MANUFACTURING PROCESS FOR COSMETIC CREAM 651 .: %.... .. Figure 7. Ilamilton Kettle (holding and/or mixing uni½. Brighton Corp., Cincinnati, Ohio Table VII Comparison of Mixer vs. Droplet Diameter Average Droplet Diameter Mixer (t•) Cream Consistency Batch method 10-15 Firm, chunky Manton-Gaulin 0.1-1 Soft, grainy Lightnin 5-10 Firm to hard, chunky Static mixer 100 Incompletely mixed Since the agitating action of the scraper in the exchanger can have a great effect on the final consistency of the cream, the heat exchangers are among the most critical elements in the cream processing operation. Scraped-wall heat exchangers are ideally suited for the continuous pro- cessing of viscous creams. The primary differences among the three units tested are in-flow path width and the geometry of the scraver. To

652 JOURNAL OF THE SOCIETY OF COSMETIC CHEMISTS NITI•OaEN • PSI i TI. Temperature indicator VA. Volt-amp meter obtain accurate scale-up information, the exchangers were run at the same flow velocities and rpm that were intended for the full-size process. In this manner, the cream received the same agitation. In these experiments, a measurement of the heat transfer coefficient and cream consistency were obtained. To do this, cream was manu- factured as described under the section on Evaluation of Miyers, pumped to a holding tank, and then passed through a heat exchanger at flow rates of 1400 to 2600 lb/hr. For this portion of the study, a higher ca- pacity Moyno pump was used. The heat transfer coefficients (U] for the exchangers studied were calculated and tabulated (Table VIII). Type A heat exchanger at 200 rpm resulted in a U of 225 and was the most efficient of the three tested. A U of 200-225 could be obtained with Type B if the rpm was increased to 500-600 rpm. Table VIII Heat Transfer Coefficients for Exchangers Evaluated in Equipment Test Loop Description rpm Transfer Area (ft 2) O•, Average Overall Heat Transfer Coefficient (Btu/ft2-øF-hr) Type A a 200 0.7 225 Type B b 200 3.0 77.5 Type Cc 52 1.3 168 a Votator Scraped-Wall Heat Exchanger, Votator Division, Chemetron Corp., Louisville, Ky. b Cherry-Burrel Thermutator Model 624, Cherry-Burrel Corp., Mount Vernon, N.Y. 10553. c Vogt Scraped-Surface Heat Exchanger, 6 in. X 8 in. lab model, Henry Vogt Machine Co., Louisville, Ky. 40201.