This section of the program calculates the back pressure developed in an Eimac
3CX5000A7 tube for various flow rates, at various temperatures. The data is
derrived by fitting a second order polynomial of the form:
BP = a1 * flow + a2 * flow
The constants a1 and a2 were estimated by fitting the data sheet air flow
data for inlet air temperatures of 25, 35 and 50C at sea level. The data
should be more accurate than that estimated in section 26, since the simple
approximation that BP is proportional to flow has not been used.
