As
an improvement on imidazolium amino acid ionic liquids, three
ionic liquids, 1-ethyl-4-butyl-1,2,4-triazolium acetylglycine [Taz(2,4)][Acgly],
1-ethyl-4-butyl-1,2,4-triazolium acetylalanine [Taz(2,4)][Acala],
and 1-ethyl-4-butyl-1,2,4-triazolium acetylcysteine [Taz(2,4)][Accys],
were first synthesized for future application as heat-transfer media.
The density, surface tension, isobaric heat capacity, and thermal
conductivity were measured in different experimental temperature ranges.
Based on the above experimental data, the isobaric thermal expansibility
and isentropic and isothermal compressibility, as well as the isochoric
heat capacity and heat-storage density, were also calculated. Compared
with several popular commercial heat-transfer fluids, it was found
that the ionic liquids studied in this work have better performance
in terms of heat-storage density of ∼2.38 MJ·cm–3·K–1 and thermal conductivity of ∼0.197
W·m–1·K–1. In addition,
the viscosity was also determined, and the results showed an unexpected
reduction by the introduction of a small amount of water for ionic
liquids and almost no influence on other thermophysical properties.
Finally, we selected a specific heat-transfer process and calculated
the heat-transfer coefficient and the heat-transfer area based on
the thermophysical properties. Meanwhile, the lower liquid temperature
limit (∼229 K) and the nontoxic, environmentally friendly anion
could provide a wider and safer environment for the application of
ionic liquids. Given this, the ionic liquids studied in this work,
especially the [Taz(2,4)][Acgly], could be considered as promising
heat-transfer fluid candidates by appropriate adjustment of the water
content.
