Measurement of Thermophysical Properties

The resonant frequencies of an acoustic resonator are determined by the dimension of the cell and by the physical properties of the gas sample determining the sound velocity such as molecular mass, heat capacity, and virial coefficient. 

An example for the accurate determination of sound velocities and heat capacities is given by Thomas III et al. Using a cylindrical resonator, they investigated mixtures of 99,1 % -I- 0,9% CH4 and of 99,1 % + 0,9%CH4 at 760Torr. 

From the resonance curves shown in Fig. 14 the authors deduced the first experimentally determined values ofy = 1,279 and v = 264,4 m/sec for C02 at 295.6 K The shift of the resonant frequency from 3032 Hz to 2994 Hz due to the mass difference of the two isotopes is in agreement with the prediction of eq. (12). Doping 

Very precise speed of sound measurements were performed by Mehl and Moldover utilizing a spherical resonator and acoustic excitation of radial modes As 

The acoustic virial coefficient ofQH was determined from the pressure dependence of the sound velocity in the temperature range of 270 K-380 K The second virial coefficient B(T) was calculated from these acoustic virial coefficients and literature values available for B(T) n r 270 K. The resulting temperature dependence and a comparison with data reported by Douslin and Harrison and by Waxman and Davis is shown in Fig. 16. The maximum deviation is 0,8cm /mole at 373 K. 

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In Chapter 2, we developed statistical thermodynamics as the central theory that enables ns in principle to calculate thermophysical properties of macroscopic confined flriids. A key feature of statistical thermodynamics is an enormous reduction of information that takes place as one goes from the microscopic world of electrons, photons, atoms, or molecules to the macroscopic world at which one performs measurements of thermophysical properties of interest. This information reduction is effected by statistical concepts such as the most probable distribution of quantum states (see Section 2.2.1). 

Experimental investigationsofthermophysicalpropertiesofsuperheatedwater do not reveal any peculiarities in their behavior. However, it should be borne in mind that by now measurements of properties of metastable water have been made in a very narrow range of state variables. In quasi-static experiments a deep entry into the metastable region of water was hindered by a great number of easily activated boiling sites. D5mamic experiments cannot as yet ensure an acceptable accuracy of measurement of thermophysical properties of metastable liquids. 

J. Pelzl, AC hot wire measurement of thermophysical properties of nanofluids with 3 omega method, Europ. Phys. J. Special Topics, 153, 349-352 (2008). 

BE/KAS] Obendrauf, W., Kaschnitz, E., Pottlacher, G., Jager, H., Measurements of thermophysical properties of nickel with a new highly sensitive pyrometer, Int. J. Thermophys., 14, (1993), 417-426. Cited on pages 79,425. 

For a spherical resonator no resonance experiments with laser excitation have been reported so far. However, acoustic excitation of radial modes with a second microphone was accomplished just recently and, as expected, very high Q factors were obtained in a high quality spherical resonator The goal of these experiments was the measurement of thermophysical properties with high precision. A spherical resonator is also an interesting candidate for photoacoustic investigations. 

As technology advances and specific needs for applications also change over time, the list of accessible thermophysical properties cannot be expected to remain static. Therefore, the following chapter can only be seen as a snapshot of the current state-of-the-art capabilities in the measurement of thermophysical properties by dynamic pulse calorimetry. 

Besides measurements of thermophysical properties, millisecond experiments are the tools of choice for metrological investigations. They have been used by NIST, USA INRiM, Italy NRLM, Japan and lately by HIT, China, for measurements dealing with radiance temperatures, radiometry, and total hemispherical emittance measurements [10,11]. 

Before submicrosecond setups were foimd to be of use for measurements of thermophysical properties, they were used to provide pulsed light sources with intense light output, or as plasma sources with imusudly high material density... 

Ghosal K, Chem RT, Ereeman BD, Savariar RJ (1995) J Polym Sci B Polym Phys 33 657 Grolier JPE, Dan E (2004) Calorimetric measurements of thermophysical properties for industry. In Letcher T (ed) Chemical thermodynamics for industry. Royal Society of Chemistry, Cambridge, p 144... 

J. Sestak Mefenl termofyzlkalnich vlastnosti pevnych latek (Measurements of thermophysical properties of solids). Academia, Praha 1982 (in Czech)... 

In this section, we discuss various techniques used for measurement of thermophysical properties at microscale. 

Containerless processing techniques have been developed to a great extent for space experiments i.e. these are electromagnetic [9], electrostatic [10], aerodynamic [11] and aero-acoustic levitations [12]. Containerless processing assures measurements of thermophysical properties of molten semiconductors usually it... 

Z.-H. Zhou, S. Mukherjee, and W. K. Rhim, 2003, Measurement of thermophysical properties of molten silicon using an upgraded electrostatic levita-tor , J. Cryst. Growth 257, 350-358. 

A review of measurement of thermophysical properties of silicon melt ,... 

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