# Thermal penetration depth experiment

## Main Question or Discussion Point

I doing an experiment that involves thermal penetration of copper. Please advise me where to post if I choose the wrong spot. This experiment is being done with what I have on hand and my ability to work the materials.
Materials
2.75 gal pot of water
6qt pressure cooker
100+lb of stripped copper wire that is .81''(2.05mm) in diameter
1 120 volt ac fan
specs
4.5 diameter
Airflow: 110 CFM
2600RPM
stove with 1250 watt burners

Ability to work materials
I can not recirculate the water
I can not melt the copper wire in to a shape
I can tightly or loosely bundle the wire together
I can vary the amount heat introduced in to the pressure cooker

I have a pot of water(2.75gal) that is being heated by steam at a rate of 25 degrees every 15 minutes at "high". The water starts out at 73 degrees F. I would like to cool this water using a bundle of copper wire and a fan on top(pic 1). I am not concerned about how fast I cool the water, but I would like to see the water stay as cool as possible for as long as possible.(EX: 100 degrees F for two hours) So my question is regarding the bundle of wire, Should I make it as tight as possible, as loose as possible, or tight layers with space in-between the layers?(pic2) Also would there be any benefit to making the bundle bigger than the fan?
I have found these two websites but I honestly don't know how to use the equation or if the number in the second webpage is what I need.
https://www.sciencedirect.com/topics/engineering/thermal-penetration-depth
http://hyperphysics.phy-astr.gsu.edu/hbase/Tables/thrcn.html

thanks

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Tom.G
You may have seen heatsinks being used in some electronic devices. They are metal shapes in contact with whatever is being cooled. They also have fins on them to present a large surface area to the air. The air flowing around the fins carries off the heat.

Those heatsinks used in electronic devices have a flat surface in contact with the device to be cooled. Flat because the devices themselves are flat, yielding maximum contact area.

With that said, your best bet is insert the wire into the water as spread out as will fit in the container. This allows maximum water circulation in contact with the wires.

The wire ends that are fan cooled should be spread out to fill the air stream from the fan. You might try with the fan blowing into the bundle of wires from the end, rather than across the bundle; in the ideal case,that should yield the greatest heat transfer. I realize your situation may not allow this air direction, next best is the most air movement you can get.

The desired result is to have maximum wire (heatsink) surface area exposed to where you want the heat transfer to occur.

Cheers,
Tom

256bits and Lnewqban
cool thanks I am off to make the oddest looking heat sink.

Tom.G