Precise Measurements of the Thermal Conductivity of Toluene and n-Heptane by the Absolute Transient Hot-Wire Method

For the purpose of obtaining precise liquid thermal conductivity data as standard reference values, a new high-precision instrument, which is based upon the absolute transient hot-wire method, has been developed. A newly built digital system is used in this instrument for recording the transient temperature rise, which eliminates the conventional difficulty of this method. The thermal conductivities of toluene and n-heptane, reference substances suggested for the liquid thermal conductivity standard, have been measured in the temperature range 0-90 ° at atmospheric pressure. The accuracy of the present measurements is estimated as ±0.5%.