Arofanatics Fish Talk Forums  

Go Back   Arofanatics Fish Talk Forums > General Aquatic Forums > Planted Tanks & Aquascaping Forum > Aquascapers Equipment, DIY and Hardware

Adv

Reply
 
Thread Tools Display Modes
Old 05-03-2006, 03:28 AM   #1
xtrekker
Guest
 
Posts: n/a
Default How to building your own Thermoelectric Chiller

Hi All , I have decided to start this thread due the renew interests in TEM cooler. The writeup below is a simplifed version of how to design and built your own chiller. The calculations are theoretical and actual value might differ. All the data used is taken from supplier's datasheet.

cheers
xtrekker
ps:Upzzz me as a form of encouragement if you find this useful.

Introduction to Thermo-Electric Module (TEM)

Xtrekker
Silane

In 1821, J. T. Seebeck (1770-1831) discovered that different metals junctions will develop a small voltage potential when both of them are at different temperature. This effect is known as the "Seebeck effect". Thermocouples are based on "Seebeck effect".
In 1834, a scientist called Peltier discovered the inverse of the Seebeck effect, known as the "Peltier effect". He found that applying a voltage to a thermocouple would induce a active heat pump. This is now known as Thermoelectric Cooler (TEC).

There are quite a few thing you need to know before everyone rush into buying TEM.

Ask yourself the following questions :

1. What is your target temperature of your tank ?
2. How much heat (Qc) you intend to remove from your tank ?
3. What type of heatsink to use ?
4. Are you willing to fork out extra $$ to power your chiller ?

Using a 1ft x 1ft x 1ft tank of 27L as a case study ,

Lets say the temperature of my 30L tank is to be cooled to 24C. The ambient temperature of my room is 28C. The temperature difference ( dT = 28 -24 ) is 4C . We can determine the heatload (Qc) this can be easily done by using any heatload calculating software. Values of Qc for typical tank volumes is plotted on the graph below for your convenience.


Step 1 : Determine the value of Qc from the graph below.
From the graph, Qc of 1ft x 1ft x 1ft tank is about 40W


Step 2 : Choosing a suitable TEM

With Qc known we can proceed to the next step of choosing a suitable TEM for the Job. Don¡¦t be confused by the power ratings of TEM. The power rating is the maximum electrical power the TEM will ¡§consumed¡¨ from you power supply. Qc is the ¡§Cooling Power¡¨ of the TEM its usually about 50% of the electrical power you supplied. Some retailers sell "80W peltier element", without stating what this value actually means. This is misleading - what you want is a high transport capability, but a low power consumption.

For Example

TEM rated at
62W will give Qc = 35.1 W (model CP1-12704)
77W will give Qc = 44.5 W (model CP1-12705)
93W will give Qc = 53.1W (model CP1-12706)

Choosing CP1-12705 77W TEM seems suitable for the rated Qc. But in this design consideration , choosing a higher rated TEM at 77W to give a some excess cooling power to play with. TEM can easily turn off when the set point temperature of 24C is reached.

dT = (1 - (heat load/max cooling power)) * max temp difference

where
heat load Qc = cooling requirement
max cooling power = TEM rating
max temp difference = TEM max dT under no load.

For example, the 77 watt TEM can cool a tank with ambient at 28 C as follows:

dT load = (1 - (40/44.5w)) * 68 C = 15.9 C

Theoretical tank temperature = 28 C - 15.9 C = 12.1 C

With an ambient of 28C, the TEM theoretically will cool the tank to 12.1 C. The actual temp will depend on how well it's insulated, power supply amperage, etc. I also took some shortcuts by using the TEM's rating from the supplier's datasheet, so actual temperature will be much higher.

Step 3 : Choosing a suitable Heatsink.

Heatsink performance is measured in C/W (or K/W ) We refer to this as thermal resistance. For this design , the lower thermal resistance the better .An example for what these values mean: if a thermal load of 20W is applied to a heatsink, and this causes the temperature of the heat source to raise by 10¢XC, the heatsink has a rating of 10C/20W = 0.5C/W. What does this number mean? A resistance of 0.5 C/W means that if one Watt of heat goes through the object, the temperature drops by 0.5 degrees.

In this case a ¡§forced Convention¡¨ type is heatsink is most suitable.

