ConcepTests in Chemical
Engineering Thermodynamics
Note: Slides marked with JLF were adapted from the ConcepTests of
John L. Falconer, U. Colorado. Cf. Chem. Eng. Ed. 2004,2007
Day1 Review
1.3 What causes an azeotrope?
A. The components can’t be distilled.
B. The components have similar boiling temperatures.
C. The components like each other in the extreme.
D. The components dislike each other in the extreme.
Day1 Review
1.4 What’s the difference between a chemist and a
chemical engineer?
A. Engineers like numbers.
B. About 20k$/yr.
C. Engineers care more about profits.
D. Engineers ask, “How does it work?”
Day2 Preview
1.1 What is temperature?
A. “Hotness.”
B. A measure of heat.
C. A measure of kinetic energy.
D. What a thermometer says.
Day1 Review
1.2 The picture below represents hard spheres
colliding in a planar box (like an air hockey table).
Which represents the area of the box that should
be used to compute density?
A. The blue area.
B. The area inside the green
(and grey) bars.
C. None of the above.
Day2 Review
2.1. Which of the following represents an ideal
gas?
(a)
(b)
10
u/k (K)
u/k (K)
10
5
0
-5
5
0
-5
-10
-10
0
0.2 0.4 0.6
r (nm)
0
0.8
u/k (K)
(c)
0.2 0.4 0.6
r (nm)
(d)
60
40
20
0
-20
-40
1
0.5
0
-0.5
-1
-1.5
0
0
0.2 0.4 0.6
r (nm)
0.8
1
2
0.8
Day2 Review
2.2 Which is characteristic of a liquid relative to a
vapor?
A. Liquid molecules move slower.
B. Liquid has a higher pressure.
C. Liquid molecules collide more.
D. The liquid has more energy.
Day2 Review
2.3 For water at 375C and 10 MPa, find the
internal energy (kJ/kg).
A. 2596.9
B. 2699.6
C. 2766.0
D. 2833.1
Day2 Review
2.4 The outlet from a turbine consists of steam at
100C and an entropy (S) of 7 kJ/kg-K. What is its
quality?
A. 5%
B. 10%
C. 90%
D. 95%
E. 100%
Day1 Review
3.1 When running a turbine, you want to recover
as much energy as work as possible. If the
efficiency is, say, 75% then 25% of the possible
work must be lost. The lost work must show up in
the turbine outlet stream somehow, but how?
A. Its pressure is relatively higher.
B. Its velocity is relatively higher.
C. Its temperature is relatively higher.
D. Its enthalpy is relatively higher.
Day3 Review
3.2 What causes the efficiency of a turbine to be
less than 100%?
A. Reversibility.
B. Pressure gradient.
C. Disorder.
D. Stirring.
Day4 begin
4.1 Two molecules are bouncing in 2D with molecular
weight of 16g/mole. Their velocities (m/s) are given by:
<555, -432>, < -555,432>. Estimate the temperature in the
box (K).
A. 700
B. 800
C. 900
D. 1000
4.2 In these piston/cylinders, when the red stop is
slipped out, the gas expands, and the piston moves
until it hits the black stops. Each system is adiabatic.
Each starts at 10 atm and 25oC and are ideal gases.
Which has the largest lost work?JLF*
vacuum
vacuum
vacuum
A
B
C
2 kg
1 kg
gas
gas
gas
4.3 The curve represents an adiabatic reversible
process for an ideal gas. Which regions cannot be
reached by an adiabatic irreversible process?
JLF
9
B
9
U
6
3
6
3
0
0.5
3.5
0
6.5
0.5
V
3.5
V
C. All regions can
be reached
9
U
U
A
6
3
0
0.5
3.5
V
6.5
6.5
Day4 Preview
4.4 High pressure steam flows through an
adiabatic turbine to steadily produce work. Which
is the best energy balance for solving this
problem?
