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The first experimental unit was therefore constructed which consisted of a rectangular tube as shown in Fig. 3a, with a cross section as shown in Fig. 3b. Air at a pressure of 3 psi was introduced at the center of the tube at a rate of approximately 150 cfm. The film was pulled through the tube by a conventional sprocket drive . Experiments with this unit during the early part of 1949 indicated that even with this elementary unit 35-mm film could be dried at a rate of 75 fpm, but a number of difficulties were observed. The film was scratched by the bottom of the rectangular tube and considerable flutter existed. Also at this large rate of evaporation the film was cooled to near the freezing point of water and this cooling caused breakage due to reduced elasticity of the film. Heating the air relieved the situation somewhat but the body of the film remained still very cool.
In order to overcome these difficulties a second unit was built as shown in Figs. 4 and 5. This unit consists of a wheel 16 in. in diameter over which the film was led, with the back side of the film resting on a wheel. Air was introduced in the rear of the unit and was first passed through a turbulent air heat exchanger contained in the wheel (see Fig. 5). This maintained the wheel at a sufficiently high temperature to prevent excessive cooling of the film due to evaporation. After the air had passed through the heat exchanger it then was introduced over the film where it passed from the top around both sides of the wheel to the bottom. A small channel in the left-hand bottom side of the wheel was used to dry the back of the film by forcing air along it to blow off any moisture droplets still retained on the back side of the film.
This unit operated quite satisfactorily and a very large amount of film was dried on this equipment at a rate of 100 fpm. This unit was also demonstrated in conjunction with the Paramount Theater-Television Equipment
Fig. 6. Experimental setup of Raytheon K-3 film drier with water tank removed showing the film-wetting assembly.
at a show in September 1949 for the Theatre Owners of America in Hollywood, Calif.
After the demonstration this unit was returned to Raytheon for further study and an extensive experimental program was begun to determine the exact characteristics of this unit. A test setup was made as shown in Fig. 6 in
L. Katz: Drying Film by Turbulent Air
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