New corresponding-states correlation model for the surface tension of refrigerants

Abstract

A new corresponding-states correlation model for the calculation of the surface tension of refrigerants is proposed. The main difference with respect to other models available in the literature is that this includes the temperature and surface tension values at the triple point as input properties to define the reduced (non-dimensional) properties, and therefore it is applicable to the entire vapour-liquid temperature range in which this property is defined. The model uses the critical point and the triple point temperature of refrigerant R142b as fixed input parameters and four numerical coefficients obtained by a fitting procedure. The adjustable coefficients were calculated by taking into account the data for 33 selected refrigerants for which the surface tension values at the triple point are known. For each fluid the input variables are the critical point temperature, the triple point temperature, and surface tension at the triple point temperature. To check the model's capacity, we used it to calculate the surface tension values of another 50 refrigerants for which the value of this property is not known at the triple point. To do this, we used as input the lowest temperature at which a value of the surface tension is available. In both cases, correlation and prediction, the calculations were done by considering the most up-to-date database presently available for the surface tension of refrigerants. Averaged absolute deviations below 5% were found for 63 of the 83 fluids considered, and only for 4 of them were they greater than 10%. Results for another four corresponding-states models available in the literature were also obtained. That proposed here gave clearly better overall results.