Fine. I'll make my own air conditioner.

[Math Is Hard]

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/%7Egmilburn/ac/geoff_ac.html

Here's the basic setup. The garbage can is filled with ice water, which is then fed by gravity (a siphon) through the copper tubing coiled along the back of the fan. The hot air passing through the tubing warms the cold water, cooling the air. Waste warm water is then pumped outside.

 

[FredGarvin]

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/catalog/productview.jhtml?sku=SI357WHT&source=10716&cm_ven=LINKSHR&cm_cat=feed&cm_ite=SI357WHT&siteid=jXot6eVeYJg-tcISPFsspHDgeZZfxKvO1g

 

[3trQN]

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?

 

[Math Is Hard]

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.

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.

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

It's like the guy who built the homebrew AC says:
I realize small air conditioners are quite cheap. But then you don't get to build anything!

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.

 

[Math Is Hard]

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?

hmm.. that's an interesting idea. The copper is quite soft but I have a tool to do the etching.

 

[Artman]

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.

 

[Integral]

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!

 

[Math Is Hard]

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.

 

[Artman]

Thanks for the advice, Artman (where the heck have you been, anyway?)

Been......me?...

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.

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.

 

[berkeman]

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)...

 

[Math Is Hard]

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.

 

[Math Is Hard]

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.

 

[Math Is Hard]

WOOHOO! Success! I've been running the MIH COOL-A-TRON 5000 and getting some nice cool breezes.
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.

I had a LOT of condensation, but I put a towel under it so it was manageable.

 

[Integral]

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.

 

[Math Is Hard]

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.

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.

 

[gschjetne]

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?

 

[Danger]

man, I hope Danger doesn't read this.

I did.

 

[Math Is Hard]

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?

The trashcan is filled with ice water.

 

[Moonbear]

Now all you need is one of those giant, industrial fans! We'll all send you paperweights for your birthday.

 

[Integral]

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. Again, you can adjust the flow rate by changing the height differential of the buckets.

 

[Artman]

To embellish on integral's great idea, get one of those insulated water jugs with a twist open spout (not a push down type) and use that for your upper bucket. The insulation will keep the ice cold longer, the twist open spout will allow you to keep the container at the same elevation and yet adjust the flowrate.

 

[Danger]

I'd be inclined to include an electric pump to transfer the water back up, but I'm just lazy.

 

[Integral]

I want to place the cold reservoir in a separate tub. So just run a few coils of the flexible hose through a cold bath. The high and low reservoirs would be room temp. You would need to figure out (by experiment) how many coils to have in the cold water and the height difference of your source and sink to get the heat transfer right.


If you want to be lazy listen to Danger!

 

[Math Is Hard]

my ideal would be a closed system where I didn't have to do any fill work, except maybe to refresh the ice.
Wouldn't it work better to run the copper coil through the ice water bath rather than the flexible vinyl tubing?

 

[Integral]

my ideal would be a closed system where I didn't have to do any fill work, except maybe to refresh the ice.
Wouldn't it work better to run the copper coil through the ice water bath rather than the flexible vinyl tubing?

Yeah, the Cu would have better heat transfer properties but the flexible tubing would be easier to work with and since you are in a liquid bath there should be good transfer, even through the plastic. You may need a few more coils, but since it is flexible it is easy.

With Dangers pump you could eliminate one reservoir. Out of the main reservoir, through the cold bath, through the fan, back to the reservoir. A small fish tank pump would do the job.

 

[Math Is Hard]

Thanks for the ideas, you guys. I really appreciate the help. I better get to work - it is going to be hot tomorrow!

 

[Math Is Hard]

oh, yeah - I'll definitely look into one of those giant fans, MB! I'll have to outfit the cat with heavy boots.

 

[Danger]

One of my sheep ran off, so I have an extra pair of gumboots that I can give you. You'll probably have to pad them up some to fit a cat, though.

 

[Danger]

Hey, you sweet young thing... something else just came to mind. You seem the type who might like a nice table-top fountain (I have a few). Why not integrate one into your design? It could be the spill-way into the top reservois.

 

[Math Is Hard]

Hey, you sweet young thing... something else just came to mind. You seem the type who might like a nice table-top fountain (I have a few). Why not integrate one into your design? It could be the spill-way into the top reservois.

what a cool idea!

 

[Artman]

Sorry to hear about the escaped sheep Danger. Where abouts do you think she got to? Just curious.

MIH, if the loop is closed, with a pump to move the transfer medium (the water) through the connecting piping and two heat exchangers, you will only need one reservoir, but it's elevation won't help you throttle down the flow. You will need to either reduce the flow rate of the pump, induce restriction on the outlet of the pump (add a throttling valve), or add restriction in the form of longer or smaller piping. Height has no impact on a closed loop other than the length of piping it adds, and the pump will function better at a lower elevation (greater NPSH).

 

[Danger]

Sorry to hear about the escaped sheep Danger. Where abouts do you think she got to? Just curious.

I strongly suspect that W sent her off to the wilds. She's very jealous.

 

[Artman]

I strongly suspect that W sent her off to the wilds. She's very jealous.

That's what you think? I'm sure that must be it...and not somebody happen along who just happens to have a certain fondness for sheep, in a perfectly innocent way and...Yeah I'm sure that's what happened.

MIH, I've been thinking about this system. In a closed loop system, throttling would only be important to control condensation formation and the amount of cooling. If condensation isn't an issue, just let the flow be what it is because the cold water return will be going back to the reservoir and pumped back through, not lost. Further more, why use ice? Use an insulated container of water, and load it with those plastic ice blocks that you refreeze. You would never have to dump the water, just grab the plastic ice blocks and stick them back
in the freezer. The water in the container could be salt water and won't effect the inside of your coils (which could be fresh water that won't hurt your pump or coils as much).

One other thing, you should consider replacing whatever outlet you have this system plugged into with a GFCI outlet.

 

[Danger]

I'm sure that must be it...and not somebody happen along who just happens to have a certain fondness for sheep, in a perfectly innocent way and...Yeah I'm sure that's what happened.

If I thought for one second that you know where I live, you would have been my first suspect.

 

[kleinjahr]

I'd suggest a small globe or needle valve at the junction where the ice water is entering your coil/evaporator. It'll work, somewhat, as an expansion valve and give proportional control of the flow.