Extended analytical equation of state for liquids from expansivity data analysis

Abstract

Studying the behavior with pressure and temperature of thermal expansivity data derived from (p,p,T) measurements of liquids, we found that a previously derived analytical equation of state is inapplicable under certain thermodynamic conditions. The main obstacle is that these conditions are determined by characteristic constants of the liquid under study. Following the same scheme used to derive the original equation of state, we propose a new analytical expression which removes this restriction. Three different substances have been used to test the ability of the new equation of state to represent the volumetric properties of compressed liquids,

New calibration methodology for calorimetric determination of isobaric thermal expansivity of liquids as a function of temperature and pressure

“…It has been shown that a p for liquids at high pressure decreases against temperature [3][4][5]14,15]. This could imply that there is one pressure point in which a p could show no temperature dependence.…”

“…Availability of these quantities over wide pressure and temperature ranges allows to check in what extent an Equation of State (EoS) can reproduce the thermodynamic behaviour [1][2][3][4][5], since usually the parameters of the EoS are fitted to experimental data of first-order derivatives of the thermodynamic potential, as densities or enthalpies. On the other hand, industry needs information about these quantities for efficiently designing; heat capacity, compressibility, and thermal expansivity for a variety of materials are often needed in most of industrial procedures.…”

Testing the ability of various equations of state to reproduce high-pressure isotherm crossings in the (α, P) plane

“…In order to catch this behavior, it is therefore necessary to consider an EoS for real fluids, accounting for intermolecular forces. Few attempts to model the aforementioned phenomena were realized in the past [8,5]. Among these, the work conducted by Deiters and Randzio [5] is particularly informative: the authors explained that the Redlich-Kwong EoS is not able to reproduce the crossing phenomena either quantitatively or qualitatively.…”

Analysis of thermal expansivity and isothermal compressibility of liquid hexane and chloroform

“…These limitations are often a direct consequence of the algebraic forms used to correlate experimental pressurevolume-temperature data. Therefore, any attempt to develop a model of equation of state of general applicability in the liquids requires the inclusion of general thermodynamic constraints [6].…”

“…The analysis of equation of state for liquid hexane in terms of derivative properties such as volume thermal expansion coefficient (a p ) or isothermal compressibility (K T ) has interesting advantages, since both are related to the first derivatives of the (pressure-volume-temperature) equation of state, and both can be accurately measured over wide ranges of pressure and temperature by different experimental techniques [7,8]. The most interesting point is that any equation of state based on the analytical intermolecular potential will be unable to describe the thermodynamic behaviour of liquid hexane because this behaviour has a several regularities [5,9].…”