# Characteristics and Properties of Crude Oil and Its Products

**NOMENCLATURE**

*API* API gravity defined in Equation 2.2 *a,b...i* Correlation constants in various equations

*BI _{vh}* Blending index for viscosity of liquid hydrocarbons (see Equation 2.64), dimensionless

*CH* Carbon-to-hydrogen weight ratio

D_{ab} Binary (mutual) diffusion coefficient (diffusivity) of component *A* in *B.* cm^{2}/s

*D _{A}.,„i_{X}* Effective diffusion coefficient (diffusivity) of component Aina mixture, cm

^{2}/s

*d _{r}* Liquid density at temperature

*T*and 1 atm, g/cm

^{3}

*d** _{20}* Liquid density at 20°C and 1 atm, g/cm

^{3}

*f,* Fugacity of component *i* in a mixture defined by Equation 2.85, bar

*fi ^{L}* Fugacity of pure liquid

*i*at

*T*and

*P,*bar

*GOR* Gas-to-oil ratio (scf/bbl)

/ Refractive index parameter defined in Equation 2.11

*K _{w}* Watson (UOP) К factor defined by Equation 2.8

*kj*Henry’s law constant defined by Equation 2.84, bar

*к gas,water* Henry’s law constant of a gas in water (Equation 2.85), bar

*M* Molecular weight, g/mol [kg/kmol]

*n* Sodium D line refractive index of liquid at 20°C and 1 atm, dimension

less, defined in Equation 2.10

*N _{c}* Carbon number (number of carbon atoms in a hydrocarbon molecule)

*P _{c}* Critical pressure, bar

*p»'i>* Vapor (saturation) pressure, bar

*P,* Reduced pressure (= P/P_{c}), dimensionless

*P _{r}^{v}“i’* Reduced vapor pressure at a given temperature (=

*P'*dimensionless

^{a}P/P_{c}),*R*Universal gas constant, 8.314 J/mol-K

*R;* Refractivity intercept in Equation 2.9

*SG* Specific gravity of liquid substance at 15.5°C (60°F) defined by Equation 2.1, dimensionless

*SG _{g}* Specific gravity of gas substance at 15.5°C (60°F) defined by Equation 2.3, dimensionless

*T*Boiling point, К

_{h}*T _{c}* Critical temperature, К

*T,* Flash point, К

*Т _{м}* Melting (freezing point) point, К

*V* Molar volume, cmVgmol

*V _{c}* Critical volume (molar), cm-Vmol (or critical specific volume, cmVg)

*x _{lvj}* Weight fraction of component

*i*in a mixture (usually used for liquids),

dimensionless

*Xp, x _{N}, x_{A}* Fractions (i.e., mole) of paraffins, naphthenes, and aromatics in a petroleum fraction, dimensionless

y, Mole fraction of *i* in a mixture (usually used for gases), dimensionless

Z Compressibility factor (= *PV/RT),* dimensionless

Z_{t}. Critical compressibility factor *(Z=P _{l}VJRT_{L}),* dimensionless

**GREEK LETTERS**

p Absolute (dynamic) viscosity, cp [mPa-s]; also used for dipole moment

*v* Kinematic viscosity defined by Equation 2.7, cSt [mm^{2}/s]

^{v}39(ioo) Kinematic viscosity of a liquid at 39°C (100°F), cSt (10^{-2} cm^{2}/s)

- 6, Solubility parameter for
*i,*(J/cm^{3})^{l/2}or (cal/cm^{3})^{1}'^{2} - 0 A property of hydrocarbon such as: M,
*T*_{c}, P_{c}, V_{c}, I, d, T_{h}, ...

p Density at a given temperature and pressure, g/cm^{3}

о Surface tension, dyn/cm [= mN/m]

cr_{H} Surface tension of a hydrocarbon at a given temperature, dyn/cm

o_{wo} Interfacial tension of oil and water at a given temperature, dyn/cm

со Acentric factor defined by Equation 2.5, dimensionless

*%* Viscosity parameter defined by Equation 2.72, (cp)^{-1}

Y, Activity coefficient of component *i* in liquid solution, dimensionless

**SUBSCRIPTS**

A Aromatic

N Naphthenic

*P* Paraffinic

*T* Value of a property at temperature *T*

r Reduced property, dimensionless

A reference state for *T* and *P *oo Value of a property at *M* -» oo

- 20 Value of a property at 20°C
- 39(100) Value of kinematic viscosity at 39°C (100°F) 99(210) Value of kinematic viscosity at 99°C (210°F)

**ACRONYMS**

API-TDB American Petroleum Institute - Technical Data Book EOS Equation of state

IUPAC International Union of Pure and Applied Chemistry

GOR Gas-to-oil ratio