All the more reason not to use a Shell and Tube. Wastewater is by definition NOT clear, treated water. Any heat exchanger can become fouled over time using properly treated water, and using wastewater it will foul MUCH faster. In this situation you really must consider a HX that can be cleaned. A single-pass S/T can be cleaned somewhat, using an auger (drill), but the act of cleaning will cause premature failure, and the tubes will sag, making it less possible to adequately clean and more likely that augering will induce tube failure. In you favor, the gas-side temperatures are low, but it is highly likely that contaminants in the wastewater will precipitate out and adhere to the tube wall, reducing the heat transfer and the flow capacity of the exchanger.
If the owner insists on a S/T, they need to be cautioned about the risks. Regardless, more information about the HX is needed to calculate or reasonably estimate the flowrate of water required.
... Bruce D. Bullough ...
Sebesta Blomberg & Associates, Inc.
2381 Rosegate
Roseville, MN 55113 USA
desk: 651-634-7344 fax: 651-634-7400
www.sebesta.com
-----Original Message-----
From: PipingDesign@yahoogroups.com [mailto:PipingDesign@yahoogroups.com]
On Behalf Of elie altawil
Sent: Monday, September 12, 2005 7:46 PM
To: PipingDesign@yahoogroups.com
Subject: RE: [PipingDesign] Water volume require to cool natural gas
[bcc][faked-from][mx][spf] [bcc][faked-from][mx][spf][sls]
I have a 6" waste water line (90 GPM) that passes by the plant. I am planning to divert the water through the heat exchanger and send it back to where it was going.
Cheers,
> Elie:
>
> You provide the needed process information, but
> nothing on the heat
> exchanger except that it is a sheel and tube. I can
> make assumptions as
> to design, materials, tube size and pitch,
> thicknesses, etc., but the
> results are not terribly representative. You could
> probably get a
> smaller flow if you can go to a plate exchanger, but
> you might have a
> larger pressure drop (but no indication of the
> pressure of the water, or
> on the pump). In general, you will have a lot of
> water use, as your
> LMTD is pretty small, assuming an approach of 10 deg
> F. Typically the
> water is reused (using a cooling tower), abnd
> especially effective at
> that altitude (rarely at that elevation is there a
> high relative
> humidity or absolute dew point - you can probably
> count on getting a 70
> deg or cooler water out of the tower, as the dew
> point is probably less
> than 50 - 55 deg F at any time).
>
> The answer is, yeah, you'll be using a lot of water.
> You can do some
> engineering design to minimize it, and add a CT to
> minimize operating
> cost (you might have to reuse water anyway, because
> getting a permit to
> use and discharge that much water is either costly
> or impossible, or
> somewhere in bewteen).
>
> ... Bruce D. Bullough ...
> Sebesta Blomberg &
> Associates, Inc.
> 2381 Rosegate
> Roseville, MN 55113
> USA
> desk: 651-634-7344 fax:
> 651-634-7400
> www.sebesta.com
>
>
> -----Original Message-----
> From: PipingDesign@yahoogroups.com
> [mailto:PipingDesign@yahoogroups.com]
> On Behalf Of elie altawil
> Sent: Friday, September 09, 2005 6:03 PM
> To: PipingDesign@yahoogroups.com
> Subject: [PipingDesign] Water volume require to cool
> natural gas
> [bcc][faked-from][mx][spf]
>
>
> The problem:
>
> I need to cool natural gas from 130 deg F to 110
> deg F using a shell &
> tube heat exchanger with 70 deg F water.
>
> Question: How much water do I need?
>
>
>
> Design conditions:
>
> Ambient Temp: 100 deg. F .
>
> Altitude: 6700 ft, atmospheric pressure 11.6 psia
>
> Process Gas: Natural gas, sweet, 95 % methane, 2%
> CO2, specific gravity
> 0.55-0.60, 46 ,000,000 scf/day ( 90,000 lb/hr) , 130
> deg F, operating
> 350 -545 psi, Relief valve set at 500 psig .
>
> Cooling Medium: Produced water,80-90 psig, 70 deg F,
> specific gravity
> 1.04.
>
>
>
> I am piping/pipeline facilities engineer (not a
> process engineer).
>
> I have requested information from a heat exchanger
> vendor. The flow rate
> of water required per vendor calculation is very
> high. I have ran hand
> calculations and compared my answer with the online
> calculation
> available at http://www.freecalc.com/hxfram.htm. The
> vendor reported
> flow rate is 3 times higher than what I came up with
> (hand calc &
> freecalc).
>
>
>
> Supported formulas with your reply are very much
> appreciated.
>
>
>
> Cheers,
>
>
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Yahoo! Groups Links Received on Tue Sep 13 09:04:00 2005
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