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EGEE 451: energy conversion set 1
questions on lecture 1
46
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Undergraduate 4
10/29/2012

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Term
why convert energy?
Definition
make energy more convenient & easy to use
make energy easier to transport
to make it cleaner
Term
how do you measure energy conversion?
Definition
efficiency
Term
is it possible to completely convert energy from one form to another?
Definition
no
Term
define efficiency
Definition
output/input
Term
what is the 0th law of thermo?
Definition
if A is in thermal equilibrium with B, and B with C, then A is in thermal equilibrium with C
Term
what does the 0th law do/tell us?
Definition
-permits conduction of heat
-basis of measuring temp with thermometers
-heat goes from hot->cold until equilibrium
Term
classical vs. statistical thermo
Definition
classical considers properties of bulk matter while statistical takes into account atoms & molecules
Term
what is the 1st law of thermo?
Definition
conservation of energy
Term
what is work?
Definition
motion against an opposing force
Term
what is the 2nd law of thermo?
Definition
can't complete convert heat into work
Term
equation for internal energy
Definition
(DELTA)U = Q + W
Term
equation for enthalpy
Definition
H = U + PV
Term
equation for entropy
Definition
(DELTA)Stot = (DELTA)S - (DELTA(U)/T
Term
equation for Helmholtz energy
Definition
(DELTA)A = (DELTA)U - T(DELTA)S
Term
if a process is spontaneous, Helmholtz energy is __ and Gibbs free energy is __
Definition
negative
negative
Term
equations for Gibbs free energy
Definition
G = A + PV
(DELTA)G = -T(DELTA)S
Term
what is the 3nd law of thermo?
Definition
no cyclic process can cool a body to absolute zero
Term
Carnot efficiency
Definition
eta = W/Q_R = (T_H - T_L)/T_H
Term
in the Carnot cycle, the work is...
Definition
the area inside the rectangle on the P-V diagram
Term
for Carnot, Q_R is
Definition
the heat from the source
the area under the upper curve on the P-V diagram
Term
for Carnot, Q_S is
Definition
the heat to the sink
the area under the lower curve on the P-V diagram
Term
for Carnot, you get more work as...
Definition
(DELTA)T increases
Term
Carnot limit represents...
Definition
the maximum work that can be obtained from a quantity of heat
Term
thermal efficiency increases as as irreversibility __
Definition
decreases
Term
Carnot cycle run forward is a __.
reverse is __
Definition
heat engine
heat pump
Term
draw the Carnot cycle on a P-V diagram
Definition
***
Term
draw the Carnot cycle on a T-S diagram
Definition
***
Term
does Carnot efficiency depend on the working substance?
Definition
no
Term
the more reversible a process, the ___ thermal efficiency
Definition
higher
Term
give 3 examples of irreversible processes
Definition
non-isothermal heat transfer
turbulent flow
friction
Term
efficiency of any actual device is __ than Carnot efficiency
Definition
less
Term
why is actual efficiency never equal to ideal efficiency?
Definition
because actual devices have irreversibility (the ideal device is completely reversible)
Term
define economic efficiency of energy
Definition
(eta)_(econ)=(money in)/(energy out)
Term
describe a low economic eff.-low thermal eff. case, and give an example
Definition
fuel is both expensive and inefficient in making energy out per energy in
ex, use Fischer-Tropsch to make liquid fuel from coal
Term
describe a low economic eff.-high thermal eff. case, and give an example
Definition
fuel is expensive but high efficiency in making energy out per energy in
ex, usually only happens in special cases, like rocket fuel
Term
describe a high economic eff.-low thermal eff. case, and give an example
Definition
cheap but low efficiency in making energy out per energy in; people don't care about the efficiency because it's cheap
ex, gasoline now
Term
describe a high economic eff.-high thermal eff. case, and give an example
Definition
fuel is both cheap and really efficient (ideal case)
Term
define carbon efficiency
Definition
(CO2 out)/(energy out)
Term
name several ways to reduce CO2 emissions
Definition
-improve thermal efficiency so that less CO2-producing fuel use is necessary
-use CCS
-switch to fuel that emits less CO2 (biomass)
-switch to carbon-free energy sources (most renewables)
Term
CCS stands for __
Definition
carbon capture and sequestration
Term
name the 3 efficiencies we are concerned about in this course
Definition
economic efficiency
thermal efficiency
carbon efficiency
Term
explain how implementing CCS on a powerplat would impact the three efficiencies
Definition
carbon efficiency would go up
CCS reduces thermal efficiency of the plant
economic efficiency goes down because the CCS equipment costs extra
Term
define energy concentration, and when it is relevant
Definition
(energy)/(area)
relevant when large amounts of land are necessary to effect the energy (biomass, solar)
Term
define energy intensity
Definition
(energy)/(mass)

materials cost of energy
Term
define energy conversion efficiency
Definition
(energy out, form B)/(energy in, form A)
ex, how much energy goes into making ethanol from corn compared to the energy we get from burning the ethanol?
Term
define social efficiency
Definition
Qualitative concept indicating
how easy or difficult it is to get public to accept new technology
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