94 PRESERVATION OF FOOD BY REFRIGERATION ; 
APPENDIX B. 
Calculation of the work done ina freezing chamber of 
the following dimensions, with walls 24 inches thick, com- 
posed of wood and charcoal :— 
2 Wail Area. 
External dimension, 64 x 40 x 11 ft., = 7,408 sup. ft. area. 
Internal dimension, 60 x 36 x 7 ft., = 5,664 sup. ft. area. 
Mean of external and internal superficial area of the walls, 
6,536 sup. feet. 
Internal area, 60 x 36 X 7 ft., = 15,120 cub. feet. 
Temperature of external air = 77° F. 
Temperature of internal air = 14° F. 
Adopting Box’s rule and notation— 
T = Temperature of external air. 
T’ = Temperature of internal air. 
= Temperature of external walls. 
Temperature of internal walls. 
The radiant power of the materials. 
= The loss by contact of cold air. 
Conducting power of the materials. 
EE Ee 
Units per square foot per hour. 
Thickness of walls in inches. 
OF 
TS 77° C55) ea eee 
i agin ey © Oe eo «= 
R for 63° diff; per table 2.= -736 mer. — sgn 
Actor Ge” dilopen tables }c Bs 64 eae 
and 7ft. high per table 4 J 440 
EO Or Aa 
To find the temperature of the external surface of the 
wall ==/t. 
, — {(Qx[ExAxT)+(CxT I} +{AxCxT} 
eS {Cx[2xA)+R]}+{ExAxQ} 
__ {1315 x [24 x 568 x 77) + (55 X 14] } + {568 x55 X77} 
{55 x [2 x 568) +°747]} + {24 x 568 x 1°315} 
=7454=1. 
To find the temperature of the internal surface of the 
wield. 
