Unit 01 QUESTION BANK
1. Define Engineering thermodynamics. Give applications of it.
2. State Zeroth law of thermodynamics
3. What is thermometer list most commonly used thermometer
4. What is an international fixed point? How it is being fixed?
5. Explain Measurement of temperature or temperature scale.
Tutorial problems:
1. In 1703 sir Isack Newton proposed a linear temperature scale for which he choose
the ice point and human point temperature as the two fixed point and assigned
numerical values of 0oS and 100oS respectively. If the human body temperature is
in centigrade 36oC. Obtain the relation between Newton scale and oC.( Ans: Tos
= 2.77 toC ,
ToC = 0.36 toN.)
2. Fahrenheit, Celsius thermometer both immersed in fluid. Fahrenheit reading
numerically twice that of centigrade reading.
What is temperature of fluid
expressed as oR and oK.(Ans:For oF = 2oC ,T= 446.7 R,)
3.
The e.m.f in a thermocouple is 0V when the test junction is at 0oC (ice point) and
12 V when it is at steam point. Find the temperature of the system when e.m.f is
3V. Use the relation.( Ans: t = 6.25oC.)
University Questions
Problems:
1. The readings TA and TB of two Celsius thermometers A and B agree at ice point
and steam point.
But else where are related by equation t A = L + MtB +
N t B2 .Where, L.M.N are constant. When both thermometers are immersed in a
system of fluid. A registers 11oC while B registers 10oC. Determine the reading
on A when B registers 37.4oC.
ii. Which thermometer is correct.( VTU-Nov 2007)
2. The Temperature t on a certain Celsius thermometric scale is given by means of a
property through a relation t = a ln p + b Where a and b are constants and p is the
property of the fluid .If at the ice point and steam points the values of pare found
to be 4 and 20 respectively, What will be temperature reading corresponding to a
reading of p = 16(VTU Dec 08 / Jan 09 )
3. The resistance of the windings in a certain motor is found to be 80 Ohms at room
temperature ( 250º ) .When operating at full load, Under steady state conditions,
the motor is switched off and the resistance of the windings immediately
measured again ,is found to be 980 ohms. The windings are made of copper
whose resistance at temperature tº C is given by R t = R0 [ 1+ 0.00393 t ] When R0
is the resistance at 0 º C .Find the temperature attained by the coil during full
load.( VTU-June /July 08)
Theory:
4. Mention the Characteristics of a thermodynamic Property (Dec 08/ Jan 09)
5. Differentiate between the following with suitable examples (June/July 2008)
i. System and control volume
ii. Intensive and Extensive Properties
iii. Path and Point function
6. Define the following (June/July 2008)
i. Thermodynamic state
ii. Quasi-Static Process
iii. Cyclic and Non – Cyclic Process.
7. Distinguish between (Dec /Jan 2008)
i. Open system and closed system
ii. Macroscopic and Microscopic approach
iii. Point function and path function
iv. Intensive and extensive properties
v. Diathermic and adiabatic walls
unit 2 question bank
Theory Questions:
1. Define Work and Heat.
2. Write the similarities and dissimilarities between work and heat.
3. How do you say heat and work are path functions?
4. Derive the work done for polytrophic and adiabatic process.
5. Draw and explain the pdv equation formation to solve the Quasi static
process, and explain about the Sign convention for compression and
expansion process
Tutorial Problems:
1. An engine cylinder has a piston area 0.12 m2 and contains gas at a pressure 1.5
MPa. The gas expands according to a process which is represented by a straight
line on a pressure volume diagram. The final pressure is 0.15 MPa. Calculate
work done by the gas on the piston if the piston stroke is 0.3 m.
( Ans: 29.7 KJ
2. A system of volume V contains a mass m kg of gas at pressure P and temperature
T. The pressure volume and temperature of gas are related by equation.
a 

 P  2  (V – b) = mRT
V 

Where, a,b,R are constants obtain an expression for the displacement work when
system is undergoing an isothermal process from V1 to V2, calculate the
displacement work. If m = 10 kg, T = 293 k and the gas expands from 1 m3 to 10
m3 at atmospheric pressure. Assume that
A = 15.7  104 Nm4,B = 1 .07  10-2 m3, R = 0.278 KJ/Kg K.
