THERMODYNAMIC STABILITY AND TEMPERATURE OVERSHOOTING IN DUAL-PHASE-LAG HEAT-TRANSFER

The dual-phase-lag model in heat transfer includes relaxation times fo r the heat flux and for the temperature gradient. Here we show that a thermodynamic stability analysis suggests that the initial value for t he temperature gradient cannot be arbitrarily high but it is bounded b y 1.42(T/tau(T)), with T the initial value of the local temperature an d t(T) the relaxation time of the temperature gradient. This could res trict the possibility of observing the temperature overshooting predic ted by the dynamical equations. (C) 1998 Elsevier Science B.V.