A. Hin*min – Hout*mout + W = d(mU)/dt
B. DU = Q + W
C. DH = Q + W
D. DU = DPV + W + mDv2/2
Day4 Preview
4.5 High pressure steam flows into a piston-cylinder
to produce work. Which is the most appropriate
energy balance for solving this problem?
A. Hin*min – Hout*mout + W = d(mU)/dt
B. DU = Q + W
C. DH = Q + W
D. DU = DPV + W + mDv2/2
Day6 Preview
6.1 Steam at 200 bars and 600C flows through a
valve and out to the atmosphere. What will be the
temperature after the expansion?
A. 550
B. 523
C. 3539
D. 3489
Day6 Preview
6.2 A gas is filling a rigid tank from a supply
line. Which of the following represents the
most appropriate energy balance?
A. DH = Q + W
B. DU = Q + W
C. d(nU)=Hdn
D. DnU = HDn
Day6 Preview
6.3 A gas is leaking from a rigid tank into the
air. Which of the following represents the
most appropriate energy balance?
A. DH = Q + W
B. DU = Q + W
C. d(nU)=Hdn
D. DnU = HDn
Day6 Preview
6.4 An ideal gas (Cp=3.5R) is adiabatically
and reversibly compressed in a steady state
process from 25C and 1bar to 10bar. What
is the exit temperature (C)?
A. 300
B. 50
C. 500
D. 100
Day6 Preview
6.5 A ideal gas (Cp=3.5R) is adiabatically
and reversibly compressed in a steady state
process from 25C and 1bar to 10bar. What
is the work requirement (J/mol)?
A. 2000
B. 8000
C. 4000
D. 9000
Day7 Preview
7.1 Two exit streams leave a turbine. One
stream is given, the other can be inferred
from the throttle. The turbine produces
100kW. Estimate the heat loss (kW).
(1)1100kg/hr
A. 0.5
3.5MPa
1.5MPa
350 C
110 kg/hr
B. 5
C. 15
D. 50
(2)
225 C
(3)
0.8MPa
990 kg/hr
1 bar
120 C
Day7 Preview
7.2 Which of the following represents the
value for the following integral?
3
 xdx
A. 1
B. 2
C. 4
D. 8
1
Day7 Preview
7.3 Which of the following represents the
value for the following integral?
3
 ln( x)(1  x  0.5x )dx
2
1
A. 5
B. 50
C. 500
D. 5000
Day7 Preview
7.4 (Ex2.15) An insulated tank initially contains 500 kg of
steam and water at 2.0 MPa. Half of the tank volume is
occupied by liquid and half by vapor. The temperature (C) of
the tank initially is closest to:
A. 25
B. 100
C. 150
D. 200
Day7 Preview
7.5 Steam at 150 bars and 600 C passes through a heater
expander and emerges at 100 bars and 700 C. There is no
flow of work into or out of the heater-expander, but heat is
supplied. Using the steam tables, compute the flow of heat
(kJ/kg) into the heater expander per mole of steam.
A. 200
B. 300
C. 400
D. 500
Day7 Preview
7.6 Steam at 150 bars and 600 C passes through a
heater expander. Compute the (dimensionless) value
of [H(150,600)-H(1,600)]/RT for steam at the inlet
conditions.
A. 0.3
B.
0.03
C. -0.3
D. -0.03
Day7 QikQiz
QQ1.1.1 What is the relationship for the force vs. distance,
F(r), between two molecules according to the Lennard-Jones
potential model?
A.
 r  

 -   r  
 0 r  

B.
  12   6 
4   -   
 r  
 r 
C.
 r 12  r 6 
4   -   
   
  
D.
12
6

-4
 
  
12   - 6   
r   r 
 r  
Day7 QikQiz
QQ1.1.2 Molecules A and B can be represented by the
square-well potential. For molecule A,  = 0.4 nm and  =
20e-22 J. For molecule B,  = 0.8 nm and  = 10e-22 J.
Which molecule would you expect to have the higher boiling
temperature?
A.
B.
Day7 QikQiz
QQ1.1.3 Steam initially at 20 MPa, T = 366C, and H = 2421.6
kJ/kg is throttled to 1.0 MPa. What % of the expanded stream
is liquid?
