Performance analysis of annular finned tubes with orthotropic fin and tube material properties

A numerical and experimental study has been carried out to compute and measure the performance of annular fin and tubes with orthotropic thermal conductivities, made by using the injection-molding technique.Three materials have been tested specifically, a low orthotropic conductive, high orthotropic conductive and isotropic material. The fin efficiency and thermal power has been computed, using a finite difference method, and is checked with CFD. The influence of fin length and fin thickness has been studied on fin performance. To study the effects of carbon fibres inside of the polymer matrix, the influence of conductivity ratio, the ratio of radial to axial thermal conductivity, and radial conductivity on fin performance is studied as well. Thermal conductivity ratio has virtually no influence on fin efficiency. Performance of fins drops when the conductivity ratio is lower than 0.2 and the conductivity in the fillers direction is less than 4. Numerical results are also compared to experimental results, where the radial temperature distribution in a carbon fibre reinforced composite material, CF30 is measured, using a thermal camera. Fin power and fin efficiency is overestimated in the numerical model, by 44.8% and 23.4% respectively. This deviation can be explained by a not accurately knowing of the convection coefficient around the fin, or the accurate knowledge of the radial thermal conductivity.