Experimental Study and Computer Modeling of the Triple Point of Argon System (NCSLI Measure reprint)

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Experimental Study and Computer Modeling of the Triple Point of Argon System (1.12 MB)

This article by R. Ding, M.J. Zhao, T. Nielson, E. Nerdrum, and D. Farley was published in the March 2012 issue of NCSLI Measure magazine.

 Abstract: The triple point of argon is a defi ned fi xed point in ITS-90 for calibration of standard platinum resistance thermometers (SPRTs). A new triple point of argon system with multiple re-entrant wells was developed. This system was tested to evaluate the duration and quality of the argon triple-point temperature plateau. The testing results showed that the plateau can be as long as 100 hours with the temperature change less than 0.05 mK. The re-entrant wells’ uniformity testing showed that the temperature is consistent among the multiple re-entrant wells. Uncertainty analysis shows that the combined uncertainty of the argon system is 0.26 mK (k = 2). In order to study the heat transfer process and the infl uence on the thermal equilibrium of the argon system during the realization of the triple-point of argon plateau, fi nite element analysis (FEA) modeling was carried out to simulate the thermal conductivity, convection, and radiation inside the argon system. The FEA simulation results are described and discussed in this paper.