Thermal Conductivity, Thermal Diffusivity, and Heat Capacity of Gaseous Argon and Nitrogen

Abstract

Low-pressure thermal conductivity and thermal diffusivity measurements are reported for argon and nitrogen in the temperature range from 295 to 350 K at pressures from 0.34 to 6.9 MPa using an absolute transient hot-wire instrument. Thermal conductivity measurements were also made with the same instrument in its steady-state mode of operation. The measurements are estimated to have an uncertainty of 1% for the transient thermal conductivity, 3% for the steady-state thermal conductivity, and 4% for thermal diffusivity. The values of isobaric specific heat, derived from the measured thermal conductivity and thermal diffusivity, are considered accurate to 5% although this is dependent upon the uncertainty of the equation of state utilized.

Determining Thermal Conductivity and Thermal Diffusivity of Low-Density Gases Using the Transient Short-Hot-Wire Method

“…It is worth mentioning that natural convection effects decrease dramatically as the density of the gas is reduced [3,6]. In fact, this principle is usually used to justify neglecting natural convection effects in the steady hot-wire method for measuring thermal conductivity.…”

“…Moreover, for refrigerants below the critical pressure, sometimes it is not even possible to extrapolate from high-density vapor data since the fluid becomes a liquid as the pressure is raised [2]. These considerations have motivated a number of authors to propose schemes to make the transient hot-wire method more applicable to measurements in low-density gas [2,5,6]. Analytical corrections are available for the outer boundary effect [1], but the accuracy of the method diminishes as the linear section of the curve becomes shorter and shorter [3].…”

“…One of the most successful methods is to use two wires of different lengths (e.g., [6,7]). A different approach is to attach potential taps offset from the ends to measure the voltage across the central region of the wire (e.g., [8]).…”

Measurements of the Thermal Conductivity of l-Menthol–Decanoic Acid Deep Eutectic Solvents in the Temperature Range from 283.15 to 363.15 K at Pressures up to 15.1 MPa

“…The combined expanded uncertainties U c (0.95 level of confidence, k = 2) were U c (T) = 50 mK, U c (P) = 0.01P, and U c (λ) = 0.02λ. b Deviation = 100•(λ exp − λ lit )/λ lit , where λ exp is the experimental thermal conductivity of toluene and λ lit is the value calculated from the reference correlation for toluene proposed by Sun et al46 …”