Reservoir Sizing - Rule of Thumbs

[slickstyles5]

Hi,
I would like to determine an adequate size of a glycol reservoir that will be used in closed circuit as the cold fluid in a fuel/glycol heat exchanger. The flow rate required in the glycol line is 20 GPM. There is a quantity of 15 Gallons of fluid required to fill the pipes. Are there any rules of thumbs in terms of an adequate size for the reservoir? I heard that 3 times the flow rate is a rule of thumb. Please provide references.
Thank you,
Gabriel

 

[FredRosse]

The size of the reservoir has virtually nothing to do with the system flowrate.

Sizing a reservoir can have several design considerations, often a combination of criteria to be met:

1. If the reservoir is for a pump suction with an exposed free surface, then fluid flow intake design criteria is applicable. The Hydraulic Institute Manuals discuss this complex problem of submerged suctions, vortex problems, etc.

If the reservoir is to serve as an inventory storage with the system operation variables (same as a conventional expansion tank), then the system volume, temperature ranges, pressure ranges, and expansion/contraction character of the fluid, fluid containers, and the piping need to be considered. See comments on "Heat Transfer & Thermodynamics" section, under "expansion tank" topic.

The reservoir may be designed to allow for some system leakrate before replenishment, to allow initial fill with standard purchased container sizes, etc. These O&M criteria may dominate the design.

 

[BigInch]

Can we say, "The size of the reservoir has virtually nothing to do with the system flowrate in glycol heat exchangers." I wouldn't want people to think that statement is true for just about anything else, where it has almost everything to do with maximum and minimum flowrates.


**********************
"The problem isn't working out the equation,
its finding the answer to the real question." BigInch

http://virtualpipeline.spaces.live.com/

 

[slickstyles5]

The reservoir will be exposed to the atmosphere with a breather installed. It will serve as a storage device. I think that if the flow rate is 20 GPM and I have a reservoir of 60 GAL. This means that the fluid in the reservoir will have 2-3 minutes to settle down and then will get re-pumped. Does this explain anything?

 

[BigInch]

I think you're talking about an expansion tank. If you have no flow variation, you have no use for a "reservoir" in the classical sense.

**********************
"The problem isn't working out the equation,
its finding the answer to the real question." BigInch

http://virtualpipeline.spaces.live.com/

 

[slickstyles5]

BigInch,
The system is like this : There is tank from which a pump is used to pump fluid through a pipe line to a heat exchanger. Then this fluid that passes through that heat exchanger is sent back to the tank. The system is not pressurized because the tank is open to the atmospheric pressure.
I hope this can help in terms of the sizing.
Thanks
Gabriel

 

[BigInch]

Since you don't mention any flowrate variation, I'd size it as already suggested, based on expansion tank criteria considering changes in volume with temperature of the contained fluid, at atmospheric pressure.

**********************
"The problem isn't working out the equation,
its finding the answer to the real question." BigInch

http://virtualpipeline.spaces.live.com/