Calculating Pressure Drop Across Valve in Horizontal Pipe

[pray4mojo]

Hi,

20m straight length horizontal pipe (60 mm internal diameter), steam flows at rate 0.5 kg/s, at midpoint there is a valve in the line. inlet pressure to this section of line is 5 bar (gauge), pressure at end of line is 3 bar (gauge). mass quality of steam is 0.8 and 2 phase flow occurs in the line.

I have calculated the mass flow of liquid and vapor in the line, the frictional pressure drop (N/m2) for the horizontal tube (without valve) using lockart martinelli correlation and also predicted the flow pattern at entry to the valve.

However,the part I am having a problem with is..When calculating the pressure drop across the valve.After calculating the homogeneous parameters and inserting them into the pressure drop equation which is: -dp/dz= [ρ*u *du/dz] + [2*f*ρ*u^2/d] + ρ*g*sinθ

First term in the equation i took equal to zero (no change in velocity assumed), but for the last term (ρ*g*sinθ), do i take theta(θ) as equal to zero as it is a horizontal pipe?

My solution is attached.
Thanks for any help!

 

[nbryan5]

Yes, you would take theta (θ) as equal to zero as the pipe is horizontal. The last term (ρ*g*sinθ) in the equation is the gravitational pressure drop which is only applicable when the pipe is not horizontal, i.e. when it has a vertical or inclined section.

 

[oswaler]

Hello,

Thank you for sharing your calculations and the issue you are facing. As a scientist, my response would be to suggest that you double-check your assumptions and calculations in order to ensure accuracy. It is important to consider all aspects and variables in a system, especially in a complex situation like calculating pressure drop across a valve in a horizontal pipe with two-phase flow.

To answer your question about θ, it is correct to assume that it is equal to zero in a horizontal pipe. However, it is important to note that the pressure drop equation you have provided includes other terms that may also contribute to the pressure drop across the valve, such as frictional pressure drop and changes in velocity. It is important to consider all of these factors in your calculations to get an accurate result.

I would also suggest consulting with a colleague or expert in the field to review your calculations and assumptions. They may be able to provide valuable insights and help you troubleshoot any issues you may be facing.

Best of luck with your calculations and I hope this helps. Keep up the good work in your scientific pursuits.