4781 - Study of Cross-Flow Cooling and Heating of Air via an Elliptical Tube Array PDF

Experiments were conducted on air cooling and heating via an array of 18 elliptical tubes with their 31.7 mm major axis parallel to the air cross-flow. These tubes had a minor-tomajor axis ratio of 0.3 and were evenly spaced by a 6.1 mm air gap. Water entered the bottom tube and exited at the top tube of the array, which was placed in a 600 mm long, 300 mm by 300 mm wind tunnel section. The temperature difference between the mean approach air and the inlet water was maintained at 15.7±1.5°C for both cooling and heating of the air. Reynolds number, based on the mean free stream air velocity and streamwise major axis length of the elliptical tube, was varied from 10,000 to 36,000. In both the cooling and heating processes, the results showed that the Nusselt number varied in a power law manner with respect to the Reynolds number. It is also observed that the heat transfer coefficient appears somewhat higher in cooling than in the heating process. The results compared well with previously established correlations.

Units: SI