1. Hydraulic & Pneumatic Systems
Pressure: Applications & Atmospheric

2. Atmospheric Pressure
Our atmosphere is comprised of many layers each pushing down on the ones below it.
As a result, we experience atmospheric pressure
Typically kPa ( Pa) at sea level.
33.76 kPa on top of Mount Everest.
0 kPa at the edge of atmosphere.
The higher we go, the less pressure we feel.

3. Examples of Atmospheric Pressure
Using a drinking straw:
By drawing in air at end of straw a partial vacuum is created.
The atmospheric pressure pushes fluid up the straw.
Crushing a can:
Heated water at atmospheric pressure is cooled rapidly.
Causes major pressure drop inside can
Pressure outside can >> Pressure inside can
Can is crushed.

4. Volumetric Flow Rate
Defined as how fast the volume of a fluid is flowing past a certain point.
Given by:
Where:
qv = volumetric flow rate (m3/s or L / min)
V = Volume (m3)
∆t = time (s)
A = cross-sectional area (m2)
v = speed (m/s)

5. Example #1
Water is flowing through a circular pipe of radius 2.5m. If the water is moving with a speed of 2 m/s, what is the volumetric flow rate?

6. Example #2
How long will it take 45 m3 of water to flow past a point in a pipe if it is flowing at 2 m3/s?

7. Water Pressure in Industry
There are two industrial processes that use high pressure water in industry:
Hydroforming: High pressure water pushes metal against a die to shape it.
Water Jet Cutting: Water under high pressure and high speed is used to cut manufactured components.
PROS: Both processes are inexpensive and can make parts that are stronger and have more accurate geometry.
CONS: Both cost a lot to get setup, lots of cleanup after each use and water gets wasted.