A. 80
B. 60
C. 40
D. 20
Day7 QikQiz
QQ1.1.4 Write the most appropriate energy balance for the
following: A compressor is filling the Goodyear blimp.
System: the blimp and its contents
A. DU = Q + W
B. d(nU) = Hdn + W
C. D(nU) = HDn + Q + W
D. DH = Q + W
Day8 Preview
8.1 An insulated tank initially contains 500 kg of steam and
water at 2.0 MPa. Half of the tank volume is occupied by liquid
and half by vapor. 25 kg of moisture free vapor is vented from
the tank so that the pressure and temperature are always
uniform throughout the tank. Analyze the situation carefully
and calculate the final pressure in the tank. E-bal?
A. DU = Q + W
B. d(nU) = Hdn + W
C. D(nU) = HDn + W
D. DH = Q + W
Day8 Preview
8.2 In an old-fashioned locomotive an insulated piston+
cylinder is connected through a valve to a steam supply line at
3MPa and 300°C. The back side of the piston is vented to the
atmosphere at the right side of the cylinder. The volume of the
cylinder is 70 liters. When the valve opens the piston is
touching the left side of the cylinder. As the piston moves to
the right it accomplishes 108 kJ of work before it touches the
right side of the cylinder. Then, the cylinder contains 0.5 kg of
steam and the temperature remains at 300°C.
A. DU = Q + W
B. d(nU) = Hdn + W
C. D(nU) = HDn + W
D. DH = Q + W
Day8 Preview
8.3 Megan is half Kevin’s age. In six more
years, she’ll be four-fifths Kevin’s age. In 10
years, she’ll be six-sevenths Kevin’s age.
Neither is a teenager. How old is Megan now?
A. 1
B. 2
C. 3
D. 4
Day8 Preview
8.4 Identify the engineer based on the
following:
A. This room is a mess!
B. Would it be too much to ask for you to put your sox in
their drawers?!
C. I know my calculator is in here somewhere!
D. The entropy in this room is 50 MJ/mol-K!
Day8 Preview
8.5 Two coins are tossed once each. If heads,
the coin is placed in boxA. If tails, the coin is
placed in boxB. What is the probability that
one coin is in each box?
A. 0%
B. 10%
C. 25%
D. 50%
Day8 Preview
8.6 Five coins are tossed once each. If heads,
the coin is placed in boxA. If tails, the coin is
placed in boxB. What is the probability that
one coin is in boxA?
A. 10%
B. 15%
C. 20%
D. 25%
Day9 Preview
9.1 Five coins are tossed once each. If heads,
the coin is placed in boxA. If tails, the coin is
placed in boxB. What is the probability that
one coin is in boxA?
A. 10%
B. 15%
C. 20%
D. 25%
Day9 Preview
9.2 Four coins are tossed once each. If heads,
the coin is placed in boxA. If tails, the coin is
placed in boxB. What is the probability that
one coin is in boxA?
A. 10%
B. 15%
C. 20%
D. 25%
Day9 Preview
9.3 Do not use a calculator to solve the
following. Compute:
log10(8000)-log10(4)-log10(2)=
A. 3
B. 2
C. 1
D. 0
Day9 Preview
9.4 Nitrogen at 300K and 10bar is adiabatically
and reversibly expanded to 1bar. What is the
final temperature (K)?
A. 150
B. 200
C. 250
D. 300
Day9 Preview
9.5 Nitrogen at 300K and 10bar is throttled to
1bar. What is the final temperature(K)?
A. 150
B. 200
C. 250
D. 300
Day9 Preview
9.6 Suppose two boxes but the one with NA
particles is three times as large as the empty
box. Then what is the change in entropy?
A. Rln(4/3)
B. Rln(3/4)
C. Rln(4/1)
D. Rln(1/4)
Day10 Preview
10.1 Three moles of N2 at 2 bars and 300K are
expanded into a box that is 33.33% larger.