( Ans : = 1.74 MJ.)
3. An Engine cylinder of dia. (22.5 Cm) has a stroke length 37.5 Cm. Swept
volume is 4 times the clearance volume. The pressure of gases at the beginning of
expansion stroke is 1569 KPa. Find the work done during an expansion stroke
assuming the process as reversible adiabatic take  = 1.4.(Ans:W1-2 == 6.97 MJ.)
University Problems:
1. A gaseous system undergoes a process of quasi-static process in sequence from
state 1 to 2 at constant pressure between state 2 to 3. The system undergoes
compression process. (PVn = C) Between state 3 to 1 the gas expands according to
(PV = C). Take P1 = 1 bar,V1 = 0.3 m3 ,P3 = 4 bar,V2 = 0.2 m3
Calculate the work interaction in each of this process and net work for the system.
(Result: Wnet = 7.37 KN – m )-VTU July 2008
2.1 Kg of air having an initial volume of 0.3 cubic meters is heated at constant
pressure of 3.2 bar until the volume is doubled. Calculate
1. Heat added. 2. Work done 3.initial and final temperature of the air.
Take, CP = 1.003 KJ/ Kg K , R = 0.2927 KJ / Kg K.
(Result: W net == 96 KJ.)VTU Dec 2007
3. 1 Kg of air contained in a closed system at 100 KPa and 300 K is compressed
isothermally till the volume halves. During this process it is also stirred with a
torque of 1 Nm at 400 rPm for 1 hr. Calculate the net work done on the system.
Assume R = 0.285 KJ/ KgK. (Result: (Wnet)System = W1 + W2, = - 59.26 +
150.796, = - 210 KJ.)VTU Jan 2008
4. As an engineering student suggest the most economical process when it is
desired to compress one mole of air (γ =1.4) from an initial state of 300 K and 1
bar to a final state of 300 K and 10 bar from an initial state of 300 K and 1 bar to
final state of 300 K and 10 bar from among the following processes:
a. Isothermal compression
b. Cooling at constant pressure followed by heating at constant volume
c. Adiabatic compression followed by cooling at constant volume and
d. Heating at constant volume followed by cooling at constant pressure Take the
value of R= 8.314 j / mol K.( VTU Dec / Jan 2008 )
5. A fluid at 0.7 bar occupying 0.09 m3 is compressed reversibly to a pressure of
3.5 bar according to a law PVn = Constant .The fluid is then heated reversibly at
constant volume until the pressure is 4 bar ,The specific volume is then 0.5 m3
/Kg .A reversible expansion according to a law PV2 constant ,restore the fluid to
its initial state .Sketch the cycle on P-V- diagram and calculate
(i) The mass of the fluid (ii) The value of ‘n’ in the first process (iii) The net work
of the cycle.( VTU June /July 08)
6.A Cylinder contains 1 Kg of a certain fluid at an initial pressure of 20 bar .The
fluid is allowed to expand reversibly behind a piston according to PV2 = constant
unti l the volume is doubled .The fluid is then cooled reversibly at constant
pressure until the piston regains its original position ; heat is then supplied
reversibly with the piston firmly locked in piston until the pressure rises to the
original value 20 bar .Calculate the net work done by the fluid ,for an initial
volume of 0.05 m3 ( VTU Dec / Jan 08 )
Unit 3 Question bank
Theory Questions:
1. State first law of thermodynamics applied to a cyclic process
2. Define internal energy and prove that it is a property
3. What are the limitations of first law of thermodynamics?
4. Explain Law of conservation of mass
5. Define mass and volume flow rate .How do they differ.
6. What is flow energy? Do fluids at rest posses any flow energy?
7. When is the flow through a control volume steady?
8. Write down the steady flow energy equation and indicate clearly the meaning of each
term in it (VTU feb 2002)
9. Derive an expression for work done in a steady flow process
10. Write down steady flow energy equation for
a) Air compressor b) Steam nozzle
Numerical problems:
1. A fluid system undergoes processes a-b, b-c, c-d, and d-a to complete a cycle, during
one cycle, the total negative heat transfer is 84 kj. The system completes 100 cycles per
minute .The energy transfers are tabulated below.
