Aspen Physical Property System - Physical Property Models

Model Type
API Liquid-vapor
IAPS Water-stream
General Pure Component Liquid Surface
Tension
288 3 Transport Property Models
Liquid-vapor
Onsager-Samaras Electrolyte Correction Electrolyte liquid-vapor
Modified MacLeod-Sugden Liquid-vapor
Liquid Mixture Surface Tension
The liquid mixture surface tension is calculated using a general weighted
average expression (R.C. Reid, J.M. Prausnitz, and B.E. Poling, The Properties
of Gases and Liquids, 4th. ed., New York: McGraw-Hill, 1987, p. 643):
Where:
x = Mole fraction
r = Exponent (specified by the option code)
Hadden (S. T. Hadden, Hydrocarbon Process Petrol Refiner, 45(10), 1966, p.
161) suggested that the exponent value r =1 should be used for most
hydrocarbon mixtures. However, Reid recommended the value of r in the
range of -1 to -3. The exponent value r can be specified using the model’s
Option Code (option code = 1, -1, -2, ..., -9 corresponding to the value of r).
The default value of r for this model is 1.
The pure component liquid surface tension �i *,l is calculated by the General
Pure Component Liquid Surface Tension model.
API Surface Tension
The liquid mixture surface tension for hydrocarbons is calculated using the
API model. This model is recommended for petroleum and petrochemical
applications. It is used in the CHAO-SEA, GRAYSON, LK-PLOCK, PENG-ROB,
and RK-SOAVE property models. The general form of the model is:
Where:
fcn = A correlation based on API Procedure 10A32 (API Technical Data
Book, Petroleum Refining, 4th edition)
The original form of this model is only designed for petroleum, and treats all
components as pseudocomponents (estimating surface tension from boiling
point, critical temperature, and specific gravity). If option code 1 is set to 0
(the default), it behaves this way. Set option code 1 to 1 for the model to use
the General Pure Component Liquid Surface Tension model to calculate the
surface tension of real components and the API model for pseudocomponents.