Peltier Cooler Temperature

[gauravkothari23]

Hi all.
I am trying to build a small cooler using peltier module 12706, as the image attached. i have connected the module to 12v 10 Amps power supply. the consumption of current is around 4 amps at 12v. also connected a Hugh heatsink with two fans on the hot side using a thermal greece, and a small heatsink on a cold side. the temperature on the hot side is around 32 degree Celsius. but the cold side is not getting cooler. the lowest temperature i am getting is around 11 to 12 degree Celsius.
what's wrong with it. can anybody please help me.

 

[FvM]

There seems to be an insulator between the peltier element and the heat sink. What is it?

 

[gauravkothari23]

There seems to be an insulator between the peltier element and the heat sink. What is it?

no.. there is no insulator between module and heatsink. i have only placed thermal greece between module and heatsink. the top part of heat sink is not colored so it looks white and rest of the part of the heat sink is colored black.

 

[FvM]

O.K., should be fine. How do you measure the cold side temperature? No sensor shown in the photo. Can you measure the hot side (metal surface next to the peltier) too?

Do you know the thermal resistance (to ambient) of the heat sink mounted on the cold side?

Is the current pure DC?

 

[j33pn]

I've never played with them, but isn't there a limit to how much of a temperature change you can have across one plate? Maybe try stacking another plate with the first one to boost your cooling.

 

[dick_freebird]

There is significant thermal back-flux when you get to a
decent temperature difference. Check out Melcor app notes
(if they are still in business). This limits the per-plate max
temp differential and the efficiency drops with delta T as
well. Used to see 2, 3, 4 plate cascades offered for higher
temperature difference. Each has to be larger than the next
as you get away from the cold end, as the successor has
to take the through-heat and the waste heat of the one
above it.

 

[gauravkothari23]

thanks a lot...
sorry for replying late...
i have made some observations about peltier cooler.(images attached).
the highest temperature of peltier module heat sink is around 36 degree Celsius.
the lowest temperature of peltier module on the cold side is itself around 5 degree Celsius.
and the temperature of the heat sink placed on the cold sided of peltier module is around 13.50 degree Celsius.
even it does not form ice when i put a 2 to 3 drops of water on cold side of peltier module. i have even checked the voltage supply which is around 12.50V and current is near about 4 amps. the cold sided heat sink i am using is from one of my old computer IC
can anybody please let me know where the error is..
what changes have to be made to get the best cooling device.

 

[KlausST]

Hi,

The error is:
12.5V x 4A is 50W. This is 50W of generated heat. This is twice than a modern soldering iron needs.

Even if you properly cool down the hot side, there will be overheat at the inner peltier elements increasing cold side temperature.

Try a smaller heat sink at the cold side and reduce the curent. Try half the current.

Klaus

 

[Warpspeed]

Try reducing your voltage below 12v.
You will find a voltage and current where the cold side temperature reaches a minimum.
Either more or less power than that reduces the performance.

 

[chemelec]

Unless you put the COLD Side in a Well Insulated Container, it is getting too much heat from the surrounding Air to get any Colder.
Also the Warmer your Hot Side Gets, The less the cooling on the Cold Side.
If your Heat Sink is at 32 degrees, The Actual Peltier's Hot Side will probably be closer to 40 Degrees.

It is Better to run the Fans on the Hot side Continuous, But Supply Intermittent Current to the Peltier.
(Example: 1 Minute On, 30 seconds Off)

I Use a Temperature Sensors on both the Hot and Cold Sides to determine ON Power Times to the Peltier.

Qauravkpthari23, Where do you Live?

And Reducing Continuous Supply Current will NOT Help as it also Reduces Cooling.

 

[dick_freebird]

Re insulation, I have seen remarks that the sides
ought to be fully insulated (esp when below 0oC
at the cold end you need to keep condensation
from forming).

Always want the best possible heat sink, this
goes directly to achievable cold side temp by
delta-T, efficiency and cold face heat flux.
You might consider (if the complexity is tolerable)
one of the PC liquid cooling kits that has a pump,
a nice muffin-fan-sized radiator and a cold plate
(which you would bond to the hot side with, say,
Arctic Silver epoxy). The radiator will have a much
superior water-to-air heat throw than a standard
aluminum heat sink's face-to-air path. Especially
if the TEC module is much smaller than the heat
sink, much of the heat sink is effectively "dead
weight" as the heat has to travel laterally to get
to the outer fins. Interposing a copper plate
between TEC and heat sink, pyramidal geometry
(or copper extent = aluminum extent) could raise
the net effectiveness of the heat sink (more
path length in the copper, but more effective use
of the aluminum).

There are newer heat sink geometries (pillars rather
than fins, more similar to the one you put on the
cold face for testing) which are more effective than
finned types.

Another thing to try is submerging the heat sink
in room temperature water (agitated / circulated)
to see how much of your problem is convection
vs conduction.

But before too much more experimenting, maybe
look deeper at the advertised capabilities of the
module in question - specifically, the delta-T
it claims you can make for a given hot side temp
and power input. There ought to be formulae
or nomographs in the applications materials from
the manufacturer (or a competitor - they all seem
to be bismuth telluride and similarly constructed).

 

[chemelec]

His heat sink appears to be a Pillar Type with quite High Elevation on each one, But its Base Plate appear Quite Thin, so may not effectively transfer the heat those pillars.