Process
§Q (KJ / min)
§W (KJ/min)
dU (KJ/min)
A–b
0
-20945
?
B–c
20945
0
?
C–d
2094
?
37700
D–a
?
?
?
Complete the table showing your method of calculation for each item and find the net
heat by KW.
Ans:
Process
§Q (KJ / min)
§W (KJ/min)
dU (KJ/min)
A–b
0
-20945
20945
B–c
20945
0
20945
C–d
2094
-35606
D–a
-31439
48151
37700
-79590
2. A closed system undergoes a process during which a heat transfer of 30 kj takes place
from the system while 5 kj of work is done by the system .If the system is returned to the
initial state by understanding another process during which there is heat transfer of 20 kj
to the system .Calculate the work done in the second process.
( Ans: U2-U1 = 35 kj, work = -15 Kj )
3. A steam turbine receives steam with a flow rate of 900 kg per minute and experience a
heat loss of 840 kj per minute .The exit pipe is 3 meter below the level of the inlet pipe.
Find the power developed by the turbine if the pressure decrease from 62 bar to 9.86 Kpa
velocity increases from 30.5 m/s to 274.3 m/s internal energy decreases by 938.8 kj/kg
and specify volume increases from 0.058 m3 / kg to 13.36 m3 / kg.(Vtu –Feb 2002 )
(Ans : m = 15 kg/sec , Q = -14 kj/ sec , U2 – U1 = -938.5 kj/kg, W = 16924.66 KW )
3. A nozzle is a device for increasing the velocity of a steadily flowing stream. At the
inlet to a certain nozzle, the enthalpy of the fluid passing is 3000 kj/kg and velocity is 60
m/s .At the discharge end, the enthalpy is 2762 kj/kg .The nozzle is horizontal and there
is negligible heat loss from it.
Find
(i)
Find the velocity at the exit section of the nozzle
(ii)
If the inlet area is 0.1 m2 and the specific volume at inlet is 0.178 m3 / kg find
the mass flow rate.
(iii)
If the specific volume at the exit of the nozzle is 0.498 m3 /kg find the
diameter at the exit section of the nozzle.
(VTU July 2004)
3
Ans (i) V2 = 692.53 m/s , (ii)v 1 = 0.187 m / kg , m =32.08 kg/s,(iii) d2 = 17.1 cm )
4.Air enters an adiabatic horizontal nozzle at 400 º C with a velocity of 50 m/s .The inlet
area is 240 m2 .The temperature of air at the exit is 80ºC .Given that the specific volume
of air at inlet and exit are respectively 0.2 m3/kg and 1.02 m3/kg .Find the area of cross
section of the nozzle at the exit .Assume that enthalpy of air is a function of temperature
only and that Cp = 1.005 kj/kg k.
(VTU July 2006)
2
Ans: A2 = 76.16 cm
5.A fluid flows through a steady flow system at the rate of 3 kg/sec the inlet and outlet
conditions are P1 = 5 bar ,V1 = 150 m/sec ,U1 = 2000 kj/kg and P2 = 1.2 bar , V2 =80
m/sec and U2 = 1300 kj/kg .The change in specific volume is from 0.4 m3 /kg to 1.1
m3/kg .Fluid loose 25 kj/kg heat during the process ,Neglecting potential energy
determine power output of the system.
(VTU Jan 2007) Ans: W = 751 KW
Unit 04 Question bank:
Theory:
1. Write the Kelvin –planks and Clausius statement of second law of thermodynamics
and prove that they are equivalent (VTU march 2000, Aug 2000,aug 2002 ,Feb 2003
,Aug 2003 )
2. Define irreversibility and mention at least 3 factors which render a process irreversible.
3. Give precisely the Kelvin –Plank statement of second law that two reversible adiabatic
paths cannot intersect each other.
(VTU feb 2004)
4. State Carnot theorem
(VTU aug 2000)
5. Show by invoking Kelvin –Plank statement of second law that two reversible adiabatic
paths cannot intersect each other.
