1. First Law of Thermodynamics
Chapter Five Part I
First Law of Thermodynamics

2. First Law of thermodynamics
States that:
“Energy cannot be created or destroyed BUT it can be changed from one form to another”

3. Therefore:
The first law of thermodynamics is an expression of the conservation of energy principle.
Energy can cross the boundaries of a closed system in the form of heat or work.

6. or

9. Example: On a hot summer day, a student turns his fan on when he leaves his room in the morning. When he returns in the evening, will the room be warmer or cooler than the neighboring rooms? Why? Assume all the doors and windows are kept closed.
Answer: Warmer. Because energy is added to the room air in the form of electrical work.

10. Use textbook page 163 to read example statement.

13. Watt (J/s)=VI

30. 5–61 Air enters an adiabatic nozzle steadily at 300 kPa, 200°C, and 30 m/s and leaves at 100 kPa and 180 m/s. The inlet area of the nozzle is 80 cm2. Determine
(a) the mass flow rate through the nozzle,
(b) the exit temperature of the air, and
(c) the exit area of the nozzle.