Virtual Experiments by a Pulse Heating Technique: Tubular Tungsten Specimens

A bi-dimensional geometrical model that includes thermal expansion effects was developed and numerically solved considering three tubular tungsten specimens, heated from room temperature to above 3600 K with current pulses of 500 ms and 750 ms duration. For comparison purposes, the same virtual experiments were performed on three tungsten rods having an identical cross section. The detailed analysis of these virtual experiments indicated in all cases significant radial temperature differences, with the tubular specimens exhibiting smaller radial temperature drops, generally less than half that of the rod specimens. The validity of the long thin-rod approximation, generally used to compute thermophysical properties from real experiments, was verified for various geometries and under different experimental conditions for both tubes and rods. Using such an approximation, tubular and cylindrical specimens exhibit similar uncertainties if the average temperature of the central portion of the specimen is known, while tubes are a better choice when only surface temperatures are available. The developed model may be used to estimate uncertainties due to the use of various approximations and to optimize experimental conditions in real measurements.