Lanthanide hexaborides. I. Heat capacities and some thermophysical properties of LaB 6, NdB6 , and GdB 6at temperatures from 5 K to 350 K

2002 ◽  
Vol 34 (2) ◽  
pp. 239-250 ◽  
Author(s):  
E.F. Westrum, Jr ◽  
J.T.S. Andrews ◽  
B.H. Justice ◽  
D.A. Johnson
2019 ◽  
pp. 18-29
Author(s):  
Maya Vladimirovna Ambrozhevich ◽  
Mikhail Anatol'evich Shevchenko

All properties of thermomechanical systems working substance are two-parameter that is determined by two parameters, the most often they are temperature and pressure which are easily measured by experiment. Representing the isobaric heat capacity as a function of temperature cp = f(T) become a thing of the past. Analytical and tabular ways are used to represent dependencies as a function of temperature and pressure. The tabular method is convenient for single calculations, but the analytical one is more convenient for a series of calculations. The advantages of an analytical description in comparison with a tabular one are obvious, namely, compactness of information storage without reference to node points, the ability to integrate and differentiate, dependencies can be embedded directly in the program body and don’t require special subroutines to access to the tables. Developers of the programs for calculating thermophysical properties, as a rule, use functional dependencies which may have a different appearance for temperature and pressure intervals of the same substance. This is explained by the fact that in the region close to the saturation curve, there is a steep change in all the thermophysical properties of substances including the isobaric heat capacity. In thermogasdynamic calculations of heat machines, the main physical parameter of the working fluid is its heat capacity, both true and average. The article presents the analytical dependencies of the average specific isobaric heat capacities of the main components of air and combustion products of hydrocarbon fuels which are united throughout the specified range of pressures and temperatures (nitrogen: p = 1 ... 200 bar, T = 150 ... 2870 K, oxygen: p = 1 ... 200 bar, T = 210 ... 2870 K, argon: p = 1 ... 200 bar, T = 190 ... 1300 K, the water vapor: p = 0,1 ... 200 bar, T = 700 ... 2600 K, carbon dioxide: p = 1 ... 200 bar, T = 390 ... 2600 K). The analytical dependencies were derived on the basis of previously obtained analytical expressions for the specific isobaric heat capacities of these gases. The average specific isobaric heat capacities of gases are also functions of temperature and pressure cp = f(T, P) and take into account the effect of thermal dissociation. Formulas for average specific isobaric heat capacities are obtained by integrating expressions for specific isobaric heat capacities. Verification of the obtained dependencies for different temperature ranges was done.


1992 ◽  
Vol 24 (12) ◽  
pp. 1251-1256 ◽  
Author(s):  
E.H.P. Cordfunke ◽  
R.R. Van Der Laan ◽  
G.P. Wyers ◽  
J.C. Van Miltenburg

2011 ◽  
Vol 2011 ◽  
pp. 1-5 ◽  
Author(s):  
Boris I. Sedunov

The extension of the saturation curve on the PT diagram in the supercritical region for a number of monocomponent supercritical fluids by peak values for different thermophysical properties, such as heat capacities and and compressibility has been studied. These peaks signal about some sort of fluid structural transition in the supercritical region. Different methods give similar but progressively diverging curves for this transition. The zone of temperatures and pressures near these curves can be named as the zone of the fluid structural transition. The outstanding properties of supercritical fluids in this zone help to understand the physical sense of the fluid structural transition.


Author(s):  
A. V. Akimov ◽  
A. V. Buketov ◽  
А. А. Sapronov ◽  
Mykola V. Brailo ◽  
S. V. Yakushchenko ◽  
...  

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