Download Document

Unit 4. 02 devices with
Entrainment
tutorial
by Elizabeth Kelley Buzbee
AAS, RRT-NPS, RCP
The lion is upstream from the crane
The crane is downstream from
The lion
The stream of water is flowing from left to right
Upstream & downstream are relative terms of
location.. It depends in what direction your flow is
going & where one [lion] is in relation to the other
[crane]
The lion is upstream from the crane
The crane is downstream from the
lion
Who is the frog downstream from?
Who is the frog upstream from?
Now, is the lion upstream or downstream from the frog? Is
the frog upstream or downstream from the crane?
Is the crane upstream or
downstream from the lion?
If beavers builds a dam, the water upstream from
the dam will back up…
there will be increased water pressure upstream
From the obstruction.
Downstream, the flow may drop down to a trickle
• The pressure upstream from an obstruction
builds up
• The pressure down stream from an
obstruction drops off
If a beaver builds a dam at point B of the river,
what happens to the flow of the water upstream
from the beaver’s dam?
What happens to the water pressure upstream
from the dam? [A]
What happens to the water pressure downstream
from the dam? [C]
A
B
C
• Downstream from the obstruction the speed
or the velocity of the gas increases
• This increase in velocity will cause the
lateral pressure to drop
• A suction is created
Gas goes into restricted orifice A where the velocity
of the gas speeds up.
Air
C
A
02
02
&
Air
B
Air
This increased velocity of gas flow creates a vacuum
In the area just downstream from the restricted orifice B
Downstream from the orifice, the pressure drops
Air is pulled into the 02 flow so that there is more flow of air & 02
downstream from the restricted orifice C
How the entrainment mask works
02
flow
3 lpm
Air
A
C
02
&
Air
B
Air
The entrainment port at B is opened so that 1 lpm of 02 will pull
in 6 lpm of air
The total flow coming out of C is 3 lpm of 02 + [3 x 6]
The total flow rate coming out if C is 21 lpm
The Fi02 upstream from A was 100% but the Fi02 downstream
From B is lower because air is mixed with the 02.