Then what is the DS?
A. Rln(4/3)
B. Rln(3/4)
C. 3Rln(4/3)
D. 3Rln(3/4)
Day10 Preview
10.2 One mole of O2 at 2 bars and 300K is
expanded into a box that is four times larger.
Then what is the DS?
A. Rln(4/3)
B. Rln(3/4)
C. Rln(4/1)
D. Rln(1/4)
Day10 Preview
10.3 One mole of O2 is mixed with 3 moles of
N2 at 2 bars and 300K. Then what is the final
pressure (bar)?
A. 2
B. 0.5
C. 0.25
D. 1
Day10 Preview
10.4 One mole of O2 is mixed with 3 moles of N2 at 2
bars and 300K. Then what is the DS?
A. Rln(4/3)
B. 3Rln(4/3)
C. Rln(4/1)+Rln(4/3)
D. Rln(4/1)+3Rln(4/3)
Day10 Preview
10.5 One mole of O2 is mixed with 3 moles of N2 at 2
bars and 300K. Then what is the DS/R?
A. 0.33ln(4/3) + 0.67ln(1/3)
B. 0.25ln(0.25)+0.75ln(0.75)
C. -0.25ln(1/4)-0.75ln(3/4)
D. ln(4/1)+3ln(4/3)
Day10 Preview
10.6 (Closed book) Estimate Cv/R for He.
A. 1.0
B. 1.5
C. 2.0
D. 2.5
Day10 Preview
10.7 (Closed book) Estimate Cv/R for N2.
A. 1.5
B. 2.0
C. 2.5
D. 3.0
Day11 QikQiz
QQ1.2.1 Identify the most appropriate energy balance for the
following situation. A pot of water brought to a boil from initially
cold water in a pressure cooker on the oven with the pressure
relief valve operating perfectly. System: the pot and its
contents.
A. DU = Q + W
B. d(nU) = Hdn + Q + W
C. D(nU) = HDn + Q + W
D. DH = Q + W
Day11 QikQiz
QQ1.2.1b A disk is initially at the position (0.2,0.2)nm
in a box that is 5nm on a side with its lower left corner
at the origin in Cartesian coordinates. The disk is 0.4
nm in diameter. The velocity of the disk is
(543,456)m/s. Compute the time (ns) when the disk
collides with the east wall.
A. 0.0101
B. 0.0085
C. 0.0110
D. 0.0088
Day11 QikQiz
QQ1.2.2 If I fill an empty helium cylinder adiabatically
to 1800 psia from a line at 300K, then seal it and
allow it to equilibrate with the surrounding air on a
300K day, what will be the final pressure in the
cylinder (psia)?
A. 1080
B. 1350
C. 1800
D. 2100
Day11 QikQiz
QQ1.2.3 For a system of 6 particles distributed
between two boxes, what is the % of distinguishable
microstates corresponding to the macrostate with 4
particles in Box A and 2 particles in Box B?
A. 20%
B. 15%
C. 30%
D. 80%
Day11 QikQiz
QQ1.2.4 One mole of O2 is mixed with 4 moles of N2
at 2 bars and 300K. Then what is the DS/R?
A. 0.2ln(0.2) + 0.8ln(0.8)
B. 0.25ln(0.25)+0.75ln(0.75)
C. -0.25ln(1/4)-0.75ln(3/4)
D. [ln(5/1)+4ln(5/4)]/5
Day12 Preview
12.1 Charlie was cleaning his living room. He
lifted a sofa cushion and found an equal
number of pennies, nickels, and dimes totaling
$1.28. How many of each coin did he find?
A. 4
B. 5
C. 6
D. 7
Day12 Preview
12.2 A steam engine is to operate between
500C and 50C. Estimate its thermodynamic
efficiency(%) according to the Carnot guideline.
A. 20
B. 40
C. 60
D. 80
Day12 Preview
12.3 A heat pump converts work into heat, extracting
heat from a colder source and supplying it to the
higher temperature sink. Suppose 30kW of heat is to
be pumped to 80 from 30F. Estimate how much work
(kW) is required if Carnot efficiency is achieved.
