The Transient Hot-Wire Instrument: Absolute Measurement of the

Thermal Conductivity of Fluids

Ramesh C. Prasad

Department of Engineering, University of New Brunswick

Saint John, NB, Canada E2L 4L5

ABSTRACT

The transient hot-wire technique is a reliable and precise method for absolute measurement of the thermal conductivity of fluids. Refinement of this technique at the University of New Brunswick (UNB) has demonstrated the capability for an accurate and simultaneous measurement of the thermal conductivity and thermal diffusivity together with a determination of the specific heat provided an appropriate equation of state is available. The measurement system developed at UNB is described in detail. The experimental system includes a hot-wire cell constructed with 12.7 μm diameter platinum wire which is submerged vertically in a test fluid. Measurement of the transient temperature rise of the wire in response to a step current through it allows an accurate and rapid determination of the thermal properties of the surrounding fluid. The system includes a pressurizing system and an isothermal block to achieve desired test conditions over a wide range of temperature and pressure. In order to demonstrate the accuracy of measurement with this system, results obtained for nitrogen are compared with available data. Measurements on propane, toluene and argon are used to show the influence of radiation effect with this instrument. Recent work includes measurements for electrically conducting fluid using a newly developed hot-wire cell utilizing anodized tantalum wire. Thermal conductivity measurements of several other fluids obtained with this instrument are also presented.

About the speaker

Ramesh C. Prasad, Professor of Mechanical Engineering at the University of New Brunswick, Saint John, NB, Canada has been associated with Engineering education for the last several decades. He obtained BScE (Mech. Eng.) from Bhagalpur University, India (1964), MTech (ME) from Indian Institute of Technology, Kharagpur, India (1970), MScE and PhD from the University of New Brunswick, Canada (1978, 1982). He is a Professional Engineer in the Province of New Brunswick, Canada.

His primary teaching and research interests are in the area of thermo-fluids. For over three decades at UNB, he has been engaged in undergraduate and graduate teaching and also carried out research work in the area of thermal properties of fluids and convective heat transfer enhancement. The experimental system for the thermal properties research includes a transient hot-wire instrument which has been developed at UNB. He has been closely associated with the design and development of this system since 1975.