Conventional techniques for thermal conductivity measurements can lead to unreliable results when

applied to nanostructures because heaters and temperature sensors needed for the measurement cannot

have a negligible size and therefore perturb the result. In this paper, we focus on the 3 omega technique,

applied to the evaluation of the thermal conductivity of suspended silicon nanoribbons. We introduce a

numerical approach based on the finite element solution of the electrical and thermal transport equations

and compare its results with those of conventional methods. We show that with our approach we achieve

an excellent fit of the experimental data, in particular.