Table 51. Thermal Conductance Conversion Factors
To Convert ↓
Btu-ft/(h-ft 2 - ° F) Btu-in/(h-ft 2 - ° F) Btu-in/(sec-ft 2 - ° F) cal/(cm-s- ° C) kcal/(cm-s- ° C) kcal/(m-h- ° C) erg/(cm-s- ° C) joules/(m-h- ° C)
watt/(ft- ° C) 0.5274738 0.04395615 158.24214 127.598424 1.276 3 10 5
watt/(m- ° K)
12
1
0.00333333 0.000277778
0.00413385 4.13386 3 10 − 6 1.488188976 173076.378 0.00034448 3.44448 3 10 − 7 0.124015748 14423.0315 1.24001574 0.001240157 446.4566929 5.1925 3 10 7
6230.0055 519.25573
1.73056 0.14421 519.167 418.63
Btu-ft/(h-ft 2 - ° F) Btu-in/(h-ft 2 - ° F) Btu-in/(sec-ft 2 - ° F) cal/(cm-s- ° C) kcal/(cm-s- ° C) kcal/(m-h- ° C) erg/(cm- s- ° C) joules/(m-h- ° C)
0.083333
1
300
3600
1
1.8693 3 10 6 1.507 3 10 6 1.507 3 10 9
0.001
360
241.9047
2902.8571 2.902 3 10 6
0.806349 806.3492
1
4.1868 3 10 7 4.1868 3 10 10
1000
360000
1
4.1863 3 10 5
2.419 3 10 5
0.671957
8.063349
0.00223985
0.00277778 2.77778 3 10 − 6
1
116300
4186.8
0.35444
1.16286 1 3 10 − 5
1
0.036
6.933 3 10 − 5 0.00192616
1.92593 3 10 − 8 5.35045 3 10 − 7 0.006319429 0.001926162
2.3884 3 10 − 8 2.3884 3 10 − 11 8.5984 3 10 − 6
5.7778 3 10 − 6 1.6051 3 10 − 4
3.0476 3 10 − 6
0.000238874 27.781095
1
6.6354 3 10 − 7 6.6354 3 10 − 10
8.4666 3 10 − 5 2.7777 3 10 − 4
1.895828 0.5778486
22.75
0.00783708 7.83709 3 10 − 6 2.821351461 328123.1749
11811.024
1
3.28
watt/(ft- ° C) watt/(m- ° K)
1 3 10 5
3600
6.934183
0.002388744 2.38874 3 10 − 6 0.859947925
0.304878
1
Figures in bold face indicate the conversion is exact Conduction.— Whenever the molecules of a working substance, whether liquid, solid, or vapor, are restrained so that no appreciable relative translatory motion occurs among them, the kinetic energies of the various molecules will be largely due to vibration. If a temperature difference exists in the working substance, some adjacent molecules will necessarily be at different temperatures, hence will possess different degrees of vibratory motion. In this case the molecule which is vibrating most rapidly will transfer some of its motion to the slower-moving molecule next to it, the one then undergoing a decrease in temperature and the other an increase. In this way, thermal energy will be transferred by the mechanism of conduction from the region of higher to the region of lower temperature. The process will continue spontaneously until the entire system has reached a uniform equilibrium temperature. In contrast to radiation, conduction only occurs when a working substance is present and when the molecules of that working substance retain practically fixed positions with respect to one another. Thus, conductive heat flow would always occur through solids, but would take place in liquids and vapors only if special conditions prevented or greatly reduced the normal translatory motion of the molecules within these materials. Fuel Oil, Coal, and Gas.— One gallon of fuel oil equals 13.1 pounds of coal, equals 160 cubic feet of natural gas. One barrel of fuel oil equals 0.278 ton of coal, equals 6806 cubic feet of natural gas. One pound of fuel oil equals 1.75 pounds of coal, equals 21.3 cubic feet of natural gas. One pound of coal equals 0.763 gallon of oil, equals 12.2 cubic feet of natural gas. One ton of coal equals 3.6 barrels of oil, equals 24,500 cubic feet of natural gas. The heating value of the average mid-continent fuel oil having a Baume gravity of 26.9 is 19,376 British thermal units per pound of oil, and 143,950 British thermal units per gallon of oil. The specific gravity and the heat value may be expressed approximately by means of a simple formula, as follows: BTU per pound = 18,650 + 40 3 (Degrees Baume − 10).
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