Heat Transport Properties of CO₂-Expanded Liquids: n-Hexane, n-Decane, and n-Tetradecane

Abstract

A number of processes involve liquids saturated with significant quantities of gases at elevated pressures, e.g., processes in gas- or CO2-expanded liquids (GXLs, CXLs), particle formation from gas or supercritical antisolvent methods (GAS, SAS, etc.), CO2 capture and sequestration, and enhanced oil recovery (EOR). In order to engineer these systems, the thermodynamic and transport properties are required. This contribution is one of the first reports for the heat transport properties of gas-expanded liquids at elevated pressures. The thermal conductivity, thermal diffusivity, and heat capacity are presented for binary systems of CO2 and the n-alkanes, n-hexane, n-decane, or n-tetradecane, at 25, 40, and 55 °C and pressures up to 106 bar. Equation of state modeling of literature vapor–liquid equilibrium data was used to determine the compositions at the conditions of the experimental heat transport measurements. All measured properties decrease with increasing composition of CO2 (pressure) in a relatively linear manner until a CO2 composition of approximately 70 mol %. The Prandtl number, Pr, is calculated and decreases with increased CO2 composition for all systems. However, as the fluid viscosity decreases with increased CO2, the heat transfer coefficient, h, in pipe flow would actually increase in a turbulent flow regime.

Thermal conductivity of the ionic liquid [HMIm][Tf2N] with compressed carbon dioxide

“…The nominal uncertainty associated with the thermal conductivity sensor given by the manufacturer is ±1%. However, we have measured the thermal conductivity of n ‐alkanes in a previous study 94 and found much less error; n ‐alkanes (e.g., C6–C14) have thermal conductivities that overlap those of the IL in this study. For instance, the difference between our measurements for n ‐hexane and n ‐tetradecane at three temperatures and well‐established experimental values had an average absolute relative deviation (AARD) of 0.25%.…”

“…We have recently reported the thermal conductivities of CO 2 saturated n-alkanes. 94 Tomida et al 95 with CO 2 (Table 1) have been measured and reported in this study.…”

“…Detailed analysis of the transient hot-wire method has been carried out by various investigative groups and the methodology has been reported in the literature. 94,98,99 We have previously reported on the use of this apparatus to measure the thermal conductivity of various systems such as CO 2 -expanded hydrocarbons. 94,100,101 An overview of the methodology will be given here.…”

“…94,98,99 We have previously reported on the use of this apparatus to measure the thermal conductivity of various systems such as CO 2 -expanded hydrocarbons. 94,100,101 An overview of the methodology will be given here. A transient-hot wire sensor manufactured by Flucon Fluid Control GmbH (Lambda instrument) has been coupled with a custom-built in-house high-pressure vessel with a view cell and an attachable heating/cooling jacket.…”

“…However, the availability in the literature of thermal conductivity data of any liquid saturated with any gas is scarce and for ILs, only a couple of studies exist. We have recently reported the thermal conductivities of CO 2 saturated n ‐alkanes 94 . Tomida et al 95 conducted one of the first studies on the thermal conductivity of sub‐saturated mixtures of CO 2 with the ILs 1‐butyl‐3‐methylimidazolium hexafluorophosphate ([BMIm][PF 6 ]) and 1‐butyl‐3‐methylimidazolium tetrafluoroborate ([BMIm][BF 4 ]) over a temperature range of 294–334 K and mole fractions of CO 2 up to 0.42.…”