• DIY Mini Chiller for Shrimp Tanks, Part 1

    This is the first installment of The Making of Mini Chiller, yes, a chiller, not a cooler. The purpose of this chiller is to cool down a nano tank, 1 feet tank and maybe a 1.5 feet tank to a temperature that cannot be achievable by cooler fan alone.

    A commerical refrigerant chiller is expensive, it take up alot of space and it's an overkill for a small tank. Noise and heat can be a problem posed by some commercial models too.

    This project is not going to drill holes to a refrigerator and run tank water through it.

    Mini Chiller is particularly useful for those having a shrimps tank or want to grow plant that cannot survive at high temperature in a nano tank.

    The above pic shows the temperature of the air in reservoir of Mini Chiller achieving 10.2¢XC after running for 8 minutes.

    Watch out for this thread for the step by step guide to make Mini Chiller.

    Ok, first test, still a little leaky, but managable. Achieved 25.2C after running Mini Chiller for 60 mins, initial water temperature was 29.6C.

    The black box on the left is Mini Chiller.

    Overall, I spent about S$34 on the parts and I have recycled some parts from my storeroom.

    Parts that I bought:
    1) Plastic project box -- S$2.50, got it from a shop in Sim Lim Tower, Silicon, 3rd floor
    2) Cold Fin -- S$5.50, got it from the same place as above
    3) Thermoelectric Module (TEM) -- S$20
    4) Tube 10/12 mm -- ~S$1
    5) Hose to go with 4) 2m -- S$5

    Parts I got from storeroom:
    6) CPU heatsink and fan or
    (work with any capable heatsink and fan), you can buy this from Sim Lim Square
    7) PC ATX Power Supply Unit (PSU)
    (work with any capable AC to DC power supply), you can buy this from Sim Lim Square

    Parts for temperature control:
    8) TBA -- S$5.

    Parts for cooling enhancement, optional:
    9) TBA
    10) TBA
    11) TBA

    Parts for self-pump enhancement, optional:
    12) TBA

    Tools needed:
    1) Selleys Silicone Sealant or equivalant
    2) Selleys All Clear, optional
    3) Files
    4) Drill and drill bits
    5) Heatsink compound

    Measuring Equipment:
    1) Thermometer
    2) Current Meter*, optional

    * Best is clamp type. You will not need a current meter if you follow the steps in choosing the parts and the parts are manufactured to their specification.

    How to choose the parts?

    You need not use the exact parts as I used. First of all, choose a Thermoelectric Module (TEM) that is either 40mm x 40mm or 50mm x 50mm with an overall thickness of not more than 4mm. The TEM should be non Power Generation type.

    Then you choose a Cold Fin that is at least 1 cm larger than the TEM, in term of width and length. I used one that is anodized and made of aluminium. Copper should not be used. Likewise, a heatsink should have a flat contact surface that is at least 2mm longer than the TEM width and length, mine is Swiftech 462, it is more than 2 years old with the fan that came with it. If you are going to buy CPU heatsink (any material) and fan, choose one that is designed to handle 3GHz or above.

    Select a box that can be sealed and work on that is just slightly bigger to house the cold fin and with the consideration of enough room for inlet and outlet tube.

    TEM is rated at Wattage(W), Voltage (Vmax), Current(Imax) and TD(C), choose one that is above 100W, mine is rated at 127W. There are 24 volt TEM in the market, you can choose to use it, powering it with cascaded PSUs.

    Choose a PSU that able to supply at the current needed as specified by the TEM. For example, the TEM is specified to operate at 15.4V max (Vmax) with a current of 16A max (Imax). You can choose a PSU that can supply current that is a few amphere less than Imax at 12V, so for this example, a 14A max at 12V is usable.

    However, if Vmax of the TEM is 12V, then you have to choose a power supply with 12V that has a max current greater or equal to Imax. For my case, it is a 50x50mm TEM with Imax=15A, Vmax=15.4V, at start, it draws 12.5A, and steady at 10.2A. My PSU can deliver 17A at 12V, it's an overkill, I know.

    If you blindly choose TEM and PSU and hope things will go well, it is likely you will burn something or the cooling effect is not there.

    I used standard silicone/zinc oxide compound for both heatsink and cold fin, if you have the money to spent, you can use Acrtic Silver X, it is known to be the best performance compound. Tests conducted by PC hardware websites showed that CPU with Acrtic Silver is 4C cooler than one with mid range heatsink compound. The performance of thermoelectric heat exchange is affected largely by the quality of the thermal junctions and the surface of the heat sink and cold fin, with the use of good heat sink compound, it translates into higher performance of Mini Chiller.

    Tape the cover of plasitic box with masking tape for easy of marking and prevent scatches.

    Locate the postion of Cold Fin and place the TEM in the center. Mark the cut out of TEM to be 1 mm larger its actual size. The below picture show the position of Cold Fin and TEM, with TEM position shaded.

    Then cut out the shaded part.

    Also cut out 2 slits, that will allow the wire of TEM to come out of the cover without hinder maximum contact of TEM to Cold Fin.

    Place TEM into the cut out to ensure it can sit right into the hole as shown in the below pic. The 2 circles are the slits.

    The below pic shows the top side of the cover with masking tap removed.

    Apply an generous amount of Silicone Sealant on the flat side of the Cold Fin, seal Cold Fin with the under side of the cover. Use something heavy to press Cold Fin onto the cover for at least 8 hours.

    Further seal the gap between the cover and Cold Fin, where the arrows points. I used Selleys All Clear, it worked well.

    Then remove the excessive sealant in the cut out, where cold side of TEM suppose to sit. It is important to keep the surface of Cold Fin to be contacted with TEM clean and shine.

    Wait for all sealant to cure before assembling TEM and Heatsink.

    Before the assembly, you have to determine which side of the TEM is cold and which side is hot. Use a AA or AAA battery, connect it between the TEM wires, red to positive, black to negative. You will feel that one side is cold and the other is hot, make a small marking on edge of the cold side.

    Spread heatsink compound to both side of TEM.

    Place TEM onto the cut out of the cover/Cold Fin assembly with the cold side touching Cold Fin. Check if TEM sat nicely on Cold Fin, press slightly to ensure proper contact.

    Then place Heatsink onto the hot side of TEM, ensure the surface of hot side completely comes in contact with Heatsink.

    Hold the Heatsink to the top side of cover by apply silicone sealant to 4 sides of Heatsink. Place weight, a couple of kg, on top of Heatsink and let the silicone sealant cured.

    You may want to hold Heatsink to the cover using screws.

    The TEM assembly is now completed.


    Article Copyright: Silane