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

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

Energy conversion - outline

• Scientific principles – App.A

• Review of Thermal Physics

• New: Power and Efficiency

• Steam plant: closed cycle

• Engine cycles: open

Laws of Thermodynamics

0. Thermal equilibrium

1. Energy can be neither created nor destroyed.

Ex: Heat in = Work done + internal energy

2. Entropy increases: useful energy is lost to heat

Heat = energy = workEnergy = 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

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

Steam plantburn fuel heat water steam move turbines electricity

Increase efficiency by

decreasing losses

Generator: motion electricity

Electric Power = Voltage * Current: P = VI

Ohm’s law: Voltage = Current * Resistance: V = IR

Higher voltage transmission: lower ohmic losses

Engine cyclescompress heat ignite expand motion

Gas engines are usually less efficient than diesel engines

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

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

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?

a. First, guess.b. What is the percent increase if it doubles?

c. Hint: D = D0 at

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

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)

Looking ahead

• Seminar in Sem II C2109 tonight

• Please put your team’s best Q on the board

before 5:00 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 – we’ll set up telescope

Heat of transformation ConcepTests

80

Work done by gas ConcepTests

Steam plant cycle

Diesel engine cycle

Hydroplant