Introduction to Chemical Engineering Processes/Notation
A Note on Notation
Base Notation (in alphabetical order)
: 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
- Unless specified explicitly, assume that a given percent composition is in terms of the overall flowrate. So if you're given a flowrate in terms of kg/s and a compositoin of 30%, assume that the 30% is a mass fraction. If a given equation requires one or the other, it will explicitly be stated near the equation which is necessary.
: Density : Sum
If a particular component (rather than an arbitrary one) is considered, a specific letter is assigned to it:
- [A] is the molarity of 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.
- is the molar flowrate in stream 1.
- is the molar flow rate of component A in stream 1.
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.
- is a property of stream n. Note is the molar flow rate of stream n.
- 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.
If A is some value denoting a property then:
denotes the average property in stream n
denotes a total flow rate in steam n
denotes the flow rate of component i in stream n.
indicates a data point in a set.
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 rather than a standard equal sign.