COOLING OF TWO CYLINDERS IN A ROW BY A SLOT JET OF AIR

The heat transfer on two cylinders in a row by a slot jet flow of air has been investigated experimentally. The slot jet has a height of S=5 mm. The cylinders diameter is D=10 mm. The first cylinder is set at a distance H/S=6 from the slot exit. The second cylinder is set a distance from the first cylinder variable from L/S=4 to L/S=8. The Reynolds number range is Re_D=4000÷20000. The influence of the first cylinder on the second one is to decrease the heat transfer in a jet flow, just opposite to what observed in a uniform flow. Local Nusselt number on the two cylinders has been investigated as a function of Reynolds number, the angle from the impinging point and the different distances between the two cylinders. A closed vortex region between the cylinders appears at a distance L/S=4 and is dependent by the Reynolds number. The best configuration of the two cylinders for obtaining the maximum heat transfer is H/S=6 and L/S=4.