Without an insulated box on the cold side, your attempting to cool the room and the heat pumping capacity won't allow for getting it cold.

 

[gauravkothari23]

Unless you put the COLD Side in a Well Insulated Container, it is getting too much heat from the surrounding Air to get any Colder.
Also the Warmer your Hot Side Gets, The less the cooling on the Cold Side.
If your Heat Sink is at 32 degrees, The Actual Peltier's Hot Side will probably be closer to 40 Degrees.

It is Better to run the Fans on the Hot side Continuous, But Supply Intermittent Current to the Peltier.
(Example: 1 Minute On, 30 seconds Off)

I Use a Temperature Sensors on both the Hot and Cold Sides to determine ON Power Times to the Peltier.

Qauravkpthari23, Where do you Live?

And Reducing Continuous Supply Current will NOT Help as it also Reduces Cooling.

thanks to you all...
i have tried using a (L=5 inch, B=5 inch, H=5 inch Styrofoam Box.) well insulated container on the cold side and sealed the container made up of styrofoam with glue from all sides and made sure it does not comes in contact with outside temperature. but still the results are same. the lowest temperature i am getting is around 12 degree Celsius after putting it ON for 2 hours. i have also run the fan continuously.
currently i am using TEC-12706 peltier module, can i use TEC-12715 instead, as it is around 150 to 160 Watts, it might help me in getting the temperature to lowest at around 0 Degree faster than TEC-12706

 

[dick_freebird]

If you know the hot and cold side temperatures and the
module voltage and current, you could compare the actual
operation to what the application notes for the particular
module indicate for its capability. This ought to tell you
whether the desired delta-T is achievable in a single
stage (often, not - for example the 12V thermoelectric
"ice chest" coolers I have seen, only advertise 40F) and
whether your problem is the hot side cooling or not
enough power for the cold side heat load.

Here's another thing to try. Put a thermocouple on the
cold side and cover that with styrofoam as well, so that
only the hot side is exposed, and operating with the
normal (or present plan) cooling hardware. What is the
ultimate, no-cold-side-thermal-load temperature?

Ain't no more (lower) to be had, than that.

And realize that for low cold-side thermal loads, more
power may hurt instead of help Tmin, because you are
dumping all that power into it and most of it wants to
bother the cold face. Maybe take the fully bundled up
configuration I describe, and record cold face temp vs
input power level (V*I). There is probably a "happy
place" (or, happiest possible, at least) which may be
away from where you're trying to push it.

 

[KlausST]

Hi,

You don't speak about current.
Did you reduce it?

Klaus

 

[gauravkothari23]

Hi,

You don't speak about current.
Did you reduce it?

Klaus

Yes I tried doing it...
the result were...
10V 6Amps = Lowest temp = 20 Degree C
10V 3Amps = Lowest temp = 22 Degree C
12V 6Amps = Lowest temp = 16 Degree C
12V 3Amps = Lowest temp = 20 Degree C

 

[KlausST]

Hi,

I don't undersrand why you have different voltages with same current and vice versa.

Do you have pure DC or is it pulsed somehow?

Klaus

 

[chemelec]

Yes I tried doing it...
the result were...
10V 6Amps = Lowest temp = 20 Degree C
10V 3Amps = Lowest temp = 22 Degree C
12V 6Amps = Lowest temp = 16 Degree C
12V 3Amps = Lowest temp = 20 Degree C

When using peltier Devices, you always get the best cooling when operating at Full current.

However you never told use What is your Ambient air Temperature?

And How Big is your Box and Thick is your Insulation.
(Insulation should be at Least 1 Inch thick, but More is Better.)

 

[gauravkothari23]

Hi,

I don't undersrand why you have different voltages with same current and vice versa.

Do you have pure DC or is it pulsed somehow?

Klaus

yes.. its a pure DC Current

- - - Updated - - -

When using peltier Devices, you always get the best cooling when operating at Full current.

However you never told use What is your Ambient air Temperature?

And How Big is your Box and Thick is your Insulation.
(Insulation should be at Least 1 Inch thick, but More is Better.)

my surrounding temperature is around 30 degree C.
my styrofoam is around L=5 Inch, B= 5 inch, H=5 Inch and thickness of styrofoam is around 1 inch.

- - - Updated - - -

so can i use TEC-12715 instead of TEC-12706 to get better and fast cooling..??

 

[chemelec]

30 Degrees Air Temperature is Hot.
So your heat sink or hot side of the peltier will probably be more like 40 to 45 degrees.

It is Unlikely you will get this to go down to even 5 Degrees.

There are STACKED Peltiers that have a Greater Cooling, but there More Expensive.

This one is rated at 15.4 volts and 6 Amps.

- - - Updated - - -

yes.. its a pure DC Current

- - - Updated - - -



my surrounding temperature is around 30 degree C.
my styrofoam is around L=5 Inch, B= 5 inch, H=5 Inch and thickness of styrofoam is around 1 inch.

- - - Updated - - -

so can i use TEC-12715 instead of TEC-12706 to get better and fast cooling..??

It is all about Maximum Temperature Difference.
Not so much the Power of the Module.

I have some modules rated at 15.4 volts and 14 Amps.
Can Kill your car battery Pretty Quick if the car is not running.