BULLETIN 420^ U. S. DEPAETMENT OF AGRICULTURE. 



j'llii 



DESCRIPTION OF EXPERIMENTAL APPARATUS. 



In order to conduct cooling experiments with forced-air circulation 

 on a small scale, an insulated box 10 feet 6 inches high, 5 feet wide, 

 and 4 feet SJ inches deep was constructed. The box was insulated 

 by a 4-inch wall of sawdust, and inside it was built a platform 2 feet 

 2 inches from the floor, composed of movable sections each the size 

 of the bottom of a milk-bottle crate. The plan of this box, together 

 with the blower set and arrangement of piping, is shown in figure 1. 



The blower set consisted of a steel-blade fan of a capacity of 2,000 

 cubic feet a minute at normal speed, and was operated by a 125-volt 

 direct-current, shunt-wound, open-type, variable-speed motor of 1^ 



Fig. 1.— General arrangement of cooling apparatus. 



horsepower. The blower was connected to the box by pipes of gal- 

 vanized iron of 14-inch diameter, which were so arranged that air 

 could be forced in at the bottom of the box and out at the top, or the 

 reverse; that is, in at the top and out at the bottom. This was made 

 possible by two inlet and outlet pipes connected with the box and 

 controlled by a system of dampers. 



Most of our experiments were conducted during the winter months ; 

 consequently the outside air was sufficiently cold for the coohng 

 process. As may be seen in the figure, the blower drew outside air 

 through pipe B and forced it into the cooUng box. 



