Introduction to Chemical Engineering Processes/Notation

Base Notation (in alphabetical order)
$$ [i]_{n} $$ : Molarity of species i in stream n a, b, c, d: Stoichiometric coefficients. A: Area C: Molar concentration (mol/L) K: Equilibrium coefficient m: Mass MW: Molecular Weight (Molar Mass) n: Moles n: Number of data points (in statistics section) N: Number of components P: Pressure r: Regression coefficient R: Universal gas constant T: Temperature v: Velocity V: Volume x: Mole fraction in the liquid phase OR Mass fraction X: (molar) extent of reaction y: Mole fraction in the gas phase z: Overall composition Z: Compressibility

Greek
$$ \rho $$: Density $$ \Sigma $$: Sum

Subscripts
If a particular component (rather than an arbitrary one) is considered, a specific letter is assigned to it:
 * [A] is the molarity of A
 * $$ x_{A} $$ is the mass fraction of A

Similarly, referring to a specific stream (rather than any old stream you want), each is given a different number.
 * $$ \dot{n}_1 $$ is the molar flowrate in stream 1.
 * $$ \dot{n}_{A1} $$ is the molar flow rate of component A in stream 1.

Special subscripts:

If A is some value denoting a property of an arbitrary component stream, the letter i signifies the arbitrary component and the letter n signifies an arbitrary stream, i.e.
 * $$ A_n $$ is a property of stream n. Note $$ \dot{n}_n $$ is the molar flow rate of stream n.
 * $$ A_i $$ is a property of component i.

The subscript "gen" signifies generation of something inside the system.

The subscripts "in" and "out" signify flows into and out of the system.

Embellishments
If A is some value denoting a property then:

$$ \bar{A}_n $$ denotes the average property in stream n

$$ \dot{A}_n $$ denotes a total flow rate in steam n

$$ \dot{A}_{in} $$ denotes the flow rate of component i in stream n.

$$ \hat{A} $$ indicates a data point in a set.

$$ A_i^* $$ is a property of pure component i in a mixture.

Units Section/Dimensional Analysis
In the units section, the generic variables L, t, m, s, and A are used to demonstrate dimensional analysis. In order to avoid confusing dimensions with units (for example the unit m, meters, is a unit of length, not mass), if this notation is to be used, use the unit equivalence character $$ \dot= $$ rather than a standard equal sign.