@mister moverz

what i know, Dc is combined diameter of suction & discharge nozzle. we use this if want to analyze suction&discharge nozzle together with respect to C.G. of the compressor.

1st, calculate De (equivalent diamter of both nozzles);

De = (Ds^2+Dd^2)^0.5
Ds = suct. nozzle diamter
Dd = disch. nozzle diameter

if De > 9in, than we need use correction factor:
Dc = (18+De)/3 (in)


similarly with individual nozzle analyses, we use Dn (nominal diameter). if its size is above 8in, than we use correction factor:

De = (16+Dn)/3 (in)


CMIIW master, please