6. Explain the various reasons of irreversibility.
(VTU Aug 2001)
7. Define the two statements of II law of thermodynamics. Show that violation of clausius
statement of II law of thermodynamics violates the Kelvin –plank statement of II law of
thermodynamics.
(VTU, Jan 2007)
8. Define heat engine draw a neat schematic flow diagram of the steam power plant
.Name the important parts and states of the working fluid .Indicates the system boundary,
heat and work interaction to justify your definition
(VTU, Feb 2002)
9. Define a reversible heat engine, show that of all reversed heat engines working
between any two constant but different temperature thermal reservoirs, the reversible
reversed heat engine will have the maximum COP.
(VTU feb 2005)
10. Demonstrate, using the second law, that free expansion is an irreversible process.
11. Prove that COP Heat Pump = 1+COP refrigerator. (VTU, Jan 2007)
Numerical problems:
1. A reversible heat engine works between the two reservoirs at 1400 K and 350 K
respectively. A reversible heat pump receives heat from the reservoir at 250 K and rejects
the heat to a reservoir at 350 K to which the heat engine also rejects the heat .The work
output from the engine is used to drive the heat pump .if the total heat supplied to the
reservoir at 350 K is to be 100 KW, Find the heat to be received by the heat engine.
(Ans: Q1 = 34.78KW Heat to be received by the engine)
(VTU, Jan, 2007).
2. Two reversible engine A and B are connected in series, Engine A receives heat energy
from a thermal reservoir at T1 and rejects at a temperature T2 while engine B receives
heat energy at T2 (at which rejected by engine A) and rejects to a thermal reservoir at
T5.If both engines are equal efficient, show that the intermediate temperature T2 if both
engines are delivering equal power? (Ans: T2 = (T1+T3) / T2 )
(VTU, Jan, 2007).
3. A reversible engine works between three thermal reservoirs A, B, C. The engine
absorbs an equal amount of heat from the thermal reservoirs A and B Kept at temperature
TA and TB respectively, and rejects heat to a thermal reservoir C kept at temperature Tc
.The efficiency of this engine is α times the efficiency of a reversible engine which works
between the two reservoirs A and C .Show that
TA / TB = (2α – 1) +2(1-α) (TA / TC)
(VTU, Aug 2004)
4. An inventor claims that his engine has the following specifications
Power developed = 76 KW
Fuel burnt per hour = 4 kg
Heating value of fuel = 75000kj/kg
Temperature limits = 727 ºC and 27 ºC
Discuss the possibility of the claim. ( Ans: η thermal = 91.2 ٪ , η reversible = 70 ٪)
(VTU Aug .2000)
5. An inventor claims to have developed a refrigerator which maintains the refrigerated
space at -10 ºC While operating in room at 25 ºC and it has a COP of 8.5 .How would
you evaluate his claim as patent officer.(Ans : 8.76 The claim is valid )
(VTU March 2000)
6. A reversible heat engine operates with two environments .In the first it draws 12000
KW from a source at 400 ºC and in the second it draws 25000 KW from a source at 100
ºC .In both the operations the engine rejects heat to a thermal sink at 20 ºC .Determine the
operation in which the engine delivers more power.( Ans: thermal efficiency =56.5
percentage, Work done = 6780 Kj/s,For the second engine thermal efficiency = 21.4
percentage, Work done =5350 Kj/sec )
(VTU ,Feb ,2004 )
ADDITIONAL PROBLEMS:
1. 2Kg of nitrogen is heated at constant volume until the pressure is doubled.
Calculate the heat transferred and change in entropy. Draw the PV and T-S
Diagram. Initial temperature is 300 0C. R=300 J/KgK and Cv =800 J/KgK.
2. A system executes a cyclic process during which there are four heat transfers as
Given below. Q12 =800KJ Q23 = -100Kj
Q34 = -720kJ Q41 =200kJ
Workdone during the three processes are given as W12 = 60kJ W23 = - 40kJ
W34 = 80kJ Find the workdone during the process 41.
