Pressure drop

[coolcando]

I am designing a sample cooler. The sample stream will come from discharge PG of the pump and run back to the pump suction.

Since the deltaP is large, the flow will be large as well.

We are going to use a globe valve to control the flow.

How can I determine the flow so there will be enough pressure for the stream to go back into pump suction.

DeltaP=1400KPa. Pipelenght=15 m

Approximate deltaP for the cooler=200Kpa

Any help appreciated

 

[sshep]

Probably not understanding this but: you already know the the dP across your valve is nearly 1200kPa less some loss for piping. You can chose a flow independently and calculate a valve Cv to use for selcting the valve.

best wishes,
Sean

 

[JimCasey]

sshep is right. Any pressure not lost in the system or the sample cooler will be lost in the valve.

If I assume that the sample line is 1/2" and the sample flow is 5 gpm (1100 kg/h) of WATER then the calculated Cv is 0.376. I assumed a Kammer control valve as a model for the calculation. If you only want to control manually, a needle-style manual globe valve would be appropriate

 

[coolcando]

My question is,

How do I make sure that for a given flow, there will be enough pressure for stream to flow back to pump suction?

Pum discharge Pre=1500KPag Suction Pr= 150 Kpag

What flow should I specify in datasheet(for vendor)of the sample cooler

 

[JimCasey]

As long as the pump is running, the flow will exist and it will flow in the proper direction.

You have specified the driving force: P1=1500 kpag, P2=150 kpag. Specify the flowrate to which you are designing the sample cooler, and specify the size of the tube/pipe that will carry the flow. If the flow is something besides water, specify the fluid and if it is not a common fluid you should lay out the density, viscosity, and vapor pressure. Then give this information to your valve vendoe and he will be able to calculate the optimal valve size to give you good control.