Author Topic: How to read this Peltier device chart  (Read 1165 times)

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Offline metrologistTopic starter

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How to read this Peltier device chart
« on: August 12, 2022, 06:53:36 pm »
I'm looking at the 50C hot side chart. What confuses me is that if I follow the 12V line and consider the current curves, it looks like less current is needed for a greater delta T.

I measure input of 12V @ 3.3A to the device. I'm using a quality AC-DC SMPS brick that is rated 12V 5A, but for some reason it's not putting out its 60W. The heatsink is hot right next to the device but I can leave a finger on it without discomfort. I have a good thermal transfer pad to the heatsink and a small tin of water on the cold side, and it feels about refrigerator cold. I was expecting to see it freeze.

Given the 40W input above, if I look at the lower right Qc chart where 3A intersects 40W, delta T is 0.  Further, it's like the current curves are sloped the wrong way.

https://peltiermodules.com/peltier.datasheet/TEC1-12706.pdf

Edit: I just measured resistance starts at 2Ω but climbs up to 7Ω when at ambient.
« Last Edit: August 12, 2022, 06:58:00 pm by metrologist »
 

Offline emece67

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Re: How to read this Peltier device chart
« Reply #1 on: August 12, 2022, 08:10:15 pm »
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« Last Edit: August 19, 2022, 05:44:30 pm by emece67 »
 

Offline metrologistTopic starter

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Re: How to read this Peltier device chart
« Reply #2 on: August 12, 2022, 08:46:08 pm »
OK, so if I want to freeze a block of something and keep it there, I have to know something about its heat transfer to the environment.

I'll know I can keep the hot side at 50C with some regulated sink system (i.e., fan control)
then I'll know I want dT of 50C, and I can use 1.5A @ 5V, 3A @ 10V, 4.5A @ 13V, etc.
But I'll have to use the second chart to know what current I need to pump the equivalent heat power, which is over 3A @ dT of 50C

So my water did not freeze because there was too much heat transfer into my tin and system on the cold side.

OT
Heat transfer was my least favorite course, and probably because the professor was a tenured penis. Every semester the kids that failed the semester before would circulate a petition to have him removed. He was a bold MF'er, would proudly announce at the beginning of the semester that half the class would not pass. And he was right. He also justified the difficulty of his program, meaning it was so hard that nobody could get 100% because if they did, he would not know how far they really could go.
« Last Edit: August 12, 2022, 08:48:10 pm by metrologist »
 

Offline emece67

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Re: How to read this Peltier device chart
« Reply #3 on: August 12, 2022, 10:57:33 pm »
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« Last Edit: August 19, 2022, 05:44:37 pm by emece67 »
 

Offline metrologistTopic starter

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Re: How to read this Peltier device chart
« Reply #4 on: August 13, 2022, 12:00:42 am »
When the equilibrium is reached, the heat transfer from the environment into the tin, and from the tin to the heatsink, will be equal. If the heat transfer from env. into the tin is big, so will be Qc, and thus deltaT will be low (or you need a greater input electrical power to achieve the desired deltaT).

Thus, if you want to minimize the required input electrical power to the cell, and still freeze the water in the tin, you need to minimize the heat transfer from the environment into the tin.

Might not be getting the point. To make heat xfer to env from cold side big is to put a hot plate there, and that makes dT low? I see a huge dT always. It's never cold enough and always too hot. When I was using a large sink. I put a fan on it and the the sink cooled a lot, and the cold was not as much. ?

This is now, a different setup using a CPU cooler with ambient desk fan... Right now I just want to see a blob of water right on the Peltier device freeze. I saw it on YouTube.

« Last Edit: August 13, 2022, 12:04:54 am by metrologist »
 

Offline metrologistTopic starter

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Re: How to read this Peltier device chart
« Reply #5 on: August 16, 2022, 12:22:12 am »
I looked into heat transfer through my thermal pad and heatsink I was using. The pad can transfer 240W heat energy, and the heatsink was ~40W as passive. I added a couple fans to the heatsink, and I have ice, even running @ 10V & 2.85A

 

Offline metrologistTopic starter

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Re: How to read this Peltier device chart
« Reply #6 on: August 16, 2022, 12:42:14 am »
One more pic because it's fun. Still doing the business @10V.

 

Offline metrologistTopic starter

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Re: How to read this Peltier device chart
« Reply #7 on: August 19, 2022, 01:32:36 am »
So I got my tin out and build an insulation box. Filled it half way with 20ml water. If I calculate correctly, it takes a total of ~3/4Whr to bring the water from 25C to 0C solid. The system ran for 1 hour @ 40W to do so, or about 1.8% efficiency, or about 1 cent US at current energy costs (not including losses of the power supply).   :(
 

Offline MrAl

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Re: How to read this Peltier device chart
« Reply #8 on: August 19, 2022, 06:08:53 pm »
I'm looking at the 50C hot side chart. What confuses me is that if I follow the 12V line and consider the current curves, it looks like less current is needed for a greater delta T.

I measure input of 12V @ 3.3A to the device. I'm using a quality AC-DC SMPS brick that is rated 12V 5A, but for some reason it's not putting out its 60W. The heatsink is hot right next to the device but I can leave a finger on it without discomfort. I have a good thermal transfer pad to the heatsink and a small tin of water on the cold side, and it feels about refrigerator cold. I was expecting to see it freeze.

Given the 40W input above, if I look at the lower right Qc chart where 3A intersects 40W, delta T is 0.  Further, it's like the current curves are sloped the wrong way.

https://peltiermodules.com/peltier.datasheet/TEC1-12706.pdf

Edit: I just measured resistance starts at 2Ω but climbs up to 7Ω when at ambient.

Hello,

From what i can gather from your post you have to consider the power not just the current.
For example, 3 amps at 8 volts is 24 watts, but 3 amps at 9 volts is 27 watts.
If you just look at the amps it looks like it gets magically better at a higher differential temperature.
 


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