AN IMPROVED CORRELATION FOR COMPRESSED LIQUID DENSITIES OF HYDROCARBONS .1. PURE COMPOUNDS

A new model for calculating compressed liquid densities is proposed. I n the new model, the Hankinson-Thomson correlation (Hankinson and Thom son, 1979) is used to calculate saturated liquid densities, and a slig htly modified Chang-Zhao equation (Chang and Zhao, 1990) is used in th e compressed liquid region. Parameters of the new model are fitted fro m a data base consisting of 4426 density points for 29 pure alkanes an d alkenes. The new model is compared with HBT (Thomson et al., 1982) a nd 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 c ompressed liquids can also be calculated in the near critical region w ith good accuracy. The average absolute deviation was 0.38% for the re gion T-r < 0.95 and 0.44% for the whole region T-r < 1.0. The new mode l is also tested against compressed liquid density data for several ot her organic substances and inorganic light compounds, that were not in cluded in the data set used to fit the parameters. The average absolut e deviation was 0.72% for the region T-r < 0.95 and 0.86% for the whol e region T-r < 1.0 indicating that though fitted from alkane and alken e data, the new model can be applied to many other compounds.