“…The coaxial-cylinder technique is a steady-state method which measures the heat exchange by conduction between two concentric cylindrical surfaces separated by a small gap fi lled with the fl uid sample, each of these surfaces being maintained at constant temperature. This technique was successfully employed to measure the thermal conductivity of pure fl uids (H 2 O, CO 2 , NH 3 , Ar, N 2 , C 2 H 6 , C 3 H 8 ) at high temperatures (Vargaftik and Smirnova, 1956;Ziebland, 1958;Ziebland and Burton, 1960;Vines, 1960;Bailey and Kellner, 1967;and Yata et al, 1979b). The method was considerably improved by Le Neindre and co-authors (Le Neindre, 1969;Tufeu 1971;Le Neindre et al, 1984).…”