A. 30
B. 20
C. 10
D. 5
Day12 Preview
12.4 Steam is supplied to a steady state
turbine at 10 MPa and 600°C. The discharge
from the adiabatic, reversible turbine is at 25C.
Determine the quality of the outlet steam (%).
A. 85
B. 90
C. 95
D. 100
Day12 Preview
12.5 Steam is supplied to a steady state
turbine at 10 MPa and 600°C. The discharge
from the adiabatic, reversible turbine is at 25C.
Determine the work generated (kJ/kg).
A. 1500
B. 2000
C. 2500
D. 3000
Day13 Preview
13.1 Steam undergoes a state change from
450 C and 3.5 MPa to 150C and 0.3MPa.
Determine DS (kJ/kg-K) from (a) steam tables.
A. 0.01
B. 0.03
C. 0.07
D. 0.14
Day13 Preview
13.2 Steam undergoes a state change from 450
C and 3.5 MPa to 150C and 0.3MPa.
Determine DS (kJ/kg-K) from (b) IG assumption.
A. 0.01
B. 0.03
C. 0.07
D. 0.14
Day13 Preview
13.3 Steam undergoes a sudden state change
from 600K and 1 MPa to double the volume.
Determine Tf (C) from (b) steam tables.
A. 300
B. 321
C. 327
D. 333
Day13 Preview
13.4 Instead of burning gas directly to get heat,
it is proposed to run a heat engine (HE) that
runs a heat pump (HP). Qh =40kJ/h.
TF =800K;TS =263; Th =293. HE exhausts to TS.
Compute QF (kJ/h)
A. 10
B. 6
C. 4
D. 3
Day13 Preview
13.5 1mol/min air enters at 500K, 2bar and
exits at 350K, 1bar. The process produces
2000J/min of work. It also exchanges heat with
a reservoir at 300K. Estimate Sgen.
A. -1.2
B. 0
C. 1.2
D. 3.3
Day14 Preview
14.1 A process produces as much work as
possible from a turbine operating between
10MPa and exhausting at 40C, sat vapor.
Estimate the entropy at the outlet.
A. 8.35
B. 8.25
C. 7.68
D. 0.57
Day14 Preview
14.2 A process produces as much work as
possible from a turbine operating between
10MPa and exhausting at 40C, sat vapor.
Estimate the work (kJ/kg).
A. 5200
B. 2625
C. 2573
D. 2406
Day14 Preview
14.3 A process heats saturated liquid water
from 40C to steam at 10MPa and 1225C.
Estimate the heat required (kJ/kg).
A. 5200
B. 5000
C. 2625
D. 167.5
Day14 Preview
14.4 A process produces as much work as possible
from a turbine operating between 10MPa and
exhausting at 40C, sat steam. The process condenses
the vapor and pumps it to 10MPa (Wp~0) then reheats
to steam at the turbine inlet conditions. Estimate the
thermal efficiency (W/QH) of this cycle.
A. 0.50
B. 0.45
C. 0.40
D. 0.35
Day14 Preview
14.5 A process produces as much work as possible
from a turbine operating with a max pressure of
10MPa and exhausting at 40C, sat steam. The boiler
temperature is constrained by the softening
temperature of steel. If you lower the temperature
entering the turbine, the quality exiting will ____.
A. Increase
B. Decrease
Day14 Preview
14.6 A process produces as much work as possible
from a turbine operating between 10MPa and
exhausting at 40C, sat steam. The process condenses
the vapor and pumps it to 10MPa (Wp~0) then reheats
to steam at the turbine inlet conditions. Compute the
thermodynamic efficiency of a Carnot cycle operating
in the same temperature range.
