Molecular dynamics simulation of homogeneous condensation and thermophysical properties of R245fa/R141b

Abstract

The use of zeotropic mixture is an effective way to improve the thermodynamic performance of organic Rankine cycle. The thermophysical properties and homogeneous condensation of zeotropic mixtures are of great significance for the design of condensers. This work conducted molecular dynamics (MD) simulation to investigate the homogeneous condensation and thermophysical properties of R245fa/R141b at various oil concentrations and mixing ratios. MD simulations provided thermophysical properties such as liquid density, specific heat capacity, internal potential energy, radial distribution function, mean squared distribution and cluster formation. The results show that simulated density and specific heat capacity of R245fa/R141b under different R245fa ratios agree well with the data from Nist Refprop 9.1. The condensation rate of R245fa/R141b is lower at higher oil concentrations or lower R245fa ratios. During condensation, the total potential energy of the system decreases rapidly, and the van der Waals energy is the main factor for the reduction. In addition, the internal molecule structure of the fluids does not change during condensation.