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DIY Aquarium Chiller




 

This aquarium chiller uses a 15V 15A peltier to cool my 20 liter fish tank. In my setup, I set the input voltage to 11V, so that the peltier generate less heat and operate at higher efficiency. There is a very useful peltier calculator that could help you to determine the optimum peltier operation point :

My design goal is to lower 6 degree of water temperature. To use the peltier calculator, there are several parameters that I need to determine : Input Voltage, Heat load and the peltier hot side temperature.

Input Voltage - I tried 12V and 11V on the calculator to see the difference between the heat generated, and found using 11V should be able to cool the aquarium while less heat is generated.

Heat load - This would means the engergy gained by the aquarium water from the ambient temperature. To find this out, I did a measurement of how much time is required to heat up the 20 liters tank water by 0.1 degree. First I used a fan to cool down the water temperature to 2 degree below ambient and then stop then fan. After 6 minutes the water temperature rised 0.1 degree.

Energy = Energy required to rise 1L of water 0.1 degree * water volume = 418 J/(L·K) * 20L = 8360 J

Time = 6 minutes = 360 seconds

Heat Load = Energy / Time = 8360 / 360 = 23W

So for a 2 degree temperature difference equals to 23W from the ambient, I estimate for a 6 degree difference, the ambient heat load will be 69W.

Hot side temperature - This would equals to ambient temperature + heatsink efficiency * total heatsink load. I assume the ambient temperature to be 32 degree, the total heatsink load from the calculator to be about 200W. Now to find out the heatsink efficiency, I refer to this CPU cooler review link for the Thermalright Ultra-120 cpu cooler, which is the previous version of the Venomous X: http://www.frostytech.com/articleview.cfm?articleid=2001&page=5 . From the test results, the test load gained 12.4 degree for 125W of heat. That means the heatsink's thermal resistance is 0.1 degree per watt. The calculated hot side temperature will be 32 + 0.1 * 200 = 52 degree.

The TEC calculator shows that with the above parameters, the peltier cold side temperature is at 18 degree, which verify this design is good for a drop of 6 degree. If I try the above calculations again for an 8 degree drop, the calculated peltier cold side temperature will be at 31 degree, which means the design won't work for a 8 degree drop.

This calculation also showed that the importance of using a good heatsink, if a heatsink with 0.3 degree per watt thermal resistance is used, the temperature drop will only be good for about 3-4 degree.

This 15V 15A Peltier has a Qmax of 150 watts.

peltier

Aluminum water cooler head.

water cooler

Foam heat insulator

foam

This temperature control has a sensor which I can drop to the tank to measure the tank water temperature, it can be programmed to turn on or off at a centain temperature.

temperature control

12V 30A switching power supply, I actually do not need 30A, but I like the power supply to work much below its rated output current.

12V30A

The most expensive component for this chiller - Thermalright Venomous X heatsink (and a 12cm 1600rpm fan), this is one of the best CPU heatsinks.

Thermalright Venomous X

An aluminum bar, bolts and nuts:

bar

The construction is faily simple, use an acrylic plastic plate as the base, put on the foam, then the water cooler head, then the peltier, then the heatsink. I used the excellent Thermaltake TG-1 thermal compound on both side of the peltier. Finally I use the aluminum bar to bolt all the pieces together.

Here is the final version which I use a bigger acrylic plate to hold the temperature control, power supply and the peltier block together :

My shrimp tank setup, the Eheim 2215 fiter pumps the water thru the chiller.

I set the temperature control to 25 degree. The hottest day here in HK since I made this chiller was 32 degree outdoor and 30 degree indoor, and it can cool the water to 25 degree. My estimation is that this chiller is able to cool 20 liter of water to about 6 degree below ambient.

 

In the tank : red crystal shrimps, big one is 1.8cm long, the baby is about 2mm long.

 

 

 

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