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You may wish to contact an evitherm expert in your area or language for the thermal property of interest.

Thermal property

Link

Notes

Emissivity / infrared-optical

evitherm

A list of evitherm project members who are willing to be approached for finding data

Expansivity / density

evitherm

A list of evitherm project members who are willing to be approached for finding data

Heat capacity / enthalpy

evitherm

A list of evitherm project members who are willing to be approached for finding data

Thermal conductivity / diffusivity

evitherm

A list of evitherm project members who are willing to be approached for finding data

Alternatively, evitherm subscribers may wish to use the evitherm Advice line.

 

Estimate data

Often, thermal conductivity is known for a dense material but is required for a porous version of the material. For porosities lower than 25% there are theoretical models to estimate thermal conductivity. One such example is given below.

λ thermal conductivity of the porous material

λ0 thermal conductivity of the dense material (continuous phase)

λP thermal conductivity of the pores (discontinuous phase)

P porosity (total pore volume)

a anisotropy factor

   


Thermal conductivity of alumina at various temperatures as a function of the porosity P calculated using the equation for thermal conductivity given below.

If the discontinuous phase is a low conducting gas and the material is isotropic, λP and a can be neglected and the thermal conductivity λ of the porous material can be calculated using the equation:

The above is one of the models described by H Kaempf and G Karsten in Effects of different types of void volumes on the radial temperature distribution of fuel pins (Nucl. Appl. Tech., 9, 288-300, 1970). Other models take account of various stereometric factors. Here are some references if you wish to delve further:

-   Die Wärmeleitfähigkeit keramischer feuerfester Stoffe, A Euken, VDI-Forschungsheft No. 353, VDI-Verlag, Düsseldorf, 1961

-   A mathematical treatment of the electric conductivity and capacity of disperse systems, H Fricke, Phys Rev, vol 24, 1924, 575-587

-   A theory of thermal conductivity of porous materials, A L Loeb, J Am Ceram Soc, 37, 1954, 96-99

-   Relation between stereometric microstructure and properties of cermets and porous materials, S Nazaré, G Ondracek, F Thümmler, in H H Hausner (ed), Modern developments in powder metallurgy, Plenum Press, New York, London, 1971, pp 171-186.

Data estimation tools may be found at the websites below:

Data estimator

Material

Notes

PoLyInfo

Link

Polymers

PoLyInfo, from the Japanese National Institute for Materials Science, is a database of synthetic polymers, providing information required for material design. The data originate from scientific journals.

Thermal conductivity calculator

Link

Metals, alloys

Using the Wiedemann-Franz law to calculate thermal conductivity form electrical resistivity. Applicable to metals and some alloys.

 

Data in the literature

You may wish to consult the following possible data sources:

Data source

Material

Notes

CRC Handbook of Chemistry and Physics, 84th Ed.

Link

Compounds, metals, ceramics, polymers, etc.

Data for chemists, physicists and engineers can be found in this well-known reference book. The website shows all the chapter headings; includes key thermal properties

Tables of physical and chemical constants, by Kaye & Laby (16th ed, pub Longman, 1995, ISBN 0582226295)

Link

Elements, common materials, metals, alloys, polymers, gases, etc.

Physical constants, thermal and other properties. Has been a longstanding reference for labs, schools and universities. An online version version is now available free from NPL.

 

Make a measurement

The most reliable way to find thermal property data is by measurement of samples of the required material. Evitherm provides links to measurement services . To choose the laboratory with the most suitable measurement technique you should take into account the following important criteria:

- type of material
- sample geometry
- temperature range

If you wish to make measurements yourself then you may wish to select a measurement equipment supplier from the evitherm database. For advice on the measurement method you may wish to visit the Measurement methods section of the technical area of interest, whether thermal conductivity, expansivity, emissivity or whatever. Select the technical title of interest from the coloured beans on the home page .

However, note that even if a commercial measurement apparatus is available, experience in its operation is vital to ensure valid measurements. It takes a long time to gain this experience and you may wish to accelerate this learning process by seeing where there is training in your area.

 

Model data

If uncertainties of 20-30 per cent or more are acceptable then it is possible in many cases to calculate thermal properties using thermodynamics. Examples include:

eFoodSolver (for foods, from Prof R P Singh at University of California's Food Engineering Lab - users input the material composition and the solver calculates the required thermal property)

MTDATA (from NPL, a software/data package for calculation of phase equilibria in multi-component multiphase systems using, as a basis, critically assessed thermodynamic data)


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