heat exchanger pressure drop 1

[dkm0038]

I am going to setup an experiment to test pressure drops of a heat exchanger and am a little niave in this area. I am going to have two buckets open to atmosphere with the liquid going through the heat exchanger. the first bucket has the hot liquid going in while the second bucket has that cooled down liquid leaving the heat exchanger.

To measure the pressure drop can I simply put a pressure gauge right before the inlet of the heat exchanger and one at the outlet and take the difference of the two? Wouldn't this give me only the static pressure and not the dynamic pressure? and wouldn't the pressure at the second bucket just be atmospheric pressure?

If anyone can give me some clearification I would appreciate it, or if you have any ideas on how to set up an experiment like this

 

[MintJulep]

Pressure drop and flow rate are related to each other.

I'm guessing that your inlet is higher than the outlet, and maybe you have a siphon hose from your in bucket to the exchanger in connection.

In that case the driving pressure difference is the elevation difference between the top surface of the fluid in the in bucket and the exchanger exit.

At that pressure drop, the exchanger will have some flow rate.

If you had a pump forcing fluid in the inlet pressure would be higher, and the flow would be higher.

 

[dkm0038]

MintJulep,

Thank you for your response but I don't think you understand my question. I will have a heat exchanger with twisted tape swirl generators in the tubes to increase turbulence of the fluid but this will also create a pressure drop in the system and I am only interested in the pressure drop due to these.

My question is more geared to what type of pressure gauges and what they will tell me. if I use just a standard pressure gauge at the heat exchanger inlet and outlet as far as I know this will tell me the static pressure, (and not the dynamic pressure?) I do want to know the static pressure build up in the inlet of the heat exchanger due to the resistance of flow the heat exchanger provides, and I also want to know the dynamic pressure drop, can the pressure gauge tell me both?

or how else would i set up this to get the total pressure drop?

 

[sterl]

Unless this a very strange form of tube, your pressure drop is entirely dynamic but...

The tube being same size end to end and same flow in as out: A PG on the entry side is connected to the tube and in the same fashion and orientation as other PG is connected on the outlet, the dynamic pressure will be the same on both sides...Therefore no change. The difference in the gauge reading will be the pressure drop across the heat exchanger. If you need to know the dynamic head for other purposes, measure the flow rate and calculate dynamic as per Bernoulli et al.

 

[Gunner777]

Hi dkm0038,.....I do hope I dont sound like im teaching you to suck eggs but here goes.

If I have got this correct you have the hot supply bucket elevated and the cooler return bucket lowered with the exchanger in the middle. If you have two gauges of the same type, one on the supply and one on the return, both the same distance away from the exchanger. If you then proceed to fill the supply bucket and let the water run through the exchanger to the return bucket the pressures that read on the gauges will be different and it is this difference that will be the static pressure drop across the exchanger. As the top bucket empties the pressure drop across the exchanger will get smaller untill the system stops flowing. To find the dynamic pressure drop the water must be mechanically forced through the exchanger with the same set up as mentioned before. This will give the dynamic pressure drop and if all of the variables stay the same from the source then the flow rate and pressure drop across the exchanger will stay the same. That is assumeing that you dont have a blockage in the exchager mid way through the experiment.