The excess enthalpies of (carbon dioxide + pentane) at 348.15, 373.15, 413.15, 470.15, and 573.15 K from 7.58 to 12.45 MPa

Excess enthalpies of binary mixtures with endothermic–exothermic changes in mixing processes: empirical correlations

“…To fit experimental data with changes of sign, Christensen et al [12][13][14] use an extended version of the Redlich + Kister model. A new polynomial is added as a denominator in equation (1):…”

“…Even when the model is appropriate for other ranges and deviations for each experimental point, and also the mean deviation, are small, the denominator can be zero for some values of x, thus leading to a discontinuity. In some cases [11][12][13][14], equation (2) has been used together with other simple models for certain ranges of the mole fraction. This possibility will not be taken into account in this present work, i.e., we shall study the fit with only a single model.…”

“…The excess enthalpy for a given mixture at fixed pressure and temperature then changes sign when it is obtained at different mole fractions. In that case, some authors have used sometimes different models for different ranges of the mole fraction (see, for example [12][13][14]). …”

“…The selected models are: (i) the classical Redlich + Kister model [15]; (ii) the extended version of the Redlich + Kister expression used by Christensen et al [12][13][14], which is a Padé type expression; (iii) the expression used by Ott et al [16] and Cordray et al [11], containing an exponential term; and (iv) the expression given by Gruszkiewicz et al [17], and recently used by Ochi et al [6]. As far as we know, the validity of all these four models has not been studied.…”

Calorimetry in the near-critical and supercritical regions. Nitrous oxide + hydrocarbon mixtures

“…Simultaneously, Christensen et al [4,5] were setting up a new highpressure flow calorimeter able to detect both exothermic and endothermic processes which was quickly applied to determine the excess enthalpies of CO 2 þ hydrocarbon mixtures in the critical region. From 1983 to his early dead, James J. Christensen published data of mixtures such as CO 2 þ ethane [6], þ pentane [7,8], þ hexane [9,10], þ cyclohexane [11][12][13][14], þ decane [15,16], þ toluene [17][18][19][20] and þ pyridine [21,22]. Figure 1 shows the experimental P,T conditions at which data are available for three of these systems.…”