The Black Beauty

As the summer progressed, I felt like I needed to improve my initial design. Luckily enough the science department had just thrown away an old freeze drying machine which had a perfect radiator. A few minutes crouched by the dumpster with some hand tools, some minor adjustments, and the Black Beauty was born.


Here’s the overall view of the unit. A high speed fan pushes the air through the perfectly sized radiator, and water flow rate is controlled by a small hand valve.


The radiator itself was horribly filthy when I first took it off, but a quick soak in some warm water and light detergent took care of it. The copper tubing inside the radiator is the exact same diameter as the copper tubing I used when I first built my original homemade air conditioner, so no need to change up the vinyl tubing.


I placed the fan fairly close to the radiator itself, and it works great. I typically put the fan on the medium or low setting, as I notice little benefit from the high speed setting other than increased noise.


The radiator was almost perfect, it only needed to be raised by a centimeter or so to align with the fan. Turns out old original Nintendo cartridges do the trick just fine. (For the record, that’s Teenage Mutant Ninja Turtles and Marble Madness. Don’t worry, I have other copies.)


Cold water is supplied from an outside garden hose. More detail can be found in the water supply section.

To calibrate the valves, the small hand valve inside is first opened wide and the garden hose opened or closed to find an appropriate upper flowrate. Then the hand valve may be used to vary the water flow or turn it off entirely.


The nice thing about this new setup is that all control is now done from inside the room. Starting and stopping the unit is far more convenient, which leads to more efficient water usage. The performance of the unit is drastically improved over the old design. Less water is needed, and the room cools quicker.

Homemade Air Conditioning Plans and Pictures
Original Design
Geoff’s Homemade Air Conditioner
Heat Exchanger Improvements
Water Supply Improvements
Technical Notes
Other Designs
Pete’s Homemade Air Conditioner
Anonymous’ Homemade Air Conditioner
Spencer’s Homemade Air Conditioner
Final Design
The Black Beauty

55 thoughts on “The Black Beauty

  1. Nice home made air con…impressive
    i have a portable evaporative cooler that i bought for aud$130 which is o.k if i sit in front of it.. just pour water in the top and the filter or net or whatever it is turns though the tank wetting it as goes along.. but it’s hard to get it in front of a window or door (my bedroom is very small and the window is blocked with stuff)..its supposed to work using the outside air hitting the back (the wet cloth/net)

    The point is, being so smart and all, can you think of anyway i might be able to drastically make this work a lot better? my room is the hottest in the house, think because it cops all of the sun all day and its very small. I just need some very cold air pumping through.

    This house isn’t actually ours, ours is being renovated (which is taking 2-3years longer that it was supposed to) so that’s why i didn’t buy a proper air con (split system etc) which is whats going into my new bedroom of course..

    anyway if you can think of any thing at all that might work I’m all ears, and i will appreciate anything at all.
    send me an email if you can.
    Thanks in advance

    • Hi Adam,

      What you have is an evaporative cooler – it relies on dry air, which has to release energy (heat) in order to evaporate the water dripping through the filter.

      This means that it won’t do a thing in a closed system such as your room – the air will just get more humid until it cannot hold any more water, and no more cooling will occur. It needs an external source of dry air.

      Is there any way to unblock your window and mount the evaporative cooler on it? It’d be a bit of work, but it would be the best way to cool your room without having to purchase anything extra.

  2. Love your work Geoff, interesting and funny at the same time.

    I am building a portable car cabin air filter for a fun project.

    So far so good, but this cooling stuff is very attractive too


    Dave ( another Australian!)

  3. Hey Geoff, ‘cool’ idea!, I’ll try to find a radiator to do this also. I live in a yearly-warm and hot area, so the house itself has plenty of ventilation. This may turn out to be the problem as the cooling that a unit like this can do may just escape out quickly.
    Writing to ask, do you have any temperature data, did you do readings of the incoming water temp, the room and outside temp, and the temp of the blowing air when the system is running?
    I use one of these digital thermometers with two sensors (in, out) whenever I’m testing engine cold air intakes, air conditioners, etc.

    Thanks in advance!.

    • Hi Hugo,

      You’re right – the cooling power of this is limited relative to a commercial air conditioning unit. My grandfather told me that he used to have a car radiator with a fan that he would run water through to cool off his barn however, so the concept is definitely nothing new and it should scale as long as your resources do too.

