ENGINEERING CALCULATIONS OF RADIANT HEAT EXCHANGE 



ation may be obtained like that of carbon dioxide, except for the use of 

 an exponent of 0.45 instead of 0.65 on {TJT\). The correction factor Cw 

 still applies. 



When carbon dioxide and water vapor are present together, the total 

 radiation due to both is somewhat less than the sum of the separately 

 calculated effects because each gas is somewhat opaque to radiation from 

 the other. The amount Ae by which to reduce the sum of eg for CO 2 and 



0.007 



500 1000 1500 2000 2500 3000 3500 4000 4500 5000 



Temperature, °R 



Fig. I,3c. Emissivity of water vapor. 



eg for H2O (each evaluated as if the other gas were absent) to obtain the 

 eg due to the two together is read from Fig. I,3e. The same type of cor- 

 rection applies in calculating a^. 



Recapitulating by the use of subscripts on eg indicating in sequence 

 the gas (c or w), the temperature on the plot, and the value of pL at 

 which e is read, one has 



fi: = ^c.r^.p.r.C, + e^.rg./viC'w — Aey^ (3-3) 



««' — ^,;T,.p^LT,/T. 



Cc + ^.y,7\.p^.LT,/Tg [rp^ j Cw — Aay^ 



< 516 ) 