A. 0.50
B. 0.65
C. 0.80
D. 0.95
Day15 Preview
15.1 A turbine compresses Freon134a
(Cp/R=10.2, MW=102) from sat vapor at
0.126MPa to 0.789MPa. Estimate the minimal
work requirement (kJ/kg) assuming the ideal
gas law. (Hint: p654 for Tsat)
A. 50
B. 45
C. 40
D. 35
Day15 Preview
15.2 A valve throttles Freon134a (Cp/R=10.2,
MW=102) from sat Liq at 0.789MPa to
0.126MPa. Estimate the enthalpy (kJ/kg) at
the outlet. (Hint: p654)
A. 415
B. 385
C. 245
D. 175
Day15 Preview
15.3 A valve throttles Freon134a (Cp/R=10.2,
MW=102) from sat Liq at 0.789MPa to
0.126MPa. The fluid from the valve is heated
to saturated vapor. Estimate the ratio of this
heat divided by the work of compressing the
ideal gas from 0.126 to 0.789MPa (QL/W).
A. 4.5
B. 3.5
C. 2.5
D. 1.5
Day15 Preview
15.4 A turbine compresses Freon134a
(Cp/R=10.2, MW=102) from sat vapor at
0.126MPa to 0.789MPa. Estimate the minimal
work requirement (kJ/kg) using the chart on
p653.
A. 50
B. 45
C. 40
D. 35
Day15 Preview
16.h1 The optimal intermediate pressure for
continuous two-stage adiabatic compression of
an ideal guess is:
A. P*=(P1+P2)/2
B. P*=(P1+P2)/3
C. P*=(P1+P2)/4
D. P*=(P1*P2)½
Day15 Preview
16.h2 HW3.17. The work produced (J/g) is:
A. 800
B. 1000
C. 1200
D. 1400
Day15 Preview
16.h2 HW3.27. The work required for
compressor 1 (J/g) is:
A. 140
B. 120
C. 100
D. 80
Day15 Preview
16.h4 HW3.33. The initial can pressure (bar) is:
A. 190
B. 180
C. 160
D. 150
16.1 Which system will have the largest entropy
change when the blue partition is removed?
The gases are ideal.
JLF
A
2 atm
N2
B
1 atm
O2
C
Vacuum
3 atm
N2
3 atm
N2
D
1 atm
O2
2 atm
N2
Vacuum
16.2 Which of the following processes could run
under continuous operation? JLF
hot
hot A. 1 + 2
B. 3 + 4
QH
QH
W
W
C. 4
1
2
D. 3
QC
QC
E. 1 + 3
cold
cold
hot
QH
3
hot
QH
W
4
QC
cold
W
QC
cold
16.3 This picture shows a DNA molecule on a surface
with vertical pillars on half the surface. What will
the DNA do? JLF
A. Move into the pillars more
B. Move out onto the open area
C. Stay where it is
16.4 Adiabatic expansions and compressions are
shown. One is reversible and one irreversible in each
figure. Which are the irreversible curves? JLF
A. 1 & 3
B. 1 & 4
C. 2 & 3
D. 2 & 4
start
P
1
2
3
P
4
start
T
T
16.5 Which diagram corresponds to a Carnot heat
pump in which both adiabatic steps in the cycle are
irreversible? JLF
A1
B1
4
T
4
T
2
C
2
3
S
D1
4
1
T
3
S
4
T
3
2
S
4
3
S
Day 16 QikQiz 3
QQ1.3.1 A process produces as much work as
possible from a turbine operating between 5MPa and
exhausting at 45C, sat steam. The process condenses
the vapor and pumps it to 5MPa (Wp~0) then reheats
to steam at the turbine inlet conditions. Compute the
work generated by the turbine (kJ/kg).
A. 2000
B. 2250
C. 2500
D. 2750
Day 16 QikQiz 3
QQ1.3.2 A process produces as much work as
possible from a turbine operating between 5MPa and
exhausting at 45C, sat steam. The process condenses
the vapor and pumps it to 5MPa (Wp~0) then reheats
to steam at the turbine inlet conditions. Compute the
thermodynamic efficiency of this Rankine cycle.
