2.2.4 Calculating the thermal conductivity Kp and Kn of the thermoelectric couple thermoelements (legs)

The thermal conductivity λ of each pellet can be found and/or measured, with a typical conductivity for a p-type Bi2Te3 thermoelectric pellet of around 1.2 � <sup>10</sup>�<sup>3</sup> W/cm K, and for an n-type Bi2Te3 pellet of 1.4 � <sup>10</sup>�<sup>3</sup> W/cm K [10]. The thermal conductivity Kp of the p-type thermoelement can be found by:

$$K\_p = \frac{\lambda\_p A\_p}{L\_p} \text{ measured in watts cm kelvin} \tag{6}$$

where λ<sup>p</sup> is the thermal conductivity of the pellet in watts/cm kelvin, Lp is the length of the pellet in cm, and Ap is the cross-sectional area of the pellet in cm<sup>2</sup> . Similarly, the thermal conductivity of the n-type pellet Kn can be found by:

$$K\_n = \frac{\lambda\_n A\_n}{L\_n} \text{ measured in watts cm kelvin} \tag{7}$$

It should be noted that the electrical resistivity ρ is the reciprocal of the electrical conductivity σ and can also be found using:

$$
\sigma = \frac{I \times L}{V \times A} \text{ measured in siemens} \tag{8}
$$

where I is the current through a constant cross-sectional area A and length L when a voltage V is applied [8].
