Choosing the Ideal Material and Thickness for Efficient Heat Conduction in a Parallelepiped

[Andrea Vee]

Hello, I have a parallelepiped that has all its faces in contact with air except one, which is in contact with a solid material. This parallelepiped produces 3 watts, and I want only one-tenth of it to be exchanged through conduction with the material. How do I decide which material to use and what thickness to choose?

 

[drawoh]

Andrea Vee,

Where does the rest of your heat go?

If you need 90% of your heat to be dumped into the ambient air, you need to control the air temperature and velocity. You need to model and analyze your whole system.

--
JHG

 

[IRstuff]

You control heat flow through materials, geometry, and ambient conditions.

The latter two can move more heat away from your structure, so lots of fins and forced convection, but material should still be aluminum or copper. Black objects radiate heat better, so blacken the structure and its fins.

You control heat flow to your solid through materials and geometry. You can employ thermal break materials like alumina or any of a number of thermal insulators, and you can minimize the cross-sectional area of the thermal contact.


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[3DDave]

It sounds like an algebra or calculus problem. At one extreme the material is so thin no heat escapes out the sides and at the other all heat escapes out the sides. You need an equation that represents the heat escaping out the sides and one that represents heat escaping out the face into the air, both dependent on thickness. Find the thickness that provides the desired ratio.

 

[BrianE22]

Compare convection/conductive thermal resistance of the side in contact to the 5 convective/conductive/convective resistances of the sides exposed to the air. Hint: the sides exposed to the air will have different resistances depending on how horizonal, vertical they are.