How to determine the thermal conductivity of a mixture of solid powders ?

Looking for Materials with high thermal expansion coefficient and high temperature resistance?

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1 nm thick MgO thin-film to be deposited on Si wafer using thermal evaporation. What will be the optimum deposition conditions?

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Why do a weight decrease for thermal degradation in nitrogen gas condition?

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Can thermal cycler machines be problematic during PCR?

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Modeling viscosity using model of Chung?

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How to increase solubility of Poly acrylic acid in Dioxane solvent?

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Dudley J Benton

This is an illusive task. You could measure the thermal conductivity of the same sample a hundred times and get a hundred different values. The bigger issue is, "Why do you need to know this?" It would be unwise to design a process that depends on transferring heat to or from a powder. Take coal ash, for example. It starts out hot and cools down as it is separated and stored for disposal but the process (i.e., boiler) doesn't depend on heat transfer to or from the ash, even though we correct the boiler efficiency to account for the energy in the coal ash stream.

Ersin Sayar

Are you seeking an experimental procedure or a theoretical one?

Ulrich Deiters

I agree with Dudley J Benton : Your task is rather indefined. The heat transmission through a powder also depends on the particle size, the pressure one exerts on the sample, and on the gas or liquid in your sample. Moreover, it may well be that the same sample may give different results once you shake it.

Jayashri Sehajpal

Thanks Ulrich Deiters and Ersin Sayar actually using the powder mixture we have made pellets with density ranging from 1.6 to 1.9 gram/ cc , the material comprises of a mixture of two powders one has k = 0.5 W/mK (powder A) and other has around k = 27 W/mK (powder B) , they are mixed in different ratios to obtain different pellets with density varying as mentioned above. I want to find the thermal conductivity of my pellets. In one paper they have mentioned that for 30% of powder A and 70% of powder B and final density of pellet 1.8 gram/ cc the k comes out to be 1.6 W/mK , they calculated this using predictor equation. Can I please ask what is this predictor equation and how I can use it to determine my desired thermal conductivity values for the pellets.

Jack Broughton

The conductivity depends more on the fluid properties than the solid. I suggest that you get a text on packed bed behaviour as the conductivity is not a simple issue due to variable voidage and surface properties. At high (and very low) temperatures radiative heat transfer becomes significant.