GAS Analyser -1 (Thermal Conductivity Type)

Thermal Conductivity of Gases different and unique for all. So this property can be used to distinguish gas concentrations in a mixture of gases.

Thermal conductivity of a mixture of gas

where is the thermal conductivity of jth gas whose concentration is ,

so that

from the above equations its confirmed that concentration of a gas in a mixture of gases can be determined from the change in thermal conductivity.

Now we have to make out some way to measure the change in thermal conductivity by addition of the gas in the mixture. So how to measure thermal conductivity of a gas.

Simple, let it conduct heat and see how fast is it conducting. So the arrangement is a hot body surrounded by cold wall and between the hot n cold bodies the media is the "gas mixture". The gas mixture will conduct heat from the hot body(an electrically heated filament) to the surrounding relatively cool walls.

Heat Gained by hot body=

Heat Lost By hot body= Convection Loss+Conduction Loss+ Radiation Loss

At thermal equilibrium heat loss=heat gained

Now we have to monitor temperature at thermal equilibrium

References:

http://www.systechillinois.com/en/thermal-conductivity_52.html

http://www.hitech-inst.co.uk/thermal_conductivity_sensors.php