3. A heat engine is supplied with 278 kJ/sec of heat at a constant fixed temperature of
2830C and the heat rejection takes place at 50C. The following results were
Reported:
(1) 208 kJ/sec of heat are rejected
(2) 139 kJ/sec of heat are rejected
(3) 70 kJ/sec of heat rejected
Classify which of these results report a reversible cycle or impossible result.
4.5 kg of Nitrogen are heated in a reversible non-flow constant volume process from
a temperature of
600C until the pressure is doubled. Determine (i) Final temperature
(ii)Work done (iii) Change in internal energy (iv) Heat transferred
(v) Change in enthalpy (vi) Change in entropy. Assume Cv =0.653 KJ/kgK
and CP =0.913 KJ/kgK.
5. Certain volume of gas at 57 0C is expanded to three times its original volume
according to PV1.25 =C. Determine the temperature at the end and change in
entropy per kg of gas. Cp =0.99 KJ/kgK; Cv =0.7 KJ/kgK
6. An engine is to operate between temperature limits of 14000C and 3270C. It
is claimed that its power output is 4.0Kw, fuel consumption is 0.45kg/hour.
Calorific value of fuel is 42,000Kj/kg. State whether the claim is justified by
comparing with Carnot cycle.
7. Air undergoes a cyclic process in a cylinder and piston arrangement. First
the atmospheric air at 1bar 270C is compressed adiabatically to 10bar, then
expanded isothermally upto initial pressure, then brought to initial
conditions under constant pressure, find out
(ii)
Change in internal energy
(iii) Change in enthalpy
(iv)
Heat transfer
(v)
Work transfer for each process and also for the cycle
Unit 05 Questioin Bank
Theory:
1. Derive Clausius inequality and hence prove that entropy is a property. ( VTU , March
2000 , Aug,2002 )
2. Derive an expression for entropy (VTU Aug, 2001)
3. Explain available of a system with heat transfer (VTU, March 2000)
4. State and prove Clausius theorem.(VTU ,Aug 2003 )
5. Define an inequality of clausius and entropy of a system .Show that for an irreversible
process ds greater than or equal to dq / T .( VTU Jan 2007)
6. Briefly explain what do you understand by reversibility in thermodynamics, and
mention at least 2 factors that render a process irreversivble.(VTU,Aug 2005 )
7. Show that the change in entropy during an irreversible process between the two states
is given by (S2-S1 ) ≥ ∫ dq/T
Numerical problems:
1. A heat engine receives 125 Kj of heat/cycle from a reservoir at 300ºC and rejects heat
to a reservoir at 0 ºC by the following hypothetical amounts
(1) 95 Kj/cycle (2) 59.5KJ.ycle (3) 31kj/cycle.Which of these represents reversible,
irreversible and impossible cycles? (VTU, March 2000)
2. Two Kg of air at 5 bar and 80 ºC expands adiabatically in a closed system until its
volume is doubled and the temperature becomes equal to that of the surroundings which
is at 1 bar and 5 ºC, Determine the maximum work (VTU, Feb 2002)
3. An insulated cylinder of capacity 4 cm2 contains 20 kg of air ( Cv = 0.718 Kj / Kg ºK
Cp = 1.005 Kj/Kg ºK) Peddle work is done on the air by stirring till its pressure increase
from 4 bar to 8 bar ,Determine (1) Change in internal energy (2)Work done (3)Heat
transferred (4)Change in entropy (VTU,Feb 2003 )
4.Two Kg of water at 80 ºC is mixed adiabatically with three kg of water at 30 ºC in a
constant pressure process at one atmosphere .Find the increase in entropy of the total
mass of water due to mixing process.(Assume Cp = 4.187 Kj/Kg K)(VTU ,Aug 2003 )
