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Fine. I'll make my own air conditioner.

  1. Jul 27, 2006 #1

    Math Is Hard

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    I bought everything I need today at the hardware store to assemble my cooling apparatus from what I have learned from this smart little whippersnapper:
    http://www.eng.uwaterloo.ca/~gmilburn/ac/

    I haven't started working on it yet, but I was wondering about any sort of condensation problems I might have with the copper tubing and it dripping near the fan and motor. Any thoughts?

    I'm following this plan: http://www.eng.uwaterloo.ca/~gmilburn/ac/geoff_ac.html
     
    Last edited: Jul 27, 2006
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  3. Jul 27, 2006 #2

    FredGarvin

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    Well, since you need the cross flow for the heat transfer, an insulating sleeve is out of the question. You may have to make some kind of drip shield to go between the coil and the fan motor.

    If you're going this route, you may just consider getting a big pile of ice and blowing the fan across it. Heck, Sharper Image sells the basic equivilent to that as a "personal AC unit." It may be a lot easier. Just a thought.

    http://www.sharperimage.com/us/en/c...WHT&siteid=jXot6eVeYJg-tcISPFsspHDgeZZfxKvO1g
     
  4. Jul 27, 2006 #3
    Maybe if you just score (cratch or groove) the tube to direct the flow of condensation to a drip point that you can collect it at?
     
  5. Jul 27, 2006 #4

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    I guess this is going to be a trial and error process and I'll have to see how much condensation I'm dealing with. Maybe a mesh screen between the coil and the fan frame would help if there is too much of it. I am thinking about put the coil on the front of the fan so it is at least blowing any droplets out and away.
    It's like the guy who built the homebrew AC says:
    I realise small air conditioners are quite cheap. But then you don't get to build anything!:smile:

    They're also sold out of the them right now. Amazon is also back-ordered. They are neat little devices though. My original plan was to buy a portable air conditioner, but there isn't one available in all of Los Angeles.
     
    Last edited: Jul 27, 2006
  6. Jul 27, 2006 #5

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    hmm.. that's an interesting idea. The copper is quite soft but I have a tool to do the etching.
     
  7. Aug 4, 2006 #6
    How much condensation you will get out of this setup depends on several factors, the humidity level of the air being cooled, the quantity of air being cooled and the amount of energy being transfered.

    The article says he gets approximately 2000 btuh out of his setup (the energy being transfered). So we can start with that.

    I picked a starting temperature of your room as being 90 deg F with a dewpoint of 75 deg F.

    Using our 2000 btuh, and our 90/ 75DP temperature the air will begin to lose its water at about 82 deg F which would be the temperature drop using 190 cfm of air or about 13.3 lbs of air at 14.3 cf/lb.

    To get more humidity out of the air (cool and dehumidify), you decrease the amount of air.

    To get less humidity out of the air (cool without dehumidifying) you increase the amount of air.

    For example, if I decrease my airflow to 50 CFM (3.5 lbs of air per minute) the leaving air conditions will be about 70 dry bulb, 69 wet bulb (nearly 95% RH) I can remove about 23 grains of moisture per pound of air per minute, which works out to be about .09 gallons per hour.

    If, however, I increase my flow rate to say 250 CFM the leaving air conditions will be 83 deg F Dry bulb and 78.5 deg F wet bulb (only 78% RH) and no condensation will form (or will evaporate quickly). This is only sensible cooling, no dehumidifying occurs.

    In other words, if you move enough air, unless the air is extremely humid in your house (90% RH or greater), you won't have to deal with any condensation.
     
    Last edited: Aug 4, 2006
  8. Aug 4, 2006 #7

    Integral

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    MIH,
    In LA humidify, therefore the condensation on your coil may be minimal, compared to most places east of Rocky's. Be careful about scoring the copper near the ends, you may lose the seal between the copper an plastic tubes.

    Good Luck!
     
  9. Aug 4, 2006 #8

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    Thanks for the advice, Artman (where the heck have you been, anyway???) and Integral. I am planning to get some more work done on it this weekend. The weather cooled off and I had a big final exam to tackle (just took this morning) so I got a little side-tracked.

