A Computational and Experimental Study of the Heat Transfer Properties of Nine Different Ionic Liquids

Abstract

New experimental thermal conductivity, density, viscosity, glass transition temperature, and heat capacity values were measured for nine ionic liquids (ILs): [emim]­[TFA], [emim]­[OTf], [emim]­[DEP], [emim]­[MeSO₃], [emim]­[SCN], [hmim]­[Tf₂N], [bDMApy]­[Tf₂N], [hDMApy]­[Tf₂N], and [hmDMApy]­[Tf₂N]. Classical molecular mechanics force fields were developed and used to calculate thermodynamic and transport properties for these ILs using molecular dynamics. Two versions of each force field were developed: one with integer charges of ± 1 and one with all charges scaled by 0.8. The force fields with total charges of ± 0.8 generally gave better agreement with experimental results. Very good agreement was obtained for density and heat capacity. Simulated values for thermal conductivity slightly overpredicted experimental results but captured trends between different ILs very well. Experimental Prandtl numbers were determined as a function of temperature and can exceed 10 000 at low temperature. Prandtl numbers on the order of 100–1000 were observed above 330 K. These values suggest that heat transfer with ionic liquids will be dominated by convective effects