Spray cooling heat-transfer with subcooled trichlorotrifluoroethane (freon-113) for vertical constant heat flux surfaces

摘要

Experiments were conducted using subcooled trichlorotrifluoroethane (Freon-113) sprayed vertically downward through vertical constant heat flux surfaces. Both local and average heat-transfer behaviors were investigated for Freon-113 sprays with 40 deg C of subcooling, dropelt sizes ranging from 200 #mu# m to 1250 #mu# m, and droplet brakup velocities ranging from 5 m/x to 90 m/s. Full-cone type nozzles were used to generate the spray. Test assemblies consisted of one to six. 7.62 cm by 7.62 cm vertical constant heat flux surfaces which were parallel with respect to each other and aligned horizontally. The distance between the heated surfaces was varied from 6.35 mm to 76.2 mm. Steady state heat fluxes as high as 13 W/cm~2 were achieved. A dependence on the surface distance from the axial centerline of the spray was found. For surfaces sufficiently removed from the centerline, the local and average heat-transfer behaviors were identical and correlated by a power relation of the form seen for normal-impact sprays which involves the Weber number, a nondimensionalized temperature difference, and a mass flux parameter. For sufaces closer to the centerline, the local heat-transfer was described by a semi-log correlation involving the same parameters. The heat-transfer behavior was independent of the distance (gap) between the heated surfaces for the gaps investigated.