POWER CORRELATION FOR PADDLE IMPELLERS IN SPHERICAL AND CYLINDRICAL AGITATED VESSELS

Power consumption for paddle impellers in both spherical and cylindric al agitated vessels was measured over a wide range of Reynolds number from laminar to turbulent flow regions. By using the friction factor f and the modified Reynolds number Re-G, which were defined by Hiraoka and Ito, a power correlation was expressed as f = C-L/Re-G + C-t{(C-tr /Re-G + Re-G)(-1) + (f(infinity)/C(t)1/m)}(m) where C-L, C-t C-tr f(in finity) and m were empirically correlated with impeller size and the n umber of impeller blades. The power correlation was applicable to both spherical and cylindrical vessels, when the apparent diameter of the spherical vessel was equal to the diameter of the cylindrical vessel w hich had a height equal to its diameter and had the same volume as the spherical vessel. The power consumption was well correlated with the experimental results of Nagata, et al. and Hixson-Baum. The critical R eynolds number, which was used for a simple estimation of power number in fully baffled conditions N-p,N-max by Nagata, was directly related to the coefficient C-tr characterizing transition from a laminar to a turbulent flow region in the correlation proposed here.