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American Society of Heating and Ventilating Engineers Guide, 1924-25
per hour per degree fahr. temperature difference. Pounds of coal used are given per 100 sq. ft. per month assuming continuous use of the apparatus, 70 per cent boiler efficiency, and 13,000 B.t.u. per lb. The "dollars" column represents the money value of the coal used per 100 sq. ft. per month assuming coal at S4.00 per ton and boiler room expense at S1.00 per ton.
TABLE 83. HEAT LOSS FROM UNINSULATED SURFACES
TbmperaTURK
Dec. Fahr.
Heat Loss*
B.t.u.
Month
Lbs. Coal Dollars
PER 100
per 100
Sq. Ft. per Sq. Ft. per
Month
Month
" ' 80 " ~ " _
............................
120 " " --
............-...............
" 160 " " ................................................
a 200 " tf
.......................................
" 200 a a and 100 deg. fahr. superheat
120 180 239 324. 350 371 388 488
1.95 2.04 2.29 2.76 2.92 . 3.05 3.15 3.88
770 1780 3065 5545 6480 7250 7950 12,830
1.92 4.45 7.65 13.86 16.22 18.13 19.87 32.05
B.t.u. per sq. ft. per deg. fahr. difference per hour.
CONDUCTIVITY OF INSULATING MATERIALS
The conductivities in B.t.u. per square feet per hour per inch thick per degree fahr. temperature difference of the various insulating materials are given in Table 84. It should be emphasized that in this table all variables due to differences in thickness, different pipe sizes, and different air conditions, are eliminated.
TABLE 84. CONDUCTIVITIES OF VARIOUS INSULATING MATERIALS
Den* CON-
SlTY
La. per
Cu. Ft.
DUC* TtVITY
Temp. Diff. which
Conductivity was
Determined
Authority
Year
Asbestos Sponge Felted 23.80
Wool Felt..................... 16.24
85% Magnesia. ....... 17.20
21.70
Nonpareil H. P.......... 17.43
Plastic. 85% Magnesia
Asbestocel-------------- ---- 12.16
Expanded Asbestos.___ 22.49
Indented ........ ........ 21.24
Molded Asbestos.
29.86
Air Cell.............................. 11.70
Vitribestos..................... 29.73
Asbestos Fire Felt__ . 26.59
Corkboard...........-......... 9.90
Hair Felt........ ................ 17.00
0.468 0.521 0.54
0.54 0.543 0.587. 0.596
0.598 0.686 0.778 0.802
1.087 1.093 0.304
0.246
300 deg. fahr.' Vol. 37. Trans. A. S. M. E.. p. 968
300 * "
"
300 300 "
"
Vol. 40. Trans. A. S. M. E.. p. 667 Vol. 37. Trans. A. S. M. E.. p. 968
300 "
300 " *
300 * "
"
300 * "
"
300 * *
"
300 " "
"
3(X) * "
300 " *
"
300 *
*
36 * * Vol. 26. A. S. H. & V. E. Journal, p. 625
36
1915 1915 1918 1915 1915 1915 1915 1915 1915 1915 1915 1915 1915
1920 1920
HEAT LOSS FROM INSULATED SURFACES
Fig. 53 gives the heat Joss per square foot of pipe per hour of piping where the pipe is covered with 1 in. thick covering. Inasmuch as the
145