Below shows the theoretical temperature of heatsink in the micro chiller using this equation ,

THS = TA + RT Qh

where
THS = Heatsink Temperature
TA = Ambient Temperature 28C
RT = Thermal resistance of heatsink = 0.15 C/watt

Thermal load on heatsink Qh = Qc + Pin
= 40 watts + (5 amps) * (15.4 volts)
= 40 watts + 77 watts
= 117 watts

Therefore THS = 28C + (0.15 C / watt) (117 watts)
= 28C + 17.55C
= 45.55C
That is to say , 45.55C is the temperature of the heatsink when the micro chiller unit when running. This heatsink temperature will play a part in the actually temperature in the tank.

As a general guide for choosing a heatsink for the TEM , look for heatsink with
- big heatsink with lots of fins and surface area.
- the fan should be higher power rating. i.e. at least above 0.4amps


Step 4 : Getting a Power Supply Unit (PSU)

There are 2 common types of PSU on the market. Switch mode power supply and Linear Power supply. The latter is common know to us as the ¡§set down transformer¡¨ . Switch mode is more efficient .At least 80% of the input power is converted while the linear PSU stands at only 60% meaning 40% is lost as heat.

When choosing a PSU, look for one that at least 1.25 times the power of the chiller. The 77W TEM, would need a PSU rated at least 77W x 1.25 = 96W


End of part 1 Choosing a Suitable TEM, Heatsink and PSU
Coming soon ,Part 2 : Assembly tips

Last edited by xtrekker; 05-03-2006 at 03:45 AM.
  Reply With Quote
Old 05-03-2006, 03:59 AM   #2
evolim83
Guest
 
Posts: n/a
Default

Upz lah!
Thanks for the enriching information!
Where is a good place to get a TEM?
Sim Lim Tower?
  Reply With Quote
Old 05-03-2006, 04:11 AM   #3
xtrekker
Guest
 
Posts: n/a
Default

Quote:
Originally Posted by evolim83
Upz lah!
Thanks for the enriching information!
Where is a good place to get a TEM?
Sim Lim Tower?
Thanks . Right now I think you can find some surplus in SLT.

xtrekker
  Reply With Quote
Old 06-03-2006, 07:28 AM   #4
bokob1uR
Dragon
 
bokob1uR's Avatar
 
Join Date: May 2002
Posts: 1,126
Rep Power: 5
bokob1uR has many friendsbokob1uR has many friends
Reputation: 136
Default

Quote:
Originally Posted by xtrekker
Thanks . Right now I think you can find some surplus in SLT.

xtrekker
thanks for the useful information guys
bokob1uR is offline   Reply With Quote
Old 06-03-2006, 03:27 PM   #5
xtrekker
Guest
 
Posts: n/a
Default

No worries. If response good i try to get my cam fix up post a more assembling pictorial guide. Meanwhile have to make to do will these old microchiller pics in my Gallery.


cheers
xtrekker
Quote:
Originally Posted by bokob1uR
thanks for the useful information guys
  Reply With Quote
Old 07-03-2006, 12:20 PM   #6
wfc31
Guest
 
Posts: n/a
Default

xtrekker & Silane,
wao..this is a good info and guideline to make a microchiller.
i'm having a 20L planted shrimp tank, very interested to make one for my tank. May i know a 75W TEM with 40W cooling capacity enough to cool down to 25C ? Must it to be on for 24hrs or alternately.

Know that the TEM can be easily get from SLT, but as i know the price of the items there varies from bottom shop to upper floor shop. I personally get a relay with S$12, but when went up to top floor, its only cost S$8.
So, could anyone know which shop selling TEM with good price?
  Reply With Quote
Old 07-03-2006, 01:11 PM   #7
xtrekker
Guest
 
Posts: n/a
Default

Quote:
Originally Posted by wfc31
xtrekker & Silane,
wao..this is a good info and guideline to make a microchiller.
i'm having a 20L planted shrimp tank, very interested to make one for my tank. May i know a 75W TEM with 40W cooling capacity enough to cool down to 25C ? Must it to be on for 24hrs or alternately.

Know that the TEM can be easily get from SLT, but as i know the price of the items there varies from bottom shop to upper floor shop. I personally get a relay with S$12, but when went up to top floor, its only cost S$8.
So, could anyone know which shop selling TEM with good price?
Hi wfc ,

Thanks.Your Qc for 20L thank is about 20.6W if you want to lower the tank temperature from 28C to 25C. If you are using any pump/filter just add the power rated for that pump to 27.47W. Example if you using ehiem liberty 100, rated at 3W , then your Qc is 20.6 + 3 = 23.6W.

Once your desired temperature is ahieved , you can turn off your TEM. After that your TEM "ON" time will depends on how well you insulate your tank.

