وبلاگ تخصصی ابزاردقیق و اتوماسیون

Composition measurement by detecting the thermal conductivity of gases is one of the simplest and oldest methods of analyzing process streams. Early developments by the British resulted in an instrument of this type, which was called a katharometer or catharometer . The name still persists in Europe.

This technique takes advantage of the facts that different substances have a varying capacity to conduct heat energy from a heat source. This ability differs for each gas. It is called thermal conductivity and can be expressed in various unit systems and so on. This is a simple, rugged, inexpensive, reliable, and easily maintained, but nonspecific, analyzer that can determine the composition of only binary mixtures. It is not very sensitive, nor is it very fast, but it is well suited for many chromatographic and leak detection applications.THERMAL CONDUCTIVITY Thermal conductivity is often expressed as a factor relating the ability of a particular gas to conduct heat to that of air at various temperatures (Table 8.57a). In practice, continuous thermal conductivity analyzers measure a change in heat dissipation by comparing the change with a reference condition.It has been known for more than a century that the heatconducting ability of various gases differs considerably. Therefore, by measuring the thermal conductivity of a binary mixture, one can determine the composition of the mixture. The accuracy of the measurement is a function of the reliability of the thermal conductivity data used for the gases making up the mixture, and those data are not always accurate.