doesn't that formula depend on absolute temperature like kelvin or so? where zero degree is minus 459 degree F or minus 273 Celsius.
the ratio of expansion should be something like:
inlet air: 20 degree Celsius (68F) or 293 Kelvin
outlet air: 50 degree celsius (122F) or 323 Kelvin
then
323 over 293 for a change in temperature gives
then the Volume change of more like 1.2

there is some additional expansion due to the pressure difference.

Regards

Marko

Marko;

You got me there.  You’re right, it needs to be the ratio of absolute temp.  That gives a ratio of inlet to outlet for the 80 F in and 135 F out of about 1.1.  Also for the case you give; 323/293 is 1.1; not 1.2, or did you factor in some additional volume change for pressure. 

Gees .. you mean now I have to go back and rework my rad outlets?

Al