Drag data of water, methanol, heptane and benzene droplets are reported here. This data together with the data of Eisenklam et al. cover the entire range of Reynolds numbers from 1 to 2000 and mass transfer numbers from 0 to 3. The present study shows that the drag coefficients as a function of Reynolds numbers correlate well with the "standard drag" curve provided the characteristic density is the free stream density and the characteristic viscosity coefficient is n r {T T ). The basis for the choice of these two characteristic properties is discussed. The present correlation is insensitive to the mass transfer number. This suggests that mass efflux has little effect on drag of evaporating droplets.Present study indicates that for the determination of the drag coefficient of any evaporative droplet at quasisteady state, one needs only to know the wet bulb temperature as a function of free stream temperature. This information is sufficient to calculate y-r {T r ). The "standard drag" curve can then be applied to determine the drag coefficient. NOMENCLATURE A -area a = acceleration C m (T s -Ta) L 4 PiiTa) mass transfer number [g-a]h/U 2 drag coefficient 3 P a (T s ) = drag coefficient of incompressible flow Cf = friction drag coefficient C m = specific heat of surrounding at arithmetic mean of droplet vapor at Ta and air at T s D = total drag d = maximum horizontal diameter of droplet g = gravitational constant h = maximum vertical diameter of droplet L = latent heat of vaporization of droplet at Ta in = total mass M = molecular weight Re = Reynolds number Pa{T s )Ud Re r = Pa(T s )Ud Re s = -T = temperature in °C U = velocity of droplet relative to free stream velocity u = radial velocity x = mass fraction Greek Symbols P = density Ta-T s T = T s /t = viscosity coefficient Subscripts a d I m r s V = air = droplet = liquid = mean = reference condition according to 1/3 rule = free stream = vapor 147 Downloaded by [New York University] at 04: