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Specialty Chemistry Forums => Chemical Engineering Forum => Topic started by: learner1 on October 25, 2009, 07:38:27 AM

Title: flowrate in piping
Post by: learner1 on October 25, 2009, 07:38:27 AM

Hi,

I am adding a new heat exchanger to my unit.

The cooling medium is a 2" piping tapped from an 8" cooling water supply.

question is how do I estimate the cooling water flowrate thru the exchanger?

Thx!

Title: Re: flowrate in piping
Post by: eugenedakin on October 27, 2009, 06:41:13 AM

Hello learner1,

A good place to start is by starting with your known values. As an example, what are the following values for :

1) input temperature
2) return temperature
3) fluid specific heat
4) Mass flowrate
5) Heat transferred
6) Latent heat

Could you provide some example calculations of your specific application?

Best wishes,

Eugene

Title: Re: flowrate in piping
Post by: learner1 on November 02, 2009, 11:31:41 PM

Hi Eugene,

I am not too concern abt the temp & other factors.

For a start, how do one estimate the flowrate for a 2" piping branch out from a 8" Cooiling water supply header?

Tx

Title: Re: flowrate in piping
Post by: coalball on November 03, 2009, 06:04:07 AM

Hi Learner1,

In my opinion, the flowrate of the cooling water is not governed by the line size. I believe you have to determine the temperature difference of the other fluid (i.e. how much should the fluid be cooled down) and then you can get the required cooling water flowrate. With that you can determine your line size.

The above are just my opinion. Please do correct me if I'm wrong.

Thanks and regards.

Title: Re: flowrate in piping
Post by: learner1 on November 05, 2009, 07:20:28 AM

Hi coalball,

Thx for the info.

So if after calcn, the required cooling water flowrate is y m3.

If my CWS piping is 8",  how do i calc what should be the piping dia. to be branched out frm the header to be linked to the new exchanger?

Tx and regards,

 

Title: Re: flowrate in piping
Post by: eugenedakin on November 07, 2009, 09:10:29 PM

Hi learner1,

Yes, coalball is correct. I was asking for information on the heat exchange flowrate, not just the flowrate.

Best wishes,

Eugene

Title: Re: flowrate in piping
Post by: technologist on November 26, 2009, 12:27:25 AM

Dear learner1
Try to understand that there is nothing absolute in chemical engineering. It is not like that max flow in a 2" line will be fixed for all conditions. NO.

"Flow depends on pressure drop & Pressure drop depends on Flow" - My Opinion.

So if you understand this, you will know that first you need to draw your system e.g. line size (you already have say 2" which may or may not be correct as you are not sure about CW requirement), no of bends, fittings, valves, etc. and most important thing is that it depends on pressure balancing in your 8" header - yes, where do you tap 2" line in 8" header and where do you return it. It also depends whether you tap it from top, bottom everything.

So unless you draw your complete system you can not assess flow rate in 2" line. For example - How much pressure drop you have considered in your exchanger 0.1 bar, 0.5 bar or may be 1 bar so it depends on that also. If you analyse my above statement you will find that it is not true.

Title: Re: flowrate in piping
Post by: eugenedakin on November 28, 2009, 02:32:13 PM

Yes technologist, you are right.

Nothing is absolute. All of the information and suggestions that we have are merely ball-park figures that get you roughly close to the answer. Each project will have its own pros and cons.

Well said,

Eugene