Thermal Properties of Ionic Liquids and IoNanofluids of Imidazolium and Pyrrolidinium Liquids

Abstract

Complex systems based on nanomaterials and common solvents have been shown to have thermophysical properties that can revolutionize current utilization of heat transfer fluids and heat storage cycles. This has been made possible by the existence of thermal conductivity enhancements derived from the presence of additional mechanisms of heat transfer in comparison with the base solvent. Ionic liquids have been shown to have thermophysical properties that justify the replacement of several of the chemical processes now under exploitation, and some of the solvents used, because they can in certain conditions, be considered as green solvents. Dissolving (or mixing as a thermally stable suspension) nanoparticles in ionic liquids, forms “bucky gels”, or IoNanoFluids, which we have recently shown to have thermal conductivity enhancements ranging from (5 to 35) %. This paper reports data on the thermal conductivity of the ionic liquids 1-hexyl-3-methylimidazolium tetrafluoroborate (CAS Number, 244193-50-8), [C6mim][BF4], 1-butyl-3-methylimidazolium hexafluorophosphate (CAS Number, 174501-64-5), [C4mim][PF6], 1-hexyl-3-methylimidazolium hexafluorophosphate (CAS Number, 304680-35-1), [C6mim][PF6], 1-butyl-3-methylimidazolium trifluoromethanesulfonate (CAS Number, 174899-66-2), [C4mim][CF3SO3], and 1-butyl-1-methylpyrrolidinium bis{(trifluoromethyl)sulfonyl}imide (CAS Number, 223437-11-4), [C4mpyrr][(CF3SO2)2N], and IoNanofluids with multiwalled carbon nanotubes (MWCNTs) as a function of temperature and discuss the molecular theories of heat transfer and storage in these types of systems. Moderate thermal conductivity enhancements, between (2 and 9) %, were found for the systems studied, showing a week dependence on temperature. It also reports heat capacity values for [C4mim][BF4] and [C4mim][PF6]. Values of the heat capacity of an IoNanofluid, C4mim][PF6] with (1 and 1.5) % Baytubes, are reported for the first time, showing also an enhancement (8 %), a fact that deserves further investigation in a near future. The behavior of these nanofluids, along with that of ionic liquids of the type studied, suggests that nanocluster formation and preferred paths for heat transfer and storage are present and are likely to be the cause of the phenomena found. However, existing theories cannot yet explain the results obtained.

Current research and future applications of nano- and ionano-fluids

“…Results from our studies [7][8]36] showed that ionanofluids containing MWCNT exhibit enhanced thermal conductivity and specific heat capacity compared to their base ionic liquids, a fact confirmed by [42].These properties further increase with concentration of nanoparticles and fluid temperature in some extend. Other attractive features of ionanofluids are that they are designable and fine-tuneable through their base ionic liquids for desired properties and tasks.…”

“…Recent studies of this group [7][8] showed that ionanofluids containing multi-walled carbon nanotubes (MWCNT) exhibit significantly higher thermal conductivity and specific heat capacity compared to their base ionic liquids and they further increase with temperature and loading of MWCNT.…”

“…Results from our primary studies [7][8] Thermal conductivity ratio (k inf /k f ) Figure 5. Thermal conductivity enhancement of ionanofluids as a function of MWCNT concentration [35].…”

Thermally conductive of nanofluid from surfactant doped polyaniline nanoparticle and deep eutectic ionic liquid

“…In this study, DBSA-PANI nanoparticles acted as surfactant and dopant [3]. DBSA modified the surface of nanoparticles and improved the stability of nanofluids [2,7] while water played as another hydrogen bond donor in this case [10,18]. Interaction of dopants and DES ions was also revealed to contribute to enhancement in thermal conductivity of DES based nanofluids.…”

“…The term of ionanofluid was defined as dispersion containing nanomaterials and ionic liquids [10]. Ionic liquids are advanced due to their high density, good heat capacity, good thermal and chemical stability and low vapor pressure [13].…”