Thermal conductivity measurement of fluids using the 3omega method

Area of Science:

• Materials Science
• Thermodynamics
• Fluid Dynamics

Background:

• Accurate measurement of thermal conductivity is crucial for understanding heat transfer in dielectric fluids.
• Existing methods may have limitations in accuracy or applicability to various fluid states.

Purpose of the Study:

• To develop and validate a new procedure for measuring the thermal conductivity of dielectric liquids and gases.
• To assess the method's capability in determining volumetric heat capacity and thermal boundary conductance.

Main Methods:

• Utilized a steady-state AC hot-wire technique with a thin metal wire as both heater and thermometer.
• Employed a four-probe geometry and an electronic circuit adapted from the conventional 3omega method.
• Processed raw data through a transformation to a linear logarithmic frequency dependence plot.

Main Results:

• Successfully measured thermal conductivity for air, water, ethanol, monoethylene glycol, and tetraethylene glycol.
• Identified an optimal frequency region for accurate thermal conductivity data extraction.
• Calculated volumetric heat capacity with associated uncertainty.

Conclusions:

• The developed AC hot-wire method provides a reliable approach for determining the thermal conductivity of dielectric fluids.
• The technique offers potential for probing metal-liquid thermal boundary conductance.
• The data transformation method enhances the clarity and accuracy of thermal property measurements.