270
APPENDIX VII
at 27° C. (80° F.). Whether these assumptions are correct cannot
be determined without further research.
In the foregoing, a checker work of square passes has been
assumed. The method of arriving at the heating surface of the
usual checker construction is somewhat similar to the above.
B. t. u. per sq. ft. per second
naao__o 0.1 Q.9 0.3 0.4 O.S 0.6 0.7 0.8 0.9 1.0 1.1 1.2 1.3
752 400
572 300"
392 200
212 100
F C
0.5 1.0 1.5 2.0 2.5
Calories per m2 per second
3.0
3.5
FIG. 165.—Curve of Heat Loss from Exterior Walls of Furnaces According
to Experiments of Charles R. Darling.
The bricks occupy 0.5526 of the volume and the pass 0.4474;
hence the number of rows per meter will be
nb=552.6 -^63 ==8.771 rows
or 0.5526-^0.21 = 2.63 rows per foot.
The gauge or space between the rows of brick will be
b0=447.4 -f-8.771 = 51 mm (about 2 in)
or 0.4474+2.63 = 0.17 ft (about 2 in).
From these figures the heating surface per square meter, or
per square foot, may be readily computed, as well as all of the
other data necessary to determine the sizes of the checker cham-