How does adding a reflective material on the inside of a Peltier cooler affect cooling & power-use?

Thread Starter

Rahulk70

Joined Dec 16, 2016
449
Hi everyone,

I've a small Peltier cooler which I used to store some chemical stuffs. So, I recently modded the design to make it more bigger and improve its cooling + insulation.

I've added an aluminium piece plate as the base which is in contact with the cold part of the Peltier, the other four sides are covered with thermocole. I keep it running 24x7 on my atx power supply. I have installed a refrigerator gas expansion thermostat in it to turn-off once it is sufficiently cool inside(-1C to 0C).

My questions are as follows:
1.How does the cooling change if I stick aluminum tape on the inside of the thermocole insulation (interior of the cooling cabin) and make it reflective?
2.Will it increase the cooling capacity and reduce the power-on time?
3.Does changing the gas expansion thermostat to electronic thermostat make any difference?
4.Also does adding a small fan inside make any change?

Thanks
 
Last edited:

OBW0549

Joined Mar 2, 2015
3,151
My questions are as follows:
1.How does the cooling change if I stick aluminum tape on the inside of the thermocole insulation (interior of the cooling cabin) and make it reflective?
It should help the cooling somewhat. How much it will help, is hard to say.

Rather than aluminum tape, you will probably get better results by alternating several thin layers of Thermocol (or other expanded polystyrene or expanded polyethylene) insulating material with layers of aluminized Mylar (polyester) film cut from what are commonly known as "emergency thermal survival blankets" such as this one.

Three or 4 such alternating layers should suffice to make a very effective insulator which will block both conducted and radiated heat from entering your cold chamber.

2.Will it increase the cooling capacity and reduce the power-on time?
It won't increase the cooling capacity per se, but it will make whatever cooling capacity you have more effective. It might even reduce the cool-down time a bit.

3.Does changing the gas expansion thermostat to electronic thermostat make any difference?
I don't know.

4.Also does adding a small fan inside make any change?
It will probably make things worse, since the fan's motor would very likely be a significant heat source.

Adding a fan on the outside to help cool the Peltier element's hot side, however, could make a big improvement.

Hope this helps a bit...
 

Alec_t

Joined Sep 17, 2013
10,746
Three or 4 such alternating layers should suffice to make a very effective insulator which will block both conducted and radiated heat from entering your cold chamber.
It would also block heat from escaping from the chamber, so would slow down the cooling effect if you put a hot object in the chamber and try to cool it.
 

OBW0549

Joined Mar 2, 2015
3,151
It would also block heat from escaping from the chamber, so would slow down the cooling effect if you put a hot object in the chamber and try to cool it.
Very true, although the easy way around that would be to let the hot object cool down to ambient (or near ambient) temperature outside the cooler before putting it in.
 

Thread Starter

Rahulk70

Joined Dec 16, 2016
449
Very true, although the easy way around that would be to let the hot object cool down to ambient (or near ambient) temperature outside the cooler before putting it in.
I was thinking maybe add thin layer of thermocole as insulator over the aluminium tape. I've stuck the aluminium tape inside of the cabin my results seem to be pretty good. The cooling time has drastically reduced and cools to -2C to 0C much faster. So, adding a 3mm thick thermocole over the aluminium tape covered cabin was what I had in mind.
 

OBW0549

Joined Mar 2, 2015
3,151
I was thinking maybe add thin layer of thermocole as insulator over the aluminium tape. I've stuck the aluminium tape inside of the cabin my results seem to be pretty good. The cooling time has drastically reduced and cools to -2C to 0C much faster. So, adding a 3mm thick thermocole over the aluminium tape covered cabin was what I had in mind.
That should help a bit. Generally, the more layers, alternating between reflector and insulator, the better (up to a point, of course).
 

Thread Starter

Rahulk70

Joined Dec 16, 2016
449
It should help the cooling somewhat. How much it will help, is hard to say.

Rather than aluminum tape, you will probably get better results by alternating several thin layers of Thermocol (or other expanded polystyrene or expanded polyethylene) insulating material with layers of aluminized Mylar (polyester) film cut from what are commonly known as "emergency thermal survival blankets" such as this one.

Three or 4 such alternating layers should suffice to make a very effective insulator which will block both conducted and radiated heat from entering your cold chamber.


It won't increase the cooling capacity per se, but it will make whatever cooling capacity you have more effective. It might even reduce the cool-down time a bit.


I don't know.


It will probably make things worse, since the fan's motor would very likely be a significant heat source.

Adding a fan on the outside to help cool the Peltier element's hot side, however, could make a big improvement.

Hope this helps a bit...
Adding the fan was a pretty bad idea in my case. I added a small 12V 0.11A thin profile DC fan from an old ATI GPU cooler I had with me. Once the fan inside started circulating the cold air inside. The temperature increased from -1C to 7C and it just stayed there. ice the fan is small wattage and doesn't produce much heat, I suspect that due to the air circulation the cold air might be leaking. Since, without fan the interior seems to retain the cold temp inside the cabin for longer periods.
 

OBW0549

Joined Mar 2, 2015
3,151
ice the fan is small wattage and doesn't produce much heat, I suspect that due to the air circulation the cold air might be leaking.
Well, you certainly should seal off all leaks, fan or no fan.

But I suspect the temperature rise is indeed coming from the heat dissipated by the fan; 1.32 watts may seem like a small amount of heat, but when compared against the heat pumping capacity of the Peltier unit vs. its differential temperature, even that small amount could be quite significant.
 

Thread Starter

Rahulk70

Joined Dec 16, 2016
449
Well, you certainly should seal off all leaks, fan or no fan.

But I suspect the temperature rise is indeed coming from the heat dissipated by the fan; 1.32 watts may seem like a small amount of heat, but when compared against the heat pumping capacity of the Peltier unit vs. its differential temperature, even that small amount could be quite significant.
Hi,
I'm going to seal the leaks completely first and then see how it goes with the fan. If the outcome isn't good then I'm going to remove the fan. You are right since in a Peltier cooler the small heat from the fan also does make a difference. I'll make the changes and post the results.
Thanks.
 

crutschow

Joined Mar 14, 2008
24,130
Use the fan to cool the outside hot side of the Peltier as OBW0549 suggested.
The fan on the inside will only hurt the cooling capability as you've already found.
 

Thread Starter

Rahulk70

Joined Dec 16, 2016
449
Use the fan to cool the outside hot side of the Peltier as OBW0549 suggested.
The fan on the inside will only hurt the cooling capability as you've already found.
This is the particular heat sink (1st image) I'm using with a 12V 0.7A DC fan. It does remove heat quickly, though I look forward to add a liquid cooled heatsink soon. The fan I wanted to add inside is a small 12V 0.11A DC fan like in below attached picture. I've removed the internal fan now. Trying to identify and remove any external air leaks to the cooler cabin now.
 

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