Description of the liquid-vapor phase equilibrium line of pure substances within the bounds of scale theory based on the Clapeyron equation

On the basis of the Clapeyron equation and the scale theory, expressions are developed for the “apparent” heat of vaporization r * = r * (T), vapor ρ- = ρ- (T) and liquid ρ+ = ρ+ (T) branches of the saturation line of individual substances for the range of state parameters from the triple point (pt,Tt,ρt ) to the critical (pc,Tc,ρc ). The peculiarity of the proposed approach to the description of the saturation line is that all exponents of the components of the equations ρ- = ρ- (T) and ρ+ = ρ+ (T) are universal up to the universality of the critical indices α, β and Δ. In this case, the order parameter ds = (ρ+ − ρ-)/(2ρc) and the average diameter df = (ρ+ + ρ-)/(2ρc) − 1 of the saturation line satisfy the saturation line model [2β,1−α], which follows from the modern theory of critical phenomena. The method is tested on the example of describing the phase equilibrium line of refrigerant R1233zd(E) in the range from Tt = 195.15 K to Tc = 439.57 K. It is found that in the temperature range [Tt,Tc ], the developed system of the mutually consistent equations ps = ps (T), r * = r * (T), ρ- = ρ- (T) and ρ+ = ρ+ (T) allows describing the data on the saturated vapor pressure ps and densities ρ- and ρ+ on the saturation line within the experimental uncertainty of these data.

Silanes and Siloxanes Thermal Conductivity in the Liquid Phase: A Critical Review and an Improved Prediction Method

The thermal conductivity λ of the silanes and siloxanes families in the liquid phase at atmospheric pressure or along the saturation line is investigated as function of the reduced temperature. Because of the large scarcity or even of the lack of accurate experimental λ data an empirical equation is proposed as a generalization based on investigations presented in previous works [1, 2]. The families of silanes and siloxanes (21 chlorosilanes, 5 cyclosiloxanes, 10 linear siloxanes, 10 silanes and 19 other silanes) are taken into consideration using a large database [3] in order to extend the use of a general formula valid for organic compounds (alcohols, alkanes, ketones,….) and to improve preceeding results obtained in the case of the cited silanes and siloxanes, for which experimental thermal conductivity data at atmospheric pressure or along the saturation line in the liquid phase are available in very few cases. The equation is proposed as acceptable for engineering purposes and comparable with the existing prediction methods [3]. The database DIPPR [3] in the version 2020 containing a linear correlation with various parameters is taken into account, also considering the results of 7 other prediction methods existing in the technical and scientific literature. An extensive and critical comparison points out that the method proposed in this work can be considered valid with absolute errors usually not greater than 5%.

Vocational Education at the University: Renewal Priorities

The priorities of updating vocational education at a university are disclosed. The characteristic of the university as a historically proven system of higher education is given. In the historical and pedagogical analysis revealed a variety of types of higher schools in different eras. The saturation line of the higher education level of the professional component in domestic and foreign experience is traced. The experience of continuing the traditions of vocational education at Gzhel State University is given.

RELATIONS BETWEEN THE DIFFERENCES OF DIFFERENT PROPERTIES OF FREONES ON THE SATURATION LINES UPON LIQUID-VAPOR PHASE TRANSITION

To construct a generalized dependency, a scale for the unknown quantities and variables must be selected. The states of points are located in P-V-T (pressure-volume-temperature) space. The scale for the construction of generalized dependences of the studied properties and variables of the problem must be sustainable. In order to find a sustainable transition from liquid to vapor the behavior of the characteristic function of free energy is investigated. Since the phase transition occurs at a constant temperature, free energy is equal to expansion work. In the analysis of the liquid-vapor transition, the curve of the temperature dependence of expansion work for all investigated substances has a maximum. The temperature corresponding to the maximum expansion work is denoted by Tm. It was noted that temperature Tm associated with Tc (critical) with the simple relation Tm =0.76Tс with a spread of 2%. Naturally, this state corresponds to the free energy minimum value, and in accordance with the principle of minimality of characteristic functions of this process is stable. Therefore, the parameters of this process were chosen as the bringing scale in the construction of dimensionless dependencies. In this paper we use the method of constructing generalized dependencies in the reduced form, based on the characteristic functions minimality principle. Approximating formulas were obtained for calculating reduced heat of evaporation from reduced density, entropy, and freons surface tension. The reduction scale is considered on the liquid and vapor saturation line under substances consideration. The characteristic functions minimality principle is used. In the course of the analysis, calculation formulas were derived for pure freons both individually and in a combined form. The interrelation between the differences of these thermodynamic properties on the saturation line during a liquid-vapor phase transition is shown. This makes it possible to determine some properties using other methods by calculation.