Basic Equations, Two Phase Flow

subscript ggas
subscript lliquid

void fraction

αV =
Vg
Vg + Vl

αA =
Ag
Ag + Al
symboldescription
αvoid fraction
Vvolume
Aarea

mass flow rate

W = Wg + Wl
symboldescription
Wmass flow rate (kg/s)

volume flow rate

Q = Qg + Ql
symboldescription
Qvolume flow rate (m3/s)

mass flux

G
W
A
symboldescription
Gmass flux, or mass velocity (kg/sm2)
Wmass flow rate (see above)
Across section area

mean phase velocity
ug and ul refer to the averaged velocity over the area occupied by each phase, respectively
ug
Qg
Ag
ul
Ql
Al
symboldescription
umean velocity
Qvolume flow rate (see above)
Across section area

slip ratio
S
ug
ul
symboldescription
Sslip ratio
umean velocity (see above)

relative velocity

urugul
symboldescription
umean velocity (see above)

superficial phase velocity (volumetric flux)
 jg =
Qg
A
 jl =
Ql
A
symboldescription
 jsuperficial velocity
Qvolume flow rate (see above)
Across section area

volumetric flow fraction (volumetric quality)
β
Qg
Q
symboldescription
βvolumetric flow fraction
Qvolume flow rate (see above)

two phase mixture density
=
Ag
A
(ρg) +
Al
A
(ρl)
symboldescription
two phase mixture density
Across section area
ρdensity