Pressure Drops in Y / Oblique Angle Globe Valves

[djeffroy]

Hi,
We are looking at actuated y globe valves for a project and I have heard that pressure loss is dependent on flow direction. The manufacturer we're dealing with has indicated that the valves we're considering can be used with flow in either direction. Just for my own knowledge, I was hoping someone could advise which flow direction provides less pressure loss (black vs red) and provide some insight / explanation as to why this is the case?
Thanks!

 

[1503-44]

I'd say pretty equal, unless inlet and outlet size vary a lot. The biggest factor IMO is the 90° turn of momentum that happens in both direction of flow. The orifice size would be the same in either case. The only difference is possible guidance of the flow into the orifice from each direction could have some bearing, but probably not much overall compared to the 90 turn. I think I'd use the same in each case, especially when full open. If partially open, you'd have some dead space above around the stem, in both flow cases, but I wouldn't think that would matter too much if from left or right. Either way, it's dead headed there.

Einstein gave the same test to students every year. When asked why he would do something like that, "Because the answers had changed."

 

[djeffroy]

Thanks for the reply! The manufacturer indicated that there is 50% greater pressure drop in the valve in one flow direction vs the other. I was just curious as to what the physics (if that's the right term) explanation might be behind that.

 

[jari001]

I would think/hope the manufacturer can answer which direction has less dP and why. Did the manufacturer indicated with direction has the lower dP? My 1 cent is that the plug component will see higher velocity with the flow coming in from the red direction and that would lead to high frictional losses before the valve orifice.

 

[LittleInch]

I would guess Black has least pressure drop because that's the way it is supposed to go and is a much smoother looking flow path.

The flow goes out from the disk area vs into the middle for the red flow direction.

I wouldn't expect it ot be "50%" worse though.

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

 

[1503-44]

Probably depends on how far the plug is from the seat. If it's nearly closed, I could see a 50% possibility. If its fully extracted allowing a more clear flow path, then same both ways.
Is it 50% for all stem positions ?

Einstein gave the same test to students every year. When asked why he would do something like that, "Because the answers had changed."