I can't rememeber the shop i got my TEM from. But those in SLT are low power one. I got mine from ebay.

cheers
xtrekker
  Reply With Quote
Old 18-03-2006, 04:08 PM   #8
wfc31
Guest
 
Posts: n/a
Default

xtrekker,
thanks for ur info, so i have got mysel a TEM from one of the SLT basement shop at S$19, the TEM is 12V 6A rating, i belif it is a 75W TEM.

after i connected the TEM with cold fin and heat sink+fan, i do a same one as ur previous box microchiller, the problem now is i cant get the water cool down to 24C, water temp only can achieve at 27.8C even i supply a 12V 5A supply to the TEM.

when i test the TEM at first, the cool fin only acheive at 21C and the heatsink at 38C, i couldnt' get the ice forming at the cold fin as what shown in ur picture, i really piss-off with the project i have done.

is there any thing wrong with my set-up? or i'm getting a lousy low quality TEM?
  Reply With Quote
Old 19-03-2006, 03:17 AM   #9
xtrekker
Guest
 
Posts: n/a
Default

thanks for ur info, so i have got mysel a TEM from one of the SLT basement shop at S$19, the TEM is 12V 6A rating, i belif it is a 75W TEM.

>> Your TEM is power rating is at 12V x 6A = 72W of Electrical Power. As for your "cooling" Qc , is should be around 45W it should be able to cool a 1ft cube. How big is your tank ?

after i connected the TEM with cold fin and heat sink+fan, i do a same one as ur previous box microchiller, the problem now is i cant get the water cool down to 24C, water temp only can achieve at 27.8C even i supply a 12V 5A supply to the TEM.

>> Try Touching your heatsink . Is it very hot ? It vry hot , Your heatsink is not big enuff to dissipate the heat conducted away from your cold plate plus heat generated by your TEM ( Due to its internal resistance )

when i test the TEM at first, the cool fin only acheive at 21C and the heatsink at 38C, i couldnt' get the ice forming at the cold fin as what shown in ur picture, i really piss-off with the project i have done.

>> To get ice forming is easy . There must be something wrong with you setup.

Its always the fan or the heatsink thats causing the problem. What the rating of your fan you use to cool your heatsink ? Have you use Thermal grease on the joint between your heatsink and TEM ?

Don't be disappointed. If it still does not work bring your unit over to my place i help you troubleshoot.

cheers
xtrekker.
  Reply With Quote
Old 19-03-2006, 05:23 AM   #10
Arolee999
Dragon
 
Arolee999's Avatar
 
Join Date: Jul 2004
Posts: 965
Rep Power: 5
Arolee999 is neutral, pH7
Reputation: 92
Thumbs up

Quote:
Originally Posted by wfc31
xtrekker,
thanks for ur info, so i have got mysel a TEM from one of the SLT basement shop at S$19, the TEM is 12V 6A rating, i belif it is a 75W TEM.

after i connected the TEM with cold fin and heat sink+fan, i do a same one as ur previous box microchiller, the problem now is i cant get the water cool down to 24C, water temp only can achieve at 27.8C even i supply a 12V 5A supply to the TEM.

when i test the TEM at first, the cool fin only acheive at 21C and the heatsink at 38C, i couldnt' get the ice forming at the cold fin as what shown in ur picture, i really piss-off with the project i have done.

is there any thing wrong with my set-up? or i'm getting a lousy low quality TEM?
I think i bought the same 6A TEM (peltier) like your's from SLT last week.
I got 1 nano tank in office which do not need chiller due to 24 hr air cond.
Today just started my chiller project for my 12.5 inch x 9 inch x 9 inch tank at home without air cond.
I do the test with direct tap water into tank. Water temperature from 28 degree bring down to 24 degree even lower at midnite like now.
My TEM(Peltier) is attached onto filter and it is detachable.
I am trying to ON it for 24 hours and monitor the temperature.
I do not know how long the TEM can last if i turn on it for 24hrs everyday.
Anyway thanks for xtrekker & silane for the info.....
Will upzz when my power is back....
Here is the step by step intro for my chiller setup.
Upzz me if you find my chiller picture is helpful to you....
Arolee999 is offline   Reply With Quote
Reply

Adv


Currently Active Users Viewing This Thread: 1 (0 members and 1 guests)
 
Thread Tools
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off

Forum Jump


All times are GMT +9. The time now is 05:05 AM.


Powered by vBulletin® Version 3.8.7
Copyright ©2000 - 2017, vBulletin Solutions, Inc.
Copyright © 2000-2008 Arofanatics.com (Since 30th August 2000)