Heat Transfer in γ-Phase of Oxygen

Abstract

The isochoric thermal conductivity of γ-O 2 has been studied on samples of varying density in the temperature interval from 44 K to the onset of melting. The thermal conductivity of nearly free sample decreases at rising temperature along the isochores. It is shown that the absolute value of thermal conductivity in the γ-phase of O 2 is close to its lower limit and most of the heat is transported by «diffusive» modes. The growth of thermal conductivity in γ-O 2 is attributed to the decay of the phonon scattering at the rotational excitations of the molecules and at the short-range magnetic order fluctuations at rising temperature.

Heat transfer in solid methyl alcohol

“…The simplest description of k II (T ) is provided by the phenomenological Cahill-Pohl model [31] which was proposed to interpret the thermal conductivity of amorphous solids at high temperatures. The model accounts adequately for the features of the isochoric high-temperature thermal conductivity of molecular crystals in the orientationally-ordered phase [32]. According to the model, the thermal conductivity is:…”

Heat transfer in solid halogenated methanes: trifluoromethane

“…This is because the translational-orientational component of the total thermal resistance decreases sharply as the rotation of the molecules becomes weakly hindered. In some crystals with reorientation frequencies up to 10 4 s -1 (CHCl 3 , CH 2 Cl 2 and CF 2 Cl 2 ) the isochoric thermal conductivity approaches its lower limit L min [5,6] and deviates significantly from the dependence L µ 1/T.…”

“…Apart from CHF 3 , a weak growth of isochoric thermal conductivity with temperature was also observed in CHF 2 Cl (I) [6]. However, in the latter case only the Raman spectra were investigated at T = 20-80 K [18] and NMR data are unavailable.…”

“…We observed this effect in methane and carbon tetrachloride [3,4]. A weak growth of thermal conductivity was also found in the high-temperature phase of solid chlorodifluoromethane (CHF 2 Cl) [6]. This behavior is not entirely clear for the lack of full information about the character of the rotational motion of the molecules in solid CHF 2 Cl.…”

“…This is particularly important at high temperatures when the thermal expansion coefficients are large. Previously, we investigated the isochoric thermal conductivity of CH 4 [3], CCl 4 [4], CHCl 3 and CH 2 Cl 2 [5], CF 2 Cl 2 and CHF 2 Cl [6]. The regularities of the heat transport in simple molecular crystals (including the methane-series freons) depending on the rotational degrees of freedom of molecules at the Debye and higher temperatures (T ³ Q D ) can be generalized as follows.…”