A

cross-sectional area, m ²

A

system matrix

b

pressure ratio

b

input vector

c

speed of sound, m/s

C

sonic conductance, m ³/(s Pa)

C _d

discharge coefficient for orifice

c _P

specific heat capacity at constant pressure, J/(kg K)

c _v

specific heat capacity at constant volume, J/(kg K)

d, D

(internal) diameter, m

F

force, N

g

gravitational acceleration, m/s ²

h

coefficient of heat transfer, J/(m ² K)

H

total enthalpy, J

i

electric current, A

L

length, m

m

gas mass, kg

mass flow rate, kg/s

M

translationally moving mass, kg

n

polytropic index of expansion or compression

n

rotation speed, rpm

p

pressure, absolute pressure Pa, gauge pressure bar

P

power, kW

Q

heat, J

q _v

volume flow rate, m ³/s

R

gas constant, J/(kg K)

Re

Reynolds number

s

displacement, distance, m

t

time, s

T

temperature, C or K

u

input signal to control block

U

internal energy, J

v

velocity, m/s

v

specific volume, m ³ /kg

V

total volume, m ³

W

total work, J

w

flow velocity, m/s

x

position, m

x

state vector

?

ratio of specific heat capacites or index of isentropic expansion or compression

?

increment

?

damping coefficient of a second order system

?

efficiency

?

friction factor

?

dynamic viscosity, kg/(m S)

v

kinematic viscosity, m ²/s

p

density, kg/m ³

?

time constant, s

?

flow...