5. Five kg of air 555 ºK and 4 bars is enclosed in a system.
(1) Determine the availability of the system if the surrounding temperature and pressure
290 ºC and 1 bar respectively
(2) If the air is cooled at constant pressure to the atmosphere and pressure and if Cp =
1.005 Kj/Kg ºK ,Cv = 0.718 Kj/Kg ºK for air .Determine the available and effectiveness
(VTU, Feb, 2003)
Unit 6 Question bank
Theory:
1. Define first law and second law efficiency
2. Analyze second law efficiency fir
(i)Heat engne(ii)Heat pump(iii)Refrgerator(iv)Heat exchanger
3. Write short notes on Helmholtz anf gibbs function (VTU,Aug2000,Feb 2003)
4. Explain briefly available and unavailable energy (VTU, Aug.2001, and Feb 2003)
5. State and prove the clausius theorem (VTU, Aug.2001, and Aug2003)
6. Derive an expression for Entropy (VTU, Aug.2001)
7. What do you understand by availability of system? Explain the terms Gibbs free
energy and Helmoholtz free energy.(VTU,Aug,2002)
8. Derive the expression for the entropy change of an ideal gas of the form
ds = Cp ln ( V2/V1) + Cv ln ( P2 / P1) with the usual notation (VTU,Aug.2002)
9. Derive available and non available energy and prove that the available portion of heat
Q withdrawn from a finite source is dq –T0 = ∆S (VTU, March 2000)
Numerical problems:
1. Explain briefly available and unavailable energy energies referred to a cyclic heat
engine. Two kg of air at 5 bar and 80 ºC expands adiabatically in a closed system until its
volume is doubled and the temperature becomes equal to that of the surroundings which
is at 1 bar and 5 ºC .Determine the maximum work.(VTU,Feb.2002)
2. 5 kg of air at 555 ºK and 4 bars is enclosed in a system.
i) Determine the available of the system if the surrounding temperature and pressure are
290 ºC and 1 bar respectively.
ii) If the air is cooled at constant pressure to the atmospheric temperature and if Cp =
1.005 kj/kg ºK, Cv = 0.718 kj/kg ºK for air. Determine the availability and effectiveness.
(VTU, Feb, 2003)
3. A gear box receives 750 KW power and delivers 745 KW power operating under a
srteady state of 280 K.Find the increase in entropy in the gear box and the surroundings.
(Ans: 55.38 kj/hr k, 68.28 kj/hr.k)
4.400 litres of furnace oil is heated from 25 ºC to 75 ºC using exhaust steam at a pressure
of 0.12 MPa and 0.85 dry.If only latent heat of steam is used for heating the oil find the
change in available energy. Assume for oil Specic gravity =0.9,Cp=3 kj/kg k and
surrounding temperature 15 ºC
(Ans: 6366.107 kj )
5.0.2 kg of air at 573 k is heated reversibly at constant pressure to 2066 k .Find the
available and unavailable energies of the heat added. Assume the atmospheric is at 303
K.Cp of air = 1.005 kj/kg k(Ans: 211.9kj,78.1 kj)
6.A perfect gas with a gas constant of 0.287 kj/kg k enters a steady flow apparatus at 1
mpa and 378 k with a velocity of 150 m/s and leaves at 0.15 mpa and 283 k.
Calculate the irreversibility if the outlet velocity of air is 70 m/s Take T0 = 283 k,Cp =
1.002 kj/kgk.)(Ans: 90.7 kj)
UNIT 07 QUESTION BANK
Theory:
1. Explain with neat sketch, the method of estimating quality of steam by a throttling
calorimeter.(VTU,Aug,2003)
2. Define critical temperature and pressure .Draw a neat sketch of temperature –volume
diagram for water showing liquid and water showing liquid and vapour phase mark all
the salient points on the diagram.(VTU,Jan,2007)
3. Draw a P-T diagrams for pure substance and indicate all necessary points on
it.(VTU,Aug2001)
4. Briefly explain what you understand by two property rule (VTU,Feb,2004)
5.Define dryness fraction and briefly explain how one could estimate the same using
separating and throttling calorimeter.(VTU,Feb 2004)
6. Define the following terms as applied to a pure substance
i) Triple point
ii) Critical point
iii) Subcooled liquid state
iv) Wet vapour state
v) Saturated liquid state
vi) Dry vapour state
7. Draw the following diagrams for water and various pressure and name the different
regions and states:
i) Pressure-temperature diagrams
ii) Temperature –volume diagram
Also comment on triple point and critical points.(VTU,FEB,2002 )
8. Define pure substance and state “Two property rule” (VTU,Aug,2005)
Numerical problem:
1. A closed vessel 0.2 m3 contains steam at 10bar and temperature 250 0C. If the
vessel is cooled so that the pressure falls to 3.5 bars determine the final
temperature of the steam, Heat transfer and change in entropy.
