## A New Four-Parameter Cubic Equation of State for Predicting Fluid Phase Behavior

A new four-parameter
cubic equation of state (EoS) is generated by incorporating the critical
compressibility factor (Z_{c}) apart from the critical pressure (P_{c})
and temperature (T_{c}). One free parameter in the denominator of the
attractive term and two parameters in the alpha function are adjusted using the
experimental data of saturated liquid density, vapor pressure, and isobaric
liquid heat capacity of 48 components including hydrocarbons and
non-hydrocarbons. Applying this equation of state, saturated liquid density,
saturated vapor density, and vapor pressure of pure components are accurately
reproduced compared with experimental values. Furthermore, the predicted
properties including derivatives of alpha function, such as enthalpy of
vaporization, entropy of vaporization and isobaric heat capacity of liquid, also
have decent accuracy. The global average absolute relative deviation (AAD) of
saturated liquid density, saturated vapor density, saturated vapor pressure,
enthalpy of vaporization, entropy of vaporization, and isobaric heat capacity
of liquid in a wide reduced temperature (Tr) range of subcritical region reproduced
by this work are 4.33%, 4.18%, 3.19%, 2.26%, 2.27%, and 5.82%, respectively. Substantial
improvement has been achieved for the isobaric liquid heat capacity
calculation.