220 U. 8. BUREAU OF FISHERIES 
per degree difference in temperature between the inside and outside of cooker, 
the temperature gradient being 300° less 50°, or 250°. Heat required for 
heating the iron, 4 18237 X 2500.18, or 634,920 B. t. u.; for heating the fish 
413215 1700.8, or 1,077,120 B. t. u.; for evaporating water and heat- 
ing the evaporated water from 220 to 300°, 4*132x15xX0.16X970, plus 
4 1382 150.16 800.47, or 1,276,830 B. t. u.; and for loss through cooker 
housing 1,152X0.5X 250, or 144,000 B. t. u.; giving a total of 3,132,870 B. t. u. 
Air supply required for cooker.—Data used: Temperature of air entering cooker, 
337.5°; drop in cooker, 75°; and cubic feet of dry air required to give one B. t. u. 
in dropping 1° at 300°, 78.5. (An equal volume of water vapor at 300° and 
atmospheric pressure gives up about the same amount of heat in dropping 1°. 
It is about half as heavy as dry air, but its specific heat is twice as large. The 
amount of water vapor in the air, therefore, is not considered in these approxi- 
, t ; . 938,132,870 X 78.5 f 
mate calculations.) Air required is 75 » or 3,279,071 cubic feet 

per hour, or 54,651 cubic feet per minute. 
Size of cooker required.—Assume that the flakes pass from one end of the tun- 
nel to the other twelve times, six times in each direction; that the tunnel is 3 feet 
wide and 12 feet high, inside dimensions, giving a cross section of 36 square feet; 
and that the flakes, fish, chains, flake carriers, and drip pans take up 8.5 square 
feet, leaving 27.5 square feet, or 76.4 per cent of the total cross section free area. 
This free area will handle 55,000 cubic feet of air per minute at a velocity of 2,000 
feet per minute. In each of the 12 runs there must be 11 flakes. A tunnel 36 
feet long will handle this number of flakes easily. 
Amount of air to be recirculated—Data used: Volume of 1 pound of water 
vapor at 300° and atmospheric pressure, 42 cubic feet. Maximum amount of 
water to be removed from the fish per hour is 4X13215X0.16, or 1,267.2 
pounds. Under the assumed conditions, this is 1,267.2 42, or 53,222 cubic feet 
of vapor. If the water-vapor content of the air passing through the cooker 
should be allowed to build up to 20 per cent by volume, or 655,814 cubic feet, 
but 8.1 per cent would have to be discarded to remove the water vapor as rapidly 
as it collects. At least 90 per cent, and undoubtedly more, can be recirculated 
without difficulty. 
Total heat required.—It is assumed that heat losses through housing for intake 
and recirculation ducts, furnace, blower, and other parts of equipment, is twice 
the amount for the cooker housing—2X 144,000, or 288,000 B. t. u.—and that 
10 per cent of the air that leaves the cooker is discarded, plus an additional 
5 per cent to care for other losses. An approximate value for the heat lost in 
discarding 15 per cent of the air is obtained as follows: Assume the loss to be 15 
per cent of the air supply required at 300°, the specific heat of air to be 0.24, the 
volume of air per pound at 300° to be 19.1 cubie feet, and that the air had been 
heated from 50° to 300°. This heat loss, then, is 0.15x 22M x0 .24x 250, or 
1,545,112 B. t. u.. This value, plus the conduction loss given above (288,000 
“ t. u.), plus the heat required for the cooker (3,132,870 B. t. u.), is 4,965,982 
sive, itl. 
Fuel required.—It is assumed that fuel oil weighing 7.9 pounds per gallon and 
having a calorific value of 18,500 B. t. u. per pound is used, and that 80 per cent 
conversion is effected in the furnace. Oil required is 1500S 82885 pounds, 
or 42.4 gallons per hour. The fish will give at least 22 cases per ton, or 110 
42. 
cases for the 5 tons cooked. Fuel oil per case is “ or 0.385 gallon. To be 
safe, it is assumed 0.5 gallon per case is required. 
Fuel required for preparing the fish by the frying-in-oil process.—Calculations 
are made on a per-hour basis. It is assumed that the amount of heat required 
per pound of fish dried is 190 B. t. u. (data for drier, B, Table 9, p. 125); that an 
additional 8.5 per cent loss in the original weight of the ‘‘cut”’ fish takes place 
in the fry bath, due to evaporation of water; that the fish enter the oil at 100° 
and leave at 220°; and that 50 per cent of the heat units in the fuel are utilized 
(a high figure for cannery practice). The heat required for drying the ‘‘cut” 
portion (66 per cent of the ‘‘round”’ weight) of 5 tons of fish is 10,000 X 0.66 X 190, 
or 1,254,000 B. t. u.; for evaporating water is 10,000 0.66 0.085970, or 

73 A ton of good-quality ‘“‘round”’ fish should give about 1,320 pounds of ‘‘cut”’ fish, and at least 1,082 
pounds of fish ready for the can. Allowing 15 ounces of prepared fish per can (a high figure), the yield 
is 1,154 cans, or 24 cases, 
es ee ee 
