
181Fluid Flow
to believe that the faster a jet exits an orice, the faster
it mixes with the surrounding uid. While it is true
thatit entrains more mass, it is not mixing at a faster
rate; that is, downstream concentrations are not affected
by the free jet exit velocity.
The mass entrainment rate of a circular, free jet can be
estimated by the following equation
31
:
m
m
x
d
=
028
.
ρ
ρ
(9.23)
where
m
.
∞
is the mass of the surrounding gas entrained
m
.
j
is the mass of the jet
ρ
∞
is the density of the surrounding gas
ρ
j
is the density of the free jet
x is the distance downstream of the nozzle exit
d is the diameter of the nozzle port
The m ...