水草情迷

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 and keep the material cost low.

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. My thought is if one does not mind a refrigerator sitting in your hall or room, and the tank is small size, might well change the door of refrigerator to glass and put the tank inside. It is quite a cool idea, I think and it will impress your guests too. Maybe that will be my next project, Tank in a Fridge.

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.

Overall, I bought these parts and I have recycled some parts from my storeroom.

Parts that I bought:
1) Plastic project box
2) Cold Fin
3) Thermoelectric Module (TEM)
4) Tube 10/12 mm
5) Hose to go with 4) 2m




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:
TBA -- $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, can get from Sim Lim Square, usually PC heatsink comes with it. Cheap (and low performance) heatsink compound is sold in Sim Lim Tower.


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.

Water from tank will go into the reservoir, brush through Cold Fin and mix with colder water inside there, then go out of the reservoir and back to the tank.

Drill 2 holes on the side of the plastic box with diametter just slightly bigger than 12mm.


Picture has been resized, click for full size pic


Cut the tube into 2 sizes, 5 cm and 16 cm. The long tube is cut with a 45 degree taper at one end. The long one will be placed near Cold Fin to use as inlet and short one as outlet.





Seal both tube in place, keep the protruding parts (out of the Reservoir) at 4cm. Position the tapered side of long tube upward, close to Cold Fin.


Picture has been resized, click for full size pic



Picture has been resized, click for full size pic


Wait for sealant to dry. Reservoir Assembly is now done.

有無成個完整相睇

wait lah... will continue tonight...

有冇師兄可以幫忙變做中文呀..><..

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http://www.aqugrass.com/phpBB2/viewtopic.php?t=39365
我的魚缸資料(2008-5-13更新)

Queries for your advice please.
1. Where is Sim Lim Square (Is it in Hong Kong?)
2. What is TBA? (Item 9 -12)
3. Is it justified to cool a 12'~ 12.5' tank by an equipment consuming nearly 250W?(in addition to those required by the fan to cool the heat sink)

Could you please give us a diagram? It aids as a help to understand. Thanks.

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琉璃世界波光影 流轉逍遙逐水城
回首前塵疑是夢 迷濛醉眼羨魚情

中文仲正呀~

Mr Juice,

1) No, you have to find your own parts, this article is not intended for HK only. If you read what I wrote, you can find the right specification parts correctly.
2) TBA=To be advised, those parts are optional. You will not need these parts for a basic system.
3)Please tell me how u derive 250W? You need to understand something, a chiller is not mean to on 24x7 hours, so the effective average wattage is alway much less than what is the rated wattage. Just like your air condition or refrigerator, the compressor is not alway running and when compressor (in this case TLM) is not running, there is no comsumption of energy and the fan consume little energy, just couple of hundreds of mA.

You don't need to on the chiller for 24 hrs, once it cool down to the temperature you want, you will need to on for X mins every 1 hour to maintain, X depends on what is the temperature you are setting at and the ambience temperature, this is open loop control, you can use thomostat for better contron. For my case, once it hit 24C, I will set it to run 15 minutes in every 1 hour to maintain around 25C (my room temperature is around 30). With this setting, the effective wattage is 35W [(120W* x 15/60)/0.85], that's pretty close to a cooling fan power comsumption. It "eats" as much electricity as a mid size fan.

* measured current draw x 12VDC.
0.85 is the estimated efficiency of switch mode power supply.

Peltier is not the highest efficience for cooling, but it can be compact in design and suitable for small tank. If want to cool down a big tank, refrigratant based chiller is needed.

As you realised the article is not yet finished submitting, I will do so when I have it. I am going to HK for a few days, so likely I will continue when I am back on Satursday.

其實只係放個致冷片diy入個箱度
因為接觸水既面積多左,應該有效d,但要多d空間
真係吾差在整埋溫度開關

我的理解是這樣的！

對嗎？

Hi blenny
Sorry for the typing error. I was halfway sleeping at that moment.
# 3 should be read as “Is it justified to cool a 12” x 18” tank by an equipment consuming nearly 250W?"
- All those figures, inch and foot… mix up……
- I refer to yours “Vmax=15.4V, at start, it draws 12.5A, and steady at 10.2A……” 15.4V X 12.5A at 75% efficiency will therefore require an input power of appro. 250W

Really nice work! Longing to hear from you soon.
Hum… You’ve a long way to go. Eg. control circuit, heat insulation, …all those stuff.

_________________
琉璃世界波光影 流轉逍遙逐水城
回首前塵疑是夢 迷濛醉眼羨魚情

tklm is a smart boy, more or less u got it correct.

Mr Juice,

Vmax is referred to the max voltage can be supplied to TEM, but I supply 12V. And it draw 12.5A during first 2 minute when it is on, after that, it draw ~10A (measured at sum current of TEM and heatsink fan) even I toggle on and off.

So the effective wattage of the system is 10 x12 x fraction of time on per hour ./. efficient of power supply.

control circuit (a timer will do, or u can use themostat), heat insulation are not really necessary but good to have.

utopia13, don;t write in Cantonese accentated Chinese, I couldn;t understand, normal Chinese will do.

blenny:
May I give you some suggestion:-
1/ Heat exchange device is a resistance relaled element, no breakdown voltage concern.
2/ If a bigger tank is used, two heat exchange device can be employed in series or parallel connection.(Series connection is more practical, additional fans and pillar type heatsink).
3/ During winter time, reverse the supply to act as water warmer.

Even this chiller is consumpt a bit large power, and the efficient is not too high, but....Easy to make of course...compare with the compressor type cooler!!