Announcements 9/21/11 Prayer Exam 1 starts a week from Saturday! a. Doodle survey about exam review times, vote for times before Friday If you emailed me about Mathematica issues on HW 7 and still need to turn it in, do so by Friday Regarding showing your work for the TA: (Foxtrot)
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Announcements 9/21/11 Prayer Exam 1 starts a week from Saturday! a. a.Doodle survey about exam review times, vote for times before Friday If you emailed.
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Announcements 9/21/11 Prayer Exam 1 starts a week from Saturday!
a. Doodle survey about exam review times, vote for times before Friday
If you emailed me about Mathematica issues on HW 7 and still need to turn it in, do so by Friday
Regarding showing your work for the TA: (Foxtrot)
Video
Adiabatic cotton burner Mist from pressurized bottle
Special Processes: Review
Constant volume (isovolumetric) Constant pressure (isobaric) Constant temperature (isothermal) No heat added (adiabatic) General process?
a. Eint = ?
b. Won gas = ?
c. Qadded = ?
A
B
P
V
Last Special Case: Cyclical Processes
Eint = ?
Is it Wby gas or Won gas?
Qadded = ?
P
V
State 1
Engines: Energy Transformation
Qin = work by gas + Qout
Notation: Qh, Qc, Th, Tc, |W|
Qh = |W| + Qc
engineheat in(higher T)
work
exhaust out (lower T)
(a) - piston atroom temp and
atmosphericpressure P
Va
Heat Engine Example
(a-b) - gasheated to keep
volumeconstant as
cart rolls ontopiston P
Va
b
Heat Engine Example
(b-c) - gasheated toincrease
volume and liftthe cart
P
Va
b c
Heat Engine Example
(c-d) - gascooled to keep
volumeconstant atcart rolls off
piston
P
Va
b c
d
Heat Engine Example
(d-a) - gascooled to
reduce volumeback to initial
level
P
Va
b c
d
Heat Engine Example
Efficiency How good is your engine? Definition
Worked Problem A car engine produces 5000 W of power,
at 20 cycles/second. Its efficiency is 20%. What are |Wnet|, Qh, and Qc per cycle?
What do those quantities represent?
Reading Quiz (graded)
What is the name we use for the cycle which models how a gas engine works?
a. Brayton cycle b. Carnot cyclec. Diesel cycled. Otto cyclee. Tri cycle
Otto Cycle: Gas Engines (Starting at 2)
Piston is com-pressed quickly
Heat is then added quickly by igniting fuel (const volume)
Piston then expands quickly
Heat is then expelled quickly (by getting rid of old air)