title: Absolute Steady-State Thermal Conductivity Measurements by Use of a Transient Hot-Wire System.
abstract: A transient hot-wire apparatus was used to measure the thermal conductivity of argon with both steady-state and transient methods. The effects of wire diameter, eccentricity of the wire in the cavity, axial conduction, and natural convection were accounted for in the analysis of the steady-state measurements. Based on measurements on argon, the relative uncertainty at the 95 % level of confidence of the new steady-state measurements is 2 % at low densities. Using the same hot wires, the relative uncertainty of the transient measurements is 1 % at the 95 % level of confidence. This is the first report of thermal conductivity measurements made by two different methods in the same apparatus. The steady-state method is shown to complement normal transient measurements at low densities, particularly for fluids where the thermophysical properties at low densities are not known with high accuracy.
authors.affiliation: National Institute of Standards and Technology, Boulder, CO 80303, USA.
authors.forename: H M
authors.initials: HM
authors.lastname: Roder
authors.affiliation: National Institute of Standards and Technology, Boulder, CO 80303, USA.
authors.forename: R A
authors.initials: RA
authors.lastname: Perkins
authors.affiliation: National Institute of Standards and Technology, Boulder, CO 80303, USA.
authors.forename: A
authors.initials: A
authors.lastname: Laesecke
authors.affiliation: Departamento de Qumica and Centro de Cincias da Universidade de Lisboa, 1700 Lisboa, Portugal.
authors.forename: C A
authors.initials: CA
authors.lastname: Nieto de Castro
keywords: argon; convection; dilute gas; hot wire instrument; steady state; thermal conductivity; transient