Peltier cooling

[3v0]

I see no problem using the Peltier coolers you have. But as pointed out you have to get rid of the heat from the hot side. Maybe run the heat sinks on the hot side in water and use a small radiator with a fan to cool it.

If you are going to run the tank much below room temperature insulating it will help.

As I pointed out submerged pumps are heaters. Switching to a non submerged pump will help. If you are on a budget think about an air driven filter. They are old tech but work well if sized correctly.

Another option is to increase the water volume by adding a sump. Pump the water from the sump to the tank above it and the water overflows back to the sump. You can use the sump for a large filter if you like. Make the sump with a large surface area and you can blow water over it. If you make the sump large enough it will also increase the O2 level in the tank due to decreased fish/water ratio. Sumps are great.

It is possible to build overflows that do not require drilling the tank.

 

[RobM]

So what would I need to power a fan and a peltier plate? would connecting it to a 12V transformer be ok?

 

[3v0]

So what would I need to power a fan and a peltier plate? would connecting it to a 12V transformer be ok?

The datasheet indicates the plates are designed to work at up to 16V. 12V will not give you max cooling but it makes it easy to use a 12V fan with it. Just make sure the transformer can provide the required current. (cooler + fan ?) It is better to get one that is larger then required.

Getting rid of the heat on the hot side is not trivial. If you do not use water cooling as I suggested use the largest heat sinks you can find or devise.

 

[ronv]

They won't like the ripple of the rectified ac supply better add a BIG cap.

 

[zipdogso]

They won't like the ripple of the rectified ac supply better add a BIG cap.

I cannot see a problem most manufacturers actually recommend using PWM.

The peltiers should NOT be run without cooling on the hotside.
If you applied the 12v without cooling you would of only had a few seconds literally before the unit burnt out.

It is quite likely you have already compromised the units and they wont work as well/as long as they should do.
You cannot cool a peltier of greater max cooling (Qmax) than 100w with a fan. So yours could be fan cooled if they have individual fans. A peltier with a Qmax of more than 100w MUST be water cooled.

it is possible to run them at a higher voltage IF the hotside is at the temperature quoted.

The problem is this:-

Peltiers work best with the maximum cooling you can provide to the hotside.

If you exceed the max input power quoted for the relevent hotside temp you will burn out the unit.

Manufacturers quote the specs at all sorts of temps the best one to use is a middling value. This is at a hotside temp of 27ºC Most Peltier users use a fan to cool the hotside with the small peltiers like yours and with an average ambient room temp and a fan on the hotside 27ºC is a nice temp to use. At 27ºC all peltiers pass 0.1277v max per couple so in your case with a standard 127 couple unit the max input at 27ºC is 0.1227 x 127 = 15.5v.

At this max input power peltiers are hideously inefficient and since at around 75% input power Peltiers can produce 80-85% of their max cooling power it is considered undesirable to power them at more than 75% power which is 11.6v. The vast majority of people run 127 couple peltiers at 12v. Some are even erronously advertised as 12v units (which of course you now know they aren't.)

So run them at 12v.
If you can find a 48v power supply run them in series, failing that get a 24v and run 2 parallel pairs in series.

At the delta you can expect for 75% input power (around 40ºC from my experience) 12v will draw just over 4.5A each.
Note your max cooling power at 12v with a delta of 40ºC will be about 20w each.

Your biggest problem will be transferring the cold from the coldside to your water it will need to very efficient.

PC enthusiasts use standard waterblocks on the coldside with another waterblock and cooling loop to a radiator on the hotside. This might be advisable for you as the radiator will stop the coolant getting too cold with a delta of 40ºC, fan cooled in average ambient room temp the coldside of the peltiers will be around 0ºC +/- 5ºC You will also need to use a thermostat/relay. Some thermostats cant pass the cuurent so get it to operate a high current relay. You should switch the peltiers with the thermo not the power supply.

4 of your peltiers will collectively have a max cooling of around 80w but in practice it will be less than this due to thermal transfer inefficiencies. probably around 70-75w.
Note you will also have to clamp the peltiers down with a pressure of 150-300 p.s.i. This is because they naturally vibrate in use. This has the effect of creating a gap between the face of the coldside and the object being cooled. If you don't tension the TECs properly you could lose as much as 50% of your cooling i.e. just 30-40w in total for all 4 peltiers !

Unfortunately Peltier usage is not nearly as easy as the majority of people think !!!

 

[ronv]

cooler

Well I see now why my pwm didn't work. Here is a nice site with lots of info.

**broken link removed**

 

[Mosaic]

This thread is a few months old but I just got into the peltier thing....to cool uPs etc.

Here is an image I took today using a 170W peltier on a Xeon copper heatsink with a standard muffin fan. The peltier is cooling a 1/4" thick piece of copper busbar as a load.

The ambient temp is 30 C, the Hottest part of the Heatsink opposing the peltier is 40 C, the peltier coldside gets to -12 C.

The 9V battery propping up the 1/4" busbar gives u the scale. The busbar 'froze' onto the peltier.

https://img181.imageshack.us/i/peltiersmall.jpg/