How will smaller orifice affect the flow rate?

[tmech77]

We are replacing an old water system with new hoses and fittings. Everything is the same except the orifice on the end of the hose going into the heat exchanger is smaller in diameter than the old legacy equipments was. How will this affect the gallons per minute flow rate of the water going into the heat exchanger? The old hose is .50 inch ID and necks down to .375 inch ID before it goes into the heat exchanger. The new design also uses a hose that has a .50 inch ID, but necks down to .25 inch ID before it goes into the heat exchanger. How will this affect the gallons per minute flow rate going into the heat exchanger?

 

[IRstuff]

4/64 divided by 9/64 to the first order

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[77JQX]

It depends on the system. If there's another, smaller, restriction in the system, than changing the entry orifice might not result in any meaningful change. If, on the other hand, all the friction in the system is from the orifice you're changing, then the ratios of the orifice areas applies, as IRstuff referenced.

 

[LittleInch]

Is this really an orifice or just a "restriction" or short section of smaller pipe?

As 77JQX says, it all depends on the lengths of the different hoses and the small section of smaller tube. In relative terms, the friction drop of the smaller ID section could be equivalent to several metres of the larger hose, but if your main hose length is quite long and the flow velocity quite low (1m/sec or less then it would have only a very small difference.

Give us some more details such as length of relative sections, flowrate etc and e might be able to be a bit more specific.

My motto: Learn something new every day

Also: There's usually a good reason why everyone does it that way

 

[Latexman]

Maybe, a dimensioned sketch would help.

Good luck,
Latexman

Technically, the glass is always full - 1/2 air and 1/2 water.

 

[tbuelna]

A significant flow restriction ahead of a water heat exchanger is probably not a good idea. The inlet flow restriction may create sufficient pressure drop to produce cavitation in the heat exchanger header tank or tubes if the inlet water temperature is high enough. Generally, your heat exchanger inlet flow area should be slightly greater than the discharge flow area. This creates positive pressure within the header tanks and tubes, and discourages cavitation.