[C₂mim][CH₃SO₃]─A Suitable New Heat Transfer Fluid? Part 2: Thermophysical Properties of Its Mixtures with Water

Abstract

Ionic liquids have proved to be excellent heat transfer fluids and alternatives to common HTFs used in industries for heat exchangers and other heat transfer equipment. However, its industrial utilization depends on the cost per kg of its production, to be competitive for industrial applications with biphenyl and diphenyl oxide, alkylated aromatics, and dimethyl polysiloxane oils, which degrade above 200 °C and possess some environmental problems. The efficiency of a heat transfer fluid depends on the fundamental thermophysical properties influencing convective heat transfer (density, heat capacity, thermal conductivity, and viscosity), as these properties are necessary to calculate the heat transfer coefficients for different heat exchanger geometries. In Part 1, the thermophysical properties of pure 1-ethyl-3-methylimidazolium methanesulfonate [C2mim]­[CH3SO3] (CAS no. 145022-45-3), (ECOENG 110), produced by BASF, under the trade name of Basionics ST35, with an assay ≥97% with ≤0.5% water and ≤2% chloride (Cl–), were presented, for temperatures slightly below room temperature and up to 355 K. In this paper, we report the thermophysical properties of mixtures of [C2mim]­[CH3SO3] with water, in the whole concentration range, at P = 0.1 MPa. The properties measured were density and speed of sound (293.15 < T/K < 343.15), viscosity, electrical and thermal conductivities, refractive index (293.15 < T/K < 353.15), and infinite dilution diffusion coefficient of the ionic liquid in water (298.15 K). The properties for the mixture like the isobaric expansion coefficient, the isentropic compressibility, apparent molar volumes, apparent molar isentropic compressions, and the thermodynamic excess properties, like excess molar volume, excess molar isobaric expansion and isentropic compression, excess viscosity, thermal conductivity, molar refraction, and infinite dilution diffusion coefficients of the cation, anion and other common anions in ionic liquids were obtained within this temperature range. The validity of the Walden relation for this ionic liquid was also determined. This amount of experimental information, in addition to recent molecular simulation studies available in the literature give a clear picture of the structure of these binary mixtures and the influence of composition and temperature, paving the way to a technological discussion of the possible application of these mixtures as new heat transfer fluids or battery electrolytes.

The Density, Speed of Sound, Viscosity, and Thermal Conductivity of 1-Dodecyl-3-methylimidazolium Bis(trifluoromethylsulfonyl)imide and Its Ionanofluid with Graphene

“…The thermomechanical coefficients (isobaric expansivity, α P , isothermal compressibility, κ T , and isentropic compressibility, κ S ), which can provide useful information about an ionic liquid’s structure and molecular interactions, can be easily derived from eqs –): α P = − true( 1 ρ true) true( ∂ ρ ∂ T true) P κ T = κ S + T V m α P 2 C P , m κ S = 1 ρ c 2 where κ S , T , V m , and C P ,m are the isentropic compressibility, temperature, molar volume, and molar isobaric heat capacity of the liquid, respectively. The possible existence of ultrasound absorption, as discussed for [C 2 mim][CH 3 SO 3 ] and as previously discussed by Dzida et al, would originate a lack of reproducibility of the measurements, which was not found for the systems studied here. Therefore, we can conclude that the speed of sound can be considered a pure thermodynamic property, and eq is applicable.…”

“…The previous analysis showed that the thermal conductivity of water was measured within a value of 0.8%, thus justifying our uncertainty estimate of 2%. The measurements for [C 12 mim][(CF 3 SO 2 ) 2 N] were performed in the LOW heating mode, , and the assumed linear variation transient temperature rise of the hot-wire with the logarithm of time, as given by the theory of the transient hot-wire (THW) method, was confirmed. Figure shows examples of two of the runs, one at 299.92 K and one at 347.95 K, using a heat input per unit length of wire of Q = 0.913 W/m, with a total temperature rise of 1.59 and 1.22 K, respectively.…”

“…The presence of the big anion [(CF 3 SO 2 ) 2 N] − and its interactions with the nanographene platelets and MWCNT’s must not contribute positively to the mechanism of heat transfer and to the storage capacity. However, the pure ionic liquid [C 12 mim][(CF 3 SO 2 ) 2 N], with its high heat capacity and thermal conductivity, may be a good choice for these applications, specifically by using dilute water mixtures, like what has been done for [C 2 mim][CH 3 SO 3 ]. ,, …”

“…The experimental methods that were used in the present work and their validations have been fully described in previous publications, and readers may refer to these details in refs and . Briefly, the following instruments were employed: a density and sound velocity meter (Anton Paar GmbH, DSA 5000 M) with the expanded uncertainties ( k = 2) U (ρ) = 0.60 kg·m –3 and U ( c ) = 1 m·s –1 , respectively; a micro-Ubbelohde viscometer (SCHOTT Instruments GmbH) for measuring the kinematic viscosity, with an expanded relative uncertainty for the dynamic viscosity (using our own data on density) of U r (η) = 0.012; and a rheometer (TA Instruments AR1500EX) for measuring the dynamic viscosity with an expanded relative uncertainty of U r (η) = 0.05.…”

Possible New Heat Transfer Fluid: The IoNanofluid of 1-Ethyl-3-methylimidazolium Dicyanamide + Nano-Titanium Oxide─Studying Its Thermal Conductivity and Viscosity

“…Thermal conductivity, λ , measurements were performed at temperatures 295.06 < T /K < 345.55, using commercial equipment from Hukseflux Thermal Sensors TPSYS02 and a non-steady-state probe (NSSP) TP08, SN# 283, with a temperature standard uncertainty of u ( T ) = 0.02 K, as reported earlier . Measurements with water permitted the validation of the probe operation, as described in a recent publication, with data obtained between 300 and 350 K not deviating from the standard reference data value (IUPAC SRD correlation) by more than 0.5%, as obtained before.…”