      My technical notes should be what you’re looking for, although it only deals with my old original design. It has incoming and outgoing water temperatures, and the resulting BTU calculations.

  4. Hi Geoff,

    Your site has definitely been an inspiration for me to build one of these of my own in time for summer!

    Do you think this radiator in front of the fan provides more efficient heat-transfer than a good length of copper coil wound in front of the fan? (as seen in your ‘Heat Exchanger Improvements’ section)

    Also, I’m thinking about using a bucket of water with a bunch of ice packs in it for rejecting the heat.. Do you think it would be better to recirc the water in the bucket through the fan coil using a submersible pump, or go with more of a closed-loop system and use a copper coil in the bucket as well?

    Thanks in advance for any advise you can give!


    • Hey Scott –

      The radiator is leaps and bounds above what I had made myself, I’m going to be honest. I don’t feel too bad about it considering that it was precision machined for precisely that purpose however. 🙂

      I think that it would be more efficient to circulate the water so that it is mixed in the bucket as it is circulated – this would lead to better transfer of heat as opposed to the few seconds of cooling it might get as it goes through a coil.

      If you’re looking for a small radiator, check out an old thrift shop and see if they have any old appliances. A broken air conditioner or an old fridge could help you out quite a bit…

  5. I tried something almost the same as this with the radiator from an old broken Air Conditioner (it was not fun taking it off when the freon decided to vent… in my face…) but it seemed like the fan was having a lot of trouble pushing any air though the fins of the radiator. It acted like all the air was just going around it, I tried building a shroud but it didn’t help much at all.


  6. I ordered one of them black condensers last summer 2008 (I got mine from surplus center}. I was thinking about putting it to use because our landlord really rips us off because we don’t have our own electric meter. Maybe hooking up a electric water valve to a thermostat some how. Might save from having to run water all the time.

    • Hi Maik –

      The air circulation isn’t the biggest factor – really, you need to push just enough air through the radiator so that it can effectively transfer the heat.

      That fan looks very similar to the one I used. I set it on the lowest setting when I used it, as anything higher didn’t seem to do much and was just louder.

      Your biggest concern should be finding a radiator that is a good fit to your fan.

  7. Just a thought here, maybe you could use one of those water cooler towers that have cold and hot water spigots so that you could switch in winter for heating as well. I don’t know if there would be enough water for the cooling but it might work.

  8. Oh goodness. This is a great idea especially if you are limited by resources (like in a dorm) but think about how much water you are wasting. It means added equipment and maybe expense but one alternative is maybe an aquarium pump running water in a closed loop through a bucket or tub full of ice. But then again you are limited in how much energy you can displace into the ice before it is no longer effective. The running water scheme is kind of unlimited in that sense. just a thought. you win some you lose some

  9. Hi,

    I’m lloking to set up a closed system like this, I like to use the water over and over again.

    Because at 5-6 feet below ground it hovers at a nice 55F, I’d like to incorpeate my system to use the earths natural thermal properities to do this.

    What I’m thinking of doing is making a heat sink and connecting it to a small tank of water underground (50gal blue plastic container), there for giving it time to cool in the heat cink and to cool more in the tank.

    It would be pumped out of the tank by a small water pump, into the house into a radiator (from a car), have the fan behind it, have the water leave, go back outside into the ground into the heat sink, where it would cool and be sent to the water tank to cool more, and then start all over again.

    I was also wondering if increasing the size of pipe in the heat sink would lower the pressure of the water slowing it down in the heat sink giving it more time to cool?

    Here’s a diagram of what I want to do.

    Hope to hear from you soon:)

    -Connor Oliver

    • Hi Connor –

      Seems like a good idea to me, although you may want to fold the heat sink and tank into one concept. While I haven’t tried it myself, I’ve heard that the biggest issue for these setups is the poor thermal conductivity of dry soil. A tank will likely heat up the soil around it and soon reach a steady state temperature, as will the heat sink (unless it’s huge). A river nearby is the perfect solution to this but not everyone has this opportunity.

      Instead, perhaps try a ~100 foot garden hose folded back and forth in layers in a deep trench. This provides far more surface area for heat to dissipate underground. You could also try splitting into several pipes for a parallel version of this.

