A freezer capacity of 100,000 cubic feet which would store 1,500,000 pounds would not appear excessive. From known results this would require about one ton refrigerating duty for 3,000 cubic feet of space or thirty-five tons machine duty. We have then:
SUMMARY OF REFRIGERATION REQUIRED
| Tons | |
|---|---|
| 143,000 cubic feet beef cooler space ÷ 10,000 | 14.3 |
| 100 cattle daily 500 pounds = 50,000 pounds | |
| 50,000 pounds meat chilled 70° or 70 B.t.u. per pound | |
| 50,000 × 70 = 3,500,000 ÷ 288,000 B.t.u. | 12.2 |
| 54,000 cubic feet hog cooler space ÷ 10,000 | 5.4 |
| 250 hogs 180 pounds each = 45,000 pounds | |
| 45,000 × 70 ÷ 288,000 = | 10.9 |
| 200,000 feet cellar space ÷ 12,000 | 16.6 |
| 15 tons ice × 2 tons refrigerating duty | 30.0 |
| 10,000 pounds lard cooler | 12.0 |
| 100,000 cubic feet freezer space | 35.0 |
| Total tonnage refrigerating effect | 136.4 |
Low Temperature Brine System.
—The use of low temperature brine, cooled by two stage compressors, a new development, is in the writer’s opinion preferable to direct expansion. (See [description] of two stage compression in Chapter IV.) A lineal foot of pipe filled with a liquid like chilled brine seems to have greater heat absorbing power than the same pipe filled with a light gas and consequently less piping can be used.
Preference Reasons.
—Occasion arose to compare for a new large installation the relative merits of direct expansion versus brine and the following items suggested themselves:
(1) The direct expansion plant would require 150,000 lbs. ammonia in excess of brine plant.
(2) There would be approximately 8,000 more joints to prevent leaking.
(3) Unavoidable ammonia leakage through rods, glands, valve stems, compressor rods and purging would amount to at least $20,000 per year based on experience with good practice.