The role of heat flux in the nonsteady thermal problem of molybdenum sphere cooling in an electrostatic levitation experiment

The method for determining time dependences of the entropy-production density, force, and heat flux are presented. This method is based on processing the experimental thermogram at electrostatic levitation during spontaneous cooling of a solid molybdenum sphere. The results of numerical simulation of cooling a spherical sample from melting temperature $T_m \approx 2880$ K showed that the isothermal approximation for the temperature field in the sphere is valid, which made it possible to pass to the entropy density and calculate its production density. It is shown that heat flux in the nonsteady thermal problem under consideration determines the time dependence of the entropy production (it tends to the minimum zero value while approaching ambient temperature) and, therefore, is responsible for the validity of the extremum principle.