TY - JOUR TI - Fractional derivatives of constant and variable orders applied to anomalous relaxation models in heat transfer problems AU - Yang Xiao-Jun JN - Thermal Science PY - 2017 VL - 21 IS - 3 SP - 1161 EP - 1171 PT - Article AB - In this paper, we address a class of the fractional derivatives of constant and variable orders for the first time. Fractional-order relaxation equations of constants and variable orders in the sense of Caputo type are modeled from mathematical view of point. The comparative results of the anomalous relaxation among the various fractional derivatives are also given. They are very efficient in description of the complex phenomenon arising in heat transfer.