Study on the Inverted Temperature Profile Based on Non-Equilibrium Molecular Dynamics(Thermal Engineering)

Abstract

Problem of the inverted temperature profile in condensation has been discussed at length in kinetic theory. The possible occurrence of the inverted temperature profile raised serious doubts about the validity of the previous theory, because the result seemed physically unreasonable. In this study, non-equilibrium molecular dynamics (NEMD) simulation with two facing surfaces of evaporation and condensation is carried out in order to obtain further evidence for the occurrence of the inverted temperature profile. Heat and mass transfer rates across the liquid-vapor interface during the condensation of argon are calculated for different non-equilibrium conditions given by changing the temperature of evaporating surface. From a view point of irreversible thermodynamics, the criteria for the inverted temperature profile are examined with the NEMD data and we have a conclusion that the inverted temperature profile may occur without contradiction to the second law of thermodynamics. In addition, we found that the molecular reflection at the condensing surface has an important role in the inverted temperature phenomenon. The reflected molecules do not accommodate with the condensing surface so that those molecules raise the temperature in the vicinity of the condensing surface under the non-equilibrium conditions.