Convection correction factor determination for use with the transient test method for thermoelectric modules

The transient test method used by TE Technology, Inc. requires a small temperature difference to be developed across a thermoelectric module in order to measure its figure-of-merit, Z. Correction factors associated with radiation, conduction, and convection must then be applied to the measurements in order to determine the actual Z of the N and P average of the thermoelectric materials comprising the module. The accuracy of these correction factors will affect the accuracy of the Z. Radiation and conduction can be calculated with the same accuracy regardless of the size of the module, but convection is inherently size dependent. Factoring in the temperature dependence for convection is also more complex. Therefore, several different sizes of modules were measured in air and in vacuum. Comparison between the Z measured in vacuum and in air were used to test the validity of convection correlations as applied to thermoelectric modules. Recommendations are made for the best correlation to use in determining the convection correction factor.