Alcohols are unsuitable at diesel engine fuels because

The cetane number of alcohol fuels is very low which prevents their ignition by compression

The cetane number of alcohol fuels is very high which prevents their ignition by compression

The cetane number of alcohol fuels is very low which prevents good combustion

The power output from a spark ignition engine is varied by

Regulating the amount of air-fuel inducted

Regulating the amount of air fuel mixture

The current level of the maximum temperature of steam turbine inlet.is much lower than that at gas turbine inlet because

The fuel combustion temperature in a steam generator is lower than that in a gas turbine engine

Of the corrosive nature of high temperature steam on super heater tubes

The materials used for the gas turbine blades are not suitabie for the steam turbine blades

Unlike the gas turbine blades the steam turbine blades cannot be cooled

Which one of the following modifications of the si mpl e i deal Rank i ne cycl e i ncr eases t he thermal efficiency and reduces the moisture content of the steam at the turbine outlet?

Decreasing the condenser pressure

Increasing the turbine inlet temperature

Decreasing the condenser pressure

Which of the following statements regarding a Rankine cycle with reheating are TRUE? (i) increase in a average temperature of heat addition (ii) reduction in thermal efficiency (iii) drier steam at the turbine exit

(i), (ii) and (iii) are correct

only (ii) and (iii) are correct

(i), (ii) and (iii) are correct

For a spark ignition engine, the equivalence ratio ( ) of mixture entering the combustion chamber has values

> 1 for idling and < 1 for peak power conditions

> 1 for both idling and peak power conditions

> 1 for idling and < 1 for peak power conditions

< 1 for both idling and peak power conditions

The silencer of an internal combustion engine

decrease break specific fuel consumption (BSFC)

has no effect on its efficiency

A Curtis stage, Rateau stage and a 50% reaction stage in a steam turbine are examples of

different types of impulse stages

different types of reaction stages

a simple impulse stage, a velocity compounded impulse stage and reaction stage

a.velocity compounded impulse stage, a pressure compounded impulse stage and a reaction stage

At the time of starting, idling and low speed operation, the carburettor supplies a mixture which can be termed as

slightly leaner than stoichiometric

248 + Mcqs in Thermodynamics Miscellaneous in Thermodynamics Page 2 McqOptions

51.	In a gas turbine, hot combustion products with the specific heats c_p = 0.98 kJ/kgK, and c_v = 0.7538 kJ/kgK enters the turbine at 20 bar, 1500 K and exits at 1 bar. The isentropic efficiency of the turbine is 0.94. The work developed by the turbine per kg of gas flow is
A.	689.64 kJ/kg
B.	794.66 kJ/kg
C.	1009.72 kJ/kg
D.	1312.00 kJ/kg
Answer» B. 794.66 kJ/kg

Discussion

52.	Select statement from List-II matching the processes in List-I. Enter your answer as A, B is the correct choice for (1) is (A) and (2) and (B). List-I 1. Intercooling 2. Isothermal compression List-ll A. No heat transfer during compression B. Reduce low pressure compressor work C. Heat rejection during compression D. Reduce high pressure compressor work
A.	C and B
B.	A and B
C.	C and A
D.	A and D
Answer» B. A and B

Discussion

53.

A mixture of ideal gases has the following composition by mass :
N₂ O₂ CO₂
60% 30% 10%

If the universal gas constant is 8314 J/kmolK, the characteristic gas constant of the mixture (in J/kgK) is _______.

A.

274.996

B.

247.996

C.

374.996

D.

174.996

Answer» B. 247.996

Discussion

54.	Nitrogen gas (molecular weight 28) is enclosed in a cylinder by a piston, at the initial condition of 2 bar, 298 K and 1 m³. In a particular process, the gas slowly expands under isothermal condition, until the volume becomes 2 m³. Heat exchange occurs with the atmosphere at 298 K during this process. The work interaction for the nitrogen gas is
A.	200 kJ
B.	138.6 kJ
C.	2 kJ
D.	200 kJ
Answer» C. 2 kJ

Discussion

55.	A frictionless piston-cylinder device contains a gas initially at 0.8 MPa and 0.015 m³. It expands quasistatically at constant temperature to a final volume of 0.030 m³. The work output (in kJ) during this process will be
A.	8.32
B.	12.00
C.	554.67
D.	8320.00
Answer» B. 12.00

Discussion

56.	A vessel of volume 1.0 m³ contains a mixture of liquid water and steam in equilibrium at 1.0 bar. Given that 90% of the volume is occupied by the steam, find the fraction of the mixture. Assume at 1.0 bar, v_f = 0.001 m³/kg and v_g = 1.7 m³/kg.
A.	5.266 10
B.	5.266 10
C.	3.442 10
D.	3.442 10
Answer» B. 5.266 10