    My biggest concern now is that I am going to have excess copper pipe after I finish the winding and I'll need to cut it. I don't have anything to cut the pipe so I might just have to take it down to the hardware store and see if they'll do it for me.
     
  10. Aug 4, 2006 #9
    Been...:uhh:...me?...:uhh:

    Yeah, you should use a tube cutter so you don't pinch the end shut. Take it to the hardware store. They should be happy to cut the pipe for you. Or go to the dollar store and pick up a cheap hacksaw, it won't be perfect, but it should work for your use, without pinching the pipe too badly.
     
  11. Aug 4, 2006 #10

    berkeman

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    If you can put a little portable refrigerator just outside your window (not inside the room), then you could make a closed-system AC unit by running the copper tubing into the freezer portion of the fridge. That would be a lot better system if you can figure out where to put the small fridge. Like if you have a porch just outside your window (and an outlet oustide on the porch).....
     
  12. Aug 6, 2006 #11

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    Thanks for the suggestion, Berkeman. Only trouble is, I would have to build some sort of platform to hold the fridge outside the window and I think my landlord would have a cow.
     
  13. Aug 6, 2006 #12

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    phew! Just finished the copper coil winding. I had to work slowly as to not to kink the copper. I thought it was easier not to try to unwind the coil as the inventor had done, but to just work naturally with the curve as I attached it. I came out with a bit more coil than I needed so I may just use the copper coil as part of the siphon end until I can get it cut.

    Now I just need to attach the vinyl tubing and get it set up. The we'll see if I can actually "suck start" the siphon for the test run.
    man, I hope Danger doesn't read this.
     
  14. Aug 6, 2006 #13

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    WOOHOO! Success! I've been running the MIH COOL-A-TRON 5000 and getting some nice cool breezes. :smile:
    It's somewhere between a real AC and a fan as far as cooling, but it definitely dropped the temp.

    Downside: getting the siphon going was a challenge. The water comes out really fast, and it drained all the water out of the garbage can before I could refill, so I had to go downstairs and re-suck-start it. The neighbors must think I am nuts. :redface:

    I had a LOT of condensation, but I put a towel under it so it was manageable.
     
  15. Aug 6, 2006 #14

    Integral

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    How warm is the water you are dumping out? If it is still pretty cold you may want to but a flow restrictor in (reduce the diameter of your tube at some point). Ideally the water exiting the system will be at room temp.
     
  16. Aug 6, 2006 #15

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    I'm glad you said that. The water in the output hose still feels pretty cold and is gathering a fair bit of condensation. I think the instructions mentioned that ideally I shouldn't be seeing any condensation on the output hose. Do you think I could do the flow reduction right where the copper tubing joins the vinyl output hose? I have some narrower vinyl tubing that I could splice in.
     
  17. Aug 18, 2006 #16
    When you're already wasting tons of mains water, why not go around the rather ugly rubbish can and take the water straight from the taps?
     
  18. Aug 18, 2006 #17

    Danger

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    I did. :tongue2:
     
  19. Aug 20, 2006 #18

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    The trashcan is filled with ice water.
     
  20. Aug 20, 2006 #19

    Moonbear

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    Now all you need is one of those giant, industrial fans! :biggrin: We'll all send you paperweights for your birthday. :rofl:
     
  21. Aug 21, 2006 #20

    Integral

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    To adjust the flow rate you should be able to just raise the output tube. I see a "closed loop" system which consists of a high bucket of water, a low bucket, a tub of ice water (brine is much colder!) and your fan/coil. The high bucket would be source, so the tube runs from the high bucket to the tub of ice water, then to the fan and finally to the low bucket. When the top bucket is low on water simply transfer the water from the low bucket to the high bucket. Keep the ice water cold and this will run on 5 gal of water indefinitely. As a bonus you get a workout lifting the water to the high bucket. :biggrin: Again, you can adjust the flow rate by changing the height differential of the buckets.
     
    Last edited: Aug 21, 2006
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