      You’ll have to calculate your flowrate and the volume of the hose/pipe – this will give you a rentention time that should allow you to estimate if the time underground is sufficient to cool the water.

  10. Hey Geoff, I’m going to buy a heater core tomorrow. My fan is a box like fan about 1 ft high and 6 in. wide. How do you suggest i hook up the heater core?

    sorry for any inconvenience thank you for your help

    • It all depends on the heater core – mine had 1/8″ outer diameter connectors which fit nicely onto standard 1/8″ inner diameter tubing, but your design may vary. Shouldn’t be too difficult to find the right parts – just check a hardware store.

  11. If you’re going to use parts from an old a/c, most like a window unit, find a really small one. When they break down its usually the compresser that goes bad. Couldn’t you just take the whole back half off. Leave the front coil and fan assembly together and run you coolant(water) lines to the evaporator.
    Or better yet. Get an ac unit with a fan only function. Take out the compresser (it looks like a little tank in the middle of the unit, be careful of the freon,and do this with the ac unplugged from the wall.), put wire nuts on the loose wire ends. Now you have 2 fans and 2 radiators. now connect you water lines to the copper tubes that were connected to the compresser.
    You should be able to also cut the copper line between the condencer (the rear radiator) and evaporator (front radiator), split your water supply, split your water supply and return. this will let run 2 units with the same power. Of coarse if your using a closed system your need more water pressure and your supply will warm faster. With a tap and drain system like geoff, that won’t be a problem.

  12. Basically you will use water and a pump to replace freon and compressor. oh yeah while you’ve got the unit apart clean it up. Old a/c’s usually have a ton of dirt and old algae in the tray.
    You won’t have to worry about the hot air coming out the back. No compressor eliminates that problem so you can set the whole thing inside. Just put it up on two chairs or crates or something so you can set a bucket under the drain hole to catch your condensation.

  13. Hi Geoff,

    If I were to use ice from my freezer, than wouldn’t it stand to reason that the only thing such a device would be able to do is offset the heat produced by my fridge to make the ice? Especially since I live in a dorm and my refrigerator would be in the same room.

    I’m thinking about building one of these, but I am worried about the cost/benefit ratio, especially if I have to constantly go out and buy ice. What would you suggest to keep the cost of running one of these low?

    • Hey Drew – Yep, making ice in the same room as the system will obviously be an exercise in futility.

      Few things: if you’re in a dorm, make friends with the cafeteria ladies. I can remember them giving us trash cans full of ice for free when a keg needed cooling. Also, if you have cold water in your room (or if you’re really bold, run a line from the bathroom…), you could simply hook it directly up to that (like the Black Beauty here – it doesn’t use ice).

  14. Hey I’m a college student who has no AC whatsoever and the heat is really bad. We are attempting to come up with a makeshift AC but were having trouble. i love the design but i need some help on a few things. First, what other kinds of radiators could i find that are similar to the one you found? Where could it come from? etc. Also, I would probably use the old cooler and water pump method. For that the water is just pumped through the radiator and back around to the cooler right? Sorry for the obvious question. I just want to make sure I fully understand the idea. Thanks!

    • Hi Peter – Try looking for a heater core from an auto pick-a-part, or keep an eye out for old fridges or broken air conditioners cast off by moving students. The cooler method works, but if you’re using a radiator you’ll likely burn through a fair bit of ice – try some of the suggestions I gave Drew above, or if your campus has an ice rink there will be a constant supply of ice out back (too Canadian a suggestion? :))

  15. Hello Geoff. I’m from Brasil. I just want to ask you about the flow velocity. If I can purchase an aquarium pump with 3000 L/h, that would be better? Or if the flow velocity is too high, that can be worse then a low one for heat exchange? Is there a optimum flow velocity that you suggest? Thank you…

  16. Hello… Me again…

    Did you ever measured the outside temperature and the inside temperature? Let’s get some exemple… Here where I live, the outside temperature is about 37ºC. Considering water at 15ºC. What would be the inside temperature? My room has 9 m². Consider the better flow rate in the heat exchanger. Thanks…

  17. hey man!
    i will be short here, but wanna leave it clear:
    my highest congratulations for your work!
    you are one of those who make me proud of being an engineer. those unsociable geek classmates, whose professional dream was some multinational admin sector, sometimes made me wish to pass by.
    anyway, i know in your country it’s mostly alreasy present in any home, but have you ever thought of a air heater?

