symbol

standard units

description

alternative units

P

Pa

Pressure

Torr, atm

V

m3

volume

cm3, liter

N

moles

number of moles

R

J/mole K

universal gas constant

liter atm/mole °C, torr liter/mole °C

T

K

temperature

°C

m

kg

molecular mass

gm, amu

k

joules/K

Boltzmann's constant

ev/K, erg/K

v

m/s

molecular velocity

cm/s

c

m/s

average molecular velocity (various)

cm/s

J

#/m2 sec

flux (number crossing unit area/time)

#/cm2 sec

n

#/m3

molecular density

#/cm3

M

g/mole

molar mass

kgm/mole

λ

m

mean free path

cm

a

m

effective molecular diameter

cm

X

[dimensionless]

utilization

R_s

moles/second

surface reaction rate

molecules/second

K_s

m/sec

surface reaction rate constant (first order)

cm/second

S

m2

surface area

cm2

[species]

moles/m3

concentration of species

moles/cm3, molecules/cm3

Q

moles

total reactant

molecules

F_in

m3/sec

volumetric flow in (or out)

cm3/sec

t_res

seconds

residence time

t_con

seconds

consumption time

N_Av

#/gm mole

Avogadro's number

D

m2/sec

diffusion constant

cm2/sec

A

m2

cross-sectional area

cm2

L_d

m

diffusion length

cm

L

m

characteristic system length

cm

Pe

[dimensionless]

Peclet number = (feature size/diffusion length)^2

ρ_m

moles/m3

molar density

moles/cm3

ρ

kg/m3

mass density

g/cm3

U

m/sec

fluid velocity

cm/sec

μ

kg/m sec

viscosity

gm/cm sec = Poise

Re

[dimensionless]

Reynolds number = (feature size/momentum diffusion length)^2

F_sccm

std. cm3/min

molar flow (standard units)

H

m

height of chamber

cm

r

m

radial distance

cm

R_c

m

radius of chamber

cm

F_m

moles/second

molar flow

C

molecules/m3

molar concentration

moles/cm3

L_Th

m

Thiele length

cm

ν

m2/sec

kinematic viscosity, μ/ρ

cm2/sec

c_p

J/kgm

heat capacity at constant pressure

J/gm

c_vol

J/m3

volumetric heat capacity

J/cm3

K_th

W/m K

thermal conductivity

W/cm K

c

m/s

velocity of light

cm/s

Sigma

W/m2 K4

Stefan-Boltzmann constant

W/cm2 K4

ϵ

[dimensionless]

emissivity

P_m

W/m2

radiated power

W/cm2

d

m

gap between planes

cm

G

Joules/mole

free enthalpy or Gibbs Free Energy

calories/mole

S

Joules/mole K

entropy

calories/mole

E

Joules/mole

internal energy

calories/mole

H

Joules/mole

enthalpy

calories/mole

ΔH_vap

Joules/mole

heat of vaporization

calories/mole

E_a

Joules/mole

activation energy

calories/mole

θ

[dimensionless]

fraction of occupied surface sites

RSC

[dimensionless]

reactive sticking coefficient