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A High-Temperature Transient Hot-Wire Thermal Conductivity Apparatus for Fluids
R A Perkins1, H M Roder1, C A Nieto de Castro2
1National Institute of Standards and Technology, Boulder, CO 80303.
Summary
A new apparatus accurately measures fluid thermal conductivity and diffusivity using a transient hot-wire technique. This instrument provides precise data for fluids like toluene, argon, and nitrogen.
Area of Science:
- Thermodynamics
- Fluid dynamics
- Materials science
Background:
- Accurate measurement of thermophysical properties is crucial for fluid characterization.
- Existing methods may have limitations in temperature, pressure, or accuracy.
- Transient hot-wire techniques offer potential for precise measurements.
Purpose of the Study:
- To develop and describe a novel apparatus for measuring thermal conductivity and diffusivity of fluids.
- To validate the instrument's performance using well-characterized fluids.
- To present new thermal property data for liquid toluene, including radiation effects.
Main Methods:
- Utilizes a step-power-forced transient hot-wire technique with two platinum wires.
- Employs a Wheatstone bridge configuration for differential measurement.
- Automated control and data acquisition using a microcomputer.
Main Results:
- The apparatus measures thermal conductivity and diffusivity for fluids between 220-775 K and up to 70 MPa.
- Verified performance with measurements on liquid toluene, argon, and nitrogen.
- Reported new, radiation-corrected thermal conductivity data for liquid toluene (±0.3% precision, ±1% accuracy).
- Achieved ±5% accuracy for thermal diffusivity measurements.
Conclusions:
- The developed apparatus is effective for precise thermophysical property measurements of fluids.
- New data for liquid toluene highlight the significance of radiative heat transfer.
- The instrument enables calculation of specific heat when density is known.
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