Thermocouple Sensor Response in Hot Airstream

Area of Science:

• Thermodynamics
• Fluid Mechanics
• Sensor Technology

Background:

• Temperature sensor response in gas streams is complex, influenced by heat transfer.
• Thermocouple hot junction temperatures are lower than stream temperatures, causing measurement errors.
• Sensor dynamics models are crucial for accurate temperature interpretation.

Purpose of the Study:

• To develop a method for identifying temperature sensor models using numerical modeling.
• To investigate the influence of fluid stream velocity and sensor geometry on sensor dynamics.
• To quantify the impact of radiative heat transfer on sensor model coefficients.

Main Methods:

• Finite element method (FEM) to solve transient heat transfer and fluid flow equations for sensor geometry.
• Numerical modeling of sensor response to fluid temperature changes.
• Model coefficient estimation using recorded input/output signal waveforms.

Main Results:

• A first-order transfer function effectively models bare-bead thermocouple sensor dynamics.
• Stream velocity and sensor wire diameter significantly affect transfer function gain and time constant.
• Radiative heat transfer influences sensor model coefficients.

Conclusions:

• The proposed method accurately identifies temperature sensor dynamics.
• Quantitative models demonstrate how stream velocity and geometry impact sensor response.
• Accurate sensor modeling is essential for reliable temperature measurements in dynamic environments.