how to size a heat exchanger? 2

[joshhamilton]

how do you size a heat exchanger...first how do you know which exchanger/cooler to use?

 

[europipe]

Please be more specific.
What service, what size, which design criteria?
No one can answer your question this way.

 

[jmw]

With unfamiliar equipment, I always start with manufacturers.
A Google search for "heat Exchangers" which will bring you some manufacturers.

First off, I look for a questionnaire or specification sheet .... another good search but manufacturers usually have them available on their websites. These list a range of pertinent questions that help the manufacturer select the most suitable heat exchanger.

I use the questionnaire to gather sufficient relevant information to have an intelligent conversation with a manufacturer.

Good sales engineers will really know their product and their speciality. It ought to be difficult to find a question they haven't been asked before.

Cheresources.com is another useful resource because of their downloads and technical articles area. You will find a variety of resources including a spreadsheet for sizing heat exchangers. You also get to a link to heat exchanger design:

http://www.cheresources.com/designexzz.shtml

Google earch terms:
Heat exchanger
Heat exchanger selection
heat exchanger sizing
Heat Exchanger cheresources

You'll get some helpful links like:

http://chemeng-processing.blogspot.com/2009/02/selecting-tema-type-heat-exchangers.html

http://www.engineeringpage.com/engineering/thermal.html

But it always helps when visiting here, to have specific questions and provide details.

 

[MortenA]

Josh: Im afraid that the answer to your question is training (education) and experience!

You may buy this from a vendor or a consultant or have it in-house.

Best regrads

Morten

 

[aabumady]

First of all, you can find all required criteria at KERN heat transfer book.

how do you know which exchanger/cooler to use?

there is a method bases upon Pinch technology. Using this criteria helps you to design a heat exchangers network with minimum driving force.This lowers utility consumption such as fuel gas and cooling water. Try to use Google to get more data regarding "pinch technology".




Now to design each heat exchanger in the network:

Try to use standard heat exchangers only. This lowers the capital costs and ease for obtaining spares.The method in detail is found in KERN heat transfer book.Simply,you can choose the heat exchanger with sufficient heat transfer area to sustain the required duty.You can get more than one suitable choice.One choice will have lower service area(lower capital cost)by increasing the fluid velocity, but with higher pressure drop(higher operating cost). Optimization will be required to ballance both effects.

I hope this will help.

 

[joshhamilton]

hello guys, never mind the sizing. I am trying to calculate the log mean temp diff from the Q = U A DT formula. But it appears the DT(lm) is diff for cross and counter flow and single n double pass???

 

[SNORGY]

joshhamilton:

See link...

Also, if GTTD = LTTD and LMTD is undefine, you can prove via L'Hopital that the arithmetic mean, rather than the log mean, applies.

Or use NTU-effectiveness method...

Regards,

SNORGY.

 

[MortenA]

You can find correction factor to LMTD for various configurations e.g. in Perry.

Best regrads

Morten