648 JOURNAL OF THE SOCIETY OF COSMETIC CHEMISTS The Reynolds number is calculated as: Nrta - Dvp _ 1.52 X 10 -2 Since Nn• 10, K = Kot, = 5.70 To calculate the pressure drop in the empty pipe of the same dia•neter and length as the device, the friction factor has to be determined. For laminar flow the following relationship holds ( 9 ) 64 rhus• 64 f = 1.52 x 10 -2 -- 4211 The pressure drop in the empty pipe is calculated using eq 4: L pt9 2 AP = f D 2 g• -- 10.64 psi Therefore, the pressure drop in the device is: APs•t = K AP = 5.70 x 10.64 = 60.65 psi The theoretical horsepower can be calculated by using eq 9. Theoretical Hp --- 0.262 APs.•r ' Q = 0.037 Since the flow is laminar, we can use eq 2 to calculate the striation thickness. D d - - 31.3 A Note that 1 A -- 10 -s cm. Example 2-A water-like fluid flows at 5 gal/min in the device of 1-in. Schedule 40. What is the pressure drop and the theoretical horsepower re- quired in the unit 0.9 ft. in length which corresponds to 6 mixer elements as recommended for mixing nonviscous fluid'? From Table I we have: D -- 1.05 in. Kon = 5.79 Kov ---- 36.3 K'on ---- 0.069 Properties of water at 20øC are: /• = 1 cps p = 62.4 lb/ft a

CONTINUOUS MIXING AND PROCESSING 649 The Reynolds number is: DoP Nxa• - -- - 15,033 The Darcy friction factor can be found to be (9) f =0.031 The pressure drop in an empty pipe of the same dimension can be calculated as: L pv 2 AP=fD 2g•--7'38x10 apsi Since Nng is greater than 2000, use Fig. 6 to obtain B = 2.6 at Nag ---- 15,033 Using eq 8, one obtains: K = Kov x B = 36.3 x 2.62 = 95.1 Thus, the pressure drop in the device is: APs• = K AP = 0.702 psi The theoretical horsepower can then be calculated as: Theoretical Hp = 0.262 APsu ß Q = 0.002 Hp The above two examples illustrate that only very small power consumption is required for processing both laminar and turbulent flows in the device. Contacting, and Dispersion Three forces are known to influence the formation of drops: shear stress, surface tension, and viscous stress in the dispersed phase (10). The viscous stress in the dispersed phase can be disregarded in the dispersion of fluids of low viscosities presented in this paper. When two immiscible fluids are sub- jected to the shear forces within the device, drops of one phase are produced within the other. Intimate contact between the two fluids is achieved because of the mixing characteristics of the device. Procedure Figure 9 is the schematic setup of the contacting experiment. Three sizes of the device were used in the mixer section: 1/2 in., aA in., and 1 in. inside di- ameter. Each device had glass housing with stainless steel elements. A plexi- glass chamber was built to enclose the exit section of the device. A camera was located outside the chamber to take pictures of the drops. The chamber was filled with water so that distortion of the drop size due to the curved sur-