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I previously worked on Virtual Reality and other hardware at Valve.  I currently work at Google[x].

Prior to starting at Valve, I built computer peripherals such as keyboards, mice, and joysticks that were designed to be used inside MRI machines.  My company, Mag Design and Engineering, sold these devices directly to researchers at academic institutions who used them to publish scientific papers in peer-reviewed journals.

After work, I spend time on many different types of projects that usually involve circuit design, machining, material selection, and general fabrication/hacking.  My favorite place to be is my home workshop.

ben dot krasnow at gmail

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Monday, April 26, 2010

Titanium heat exchanger for DIY aquarium chiller

In my first post about building an aquarium chiller, I used a coiled stainless steel heat exchanger that I bought at a lab surplus sale. It was very likely built from 316 stainless steel, but it eventually corroded. Despite my attempts to repair and passivate the stainless steel, the coil continued to corrode, and I permanently removed it from the aquarium.


Since the weather is starting to heat up, I decided to build a titanium replacement for the chiller heat exchanger. I bought some 1" dia x 0.025" wall titanium tubes on eBay after fruitlessly searching for a coil or something that I could bend into a coil. The surface area is about 16 in^2. The stainless coil had a surface area of about 20 in^2, so the heat transfer should be comparable.


The heat exchanger is built so that the metal tube is pinched between the plastic end caps when they are threaded onto the internal aluminum shaft. There are rubber washers to seal the metal to the end caps.

The device fits into my hang-on filter in the same position as the stainless coil did. I'll let everyone know how it works.

18 comments:

  1. Hi Ben,
    I was thinking about the same usage of a water cooler and titanium coil for cooling my aquarium.

    But in your case you are cooling a nano reef, where I have a 75 gallon tank.
    Will this work or will the low btu on the cooler make it work continuously and eventually burn?

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  2. Nikolas, cooling a 75 gallon tank with presumably more lighting, bigger pumps, and more surface area will take more cooling power. However, water coolers are so cheap (get a used one on craigslist), it's probably worth a try. Maybe you could even running two coolers. Even if the water cooler needs replacing every other year, it is still cheaper than a commercial chiller. Good luck

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  3. I recently read that suing fans on the surface of the water you can achieve up to 8000 BTUs of cooling. I will try and find a stainless steel tubing to make a coil that doesn't cost as much as a titanium coil and just try to see if it works. If it does I will replace with a titanium coil.

    For a titanium heat exchanger you can try this guy(or alibaba website for more sellers)
    http://www.alibaba.com/product-gs/229288017/titanium_heat_exchanger.html

    The heat exchanger shown in the link is air to water, but he also sells water to water.

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  4. Nikolas, have you ever ordered anything through alibaba? I was under the impression that the vendors only sell large quantities to distributors on that site.

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  5. It depends on the vendor. Some will sell by 1, other will require a minimum quantity.
    You can always ask those that require minimum quantity for a sample. They will always provide a sample for a little bit extra than the FOB price.

    For example FOB price for a salinity refractometer is $17 per unit when you order 500.
    But the sample price is 25+ shipping cost. For US this is close to market price, but when I asked to buy one here in Cyprus they asked for 95 euros($120). So sometimes shopping in Alibaba and asking for "samples" has its benefits :)

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  6. Hi Ben, im happy that can see you still active on your blog. :) Actually now i planing order some peltier device from Alibaba and DIY a chiller for myself using 2 12V 5A peltier device and after reading your blog know that you have do peltier chiller before and need collect some data from you. :)

    My concept is like this:
    -get 2 peltier device 12V 5A and the hot side stick to heat sink with fan.
    -get a ~10L rectangular ice box. At the cover of ice box cut a shape which will match with the 2 peltier device. After that drill 2 hole at the cover on left and right for IN/OUT pipe.
    -put the stainless steal coil with piping for IN/OUT (like what you did) inside the ice box and connect the the piping to IN/OUT on the cover.
    -after that fill cool water into the ice box.
    -then cut the output of aquarium pump pipe one head join to ice box IN and another side join to OUT.

    Do you think this work? Have you done this before? It was like mini refrigerator.

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  7. Cheok, as I noted in my original blog post (http://benkrasnow.blogspot.com/2009/03/diy-aquarium-chiller.html), I think that Peltier junctions are not well suited to moving appreciable amounts of heat. They have applications for spot cooling, but a refrigerant-cycle cooling device will be much more efficient for cooling an aquarium. If your tank is very small, you might have some success with Peltier junctions.

    I agree that using a separate tank of water for chilling the heat exchanger is a good idea. This way, the chilled water does not mix with the aquarium water, and it is nearly impossible for the system to overflow. Good luck, let me know how it turns out. -Ben

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  8. My tank is 110L. After try let you know the result. But wont so fast.... havent import the peltier parts yet... my country hard find peltier.... :)

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  9. Cheok, I'm afraid it is very unlikely that two 12V 5A peltier devices will have enough power to make any helpful change in your 110L tank's temperature. Try searching locally for a water cooler, air conditioner or refrigerator and use a refrigerant-based cooling solution. You will be much happier.

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  10. Oh really? Is it the peltier device is equal to the market mini chiller? Then i take your advice... try find water cooler.... :)

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  11. You can move a lot more heat by compressing and expanding a refrigerant than you can by using the Peltier effect. I would definitely recommend a refrigerant-based cooler device, not a Peltier device.

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  12. hello everyone
    i want to build the devices that can feed the fishes on time , control the light for fishes, control the temprature and this device also have LCD for display situation of aquarium.
    everything is ok but I dun know how to cool or heat the water automatically
    ofcurs im using temp sensor, bt dun know how to make the water cold or heat the water automatically
    is anyone have idea?

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  13. Erfan, I've written articles on this blog about aquarium temperature control:
    http://benkrasnow.blogspot.com/2009/03/aquarium-temperature-controller-pid.html

    http://benkrasnow.blogspot.com/2009/03/diy-aquarium-chiller.html

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  14. Hello:
    I wanted to mention an alternative to your plug-in cooler with the recirculating pump. It may have an application for those trying to reduce their electrical power footprint. I tapped into my cold water line and ran that through a valve actuated by a temperature sensor in the aquarium. Using a common thermostat, I was able to set the target tank temperature. WHen the temperature of the tank exceeded the setpoint, the valve would open and cold water would run through the coil in the aquarium then to a sink in the basement. Worked well, didn't use too much water, but was a bit of a pain running water lines up through my floor from the basement.

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  15. R. Reaudry, I guess it depends where you live. Here in California, letting water run down the drain is often a bigger problem than using electricity. It sounds like the plan would work pretty well, though.

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  16. This is so great.

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  17. Ben,
    Your post is quite entertaining. I am interested in building pool chiller (600 gallons). I want to achieve a temp drop of 10 degrees. I was thinking that I could surround the cooling coils on a window air conditioner with a water proof box. Then recyculate the pool water past the coils. With your background in cooling, does this seem like a feasable construction?

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  18. Peter, a window air conditioner would require an extremely long time to lower the temperature of 600 gallons of water by 10 degrees -- assuming no heat load. I would say it is not feasible.

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