I N 0 USTRIAL A N D ENGINEERING CHEMISTRY
May, 1924
. 12-For approximate calculations of the heat transfer from large smooth surfaces we take a! = 1, /3 = I/*, and KO = 350 in Equation 60. This gives for ideal gases and smooth surfaces We = 0.00246 ApokAt/p
(watts)
(71)
and for air We = 0.0012 A@At/T,,,. (watts) (72) For moderately rough surfaces we may employ Equations 67 and 68, and for very rough surfaces in ideal gases We = 0.010 ApwkAt/p
(watts) (73)
13-The heat transfer in mixtures is covered by the same general equations that apply to liquids and gases. 14-For mixtures of a light with a heavy gas the forced convection a t high velocities over plane surfaces may be greater than in either gas alone. For air, (pc,/k)L/a ( k p / p ) = 0.41 p/Tsvg. Pure hydrogen, ( p c / k ) I / 9 ( k p / p ) = 0.40 p/T,,,. 95% hydrogen 5
