This is a hypothetical question. Consider air blower(pick any size say
1000 cfm at stp and 40" water col). Suction side of fan hooked to a
chamber with no inlet. Discharge side of fan hooked to a chamber no
outlet. Turn on blower. What if any will be the guaged w.c. on suction
side and discharge side? What will be the readings if a check valve is
installed on the system? neglect friction and temperature.

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Request for Question Clarification by hedgie-ga on 16 Apr 2003 13:15 PDT

Hello Robert

 Since we did some business before, perhaps I may provide additonal
 insights. Please let me know if you are satisfied or if you want more
 analysis of the case.
1) You cannot fax researchers, but you can post diagrams on free websites,
such as tripod. (That - the instructions how, may be a separate question).
2) The fans become less efficienwill reach a steady state where all energy
supplied to fans is dissipated (wasted as heat), maintaining the preasure
diffrential.
Do You want links, to read more  on this?

hedgie

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Clarification of Question by 3rrotec-ga on 21 Apr 2003 05:32 PDT

To hedgie-ga Thanks for the response. The air fan question has been
cleared up in my mind, however this is just one of many to be
clarified. I am interested in a process that will use temp, pressure,&
vacuum to remove clorides from waste water. We are in the waste water
treatment business. <sludgemasterrk@hotmail.com>. We also build
evaporators. Why not reclaim water vapor? Is this feasible? I know
this question has been addressed somewhere, but I don't know where.
Here is my line of thinking: 1. pull vacuum on chamber containing
waste water. 2. apply heat to vaporize. 3. pressurize vapor and
condense. Please respond in "answer mode" so I can ask more questions.
Comment on what you consider a fair price per question. Thanks for the
help Robert 3rrotec

Hello again, Robert

1) The Rules of Service, do not alow direct communication between
asker
    and researchers, such as e-mail ot FAX. Please do look at:
http://answers.google.com/answers/termsofservice.html

 It may be possible to upload a digram on some public server and point
to it
 in a question. If you would need that, I can describe that method.

  There are services which have different format then Google Answers
  such as elance, some allow direct, on-going contact with a
consultant. See
http://answers.google.com/answers/main?cmd=threadview&id=184926
 and
http://answers.google.com/answers/main?cmd=threadview&id=137545

2) Water reclamation by phase change (evaporation, distillation,..)
 is feasible. Main issues are energy cost and 
 heat pollution (which is an enviromental issue).

 It is done in special situations, e.g. as a part of life support 
 on a spaceship:
http://oregonstate.edu/~atwaterj/h2o_rec.htm

 In most industrial processes, evaporation is used to reduce the
  volume of the waste, rather than to reclaim water.
 Here, on GA we had one interesting brainstorm on that:
http://answers.google.com/answers/main?cmd=threadview&id=100473

 Local factors may dictate an unconventional solution.
 Here is a cost analysis and description of evaporators, currently
used.
http://www.waterblaze.com/news.asp

 This issue (reclamation of water itself) is often classified under
 desalination. For reasons given above, filtration or inverse osmosis
 are usually the preffered solutions. In special situations, 
 (e.g. available solar energy) evaporation may be economicaly
feasible.

 This is a subject of federally  funded research:


 "The University of Arizona will study "Halophyte Crops and a Sand-Bed
Solar Evaporator to Reduce and Recycle Industrial, Desalination, and
Agriculture Brines." This study will develop the best management
practices for halophytes and a sand-bed solar evaporator for disposal
of high total dissolved solids brine.
http://www.usbr.gov/water/newsletters/c_97win.html
and
www.usbr.gov/water/newsletters/c_97win.html

 So, in conclusion:

 It is prefectly feasible and reasonable solution from the
 physics point of view. The devil is in the engineering details.

Search Terms
water reclamation  (combined with)
phase change
evaporation
solar
desalination

 Rating of answers is always appreciate. This amountof work
 is about the current price. It is better to formulate the next
 problem as a separate question, due to the GA format (one shot 
with clarifications), rather then on-going discussion.

Hedgie

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Clarification of Answer by hedgie-ga on 22 Apr 2003 04:43 PDT

As I said, Reverse Osmosis (sort of ultra-filtration) is
 usually  less expensive for removal of dissolved salts
to produce clean water then distillation. I want to add few
links on physics of  that, and few links on the industrial use.

Here is description of the process:
http://www.osmonics.com/products/page833.htm

and the physics basis:
http://urila.tripod.com/

There are industrial scale plants in Middle East, where
water is scarce and of poor quality, which use this process:
http://www.export.gov.il/export/doa_iis.dll/Serve/item/English/agrisrael.htm

Here is a technical report:
The Role of Desalination in Water Management in the Gulf Region
 ... is incorporated in a hybrid RO/MSF desalination system.
The RO unit has the following
 design criteria: * feed water quality: TDS = 43,300 mg/l, chlorides as Cl ...
circe.cps.unizar.es/spanish/ waterweb/ponen/elnashar.pd


Here is a sample cost analysis:
desalination -cost  (drinking water production)
http://www.oceanit.com/environ_industrial_tech/desalination_system/desalina.htm

Available technology : ectrodialysis
http://www.apctt.org/database/to0797.html

  Search Terms

chlorides desalination water
reverse osmosis

Thanks! More on the way soon!

In theory the low pressure side could go to high vacuum and the other
to double pressure at somewhat warmer than stp. Typical fans have
considerable blow by even at 1% pressure difference, so more than a
10% pressure difference is unlikely unless the fan is designed to
minimize blow by. I think air friction is necessary for a fan to blow
air. If there was zero friction the fan might not produce any pressure
difference. Are we to assume the check valve connects the high and low
pressure sides? If so 1000cfm would flow though the frictionless check
valve.
 At zero friction the fan would run long term with no energy input
after it reached speed. Typical fans with normal friction would
convert all the input energy to heat after the 40 inches of water
heigth pressure difference was achieved and the fan and air would get
very hot even with the check valve open.  Neil