Chiller Flow

[JimD1]

What is the formula to calculate a chiller bundle flow in GPM if the only info you have is the delta T in Fahrenheit and the pressure drop across the bundle in ft/min?

Jim

 

[TBP]

You'll need to get hold of the manufacturer's data for the particular unit's HX. It'll give you the GPM for a given pressure drop, with clean tubes. You don't need delta-T for this, but you do need it to determine the BTU/hr, and that can be easily flipped into tons of cooling.

 

[JimD1]

If I don't have the mfg's data, but I do have flow velocities, pressure drops and temp differenced, is there a way I can determine flow in GPM?

Jim

 

[SAK9]

Jim,

The most practical option for you now is to clamp an ultrasonic flow meter onto the pipe and get areal reading!

good luck

 

[lilliput1]

Check piping diagram. See if there is a dedicated pump for the chiller and if it is provided with a balancing valve. You would need to read the pressure drop across the valve & look up the valve chart of pressure drop versus flow. Otherwize do as what SAK9 says. You can rent the flowmeter. Make sure you have the recommended straight run piping distance for the meter. You would need to remove the pipe insulation & wire brush the piping portion under the ultrasonic sender & receiver heads.

 

[katmar]

Jim,

you say you have flow velocities. For what point in the circuit do you have these? Can't you work out the GPM from that velocity and the ID of the pipe?

Alternatively, if you know what duty the chiller is performing you can work back to the GPM via the delta T.

 

[atilashorse]

To relate DT with flow will involve a substantial amount of data, in particular, the exact heat load of the building.
Be careful with velocities, because in order to determine flow, you will need the average velocity across the pipe cross section. Velocity is max at center of flow, and near zero at pipe walls. Ultrasonic flowmeters are not acurate with clean brine or water, as far as I know, they are useful with slurry water, they need some solid particles to make the ulstrasound bounce.
Get the pump curves, they will give you the flow for certain pressure. If this data is not available either, and this is an important project, say more than 100 tons, have an in-line flowmeter installed, and determine the exact flow.