A. 0.60
B. 0.55
C. 0.50
D. 0.45
Day 16 QikQiz 3
QQ1.3.3 A process produces as much work as
possible from a turbine operating between 5MPa and
exhausting at 45C, sat steam. The process condenses
the vapor and pumps it to 5MPa (Wp~0) then reheats
to steam at the turbine inlet conditions. Compute the
thermodynamic efficiency of a Carnot cycle operating
in the same temperature range.
A. 0.65
B. 0.70
C. 0.75
D. 0.80
Day 16 QikQiz 3
QQ1.3.4 A turbine operates between 5MPa,
550C and 45C, sat steam. Compute the
efficiency of this turbine.
A. 0.65
B. 0.70
C. 0.75
D. 0.80
Day 17 PracTest (cf. 1993)
17.1 An adiabatic turbine is supplied with
steam at 2.0 MPa and 600C and it exhausts
at 98% quality and 24C. Compute the work
output (kJ/kg).(15)
A. 3691
B. 2496
C. 1259
D. 1194
Day 17 PracTest (cf. 1993)
17.2. An adiabatic turbine is supplied with
steam at 2.0 MPa and 600C and it exhausts
at 98% quality and 24C. Compute the
efficiency of the turbine.(20)
A. 0.76
B. 0.80
C. 0.84
D. 0.88
Day 17 PracTest (cf. 1993)
17.3. An ordinary vapor compression cycle is to be
operated on R134a (Cp/R=10.2,MW=102) to cool a
chamber to 260K. Heat will be rejected to air at
308K. The temperatures in the coils are 256K and
312K. Estimate the compressor work (J/g).
(Hint: Use IG estimate )(10)
A. 4400
B. 420
C. 250
D. 43
Day 17 PracTest (cf. 1993)
17.4. An ordinary vapor compression cycle is to
be operated on R134a (Cp/R=10.2,MW=102) to
cool a chamber to 260K. Heat will be rejected to
air at 308K. The temperatures in the coils are
256K and 312K. Estimate the COP.(10)
A. 3.3
B. 3.1
C. 2.9
D. 2.7
Day 18 QQ1.4
QQ1.4.1. An ordinary vapor compression cycle is to be
operated on propane (Cp/R=8.85,MW=44) to cool a
chamber to 260K. Heat will be rejected to air at 308K. The
temperatures in the coils are 256K and 312K. Estimate the
pressure in the condenser.
TK
PMPa
HL(J/g)
HV(J/g)
SL(J/g)
SLJ/gK
256
0.2707
482
879
4.131
5.682
B. 0.3108
260
0.3108
490
883
4.158
5.669
C. 1.2150
308
1.2150
619
935
4.585
5.611
312
1.3350
624
942
4.600
5.619
A. 0.2707
D. 1.3350
Day 18 QQ1.4
QQ1.4.2. An ordinary vapor compression cycle is to be
operated on propane (Cp/R=8.85,MW=44) to cool a
chamber to 260K. Heat will be rejected to air at 308K. The
temperatures in the coils are 256K and 312K. Estimate the
work of compression (J/g).
TK
PMPa
HL(J/g)
HV(J/g)
SL(J/g)
SLJ/gK
256
0.2707
482
879
4.131
5.682
B. 50
260
0.3108
490
883
4.158
5.669
C. 85
308
1.2150
619
935
4.585
5.611
312
1.3350
624
942
4.600
5.619
A. 45
D. 90
Day 18 QQ1.4
QQ1.4.3. An ordinary vapor compression cycle is to be
operated on propane (Cp/R=8.85,MW=44) to cool a
chamber to 260K. Heat will be rejected to air at 308K. The
temperatures in the coils are 256K and 312K. Estimate the
COP.
TK
PMPa
HL(J/g)
HV(J/g)
SL(J/g)
SLJ/gK
256
0.2707
482
879
4.131
5.682
B. 2.7
260
0.3108
490
883
4.158
5.669
C. 2.2
308
1.2150
619
935
4.585
5.611
312
1.3350
624
942
4.600
5.619
A. 3.1
D. 1.7
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