CORRECTIVE MODEL OF THE GAS TEMPERATURE T HERMOCOUPLE MEASURE - APPLICATION TO AN IMPORTANT THERMAL-GRADIENT ZONE

The gas temperature measurement with a thermocouple in important therm al gradient zones requires a corrective model. For example, such zones exist for thermal boundary layers near active walls. We have calculat ed these thermocouple thermal exchanges where connection wires are con sidered as fins with a variable ambient gas temperature. The heat exch anges by convection and radiation on the thermocouple head are analyti cally calculated, then a numerical method is used for fins where the s pace increment is the same as for the experimental measure. The correc tive model in steady state is semi-analytical. Its validation is made with experimental results from studies of flows along a non-isothermal vertical wall in a cavity filled with wet air. Several applications a re offered for many thermal curves, for more important gradient zones corrections are larger than 1.5 K for a K type thermocouple of 0.08 mm wire diameter.