This interactive simulation models an ideal
nozzle for an ideal diffuser.
This case we are fixing the outlet pressure,
P2, we fixed the inlet temperature and then
we can change the inlet velocity with this
slider.
And we can change the outlet diameter with
this slider.
And the idea is then we can solve mass balances,
energy balances, this is for ideal gas, compressible
fluid, and calculate the outlet velocity,
outlet temperature, the inlet pressure.
Here we are looking at the case of a nozzle,
meaning the outlet diameter is smaller than
the inlet diameter so for the case where a
small outlet diameter and a high velocity,
notice that the velocity increases significantly
and correspondingly kinetic energy is higher
than the enthalpy and the temperature is lower,
and there is a significant pressure drop for
this to be accomplished.
We have this high flow rate and this small
diameter.
If we make the outlet diameter larger than
the inlet diameter, the inlet diameter is
fixed in the simulation.
So if we make the outlet diameter larger then
this becomes a diffuser, when the outlet diameter
is larger than the inlet diameter.
And a diffuser, the temperature will increase
slightly, the pressure will increase, so our
way of looking at it is this inlet pressure
will be lower than 101.3 since that is fixed.
And the outlet velocity will be lower than
the inlet velocity because we have a much
bigger diameter.
So this simulation assumes no heat transfer
and again assumes ideal.
And subsonic flow.
So all the conditions are such that velocity
does not get to supersonic velocity.
So let's look at the interactive simulation.
So here we are looking at the interactive
simulation, we are at conditions where it
is a nozzle meaning that the outlet diameter
is smaller than the inlet diameter.
And so notice the velocity increases.
So we have more kinetic energy, and correspondingly
the temperature decreases slightly and the
pressure decreases.
Again, slight change in pressure.
And then the simulation, the outlet pressure
is fixed, so as I change the inlet velocity
for example.
Now it takes a higher pressure, and more temperature
decrease.
And then of course a higher outlet velocity.
So this is a nozzle, so let's look at if I
change the diameter, now the velocity change
is much smaller, the temperature change is
much smaller and I will get to the point where
these are equal.
Straight tube, well then nothing is happening.
If I have the outlet diameter larger, a diffuser,
now the velocity is lower.
The temperature is slightly higher and notice
the pressure is slightly higher.
We fixed the outlet pressure, that means we
calculate the inlet pressure to give these
values.
This is the diffuser, when the outlet diameter
is larger.
We can also look at plots, The dot shows where
we are in the system.
And the plot, excuse me, you will notice is
as a change the outlet diameter and move from
the case where we have a diffuser to the case
where we have a nozzle.
I increase the inlet velocity.
And you can see there is a bigger temperature
difference for the nozzle.
And also on this plot, we are showing incompressible
flow.
The diagram here is compressible flow, but
we are also showing what would happen if we
had incompressible flow.
And then likewise we are showing velocity
on this plot.
So the idea of this simulation is to get a
little better physical feeling of what happens
in a nozzle and a diffuser and what is the
difference between the two, as we saw the
energy balance, the mass balance, is for a
reversible.
This is an ideal nozzle or ideal diffuser.
