Computational analysis of heat rectification in composition-graded systems: From macro-to-nanoscale

The heat rectification coefficient of a composition-graded system of the type A(x)B(1-x),, with A and B being theoretical materials, and composition x changing along the length of the system, is considered. By starting from a mathematical model for the thermal conductivity of the material lambda in terms of temperature T and composition x, the influence of composition spatial distribution, heat flux, length of the system, and minimum of lambda(T, x) on the rectification coefficient is explored. In some circumstances, a reversal in the direction of the rectification is observed for increasing heat flux. (C) 2015 Elsevier B.V. All rights reserved.