinder. Turbulent heat transfer occurs when the stand­ off distance between two parallel, slender cylinders is sufficiently small to affect the axisymmetry of the boundary layer. An enhancement factor of three can be achieved at the transition region. In the turbulent regime, the curvature parameter alone does not describe the thermal exchange.

The convective heat transfer at the impingement of a vertical turbulent circular air jet on a horizontal flat plate is inferred from temperature measurements performed by quantitative infrared thermography. Steadystate experiments are conducted with the heating-thin-foil method. The effects of the jet Reynolds number and the stand-off distance on the thermal exchange coefficient are emphasized. The influence of jet confinement is determined. The IR results agree with published data and are reproduced by numerical simulations performed with the code FLUENT.