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Development of THW Instruments for melts & solids

Development of THW Instruments for melts & solids Development of THW Instruments for melts & solids Development of THW Instruments for melts & solids Development of THW Instruments for melts & solids

In order to overcome the difficulties rising from the contact resistance between solids, and the end effects of the wire, the experimental setup with two tantalum wires was adjusted for the measurement of solids and melts. Two recent designs can be seen in the Figure. In order to avoid air gaps, in design (f), the two wires are placed inside a soft silicone layer which is squeezed between the two solids. This way the contact is excellent. By obtaining the temperature rise from the wire’s resistance measurement, at very short times the properties of the silicone layer are first obtained, and then at longer times the properties of the solid. The absolute uncertainty achieve in this way is about 1%, and the technique is only hindered in temperature by the melting temperature of the soft silicone layer.

Design (g) is based on the same idea but here the wire is placed between soft alumina layers which are consequently fired under pressure to become solid. This arrangement worked very well for measurements of the thermal conductivity of molten metals at high temperatures; Peralta et al. reported such measurements for molten mercury, gallium, tin, and indium up to 750 K.
 
Designs (h) and (i) represent two commercial sensors, the first one developed by U. Hammerschmidt and based on the transient strip principle, and the second developed by Gustafsson, and based on the transient spiral strip idea.
 

(f)  M.J. Assael, K.D. Antoniadis, K.E. Kakosimos, and I.N. Metaxa, Int. J. Thermophys., 29:445-456 (2008).
(g)  M.V. Peralta-Martinez, M.J. Assael, M. Dix, L. Karagiannidis, and W.A. Wakeham, Int. J. Thermophys., 27:353-375 (2006).
(h)  R. Model, R. Stosch, and U. Hammerschmidt, Int. J. Thermophys., 28:1447-1460 (2007).
(i)  S.E. Gustafsson, Rev. Sci. Instrum., 62:797-804 (1991).

 

 

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