  18. Love the idea of using ground temp water to cool the house
    though there is a problem if you are paying for water.

    My first question/comment would be:
    Is it better to return the water down the drain?
    Probably so in a leech bed septic system though in a city sewer situation I contend that it would be better to drain it through a sprinkler system in your yard at least you would get another benefit from your water use and the city wouldn’t have to treat clean water.

    Second I would say dependent on your outgoing water temp, multiple radiators in a 2,3,4 stage system might make this system more efficent.
    time for crude ascii graphics

    Key: [=Radiator #1 |=Radiator #2 x=Fan
    (2 Stage)
    ‘>Air Flow> |x[ <Water FlowAir Flow> x|[ <Water Flow<'

    note: you want the air to hit the coldest water last (Radiator #1)
    so it gets the water first

  19. I have a simple question instead of using water could you use cooking oil of some sort in a closed system would it hold the cooler temp longer than the water and maybe make it more effiecent.
    thanks for all the other ideas.

    • Hi Tony,

      A fluid with a higher heat capacity will tend to perform better than fluids with a lower heat capacity.

      Water’s heat capacity is roughly 4.2 J/(g K), while canola oil’s is roughly 1.9 J/(g K). The same volume of water has the capacity to move more heat as it warms up to room temperature than canola oil – so I’d definitely recommend water. Other fluids may have a higher heat capacity but may be less practical to use.

  20. Hi Geoff:

    Thanks for the really practical engineering help.

    Here’s my situation: I have a small room, about 32 sq.ft, that gets to about 30-32 (Celsius). It’s a long story, but conventional A/C is not an option. My water supply is about 28 degrees on an average summer day, and ice is way too expensive to put in anything but beer (yes, we put it in the beer).

    However, I can get a dorm-sized mini-fridge, and I can set it up so the backside sticks out the window like a conventional A/C unit. I would then just drill a couple of holes in the top of the fridge, put a container of (salt?) water inside, and run the water through the raditator using a aquarium pump (submersible powerhead) in the normal way (well, “normal” for people who build their own A/C).

    These seems like such an obvious solution and straightforward application of junkyard technology that I can’t imagine no one has already thought of it. So what do you think? Is it impossible just because a mini-fridge could not generate the BTUs to do any real good? Maybe no one has tried it because they don’t have a handy window to stick the mini-fridge out of.

    One more thing… why doesn’t anyone seem to bother with thermostats for these contraptions? I seems that one could easily put a thermostat into the water pump circuit, and since the whole contraption is wired ad lib anyway, locate that thermostat in whatever part of the room you most care about the temperature of.

    Best regards..


    • Like most engineering projects, this comes down to the critical metric of the “wife acceptance factor”. Many of us cannot put a fridge halfway out our window and seal it up without someone asking us what the hell we’re doing. You appear to be at a wonderful junction in your life where no one seems to ask this, and if they do, it’s because they think there might be beer left over in there.

      Biggest issues are going to be structurally supporting the fridge in a safe manner and providing an adequate air seal around it in the window. Thermostat regulation is certainly a possibility, but it’s more due to practicality reasons than anything else (ie many simple circuits could lead to issues in this sort of setup).

      Let me know how it goes, and send pictures if you can!

  21. Greetings Geoff.

    Would using a low percentage ethylene glycol mixture (~10%) improve the cooling of the air conditioner?

    (Yes, I realize it’s potentially hazardous).

    • Hi Ingemar,

      I’m not sure that it would. The only reason to use ethylene glycol would be to drop the freezing point of the liquid in the cooling loop, and most people don’t use a cooling source that reduces temperatures significantly enough to require this.

      If you were using dry ice or similar such that these low temperatures would occur however, there would be a significant benefit (ie less likely to freeze!).

  22. Hi Geoff, I could really use your advice!

    I live in a college dorm… and i haven’t got an air conditioner, and one isn’t allowed (due to high electricity costs to the university).

    I have a honeywell turbo fan, similiar to the one you used, and i’m thinking of following your black beauty design.. however, i have one problem: i don’t have running water in my room.

