Pressure drop - low quality steam at low pressures
Pressure drop - low quality steam at low pressures
(OP)
Hi,
I was wondering if anyone know a proper pressure drop correlation for
1. Low quality steam x=0.1-0.3
2. Low pressure 0.2-1.5 bar(a)
I have a flash tank connected to the condenser by a short pipe. At a disturbance case I expect extreme flow to the tank and would like to calculate what the pressure in the tank needs to be to push out the two-phase steam.
Drex
I was wondering if anyone know a proper pressure drop correlation for
1. Low quality steam x=0.1-0.3
2. Low pressure 0.2-1.5 bar(a)
I have a flash tank connected to the condenser by a short pipe. At a disturbance case I expect extreme flow to the tank and would like to calculate what the pressure in the tank needs to be to push out the two-phase steam.
Drex





RE: Pressure drop - low quality steam at low pressures
RE: Pressure drop - low quality steam at low pressures
http://www.google.com/url?sa=t&rct=j&q=&am...
Good luck,
Latexman
Technically, the glass is always full - 1/2 air and 1/2 water.
RE: Pressure drop - low quality steam at low pressures
In situations like this it is good to remember than an engineering design is a decision and not a calculation. You do all the calculations that you think will give you useful information, and then you apply your engineering experience and judgement to decide on the solution. In this case the decision may even be that there is no reliable way to predict the pressure drop and that it is necessary to go back a step and fix the upstream problem that is giving rise to the 2-phase flow.
Katmar Software - AioFlo Pipe Hydraulics
http://katmarsoftware.com
"An undefined problem has an infinite number of solutions"
RE: Pressure drop - low quality steam at low pressures
Fritzche Equation
Spitzglass Equation (saturated steam < 200 psig)
Can all be used for typical steam flow.
Now, given that allowing slugs of liquid to fly about a piping system can actually be dangerous, would it not be better to ensure that the condensate be drained from the condenser by other means... a drain valve for example.
Contrary to popular belief, everything in this world does not require a process engineer. Thermodynamics is usually an ME topic. At least I learned it in the ME school of things.
RE: Pressure drop - low quality steam at low pressures
katmar, since I have very high velocities and high void it will be mist flow or in some cases perhaps annular mist. Likely some critical two phase model would be most useful. Since this is a exceptional disturbance case and existing installation I don't want to redesign unless absolutely necessary. A proper separation of steam and condensate for this case is not reasonable I think as flow is so much higher than at normal operation.
BigInch, the listed correlations are to my knowledge used for single phase pressure drop. With steam quality this low the homogeneous density will be 3-10 times that of the pure steam and the viscosity for calculating Reynold number needs some adapted equations. If you have used 1-phase pressure drop correlations for 2-phase with only compensation for density and viscosity I would be very interested. Do you have any reference for this. The installation investigated has a few drainage valves from preheaters via a flash tank to the condenser. The condensate will always flash heavily in the control valve so the flow to the flash tank will always be low quality steam. The flash tank has a steam pipe and a condensate pipe connected to the condenser. At this disturbance case the mass flow will be so high that proper separation is unlikely and the condensate U-tube will likely blow out and the 2-ph. steam will blow out both through steam and condensate pipe.
RE: Pressure drop - low quality steam at low pressures
Shouldn't you be preventing two phase flow and condensate blowout.
If so, why do you think not?
http://www.kirsner.org/pages/condInduceWatHamText....
RE: Pressure drop - low quality steam at low pressures
Good luck,
Latexman
Technically, the glass is always full - 1/2 air and 1/2 water.
RE: Pressure drop - low quality steam at low pressures
Best of luck!
RE: Pressure drop - low quality steam at low pressures
RE: Pressure drop - low quality steam at low pressures
HEM looks interesting and I would be interested in a textbook describing it in detail (google doesn't give anything of substance).
RE: Pressure drop - low quality steam at low pressures
Select the Best Model for Two-Phase Relief Sizing
Good luck,
Latexman
Technically, the glass is always full - 1/2 air and 1/2 water.