1. Chapter 2.2 Notes Work in Fluids

2. When work is done, we measure the force that moves a certain distance. In a fluid system, it is easier to measure the change in pressure. The change in pressure is what causes a fluid to move.

3. A Closed fluid system retains and re-circulates a working fluid. Examples of a closed fluid system include a hydraulic jack and the body’s circulatory system.

4. Fluid flows through an open fluid system only one time - it is not retained or re-circulated. Examples of an open fluid system include city water systems, an irragation system, and a fire truck water system.

6. A Hydraulic actuator is a closed system and uses hydraulic fluid to exert pressure on a piston and work is done when the piston moves a load. Hydraulic actuators are commonly used in airplane landing gears, bulldozer shovels, and forklifts.

7. A pump draws hydraulic fluid from a reservoir, creates a pressure difference, and forces fluid through the pipes under pressure. This pressure causes the system to either push or pull the load.

8. In a closed system, when heat is added to a gas in a cylinder, the gas expands to a new volume. The piston rises when heat is added to a gas in a cylinder, but the area of the cylinder does not change.

10. Work = Pressure x (Volume final – Volume initial ) (with a volume change) W = P x (V f – V i )

11. The pressure is 80 N/m 2, while the original Volume is 50 m 3 and the final volume is 60 m 3, how much work is done? W = P x (V f – V i ) W = 80 N/m 2 x (60 m 3 -50 m 3 ) W = 80 N/m 2 x 10 m 3 W = 800 N/m or 800 Joules

12. In an open system, such as a water pump, the water enters the system as a set pressure and the pump does work to increase the pressure of the water. If the same amount of water enters the system and leaves the system in a set amount of time, this is called a Steady Flow Process.Steady Flow Process

13. Work = (Pressure final – Pressure initial ) x Volume (with a pressure change) W = (P f – P i ) x V

14. The volume of water moved by a pump is 5000 ft 3. The pressure starts at 50 lb/ft 3 and increases to 60 lb/ft 3, what is the work done? W = (P f – P i ) x V W = (60 lb/ft 3 –50 lb/ft 3 ) x 5000 ft 3 W = 10 lb/ft 3 x 5000 ft 3 W = 50,000 lb

15. What type of fluid system are each of these, open or closed? Combustion Engine Circulatory System Refrigerator Compressor Rocket

16. Internal Combustion Engine The fuel is burned and not reused Open

17. Circulatory System Blood is re-circulated unless you’re bleeding profusely! Closed

18. Refrigerator Compressor The fluid is recycled Closed

19. Rocket The fuel is burned and cannot be reused Open