What is the difference between an ISA 1932 nozzle and a long radius nozzle?
Both nozzles are standardized, the details of their characteristics are explained in the standards.
We can specify that, in general, an ISA1932 nozzle has an input plane perpendicular to the axis of the fluid, a convergent, a cylindrical throat and a possible bevel to avoid damaging the output edge. On a long radius nozzle, it is also possible to see a convergent portion and a cylindrical throat, but they have a different shape from the ones of the ISA1932 nozzle. In addition, the ISA1932 nozzle must be mounted with corner pressure taps (0/0) or an annular chamber while the long radius nozzle will have a D-D/2 (D upstream and D/2 downstream) of the inlet face of the nozzle. More over, the standard specifies that the uncertainty on the discharge coefficient of the ISA 1932 nozzle is 0.8% while it is 2% for the long radius nozzle.
Only a calculation integrating all the characteristics and the requirements of your process will allow us to guide you in your choice.