ACHE Fin Fan Design Procedure 1

[denniskb]

I am trying to set up an Excel spreadsheet to do a basic sizing of an ACHE for gas transmission pipeline aftercoolers. I need this so I can select an appropriate design then use the spreadsheet to simulate the selected unit under real operating conditions, not just the original design conditions.
I have used the methods set out in the Campbell's books and the GPSA data books and while they give different results they are in the same ball park. We have now had a unit designed by a reputable vendor and the air flow and surface area are significantly different to that calculated using my spreadsheet. I therefore no longer have a reliable way to do what I want with my spreadsheet.
The problem appears to be in two areas:
- the recommendations for ideal air temperature rise appear to be very inaccurate. Can anyone suggest an alternative method to determine this?
- the overall heat transfer coefficients from the books do not extend to the pressure I require (15,000 kPa or 2000 psi). I am now attempting to calculate this directly from heat transfer theory, but of course I need to know the air velocity to get Reynolds number for the film coefficient. Is there a typical air velocity that I can use for this type of unit?
- finally the typical overall heat transfer coefficients in the books do not state whether they include an allowance for fouling or are for new and clean service. Can anyone comment on this please?

Thanks in advance for any advice you can offer. Dennis Kirk Engineering

http://www.ozemail.com.au/~denniskb

 

[pmover]

dennis,

i commend you for your efforts. i've longed to develop the same, but recognized that it would be a significant exercise for what little time i have to devote to the matter.
may i suggest that you contact the vendors themselves. i know of two vendors in the usa that may likely help you with your situation, or at least provide certain documentation to further your work. go to hudson products web site and they have a simple program you can download that conducts a preliminary analysis (i.e. sizes) air exchangers. they also have documentation available that may be of some help.
the pro's use industrial strength software to develop, rate, size, etc. exchangers. suggest contacting these orgainizations (i.e. htri, having a brain spasm and can't recollect the other two i was going to list.) as they may further help you.
in the world of designing air exchangers, once the design UA is determine, mfg's proceed to maximize the U and minimize the A, while considering costs and fluid properties (mass flow, p & t). believe me there are various components and design factors that achieve the same result.
i am fairly certain that the heat transfer coefficients are specifically that and do not include fouling factors.
sorry, i'm not much help, but i wish you luck.
g-day!
-pmover

 

[pmover]

while i have not thoroughly investigated this site, you might find it helpful as well.

http://www.wlv.com/products/databook/databook.pdf

g-day!
-pmover