1. Energy in Thermal Processes
Chapter 11
Energy in Thermal Processes

2. Temperature and heat
Heat (Q): energy transferred between a system and its environment because of a temperature difference that exists between them
SI Unit: Joule
Alternative unit: calorie (cal):

3. Q Q Absorption of heat Specific heat (c): heat capacity per unit mass
Common states (phases) of matter: solid, liquid, gas
Latenet heat (L): the amount of energy per unit mass transferred during a phase change (boiling, condensation, melting, freezing, etc.) Q Q

4. Absorption of heat Q Q

5. Absorption of heat

6. Absorption of heat

7. Chapter 11
Problem 17
A 100-g aluminum calorimeter contains 250 g of water. The two substances are in thermal equilibrium at 10°C. Two metallic blocks are placed in the water. One is a 50-g piece of copper at 80°C. The other sample has a mass of 70 g and is originally at a temperature of 100°C. The entire system stabilizes at a final temperature of 20°C. Determine the specific heat of the unknown second sample.

8. Heat transfer mechanisms
Thermal conduction
Conduction rate:
Thermal resistance:
Conduction through a composite rod:
Thermal conductivity

9. Heat transfer mechanisms

10. Chapter 11
Problem 36
A box with a total surface area of 1.20 m2 and a wall thickness of 4.00 cm is made of an insulating material. A 10.0-W electric heater inside the box maintains the inside temperature at 15.0°C above the outside temperature. Find the thermal conductivity k of the insulating material.

11. Heat transfer mechanisms
Thermal radiation
Radiation rate:
Stefan-Boltzmann constant:
Absorption rate:
Emissivity
Josef Stefan
( )

12. Chapter 11
Problem 46
At high noon, the Sun delivers 1.00 kW to each square meter of a blacktop road. If the hot asphalt loses energy only by radiation, what is its equilibrium temperature?

13. Heat transfer mechanisms
Convection

14. Heat transfer mechanisms

15. Questions?

16. Answers to the even-numbered problems
Chapter 11
Problem 4
0.152 mm

17. Answers to the even-numbered problems
Chapter 11
Problem 12
467 pellets

18. Answers to the even-numbered problems
Chapter 11
Problem 16
1.7 kg

19. Answers to the even-numbered problems
Chapter 11
Problem 20
49 kJ

20. Answers to the even-numbered problems
Chapter 11
Problem 40
7.2 × 10-2 W/(m °C)

21. Answers to the even-numbered problems
Chapter 11
Problem 50
14.1 h