The effects of forced convection on the power dissipation of constant-temperature thermal conductivity sensors

The effect of forced convection on the power dissipation of cylindrical and planar, constant temperature, thermal conductivity detectors (TCDs) is investigated theoretically. Such detectors can be used either for on-line continuous sensing of fluid thermal conductivity or for determining the sample concentrations in gas chromatography. A low peclet number, asymptotic theory is constructed to correlate the TCD's power dissipation with the Peclet number and to explain experimental observations. Subsequently, the effect of convection on the TCD's power dissipation is calculated numerically for both time-independent and time-dependent flows. The theoretical predictions are compared with experimental observations.