Forced convection heat transfer from vertical cylinders normal to an air-water spray flow stream was measured over an air velocity range from 60 to 140 ft./sec. and a water spray density range from 0.03 to 0.50 Ib.,,,/(min.) (sq. in.). Local heat transfer coefficients were determined a t 15 deg. intervals around the circumference of both a 1.5 and a 1.0 in. diam. cylinder.It was found that the addition of 0.426 Ib.m/(min.) (sq. in.) of water spray to a 133 ft./sec. air stream raised the stagnation point heat transfer coefficient from 45 to 1,650 B.t.u./(hr.) (sq. ft.) ("F.). Similar intensification was found for other angles around the cylinder circumference; however, the magnitude decreased with increasing distance from the stagnation point. Local heat transfer coefficients were normalized with respect to their corresponding stagnation point values and plotted parametrically as a function of angle and air velocity. These profiles showed that the normalized heat transfer coefficients decreased with increasing air velocity a t angles other than the stagnation point. Average cylinder heat transfer coefficients were calculated from the air-water data and two correlations were obtained relating these coefficients to the air and the water spray Reynolds number.In recent years, forced convection heat transfer around submerged bodies has been extensively studied. Although heat transfer from a body submerged in a flowing fluid is a complicated process due to such factors as turbulence, body shape, and flow regime, it is quite well understood for a wide range of these parameters. The addition of a second phase to the flow stream makes the situation extremely complex. In the case of a liquid spray in a gas stream, additional parameters such as droplet size, quality, relative velocities, relative temperatures and relative flow rates could become important. Even with its complexity, such a system merits investigation because of the high heat transfer rates obtainable with relatively small amounts of liquid injected into the gas stream. Information derived from such an investigation can be useful in predicting behaviors in aerodynamic systems as well as in heat exchange equipment.
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