1. Instructor’s Visual Aids Heat Work and Energy. A First Course in Thermodynamics © 2002, F. A. Kulacki Chapter 4 Module 2 Slide 1 The Energy Balance for Closed Systems: The First Law and Heat The Energy Balance for Closed Systems The First Law and Heat

2. Instructor’s Visual Aids Heat Work and Energy. A First Course in Thermodynamics © 2002, F. A. Kulacki Chapter 4 Module 2 Slide 2 The Energy Balance for Closed Systems: The First Law and Heat Definition of heat...

3. Instructor’s Visual Aids Heat Work and Energy. A First Course in Thermodynamics © 2002, F. A. Kulacki Chapter 4 Module 2 Slide 3 The Energy Balance for Closed Systems: The First Law and Heat The First Law The adiabatic work done on a closed system is independent of path for two given states.

4. Instructor’s Visual Aids Heat Work and Energy. A First Course in Thermodynamics © 2002, F. A. Kulacki Chapter 4 Module 2 Slide 4 The Energy Balance for Closed Systems: The First Law and Heat Heat: The result of non-adiabatic processes Non-adiabatic path, i.e., Q 1-2 > 0. Adiabatic path, i.e., Q 1-2 = 0. P1P1 P2P2

5. Instructor’s Visual Aids Heat Work and Energy. A First Course in Thermodynamics © 2002, F. A. Kulacki Chapter 4 Module 2 Slide 5 The Energy Balance for Closed Systems: The First Law and Heat Heat defined

6. Instructor’s Visual Aids Heat Work and Energy. A First Course in Thermodynamics © 2002, F. A. Kulacki Chapter 4 Module 2 Slide 6 The Energy Balance for Closed Systems: The First Law and Heat Heat defined Heat transfer to the system: Heat transfer from the system:

7. Instructor’s Visual Aids Heat Work and Energy. A First Course in Thermodynamics © 2002, F. A. Kulacki Chapter 4 Module 2 Slide 7 The Energy Balance for Closed Systems: The First Law and Heat Energy balances...

8. Instructor’s Visual Aids Heat Work and Energy. A First Course in Thermodynamics © 2002, F. A. Kulacki Chapter 4 Module 2 Slide 8 The Energy Balance for Closed Systems: The First Law and Heat Energy Balances = Change of Energy in the System Change of Energy in the System - Heat Transfer at System Boundary Heat Transfer at System Boundary Work Done by the System Work Done by the System These terms are evaluated at the system boundary. They represent energetic interactions between the system and its surroundings.

9. Instructor’s Visual Aids Heat Work and Energy. A First Course in Thermodynamics © 2002, F. A. Kulacki Chapter 4 Module 2 Slide 9 The Energy Balance for Closed Systems: The First Law and Heat Mechanical Work Out Heat Loss, (W) Motor Electrical Power Input (W) m z Example 1

10. Instructor’s Visual Aids Heat Work and Energy. A First Course in Thermodynamics © 2002, F. A. Kulacki Chapter 4 Module 2 Slide 10 The Energy Balance for Closed Systems: The First Law and Heat Motor m Example 1 For steady operation, there is no change of the state of the system, and

11. Instructor’s Visual Aids Heat Work and Energy. A First Course in Thermodynamics © 2002, F. A. Kulacki Chapter 4 Module 2 Slide 11 The Energy Balance for Closed Systems: The First Law and Heat Example 2 Mechanical Work to Raise the Mass, m Heat Loss from from Motor Force = mg Battery has stored energy. It is released via electrical current. M B m System Boundary

12. Instructor’s Visual Aids Heat Work and Energy. A First Course in Thermodynamics © 2002, F. A. Kulacki Chapter 4 Module 2 Slide 12 The Energy Balance for Closed Systems: The First Law and Heat Example 2 M B m For transient operation, chemical energy stored in the battery is converted to electrical power and to mechanical work and heat.

13. Instructor’s Visual Aids Heat Work and Energy. A First Course in Thermodynamics © 2002, F. A. Kulacki Chapter 4 Module 2 Slide 13 The Energy Balance for Closed Systems: The First Law and Heat Example 3 Q5Q5Q5Q5 To correctly analyze this arrangement, all energy & work transfers must be counted. Where is the primary energy source? What are the possible systems for analysis? B W Motor Q1Q1Q1Q1 Q2Q2Q2Q2 Q3Q3Q3Q3 Q4Q4Q4Q4 Fan Battery

14. Instructor’s Visual Aids Heat Work and Energy. A First Course in Thermodynamics © 2002, F. A. Kulacki Chapter 4 Module 2 Slide 14 The Energy Balance for Closed Systems: The First Law and Heat Example 4 Solar Pond

15. Instructor’s Visual Aids Heat Work and Energy. A First Course in Thermodynamics © 2002, F. A. Kulacki Chapter 4 Module 2 Slide 15 The Energy Balance for Closed Systems: The First Law and Heat Cyclic processes...

16. Instructor’s Visual Aids Heat Work and Energy. A First Course in Thermodynamics © 2002, F. A. Kulacki Chapter 4 Module 2 Slide 16 The Energy Balance for Closed Systems: The First Law and Heat Cyclic Processes P1P1 P2P2 S1S1S1S1 S2S2S2S2

17. Instructor’s Visual Aids Heat Work and Energy. A First Course in Thermodynamics © 2002, F. A. Kulacki Chapter 4 Module 2 Slide 17 The Energy Balance for Closed Systems: The First Law and Heat Equivalence of heat and work This is an important result that says the cyclic heat and work are the same. It establishes that heat and work are different forms of energy.

18. Instructor’s Visual Aids Heat Work and Energy. A First Course in Thermodynamics © 2002, F. A. Kulacki Chapter 4 Module 2 Slide 18 The Energy Balance for Closed Systems: The First Law and Heat Key concepts and terms Adiabatic Process Cycle Cyclic Heat Cyclic Work Energy Heat Heat Transfer Internal Energy