It has been proved in the past, with common liquids, that the values of their thermophysical properties have a significant effect on the design of physicochemical processing and reaction units, influencing directly the design parameters and performance of equipment like heat exchangers, distillation columns, and reactors. In this paper we have analyzed the effect of the uncertainty of thermophysical data of ionic liquids (density, heat capacity, thermal conductivity, and viscosity) in the design of some current equipment, used in processes as solvents or heat transfer fluids. Data have been collected from the IL Thermo database for alkylmethylimidazolium (C n mim) liquids, with [BF 4 ] and [PF 6 ] anions. Results obtained show that the influence of actual errors in the thermophysical properties of ionic liquids can render any future design as not working or excessively costing. Moreover, the heat storage capacity of these ionic liquids has been analyzed, and it is possible to consider them as possible replacements of current silicon-based heat transfer fluids. The results obtained support that the implementation of those applications needs a careful selection of experimental data, otherwise equipment will be either under-or overdimensioned, with the consequent ill operation or increased capital costs. In addition, they recommend a revision of the present methods of measurement of thermophysical properties of ionic liquids and the establishment of reference data on thermophysical properties with low uncertainty, to avoid the actual status of experimental data.
Ionic liquids and ionanofluids were studied in recent years as possible alternatives to current engineering fluids, namely in the area of heat transfer. Excellent thermal properties, like high heat capacity per unit volume and thermal conductivity, allied to the dispersion of nanoparticles in them, have created great expectations, as the enhancement of their thermophysical properties liquids can contribute to better efficiency in heat transfer. The thermal conductivity of [P66614][N(CN)2], [P66614][Br], [C2mim][SCN], [C4mim][SCN], [C2mim][C(CN)3], and [C4mim][C(CN)3] in the temperature range of 293–343 K at 0.1 MPa and their ionanofluids with multiwalled carbon nanotubes are reported in the present work. While we could not obtain stable suspensions with phosphonium based ionic liquids, thermal conductivity enhancement of cyano-based ionic liquids was compared with our previous work using dicyanamide ionic liquids. The thermal conductivity of C2mim+ ionic liquids and ionanofluids is generally higher than the corresponding C4mim+ fluids. Temperature dependence of thermal conductivity enhancement hinders the conception of a unified thermal conductivity enhancement predictive model of the presented ionanofluids, current theories under-predicting its value for the dispersions studied. Finally, we selected a specific heat transfer process and calculated the heat transfer area necessary using currently commercialized heat transfer fluids, ionic liquids, and ionanofluids. While the addition of nanomaterial to the ionic liquids leads to an increase in the heat transfer available area, the enhancement of the thermophysical properties leads to a smaller variation of the area with temperature. Depending on the ionic liquid, some of the ionanofluids studied are head-to-head with a significant number of currently used heat transfer fluids concerning the heat transfer area necessary to transfer the same amount of heat.
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