Two phase nh3 flow pressure drop through valves

[virk]

Who of you is a little bit familiar with following problem:

0,09 kg/s ammonia gas flow at 0,408 bara pressure through 3 valves in series, each kvs=246m3/h (approx.cv 211)

Density at entrance pressure is 0,38 kg/m3.
Which value will have friction pressure loss? (I calculated roughly 10 mbar and I think I am right.)

Now additionally 0,36 kg/s ammonia liquid flows through the same system. Density of liquid ammonia is 700 kg/m3.

What about pressure loss now?
I calculate an enormous increasement of pressure drop and must convince other people about this (If this is really the case)

kin. visc. liquid 0,5645 cP
kin. visc. gaseous 0,0075 cP

Any advice welcome.

 

[sterl]

I make the Dry Gas almost 10 through the first valve....

The proportion of liq to vap in aerosol, such that the liquid drops and vapor are moving at anything like the same speed on their trip through the valve, represents a mixture having only about 125% of the density of the dry vapor, the rest of it travels as film on the walls.

The refrigeration people have been running 4:1 recirc plants for a very long time, and they don't encounter anything greater than about a 55% Increase in Pressure drop even at these pressures.....With globe style valves which inherently have a more contorted path and tend to remix liquid into the flowing vapor, moreso than would say a Full Port Ball Valve.

If these are globe style valves, do everything you can to ensure that the orifice is in vertical plane, nominally then stem horizontal.

 

[virk]

How do you calculate this density of about 125%. I calculate density of about 2 kg/m3 for the mixture of both streams, if they move with same velocity.

Circulation factor is not 1.25 but roughly 4.

Do you perhaps know, where I could find some literature about this. For us it is important, whether we loose 0,5 K or 1,5 K temperature at the evaporators.