A corresponding states predictive viscosity model based on a new scaling parameter: application to hydrocarbons, halocarbons and mixtures

Scalabrin, G.; Cristofoli, G.; Grigiante, M.

doi:10.1002/er.759

Cited by 19 publications

(16 citation statements)

References 88 publications

(48 reference statements)

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“…This analysis, simply deduced from an heuristic point of view, is sufficient to conclude that the examined fluids have, with respect to the TC, a low degree of conformality. The results of the conformality analysis for TC show a relevant different behavior with respect to that observed for thermodynamic properties [1] and for viscosity [2]. Going back to such studies, the high degree of conformality of these properties, enabled the determination of specific scaling parameters for setting up predictive and generalized models as a direct application of the CS principle.…”

Section: Conformality Analysis Of the Thermal Conductivitymentioning

confidence: 91%

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Thermal Conductivity Modeling of Pure Refrigerants in a Three-Parameter Corresponding States Format

et al. 2005

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The potential of the corresponding states (CS) principle for modeling a pure fluid thermal conductivity surface is studied here. While for thermodynamic properties and for viscosity, successful results have been previously obtained by directly applying an improved three-parameter CS method, significant difficulties were encountered while trying to extend this method to thermal conductivity and, in particular, it fails if applied without separately dealing with the dilute-gas term, and the residual and critical enhancement contributions. These last two parts are also combined in the excess term. It is shown that the dilute-gas term cannot be expressed in such a format, and it has necessarily to be individually modeled for each target fluid. On the contrary, the excess contribution can be described through a specific conductivity scaling factor that can be individually determined from a single saturated liquid conductivity experimental value. The model for the excess part is set up in a three-parameter CS format on two reference fluids, in the present case, methane and R134a, for which dedicated thermal conductivity equations are available, and it has a predictive character. The models for the dilute-gas and for the excess contributions are then combined to give the final TC model. The model has been successfully validated for two homologous families of refrigerant fluids obtaining an AAD of 3.67% for 3332 points for haloalkanes and an AAD of 2.87% for 354 points for alkanes.

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Section: Conformality Analysis Of the Thermal Conductivitymentioning

confidence: 91%

“…The problem is to find a property-specific scalar parameter which allows shifting from the conductivity surface of a reference fluid to one of interest. The procedure for the determination of the scalar parameters is similar to that adopted for viscosity [2] and for recent thermodynamic properties modeling [1]. …”

Section: Excess Term Analysismentioning

confidence: 99%

Thermal Conductivity Modeling of Pure Refrigerants in a Three-Parameter Corresponding States Format

et al. 2005

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“…The classical method, common to CS techniques, of modifying the critical properties of the components by suitable mixing rules, is obtained here by a rearrangement of the mixing rules of Wong et al [17], also previously tested for mixture viscosity modeling [13]. The original form has been maintained in this work while only substituting for the acentric factor ω with the new TC specific scalar parameter κ i previously defined.…”

Section: Mixture Model For the Excess Term Contributionmentioning

confidence: 98%

“…Until now, models based on a three-parameter CS scheme have been successfully applied for thermodynamic properties [5][6][7][8][9] and for viscosity [10][11][12][13]. The proposed model extends the potential of CS assuming a fluid specific scaling parameter for TC [14].…”

Section: Introductionmentioning

confidence: 98%

Thermal Conductivity Modeling of Refrigerant Mixtures in a Three-Parameter Corresponding States Format

et al. 2005

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A predictive model for the thermal conductivity (TC), in a corresponding states (CS) format, is proposed here for mixtures of homologous fluids such as the halogenated alkanes (HA) and the alkanes (A), most of which are used as refrigerants. The predictive nature of the model originates from a new study carried out for the TC of pure fluids. For the dilute-gas term the model requires an individual correlation for each component, whereas for the excess contribution the model structure makes use of TC dedicated equations (TCDEs) of two reference fluids, which in this work are methane and R134a. The mixture model adopts specific mixing rules for each of the two TC contribution terms: the dilute-gas term λ 0mix is obtained from the Mason and Saxena mixture model, while the excess term ∆ E λ mix is determined from the Wong et al. mixing rules in the one fluid model approach. Setting the mixing rules interaction coefficients to unity, the resulting model presents a completely predictive character. The model has been tested on both liquid and vapor phases of the following systems: R32/R125, R32/R134a, R125/R134a, R404a, and R32/R134/R125. For a total of 1223 experimental points in the liquid phase, the overall AAD is 5.39%, while for a total of 2358 points in the vapor phase, the AAD is 2.62%. These predictive mode performances can then be regarded as particularly satisfactory and are of a level similar to the claimed experimental uncertainty. An improved version of the model is also proposed for modeling azeotropic mixtures. The results reached in this case for a total of 1989 experimental points give an average AAD of 5.30%. Considering both the predictive nature and the simple computational procedure of the model, it significantly enhances the calculations of the TC of mixtures.

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“…The first approach includes predictive or semi-predictive models which are often based on corresponding states theory [1][2][3][4][5][6][7][8][9][10], and in many cases, they can be used to estimate the property with an accuracy level which is considered sufficient for engineering calculations. Theoretically based models, for instance, those including the evaluation of collision integrals, have also been developed.…”

Section: Introductionmentioning

confidence: 99%

A Multiparameter Viscosity Equation for 1,1-Difluoroethane (R152a) with an Optimized Functional Form

2006

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This paper presents a new formulation for the viscosity surface of 1,1-difluoroethane (R152a). The formulation is a multiparameter equation η = η (ρ, T ) obtained from an optimization technique of the functional form based on available experimental data. The equation is valid for temperatures from 240 to 440 K and pressures up to 20 MPa. Two lines of viscosity minima have been observed, and they have been analytically defined. A high accuracy equation of state for R152a was used to convert the experimental variables (P , T ) into the independent variables of the viscosity equation (ρ, T ). Comparisons with data are given to establish the accuracy of the viscosity values calculated using this equation. The obtained results are very satisfactory with an average absolute deviation of 0.27% for the selected 264 primary data points, and this is a significant improvement with respect to other equations in the literature.

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A corresponding states predictive viscosity model based on a new scaling parameter: application to hydrocarbons, halocarbons and mixtures

Cited by 19 publications

References 88 publications

Thermal Conductivity Modeling of Pure Refrigerants in a Three-Parameter Corresponding States Format

Thermal Conductivity Modeling of Pure Refrigerants in a Three-Parameter Corresponding States Format

Thermal Conductivity Modeling of Refrigerant Mixtures in a Three-Parameter Corresponding States Format

A Multiparameter Viscosity Equation for 1,1-Difluoroethane (R152a) with an Optimized Functional Form

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