    I am thinking of filling buckets with ice (if i can obtain) or otherwise cold water from the bathroom, and making a closed loop, with an open reservoir, similair to spencer’s build.

    Will this heat core be good:?

    are the 5/8″ pipes too big?

    How powerful will the pump need to be?

    i can obtain pumps from 300L/hr to 1500L/hr for nearly the same cost..

    Any ideas on how to make it better?

  23. Also, one last question.. would it be okay if i used a 1/2″ ID pump with a 5/8″ ID heat core? Would i want to get a stronger pump to compensate as the water pressure will decrease once it hits the 5/8″ tube?

  24. dear Geoff , want to know that what was the temp of water u were using and what is the change in the ROOM AIR TEMP after what time u run this gadget ? m planning to make one same like yours but a bigger in size with a circulation of chilled water in the copper lines , i will use 2 or 3 car radiators or the vaporizers of old window A/C or the condensers of the split units (out door unit condensers) the room size is about 150 sq feet so what you suggest should i use a small compressor too in the reservoir of water (must b in the heat proof bucket or custom made reservoir) please answer the question asked in the above lines. thanks

  25. Okay so I’ve been reading up on this all day, and I have a basic idea of what I’m doing but I’ve honestly never built anything like this or pretty much at all before, and as I will be in a dorm I don’t have the ability to have the water empty out (I can’t have and don’t want a large trash barrel in my room either haha) would I be able to have a close circuit system with an aquarium pump with this design?

  26. Hi,
    The black beauty is, well… a beauty! 🙂

    Could you give us some readings on the water temperatures in and out of the radiator?

    Regards from Portugal,

  27. Hi Geoff,

    Would like to know if the scrap radiator have hazardous chemicals? Do I need to pump out with soapy water the radiator for it to free hazardous chemicals? Correct me if my analysis is wrong, radiator will not emit heat since the water running to copper coil is cold water? Did you recycle the water coming out from the outlet of the radiator? Thanks.

  28. Hi Geoff,

    Im from Phil and we have here around 60% humidity. If I used your homemade AC, do my room will be moisty? Do I need to have larger open space? There are readily available air coiler in the market, what are their differences? Sales Attendant says that it’s need open space so that it will have less moisty. Thanks.

  29. Hi Geoff,

    Really nice work you’ve done, Black beauty really awesome.. congrats first for that.. May i know the temperature difference between room and outside, after installing black beauty? How far it’ll cool the room? My bedroom straight a way facing sun, in between no protection whatsoever.

    I’ve planned to do the same because my room temperature crossing 42 deg Celsius :O something i’ve to do…

    Thank you Geoff

  30. Hello,

    I see this page is rather old, but I still wanted to share, because I have a very similar rig…with one incredible bonus.

    I am uber-fortunate…I have a 400 gallon a minute spring-fed-creek….48 inches from my house!

    I started with 2 “Ice-boxes”

    but have since switched over to a dramatic 16 x 16 Brazetek heat-exchanger.

    I applaud your efforts!

    I must disagree with one statement you made….regarding airflow.
    You opine that airflow can be kept minimal..which is somewhat a conservative viewpoint.
    The dynamics are as follows: The more air you move thru it, the more heat will be stripped away. Period. (providing your water flow rate is adequate)
    There is no reason to be conservative, and indeed: cooling-gains will be seen by increased airflow.


  31. Sorry…forgot the details :
    I use a 2000 gallon an hour waterfall-pump from HomeDepot.
    I ran about 35ft of 1″ PVC-pipe to get to my rig, and another 35ft to return-to-creek.
    I have a pressure gauge in-line outside, which tells me at a glance that there are no leaks, and whether pump is on or not.
    That’s about it 🙂


    I live in India and want to make this air conditioner but don’t want to use ice or running water as it will increase the electricity consumption (electricity is costly here) and we have limited water…

    My question is, Is it possible to use two radiators, One inside the room and one outside, One fan on each radiator and will make it Closed circuit with Car coolant filled in the radiators… And I will drop water (just like evaporative coolers) on the outside radiator to cool it more rapidly…

    I think it should work as efficiently as ice and if it does, then one will not have to refill ice and one can make it run for as long as we wish…

    Please reply and tell me your suggestions about my idea of two radiators and using Car’s radiator coolant liquid…

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