insulating two ends of a rod with another

[Engg56]

Hallo,
I have an aluminium rod (crossection: 10mx10m and Length: 80 mm, heat capacity 0.9) placed inside a chamber of 100m3. The rod consists of three sections along its length (20mm sections on both ends and a 40mm section in the middle). All sections are of aluminium.
I want to find out the influence of heat sources present in chamber on the ends of the rod (or locations where ends present inside the chamber). Thus I mounted two temperature sensors on the surface of the both sections on both ends.
The readings of the sensors would not be precise representation of the temperature of the ends due to heat flow (conduction) through the middle section. The middle section is mandatory in my system design. My idea is to replace the middle section with a section of an insulating material (eg. plastic). Which material should I select? The goal is to disconnect the heat flow between ends without inducing any other factor of measurement uncertainty. What factors to consider (eg. heat capacity).
Thnaks
simon

 

[EdStainless]

At what temp?

= = = = = = = = = = = = = = = = = = = =
P.E. Metallurgy, Plymouth Tube

 

[chicopee]

Draw a sketch showing chamber, rod placement, location(s) of heat source(s) and any existing insulation beside the replacement of the inner rod with non conductive material. Also EdStainless' inquiry is legitimate due to temperature limitation with plastic.

 

[IRstuff]

You have only 20mm of aluminum, so why bother keeping that tiny bit conductive? Why not make the rod out of alumina?

For that matter, in a 100 m^3 chamber, why would you expect much temperature gradient over 0.04 m?

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[chicopee]

To me, 10m X10m x 20mm long would not be considered rods but merely plates.

 

[Engg56]

a correction: ends are 10 mm each not 20 mm. A sketch is attached.

 

[IRstuff]

Again, given that you want 80% of it non-conductive, why not use wood or alumina?

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[dvd]

It is hard to beat "nothing" as a non-conductive medium. What is the point of the portion in the middle - why not engineer it out of the picture?

 

[Engg56]

The middle section can’t be replaced by anything to maintain the configuration of the original system and holding the rod inside the chamber. The relative temperature of the area inside the camber where 2 ends are present can very within 15 min time upto 15 mK.
Does a plastic insulator ensure me complete insulation between the ends? What to consider about the heat capacity of the insulation?

 

[IRstuff]

As yet, you still have not given the temperature range; it's unclear whether the temperature in your figure is the operational temperature or just an arbitrary example.

Insulators tend to have low heat capacities as well, since their density tends to help with thermal resistance. If 15C is a realistic temperature, then pretty much any insulator will work.

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[chicopee]

So are still dealing with plates 10mX10mx10mm or are the dimensions 10mx10m incorrect? There is a big difference on the application of heat transfer equations between plates and rods.

 

[Engg56]

The dimention are: 10 mm x 10 mm in crossection and 100 mm in length. Where 100 mm length consist of three sections 10+80+10 mm. The middle sections should be made of an insulator.
The temperatute in chamber of mostly 15 C°+/- 0.1C° but it can also be 20 C°+/- 0.1C° in very few cases.
Should the heat capacity of the selected insulator should match the heat capacity of aluminium (orignal material) for high accuracy of the temperature measurements on ends? I am considering Teflon due to heat capacity close to the heat capacity of the Aluminium (?)

 

[IRstuff]

Why do you need to worry about heat capacity?

Your statements are not making any sense. Why do you not want a continuous rod of the same insulator?

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[Engg56]

I have to have two ends of Aluminium in the system and can only replace the middle part.
I guess many insulators materials would work for this application. Heat capacities may not be a worry.

 

[chicopee]

Do a search of porcelain insulators. You may even be able to make you own kiln fired type.