46 BULLETIN 98, U. S. DEPARTMENT OF AGRICULTURE. 



order that the room may be cooled more quickly when the plant is 



started after being shut down for several hours, the remaining 



one-third or two-thirds, as the case may be, being submerged in the 



solution of brine. 



Allowing a 3° rise in temperature of the air inside the room (32° 



to 35°) and a rise of calcium chlorid brine of 16° (6° to 22°), and 



as a cubic foot of brine will absorb about 52 B. T. U. per degree 



rise in temperature, the heat absorbed by the brine per cubic foot 



will be 52 (22-6) =832 B. T. U. The volume of brine necessary to 



hold over temperature under the foregoing conditions will then be 



34 400 

 o' =41.3 cubic feet, or 1 cubic foot of brine for each 24.2 cubic 



feet of room space. In other words, the heat that will be absorbed 

 by the 41.3 cubic feet of brine for a 16-degree rise will be 41.3 X 52 X 

 16 = 34,362 B. T. U. Therefore, the hold-over period due to the brine 



* s — 04 ao(\ — = 16 hours. The 2,000 pounds of butter in storage will 



hold the temperature for 2.1 hours for a 3-degree rise in the room 

 temperature. Consequently the total hold-over period due to both 

 the brine and the butter will be 16 + 2.1=18.1 hours, or for a 16-hour 

 shutdown the rise in room temperature will be 2.6°. During the 

 hold-over period the average temperature difference between the 

 ah* and the brine is about 19° F., and with a coefficient of heat trans- 

 mission through the walls of the brine tanks of 1.5 B. T. U. per 

 square foot per hour per degree difference in temperature of the 

 brine and air, the effective square-foot surface of the tanks should not 



34 400 

 be less than ., „ w ' w ., - = 75 ; say two tanks 8 feet long, 1 foot 

 16X19X1.5 J ° 



wide, and 2 -J feet deep. 



One linear foot of 1^-inch pipe when submerged in still brine will 



absorb about 4 B. T. U. per hour per degree difference in temperature 



between the inside and outside of pipe, and as this difference is 



about 13.5°, the amount of 1^-inch submerged piping required is 



Cv ' _ . =117 linear feet, or 58.5 feet per tank. 

 o X lo.o X 4 



This method, however, is only a compromise between the brine- 

 circulating and the direct-expansion systems, but has been found 

 satisfactory and compares very favorably with the brine-circulating 

 system of the same capacit}^. When used for holding over tempera- 

 tures when the plant is shut down, either in case of breakdown of 

 machinery or to avoid keeping an experienced attendant on duty 

 continuously, the tank system for small plants possesses advantages 

 over either the direct-expansion or brine-circulating systems. 



