Method and apparatus for determining specific thermal conductivity parameters of gases

摘要

A method of determining a specific thermal conductivity parameter of a target gas having a known general thermal conductivity and being contained at a concentration of interest in a fluid medium (F) and comprising: contacting said fluid medium with an organic polymer membrane (11) provided at an interface between said fluid medium (F) and a sensing volume (12) containing a thermal conductivity sensor (13); the membrane (11) is substantially impermeable for any liquid components of the fluid medium (F) but has a known permeability for the target gas; the sensing volume (12) is periodically purged or flushed with a gas having a general thermal conductivity that differs from the thermal conductivity of the target gas; permeation of the target gas through the membrane (11) into the sensing volume (12) is permitted intermittently; at least one time-dependent parameter of the known general thermal conductivity of the target gas that has permeated into the sensing volume (12) is measured; and a parameter of analytical interest, e.g. a partial pressure of the target gas in the fluid (F), is calculated (14, 15) from the time-dependent value obtained and the predetermined permeability of membrane (11) for the target gas.