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, 400XH.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 
mi _. . . , , 31,824,000 ,,, vc . 
This is equivalent to ' ' =110.5 tons. 
Zoo, UUU 
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, 400X2 (70-30)X90 - 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 
„ . , '4, 320, 000 - K . 
Equivalent to ^ gg ^ =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. 
