Bulletin . < 320 °g300 E-i «3 fe O 280 dg WC 260 1-1 O j 0 \ \ \ \ 1 L8C oc \ \ \ \ \ \ 1 82™ fe K 22C H < Pt* 200£g 180 \ ? \ \ \ ^ 1 1700^ \ \ \ J \ 1 i \ \ aS 160 | \ a w 140 1 \ l h E-iO < H 120 U \ \ \ fiCG<H 100 \ \ \ 1400: \ p£ 80 L, \ 1 \ \ r- < -1300 l_l ~ ?: ~ S 60 \ \ \ \ \ | | &?, 40 -12C \ 1 _no 100 u \ \ I *-* Eh 20 tn$ N \ \ w — \ \ \ ... 1 s\ \ \ \ \ 3 cc 33 4 s 3 33 c 33 e 33 c< 2 - -• 3 ; 33 3 C 3I \C c 331 3 5?4 i ABSOLUTE , OF SOOTED SURFACEABSORBING NET HEAT RADIATED BYHOTTER 17.—Radiation of heat from a hot surface to a cooler sur
Bulletin . < 320 °g300 E-i «3 fe O 280 dg WC 260 1-1 O j 0 \ \ \ \ 1 L8C oc \ \ \ \ \ \ 1 82™ fe K 22C H < Pt* 200£g 180 \ ? \ \ \ ^ 1 1700^ \ \ \ J \ 1 i \ \ aS 160 | \ a w 140 1 \ l h E-iO < H 120 U \ \ \ fiCG<H 100 \ \ \ 1400: \ p£ 80 L, \ 1 \ \ r- < -1300 l_l ~ ?: ~ S 60 \ \ \ \ \ | | &?, 40 -12C \ 1 _no 100 u \ \ I *-* Eh 20 tn$ N \ \ w — \ \ \ ... 1 s\ \ \ \ \ 3 cc 33 4 s 3 33 c 33 e 33 c< 2 - -• 3 ; 33 3 C 3I \C c 331 3 5?4 i ABSOLUTE , OF SOOTED SURFACEABSORBING NET HEAT RADIATED BYHOTTER 17.—Radiation of heat from a hot surface to a cooler surface; relations expressed in British thermal units, degreesFahren-heit, and square feet. DISCUSSION OF PHYSICAL LAWS. 29 brick remains constant no matter what the temperatures of the sur-faces are, so long as the temperature difference remains equal to100° C. The lower horizontal straight line shows the same relation for abrick wall 4 inches thick. The heat passing through the 4-inch. FlGUBE 18. ABSOLUTE TEMP.,°F., OF SOOTED SURFACE ABSORBING NET HEAT RADIATED BY HOTTER of heat from a hot surface to a cooler surface; relations expressed in Britishthermal units, degrees Fahrenheit, and square feet. wall is one-half of that passing through the 2-inch wall, which, ofcourse, might be expected. The chart shows that the curves ofradiation start below the lines of conduction, but as the temperaturesincrease both of the radiation curves cross the lines of conductionind beyond that rise very rapidly. 30 \ FLOW OF HEAT THROUGH FURNACE WALLS. APPLICATION OF THE LAWS. The chart further shows that an air space is more advantageousthan a 2-inch brick wall if the temperature of the hotter surface isbelow 625° C, absolute, or 565° F., ordinary scale, but above thattemperature the brick wall is better. With a 4-inch wall the limit-ing temperature drops down to 500° C, absolute, or 440° F., ordinary 360 ABSOLUTE TEMPERATURE720 1080 1440 1800 OF HOTTER SURFACE
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