Measurement of the Thermal Conductivity of Gases, Liquids, Nanofluids, Melts & Solids: Is the Transient Hot-Wire Technique the Answer to Everything?

Abstract

In a recent paper the historical evolution of the transient hot-wire technique was presented [1]. In this paper the main emphasis is on theory and the applications. The theory of the technique, as well as the restrictions imposed by the analytic solution of the governing heat-transfer equations are examined. The effects of convection, radiation, finite wire properties, wire diameter and variable fluid properties on the ideal heat transfer model are depicted through examples and prove the need for correct application of the technique. On the other hand, the use of the finite elements has extended the application of the technique to the measurement of the thermal conductivity of melts and solids. The methodology followed in the creation of the finite element model is analyzed and the steps to acquire the thermal conductivity value are described. For all cases (fluids, solids and melts) an uncertainty analysis is provided.