Desktop Air Conditioning

There's heat and then there's heat.  Usually when I get too hot I go inside, but some heat is inescapable, like at work.  I work in a building who's age has come and gone. The on again off again air conditioning system is older than I am and I've been around since man first landed on the moon.  It is not too infrequent that temperatures in the office get in the 80's and one hellish day was 98F.  The only relief on days when the temperature rises, without burning a sick day, is a tall cup of ice water from the ice dispenser. Jokes fly about knocking holes in walls and sticking in window units but as you know they have to vent heat somewhere.  If only I could build an air conditioner that didn't need to exhaust heat.  hmmmm...I thought.....ice.



By combining a few empty cans, some electrical connections and and old CPU fan we can bring the cooling power of ice into a focused stream of relief on hot days. A heat sink is usually used to take heat from an object and whisk it away into the atmosphere.  We will be utilizing this heat transference property, but in reverse.  By passing warm air past a cold heat sink we will be transferring heat from the air into the object thereby cooling the air.  In this design, the choice of heat sink is one taken from a dead computer (now there are 1001 uses for an old PC).  It is important that the style of CPU fan is one that vents to the side, and one that is roughly the same size as the larger can size used.

MATERIALS:
2 28oz cans (one end removed, cleaned and optionally painted black)
1 20oz can (one end removed, cleaned)
1 side vented CPU fan with attached heat sink
1 12v power supply
1 12v switch
1 Self-tapping screw
Heavy, strong glue such as Gorilla Glue
Aluminum foil

STEP 1: Attach the Upper Cooling Chamber


Locate the CPU side of the heat sink and firmly attach one of the larger 28oz cans to the heat sink with a self-tapping screw, this may require a pilot hole and a lot of cussing. It is important to not use glue to attach the cooling chamber as this will cause a thermal break and reduce the ability to transfer heat.

The "CPU side" of the heat sink



STEP 2: Level the Cooling Chamber

The mounting screw in the center of the cooling chamber will cause a high spot that will lift our ice bucket away from the base.  It is important that we get as much physical contact between the ice and the heat sink.  the easiest way to level the base of the cooling chamber without insulating it is by lightly crumpling a ball of aluminum foil roughly the width of the cooling chmber, placing it inside and pressing the ice bucket (the smaller 20oz can) firmly into place.  The compressed aluminum foil will create a custom fit from one can to the other maximizing heat transfer.





STEP 3: Make Some Holes in the Base

The second 28oz can will become the base.  The base is open at the bottom with a flat top that the CPU fan will eventual sit on. You will need to drill a hole in the top of the can close to where the wires from the CPU fan will be.  A Hole will be needed on the front to accommodate the power switch. Finally, a hole will need to be added to the rear for the power cord.



STEP 4: Electricity

First cut the ends off the CPU fan wire (there is usually a 3 wire connector) and cut the adapter off the 12v end of your power supply.  Thread the power lead through the rear power hole in the base and tie a knot in it for stress relief (the wire, not you). Feed the fan wires through the hole in the top of the base and wire everything to the switch. The exact wiring will depend on the switch type and colors of the CPU fan wire (you should only need two of the three).  The switch I have is a bit fancier than the average toggle switch as its a light up rocker switch that looks really cool when turned on, but any ON/OFF switch will do.



STEP 5: Attach the Base

Once the wiring is firm and tested, go ahead and glue the CPU fan to the top of the base.  You need to be sure that the base and the cooling chamber are relatively in line with each other so they don't look all cattywampus. Once the glue is dry and everything is secure, fill the ice bucket with ice and put it in the cooling chamber.  It will take 20-30 seconds for the ice to start chilling the heat sink but once it does and the fan is turned on, you will receive a nice blast of chilled air.  If you don't have an ice machine in your office, you can fill an empty can with water and just put it in the freezer for a solid block of ice.  DO NOT PUT ICE DIRECTLY IN THE COOLING CHAMBER.


I can't wait for the ice to melt outside and the heat to start just so I can test this puppy out.  The ice cold air coming out of it in a comfortably cool room is enough to give you chills.

As seen on HackADay.com

16 comments:

  1. Instead of the screw, you could glue the heatsink to the base of the can. I would suggest an epoxy glue mixed 50:50 with zinc oxide powder. The zinc oxide will minimise the thermal brake you mention.

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    Replies
    1. Excellent idea, I'll have to give that a shot on the next build.

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  2. I wouldn't glue anything. Just screw it securely together and use plenty of heat sink grease for efficient transfer.

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  3. Excellent design! One question, with the melting of the ice, is there a problem of condensation forming on the ice container that could cause problems of shorting out? I suppose it could be insulated on the sides of the can, but the bottom contact with the foil would still need to be uninsulated. Also, have you had any problems with the increase in humidity due to the melting ice?

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    1. This is really a new design, my previous versions have been of a more horizontal nature. My testing has only been inside, short term and in dry winter air. I would be cautious and take note to see if it is much of an issue. I haven't noticed condensation issues much with previous designs. A small dab of glue around the screw would likely solve an run-off issues and if you use a slightly smaller can (15oz I think) you can add a bottomless coozie to the ice bucket witch should really eliminate any condensation.

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  4. Hi!
    do you have specifics on how long the 20oz can of ice will last? and if a tower fan will help keep the room cool faster and hopefully make the ice melt a little slower?

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    1. The speed of the ice melt is highly dependent on the temperature of the room and the speed of the fan. I should also note; don't think this will cool a room, it is intended to cool the air that is blown directly on you. Think of it like drinking a glass of water with ice in it without having to visit the mens room when you are done. :)

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  5. What about something with a peltier cooler?

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    Replies
    1. The problem with using a peltier is you have to vent the heat somewhere (the next cube?)

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  6. Thanks for the tutorial, Mike! I can only imagine how helpful this DIY aircon unit will be for those who are having troubles with their ACs. As summer approaches, it’s more advisable to check the status and efficiency of your HVAC system to avoid inconvenience. Well, I’ll try making this one so that I can use something in case of emergency. :)

    Jim Corrion

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  7. Wow. That is a really great idea. While I believe this won’t exactly be a permanent solution and you can still ask your boss what can be done about the heat, this would suffice for the time being. Maybe others who have emergency situations can also copy your idea. 
    Dennis Day

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  8. Where do you recommend getting one of those side venting cpu coolers? I have just spent the last 15 minutes on google and newegg, and can't find them using those search terms. Great build BTW. I am getting ready to build my own, because all of my co-workers like it toasty, and I like it cool. Thanks!

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    Replies
    1. I actually salvaged mine from an old Compaq D530. I found the same model fan here; http://www.partsint.com/servlet/the-436/p-fdsh-n-336580-dsh-001-Compaq-HP/Detail?gclid=CMSO0Knm970CFRFp7Aodh2IAZg

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  9. When it comes to computers and cooling, it's really amazing what AC can do to increase or improve the clock speed of a computer. - ac repair in bergen county nj

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  10. Interesting invention! My desktop heats up very easily as well.. wonder if any of the people that do AC Repair in Morris County NJ do anything related.

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