Thermal Conductivity and Thermal Diffusivity of Sixteen Isomers of Alkanes: CnH2n+2 (n = 6 to 8)

Experimental values of the thermal conductivity λ and thermal diffusivity κ of sixteen pure branched alkanes (C n H 2 n +2; n = 6 to 8) are presented in the temperature range −15 °C to 70 °C under atmospheric or saturation pressure. Measurements were made with the transient hot-wire method, and in the analysis, the temperatures T λ and T κ (associated with both λ and κ ) were used. The thermal diffusivity values are corrected by the factors k f (=1.0076 to 0.9892), which are determined by reference to the heat capacity (at 298.15 K) of heptane as a reference material, for data sets obtained with different configurations of the experiments. Heat capacities [volumic, c p ρ; specific, c p; and molar, C m,p ] are derived from the relationship c p ρ = λ / κ, with values for the density and the molar mass. The relevance of these thermal properties to the boiling point, density, molar density, and velocity-of-sound is examined, together with the results of normal alkanes ( n = 6 to 8) and isopentane. The uncertainty of the data is estimated to be 0.4% for the thermal conductivity (absolutely measured) and about 1.8% for the thermal diffusivity (with a coverage factor k p = 2; p = 95%), although that of λ (not for κ ) is possibly inferior for a few substances containing a little larger impurity (i.e. mainly other isomers).