Discussion

57.	A reversible thermodynamic cycle containing only three processes and producing work is to be constructed. The constraints are: (i) there must be one isothermal process, (ii) there must be one isentropic process, (iii) the maximum and minimum cycle pressures and the clearance volume are fixed, and (iv) polytropic processes are not allowed. Then the number of possible cycles are
A.	1
B.	2
C.	3
D.	4
Answer» B. 2

Discussion

58.	A piston-cylinder device initially contains 0.4 m³ of air (to be treated as an ideal gas) at 100 kPa and 80 C. The air is now isothermally compressed to 0.1 m³. The work done during this process is ______kJ. (Take the sign convention such that work done on the system is negative)
A.	55.45 kJ
B.	-21.45 kJ
C.	-55.45 kJ
D.	-15.45 kJ
Answer» D. -15.45 kJ

Discussion

59.	Alcohols are unsuitable at diesel engine fuels because
A.	The cetane number of alcohol fuels is very low which prevents their ignition by compression
B.	The cetane number of alcohol fuels is very high which prevents their ignition by compression
C.	The cetane number of alcohol fuels is very low which prevents good combustion
D.	None of these
Answer» D. None of these

Discussion

60.	Knocking tendency in a Sl engine reduces with increasing
A.	Compression ratio
B.	Wall temperature
C.	Supercharging
D.	Engine speed
Answer» E.

Discussion

61.	The power output from a spark ignition engine is varied by
A.	Changing the ignition timing
B.	Regulating the amount of air-fuel inducted
C.	Regulating the amount of air fuel mixture
D.	Regulating the amount of fuel
Answer» D. Regulating the amount of fuel

Discussion

62.	An ai r st andar d Ot t o cycl e has t her mal efficiency of 0.5 and the mean effective pressure of the cycle is 1000 kPa. For air, assume specific heat ratio = 1.4 and specific gas constant R = 0.287 kJ/kg.K. If the pressure and temperature at the beginning of the compression stroke are 100 kPa and 300 K, respectively, then the specific net work output of the cycle is ___ kJ/ kg
A.	808.77 kJ/kg
B.	808.77 kJ/kg
C.	709 kJ/kg
D.	708.77 kJ/kg
Answer» D. 708.77 kJ/kg

Discussion

63.	In a power plant, water (density = 1000 kg/m ) is pumped from 80 kPa to 3 MPa. The pump has an isentropic efficiency of 0.85. Assuming that the temperature of the water remains the same, the specific work (in kJ/kg) supplied to the pump is
A.	0.34
B.	2.48
C.	2.92
D.	3.43
Answer» E.

Discussion

64.	When an ideal gas with constant specific heats is throttled adiabatically, with negligible changes in kinetic and potential energies.
A.	h = 0, T = 0
B.	h > 0, T= 0
C.	h > 0, S > 0
D.	h = 0, S > 0
Answer» B. h > 0, T= 0

Discussion

65.	The density of air in kg/m at the nozzle exit is
A.	0.560
B.	0.600
C.	0.727
D.	0.800
Answer» D. 0.800

Discussion

66.	The current level of the maximum temperature of steam turbine inlet.is much lower than that at gas turbine inlet because
A.	The fuel combustion temperature in a steam generator is lower than that in a gas turbine engine
B.	Of the corrosive nature of high temperature steam on super heater tubes
C.	The materials used for the gas turbine blades are not suitabie for the steam turbine blades
D.	Unlike the gas turbine blades the steam turbine blades cannot be cooled
Answer» E.

Discussion

67.	One kilomole of an ideal gas is throttled from an initial pressure of 0.5 MPa to 0.1 MPa. The initial temperature is 300 K. The entropy change of the universe is
A.	13.38 kJ/K
B.	4014.3 kJ/K
C.	0.0446 kJ/K
D.	0.0445 kJ/K
Answer» B. 4014.3 kJ/K

Discussion

68.	Which one of the following modifications of the si mpl e i deal Rank i ne cycl e i ncr eases t he thermal efficiency and reduces the moisture content of the steam at the turbine outlet?
A.	Increasing the turbine inlet temperature
B.	Decreasing the condenser pressure
C.	Increasing the boiler pressure
D.	Decreasing the boiler pressure
Answer» B. Decreasing the condenser pressure

Discussion

69.	Which of the following statements regarding a Rankine cycle with reheating are TRUE? (i) increase in a average temperature of heat addition (ii) reduction in thermal efficiency (iii) drier steam at the turbine exit
A.	only (i) and (ii) are correct
B.	only (ii) and (iii) are correct
C.	only (i) and (iii) are correct
D.	(i), (ii) and (iii) are correct
Answer» D. (i), (ii) and (iii) are correct

Discussion

70.	Steam at an initial enthalpy of 100 kJ/kg and inlet velocity of 100 m/s, enters an insulated horizontal nozzle. It leaves the nozzle at 200 m/s. The exit enthalpy (in kJ/kg) is ________
A.	85 10 J/Kg
B.	65 10 J/Kg
C.	85 10 J/Kg
D.	95 10 J/Kg
Answer» D. 95 10 J/Kg

Discussion

71.	Which among the following relations is/are valid only for reversible process undergone by a pure substance?
A.	Q = dU + W
B.	TdS = du + W
C.	TdS = dU + PdV
D.	Q = PdV + dU
Answer» E.

