MJCronin,
Actually, a little of both. With the NBIC NB-27 publication, we found a few errors and technical limitations, which davefitz illuminated above. I like the publication quite a bit, but we had conditions not covered in the graphs and curve-fit equations in NB-27, so I wanted to see...
I have been looking everywhere (especially at ASME.org) for how to get a copy of "The Flow of a Flashing Mixture of Water and Steam through Pipes" by M.W. Benjamin and J.G. Miller from the "Transactions of the ASME" 64, from October of 1942. I know it is often referenced for blowdown vessel...