Dear

I want to avoid cavitaion in RO for flashing liquids?Reason of cavitation is as below:

When liquid reachs to the converging portion(vena contra) velocity increases as result of which pressure falls and some times falls slightly below the vapor pressure of fluid and liquid flashs out.But after pressure recovery in divergent portion condensation of begins and cavitaion comes in to the picture.The line amy fail due to high virations as well.


Regards
SAM

Limit the pressure drop.
There are special designs available that help you avoid cavitation, you can probably find them on the web.

You could try further cooling of the liquid upstream of the RO, but if you have no control over the temperature or the pressure drop, then there's not much you can do. I think for a high pressure drop, you have no options, but that may not be a big problem. Cavitation is not necessarily disasterous; just design for it.

(If you don't find this response satisfies your needs, then please provide more information. Especially, will there be two phases downstream of the orifice?)

The magnitude of Cavitation may be reduced by multiple ROs.

For information on multiple orifices to avoid cavitation see the article by Tung and Mikasinovic in Chemical Engineering, December 12, 1983, pgs 69-71 and by Lin S.H. Hydrocarbon Processing, July 1985, pgs 93-95.