Calculate the flow coefficient and pressure drop through valve?

[daftdave11]

Hi
I am wondering would ye be able to help me out? I am instructed with the task of calculating the pressure drop and flow coefficient for a valve. Please see basic diagram attached for layout of valve. I need to find the pressure drop and flow coefficient when the ram is closed at different percentages. would ye be able to tell me the necessary equations that i need to do this. note internal diameter is 100mm at inlet and 50mm at outlet.The valve shown would be connected to the bottom a reactor etc. the pressure entering is set at 6 bar and the temperature is to be 100 C. i know that the fluid been tested is to be natural gas and also water, which i have the properties of both. is there any formula i could use to get a ruff estimate of valves for the flow coefficient and for the pressure drop.. badly stuck for this info? thanks in advance

Regards Dave

 

[sina_kz]

Hi,
i think if you're going to take it easy,easily can divide your valve to tree domains,1.the domain between entrance of valve and entrance of the gate(as an example for a gate valve),2.between entrance of gate and gate exit,3.gate exit and valve exit.
then taking use of continuity and energy equation for each control volume(having pressure and temprature in the entrance and geometry properties in each domain) you can take care of such a problem.
assumptions such incompressibility for liquids or Gases with Makh<0.3,ideal flow for gases,same area just in start and end of gate,absence of friction forces,etc would make it much more easy.

 

[daftdave11]

thanks for your reply sina kz.. i don't really understand what your trying to say in your post. could you eplain it with a bit more detail maybe? are you saying that i should treat my valve as just three simple sections of pipe? and carry out my calculations that way??

what equations would i need to use to do this ? thanks in advance.. regards david

 

[sina_kz]

Hi,
i confess that i wanted to help you whithout engaging with the problem,
but i still think you can take it easy,i have written my idea on a paper i would be happy to send it,just email me(khajehzadeh.sina@gmail.com)