APPLICATION OF REFRIGERATION TO HANDLING OF MILK. 53 



thick, the floors and ceiling of concrete slabs 5 inches thick, the floors 

 resting directly on the ground in both cases. The inside temperature 

 of the two rooms is held at 30° F. by refrigeration and the average 

 outside temperature is assumed to be 70° F. for 90 days. Suppose 

 one building is not insulated at all and the other is insulated for a 

 heat transmission of 2 B. T. U. per square foot of surface per 24 hours 

 for each degree difference between inside and outside temperature. 

 The heat transmission through the 13-inch insulated brick walls is 

 taken as 11.3 B. T. U. per square foot per degree difference of inside 

 and outside temperature in 24 hours, and that for the 5-inch con- 

 crete slabs forming the floor and ceiling 28.8 B. T. U. In view of the 

 earth offering a certain amount of protection to the floor slabs, which 

 were assumed to rest on the ground in both cases, only half of the 

 temperature difference between the outside and inside air is taken 

 in computing the heat transfer through the floor in the uninsulated 

 room. Then, for the uninsulated room the transmission will be: 



B. T. U. 



Brick walls, 400X11.3 (70-30)X90 16, 272, 000 



Ceiling, 100X28.8 (70-30)X90 , 10, 368, 000 



Floor, 100X28.8 (50-30)X90 5, 184, 000 



Total heat transmitted through the walls, floor, and ceiling 31, 824, 000 



mu- • • i ++ 31,824,000 ,, AC . 



This is equivalent to ' ' —110.5 tons. 



Zoo, 00U 



Therefore there will be 110.5 tons refrigeration required to remove 

 the heat which comes through the walls, floor, and ceiling, and assum- 

 ing that it cost $1 per ton to produce the refrigeration, it will amount 

 to, in 90 days, 110.5 X 1 =$110.50. Now, in the case of the insulated 

 building we have: 



B. T. U. 



Brick walls, 400 X2 (70-30) X 90 2, 880, 000 



Ceiling, 100X2 (70-30)X90 720, 000 



Floor, 100X2 (70-30)X90 720, 000 



Total heat transmitted through the walls, ceiling, and floor 4, 320, 000 



■c . , . , 4, 320, 000 , _ . 

 Equivalent to ^^ =15 tons. 



At a cost of $1 a ton for the refrigeration, it will amount to 

 15Xl=$15. 



Therefore, there will be a loss of $110.50 -$15 = $95.50 on the 

 uninsulated building in 90 days. It will cost approximately 40 

 cents per square foot to insulate the above-described building for 

 a heat transmission of 2 B. T. U. per square foot per degree difference 

 of outside and inside temperature per 24 hours, or a total of 

 600x0.40 = $240. Consequently the insulation would pay for itself 

 in about seven and a half months' operation. 



