Pressure loss steam through contraction
Pressure loss steam through contraction
(OP)
Hi Guys,
Interesting forum :). I have question regarding pressure drop calculation for a inlet line to a PRV. Medium is steam 4 barg. In this inlet line we reduce (contraction) from DN65 (inside 62 mm) to DN 32 (inside 32 mm). The pressure drop accros this contraction is really huge! I have to reduce one way or another to adjust to the prv inlet connection (inlet DN32 outlet DN50). I calculated it with the standard HL=K*(V2^2/2G). PRV certified massflow is 1775 kg/h, I have to size my inlet and outlet according to this, but with this contraction it gives problems relating to alowable pressure loss.
My feeling is that this formule is not applicable for steam anymore, is there any 2 phase formulas needed?
Interesting forum :). I have question regarding pressure drop calculation for a inlet line to a PRV. Medium is steam 4 barg. In this inlet line we reduce (contraction) from DN65 (inside 62 mm) to DN 32 (inside 32 mm). The pressure drop accros this contraction is really huge! I have to reduce one way or another to adjust to the prv inlet connection (inlet DN32 outlet DN50). I calculated it with the standard HL=K*(V2^2/2G). PRV certified massflow is 1775 kg/h, I have to size my inlet and outlet according to this, but with this contraction it gives problems relating to alowable pressure loss.
My feeling is that this formule is not applicable for steam anymore, is there any 2 phase formulas needed?





RE: Pressure loss steam through contraction
Your velocities are too high.
Good luck,
Latexman
To a ChE, the glass is always full - 1/2 air and 1/2 water.
RE: Pressure loss steam through contraction
RE: Pressure loss steam through contraction
My question is about the contraption pressure loss for steam is the formula HL=K*(V2^2/2G) still applicable?
RE: Pressure loss steam through contraction
Since the inlet steam does go through a physical contraction, the contraction pressure drop does apply. So far, I have not heard a reason why two phase flow might exist in a significant amount in this case. Why do you think two phase correlations apply?
Can you give more details on the contraction and your calculations? Is it a welded bushing reducer, a screwed bushing reducer, a butt welded commercial reducer? What K value are you using? For a butt welded commercial piping reducer I use a K = 0.1 (based on smaller end/higher velocity) as a first pass.
Good luck,
Latexman
To a ChE, the glass is always full - 1/2 air and 1/2 water.
RE: Pressure loss steam through contraction
K = 0.5 x (1 - A2/A1) = 0.5 x (1 - (D2/D1)^2)) = 0.367
The total dynamic loss should also include the pressure loss term due to kinetic energy gain across this reducer - see example 5 on page 6-16 of Perry Chem Engg Handbook (7th edn)
Obviously the total inlet loss for this PSV should also include all other fittings, vessel nozzle losses(if this PSV is connected to a vessel) etc.
The formula you've listed is for an exit - contraction loss across a vessel nozzle where V1 is negligible.
RE: Pressure loss steam through contraction
RE: Pressure loss steam through contraction