How to calculate check valve pressure drop for 2 phase flow (lig/gas)?

[smh345]

Can anyone point me in the right direction? I need an accurate method. Thanks.

 

[Latexman]

First of all, there is no accurate method for two phase flow! Using the *best* correlations available and for 95% confidence limits on flow, multiply and divide the calculated flow by 1.3. For 95% confidence limits on pressure drop, multiply and divide the calculated pressure drop by 1.8. For typical pressure drop methods, a factor of 3 is not uncommon.

To get started, I'd suggest the latest edition of Perry's for the basics. For relief work, we use the Homogeneous Equilibrium Model where I work.



Good luck,
Latexman

 

[vanstoja]

You haven't said what kind of check valve you're interested in. Four main types are lift checks, swing checks, tilting disk checks and membrane check valves [Plant Engineering, Mid-July 1997, pp.8-12, "Check Valve Basics"]. Check valve manufacturer's curves usually provide pressure differential vs flowrate for a range of valve sizes and should be used if valve type is known. Water data for pressure losses of lift, tilting disk and swing check valves, respectively, can be found in
Power, Aug. 1976, pp.25-36, "Check Valves", W.O'Keefe
ASCE Proc. V102, Jan.-July 1970, 57-72, Kane & Cho
Handbook of Hydraulic Resistance, 2nd Ed. 1986, Diagram 9-21, Idelchik

 

[smh345]

Thanks. I know the Cv for the valve in question (dual-plate check) but need a formula / correction method for two-phase flow. Have already checked 6th Ed. of Perry's - couldn't see anything for valves. Latex - not with you on "multiply and divide..." - can you explain?

 

[Latexman]

Did you find anything on 2 phase flow in pipe? Can you convert the resistance of the check valve into equivalent length of piping? Is the check valve in a vertical run or horizontal run? Can you determine the flow regime? If these questions don't ring a bell, start giving us the details of the check valve, like T, P, flow rate, volume fraction gas, MW of gas, density of liquid phase, what are the components, etc.

Let's say you use the homogeneous equilibrium model and it estimates the dP = 18 psi. For 95% confidence limits on the *actual* dP, the lower limit = 18/1.8 = 10 psi and the upper limit = 18x1.8 = 32 psi. So, you can be 95% confident the actual dP is going to be between 10 to 32 psi. Not too accurate, huh?

Good luck,
Latexman

 

[smh345]

Thanks again. I did see the formula for pipes but thought there may be someting easier to work with. I guess not! Appreciate your help.