Original: Theoretical temperature rise is T2 = T1·Rc(k-1)/k, with T1 and T2 in degrees Rankine or kelvin, and k = ratio of specific heats (approximately 1.4 for air).
Simplified: Theoretical temperature rise is T2 = T1·Rc((k-1)/k)), with T1 and T2 in degrees Rankine or kelvins, and k = ratio of specific heats (approximately 1.4 for air).