10 
BULLETIN 85, U. S. DEPARTMENT OF AGRICULTURE. 
obvious that the 380,800 B. t. u. represented so much additional 
heat over the exhaust-steam systems in tests Nos. 1, 2, and 3. 
As stated above, in test No. 4 the pasteurizing was done by live 
steam from the boiler instead of exhaust steam, and by referring 
to the tabulated results of tests it will be noted that the over-all 
thermal efficiency of test No. 4 is only 43.7 per cent while that of 
tests Nos. 1, 2, and 3 is 69.1, 60.6, and 69.7 per cent, respectively) 
although the thermal efficiency of the heater in test No. 4 was the 
greatest. 
The over-all efficiency is here taken as the ratio of the heat supplied 
by the boiler to the steam to that absorbed by the cream. 
The thermal efficiency of the heater is the ratio of the available 
heat in the steam supplied to the heater to that absorbed by the 
cream. 
HEAT BALANCE. 
No heat balance is given in Table 2 because the pasteurizing 
equipments in tests Nos. 1,2, and 3 were installed in market cream 
plants, that is, plants whose business consisted in the handling 
and marketing of cream. The cream as received from auxiliary 
creameries was first run through separators, the result being a 
heavy cream containing about 40 per cent fat. This heavy cream 
on the way to the coolers was mixed with skimmed milk in the correct 
proportion to produce a cream containing a predetermined amount 
of fat. In view of the methods employed in these plants, it was 
impractical to get out a heat balance showing the distribution of 
heat in the pasteurizing cycle. 
Table 2. — Results of tests of four cream-pasteurizing plants. 
HEATING. 
Time of operation hours. . 
Amount of cream pasteurized pounds. . 
Amount of steam used in the pasteurizer do 
Heat supplied by boiler to steam, 80 pounds pressure, 
B.t.u.. 
Heat in steam required to drive pasteurizing equipment, 
B.t. u.. 
Heat supplied to pasteurizer do 
Total boiler horsepower developed for pasteurizing, 
B.H.P.. 
Boiler horsepower per hour developed for pasteurizing, 
B. H. P.. 
Total heater horsepower consumed for pasteurizing .do 
Heater horsepower per hour consumed for pasteurizing, 
B. H. P.. 
Cream pasteurized per boiler horsepower pounds. . 
Cream pasteurized per heater horsepower do 
Coal burned in pasteurizing do 
Cream pasteurized per pound of coal do 
Total B. t. u. absorbed by cream B. t. u.. 
The over-all thermal efficiency of pasteurizing equip- 
ment per cent. . 
Thermal efficiency of heater do 
Plant No. 
3. 
50, 683 
5, 589. 
6,437,646 
,589,500 
193. 
54. 
167. 
47. 
262 
302 
1,030 
49. 
, 447, 433 
1 
1,253 ; 
1.733 
928 
088 
478 
1, OSS, 000 
37. ( 
21.7 
32.6 
18.8 
184 
212 
200 
34.6 
030 
60.6 
69.8 
L 
5,019. 
647. 
746,003 
647,500 
14. 
19. 
13. 
224 
258 
119 
42. 
520, 171 
L 
4,571 
629 
617,113 
3S0,800 
529,000 
25.6 
15.9 
13.6 
153 
287 
160 
29.0 
436,176 
43.7 
82.5 