2. A cylinder fitted with a piston contains 0.5 kg of steam at 4 bars. Initial volume of
the steam is 0.1 m3. Heat is transferred to the steam until the temperature becomes
300 0C determine the heat transferred and the work done during the process. State
what type of process is taking place?
3. Saturated steam at 6 bar pressure undergoes a reversible isothermal process in a
cylinder until the pressure reaches 4 kPa. Calculate the work done and heat
transfer per kg of steam during the process.
4. A cylinder fitted with piston is filled with steam at 600 kPa and 260 0C. Steam
expands isentropicaly until the pressure falls to 150 kPa. If the initial volume is
0.04 m3 , determine the work done during the process and the change in enthalpy.
5. Steam is expanded according to the law PV1.15 =C from a condition of 10 bar and
200 0C to 1 bar. Find the final specific volume, temperature, heat transfer, change
in enthalpy and change in entropy during the process per kg of the steam.
6. Boiler steam at 8 bar 2500C reaches an engine control valve through a pipe at 7
bar 2000C. It is throttled to 5 bars and then expanded to 0.1bar and 0.9 dry in the
engine. Find per kg of steam (i) Heat loss in the pipe (ii) Temperature drop
through the pipe (iii) Work done in the engine (iv) Change in entropy during the
throttling (v) Change in entropy during expansion in the engine.
7. Steam at 10bar and 0.95 dry flows at 130m/sec in a pipe. It is throttled to 8bar and
the flow rate is 12kg/sec. Assuming velocity in the pipe on the down stream side
of the valve is 160m/sec. Find the final condition of steam and the pipe diameters
before and after the valve.
8. Steam at 20bar and 3000C passes through a pipe with a velocity of 120m/sec. If
steam flows at the rate of 500kg/hr find the diameter of the pipe.
9. Dry saturated steam at 15bar is supplied to an engine in which it expands
isentropically to 1.5 bar and then at constant volume to 0.5bar. Calculate the
work done during the isentropic expansion and the final condition of the steam.
10. Steam engine operates between the pressure limits 50 bars and 1 bar. Initial
temperature of the steam is 300 0C. Find the Rankine cycle efficiency of the
engine
(a) With pump work
(b) with out pump work
11. Steam at 20 bars, 360˚ C is expanded in a steam turbine to 0.08 bars. Then enters
a condenser, where it is condensed to saturated water. The pump feeds back the
water into the boiler. Assuming ideal process, find the network per Kg of steam
and the cycle efficiency.
12. A steam power station uses the following cycle: Steam at boiler outlet is 150 bars
and 550˚C.The steam is reheated at 40 bars to 550˚C.Then the steam is expanded
till the condenser pressure of 0.1 bars. Using the mollier chart and assuming ideal
processes, find the A] quality of exhaust steam B] Cycle efficiency C] steam rate
13. Find the ideal cycle efficiency and specific steam consumption of a reheat cycle
operating between pressures of 30 and 0.04 bar, with a superheat temperature of
450˚C assume that the first expansion is carried out to the point where the steam
is dry saturated and that the steam is reheated to the original super heat
temperature. The feed pump term may be neglected.
14. Calculate the ideal cycle efficiency and specific steam consumption of a
regenerative cycle using three closed heaters. The steam leaves the boiler at 30
bar super heated to 450˚C, and the condenser pressure is 0.04 bars. Choose the
bleed pressures so that the temperature difference [T2-T9] is divided in to
approximately equal steps.
