Fall wk 3 Mon'11'Oct'04

1
Fall wk 3 Mon.11.Oct.04

• Welcome, roll, questions
• Thermal physics and Energy Ch.3
• break
• continue Calculus Ch.1
• Looking ahead

Energy Systems, EJZ
2
Discuss Ch.3, Conventional conversion of energy

• Key points?
• Insights from team discussion?
• Questions?
• questions of fact Can we find answer in the
  text? What page?
• Outstanding questions of fact
• Outstanding significant questions

3
Energy conversion - outline

• Scientific principles App.A
• Review of Thermal Physics
• New Power and Efficiency
• Steam plant closed cycle
• Engine cycles open

4
Laws of Thermodynamics

• 0. Thermal equilibrium
• Energy can be neither created nor destroyed.
• Ex Heat in Work done internal energy
• 2. Entropy increases useful energy is lost to
  heat

5
Heat energy work
Energy force distance Joule Newton meter
J kg m2/s2, cal 4.1868 J 4 x 10-3
BTU Horsepower 1 hp 550 ft lb/s 746
Watt POWER rate of doing work
Energy/time Watts Joules/sec Efficiency
Energyin / Energyout Powerin / Powerout Q
What is a kilowatt-hour? A measure of A. Energy
B. Power C. Efficiency
6
Thermal energy ? heat engine

• Steam power plant
• closed cycle, external combustion
• burn fossil fuel ? heat water ? steam ? move
  turbines ? electricity
• Gas and diesel engines
• open cycle, internal combustion
• compress ? heat ? ignite ? expand ? motion

7
Steam plant
burn fuel ? heat water ? steam ? move turbines ?
electricity
Increase efficiency by decreasing losses
8
Generator motion ? electricity
Electric Power Voltage Current P VI Ohms
law Voltage Current Resistance V
IR Higher voltage transmission lower ohmic
losses
9
Engine cycles
compress ? heat ? ignite ? expand ? motion
Gas engines are usually less efficient than
diesel engines
10
Work done by a gas (CT 3, 64, green)
Work done pressure volume area under curve
(clockwise) Heat added work done change in
internal energy of gas
11
How to improve engine performance?

• thermal efficiency is limited, since waste heat
  is exhausted
• compression ratio diminishing returns, and
  higher temps ? preignition
• lower weight ? better performance a F/m
• aerodynamics small effect
• power train designs gradual improvements
• driving habits, mass transit

12
Calculus - outline

• Modified Calc HW
• Practice with logarithmic functions
• (Pre)Calculus question for seminar
• If global energy use increases by 2.5 per year,
  how long will it take for global demand to
  double?
• First, guess.
• What is the percent increase if it doubles?
• Hint D D0 at

13
Calc 1 HW 2

• Homework due this Thus Calc 1 HW 2 without
  Ch.1.5
• 1.4 1, 2, 9, 11, 14, 18, 26, 35
• 1.6 2, 4, 14, 28
• Next Thus Calc 1 HW 3
• 1.5 1, 10, 14, 16, 20, 29, 31, 34, 36
• 1.6 8, 18, 23

14
Phys 18 HW 1

• Thermal (and basic) physics problems due this
  Thus
• Ch.1 5, 7, 16, 18, 24, 26, 29
• Ch.18 4, 5, (24), 26, 28, 35, (73, 85)
• Problems in (parentheses) are not available on
  eGrade.
• Hand them in separately?
• I will post solutions after class Thus.
• Phys 18 HW 2 due next Thus
• Ch.18 (27), 29, 32, 33, (94)

15
Looking ahead

• Seminar in Sem II C2109 tonight
• Please put your teams best Q on the board
• before 500 so we can start on time
• Tomorrow
• Debate Coal vs Fission
• visitors will discuss sustainability and solar
  panels on Tuesday and Wednesday
• Later
• - TA available here Wed 1-3, QRC Fri 10-12
• - Next Mon. CE Fair well set up telescope

16
Heat of transformation ConcepTests
17
Work done by gas ConcepTests
18
Steam plant cycle
19
Diesel engine cycle
20
Hydroplant