An improved correlation for compressed liquid densities of hydrocarbons .1. Pure compounds

A new model for calculating compressed liquid densities is proposed. In the new model, the Hankinson-Thomson correlation (Hankinson and Thomson, 1979) is used to calculate saturated liquid densities, and a slightly modified Chang-Zhao equation (Chang and Zhao, 1990) is used in the compressed liquid region. Parameters of the new model are fitted from a data base consisting of 4426 density points for 29 pure alkanes and alkenes. The new model is compared with HBT (Thomson et al., 1982) and Chang-Zhao (Chang and Zhao, 1990) models, and it is found to be the most accurate of the three models. With the new model, densities of compressed liquids can also be calculated in the near critical region with good accuracy. The average absolute deviation was 0.38% for the region T-r < 0.95 and 0.44% for the whole region T-r < 1.0. The new model is also tested against compressed liquid density data for several other organic substances and inorganic light compounds, that were not included in the data set used to fit the parameters. The average absolute deviation was 0.72% for the region T-r < 0.95 and 0.86% for the whole region T-r < 1.0 indicating that though fitted from alkane and alkene data, the new model can be applied to many other compounds.