Unit 08 QUESTION BANK
Theory:
1. Define perfect gas.(VTU.Aug,2001)
2. Define specific heat of a gas.(VTU,Aug,2001)
3. State amagat’s law and prove that for each components of a mixture of a ideal gases
the volume fraction equals its mole fraction (VTU, Feb, 2002)
4. Show that ( T2/ T1) = (P2/P1) γ-1/ γ for a perfect gas.
5. Define Real gas, ideal gas, universal gas constant (VTU, Feb, 2003)
6. Clearly distinguish between ideal and real gas .Mention any two equation of state you
know off (VTU, Feb, 2004)
7. Write short notes on Amagats leduce law compressibility factor (VTU, Aug, 2000)
8. Write short notes on any two of the following (VTU, Feb2002, Aug, 2003)1) BeattieBridgeman equation
2 ) Clausius – clapeyron and
3)
Maxwells equation
9 What are the limitations of vander waals equation (VTU, Feb 2003)10. Explain briefly
the generalized compressibiltity chart and its application (VTU,Aug 2003)11. Explain the
following (VTU, Feb, 2005)
i) Generalized compressibility chart
ii) Law of corresponding states
iii)Van der Walls equation of state.
12. Explain law of corresponding states.(VTU,Aug,2004)
13. Derive the maxwells relation (VTU, Aug, 2001, August 2003)
14. Determine the Vander wall’s constant a, b in terms of critical properties.
Ans: At critical point there is an inflexion pressure for the isotherm. i.e, slope of the line
is zero at critical point and also it changes its direction of slope.
15. Find the compressible factor at critical points.
16. Write the vander wall’s equation in terms of reduced properties.
Numerical Problems:
1. A gas mixture has the following composition on a mole basis: 60 percent N2 and 40
percent Co2.determine the gravimetric analysis of the mixtures, its molar mass and gas
constant.
2. A gas mixture consists of 5kg of O2, 8kg of N2, and 10 kg of co2. Determine (a) the
mass fraction of each component, (b) the mole fraction of each component, and (c) the
average molar mass and gas constant of the mixture.
3. Determine the mole fractions of a gas mixture that consists of 75% CH 4 and 25 % CO2
by mass. Also, determine the gas constant of the mixture.
4. A gas mixture consists of 8 Kmol of H2 and 2Kmol of N2. Determine the mass of each
gas and the apparent gas constant of the mixture.
5.A rigid tank contains 4Kmol of O2 and 5Kmol CO2 GASSES AT 290 K and 150 Kpa.
Estimate the volume of the tank.
6.A rigid tank contains 0.5 kmol of Ar and 2Kmol of N2 at 250Kpa and 280K .the
mixture is now heated to 400K .Determine the volume of the tank and final pressure of
the mixture.
7. A gas mixture at 400K and 150Kpa consists of 1kg of CO2 and 3kg of CH4 .
Determine the partial pressure of each gas and the apparent molar mass of the gas
mixture.
8.A 0.3m3 of rigid tank contains 0.6 kg of N2, 0.4 kg of O2 at 300K. Determine the partial
pressure of each gas and the total pressure of the mixture.
9.A gas mixture at 290K and 250 Kpa has the following volumetric analysis: 65% N2,
20%O2 and 15% CO2 . Determine the mass fraction and partial pressure of the each gas.
10. A rigid tank that contains 2 kg of N2 at 25C and 200Kpa is connected to another
rigid tank that contains 3kg of O2 at 25C and 500Kpa .The valve connecting two tanks
opened ,and the two gases are allowed to mix. If the final mixture temperature is 25 C,
determine the volume of each tank and the final mixture pressure.
11. A volume of 0.3m3 of O2 at 200K and 8Mpa is mixed with 0.5m3 of N2 at the same
temperature and pressure, forming a mixture at 200K and 8Mpa. Determine the volume
of the mixture using (a) the ideal gas equation of state and (b) the compressibility chart
and Amagat’s law.
12.The pressure in an auto mobile tyre depends on the temperature of the air in tyre in the
tyre.When the air temperature is 25˚C the pressure gauge reads 210Kpa .If the volume of
the tyre is 0.025m3, determine the pressure rise in the tyre when the air temperature rises
to 50˚C. Also determine the amount of air that must be bled off to restore the pressure to
its original value at this temperature. Assume the atmospheric pressure to be 100Kpa.