Discussion

72.	A calorically perfect gas (specific heat at constant pressure 1000 J/kgK) enters and leaves a gas turbine with the same velocity. The emperature of the gas at turbine entry and exit are 1100 K and 400 K, respectively. The power produced is 4.6 MW and heat escapes at the rate of 300 kJ/s through the turbine casing. The mass flow rate of the gas (in kg/s) through the turbine is
A.	6.14
B.	7.00
C.	7.50
D.	8.00
Answer» C. 7.50

Discussion

73.	A 1500 W electrical heater is used to heat 20 kg of water (cp = 4186 J/kgK) in an insulated bucket, from a temperature of 30 C to 80 C. If the heater temperature is only infinitesimally larger than the water temperature during the process, the change in entropy for the heater is _________ J/K and for water J/K.
A.	12786.99 J/kg
B.	22786.99 J/kg
C.	1200.99 J/kg
D.	12786.99 J/kg
Answer» E.

Discussion

74.	The slopes of constant volume and constant pressure lines in the T-s diagram are _______ and _________ respectively.
A.	<table><tr><td rowspan="2"><img src="https://www.indiabix.com/_files/images/data-interpretation/common/15-sym-oparen-h1.gif"></td><td style="border-bottom:1px solid #000000;vertical-align:bottom;padding-bottom:2px;"><center>ds</center></td><td rowspan="2"> = </td><td style="border-bottom:1px solid #000000;vertical-align:bottom;padding-bottom:2px;"><center>C<sub>P</sub></center></td><td rowspan="2"><img src="https://www.indiabix.com/_files/images/data-interpretation/common/15-sym-cparen-h1.gif"></td></tr><tr><td style="text-align: center;">dt</td><td style="text-align: center;">T</td></tr></table>
B.	<table><tr><td rowspan="2"><img src="https://www.indiabix.com/_files/images/data-interpretation/common/15-sym-oparen-h1.gif"></td><td style="border-bottom:1px solid #000000;vertical-align:bottom;padding-bottom:2px;"><center>dt</center></td><td rowspan="2"> = </td><td style="border-bottom:1px solid #000000;vertical-align:bottom;padding-bottom:2px;"><center>C<sub>P</sub></center></td><td rowspan="2"><img src="https://www.indiabix.com/_files/images/data-interpretation/common/15-sym-cparen-h1.gif"></td></tr><tr><td style="text-align: center;">ds</td><td style="text-align: center;">T</td></tr></table>
C.	<table><tr><td rowspan="2"><img src="https://www.indiabix.com/_files/images/data-interpretation/common/15-sym-oparen-h1.gif"></td><td style="border-bottom:1px solid #000000;vertical-align:bottom;padding-bottom:2px;"><center>ds</center></td><td rowspan="2"> + </td><td style="border-bottom:1px solid #000000;vertical-align:bottom;padding-bottom:2px;"><center>C<sub>P</sub></center></td><td rowspan="2"><img src="https://www.indiabix.com/_files/images/data-interpretation/common/15-sym-cparen-h1.gif"></td></tr><tr><td style="text-align: center;">dt</td><td style="text-align: center;">T</td></tr></table>
D.	<table><tr><td rowspan="2"><img src="https://www.indiabix.com/_files/images/data-interpretation/common/15-sym-oparen-h1.gif"></td><td style="border-bottom:1px solid #000000;vertical-align:bottom;padding-bottom:2px;"><center>ds</center></td><td rowspan="2"> + </td><td style="border-bottom:1px solid #000000;vertical-align:bottom;padding-bottom:2px;"><center>T</center></td><td rowspan="2"><img src="https://www.indiabix.com/_files/images/data-interpretation/common/15-sym-cparen-h1.gif"></td></tr><tr><td style="text-align: center;">dt</td><td style="text-align: center;">C<sub>P</sub></td></tr></table>
Answer» C. <table><tr><td rowspan="2"><img src="https://www.indiabix.com/_files/images/data-interpretation/common/15-sym-oparen-h1.gif"></td><td style="border-bottom:1px solid #000000;vertical-align:bottom;padding-bottom:2px;"><center>ds</center></td><td rowspan="2"> + </td><td style="border-bottom:1px solid #000000;vertical-align:bottom;padding-bottom:2px;"><center>C<sub>P</sub></center></td><td rowspan="2"><img src="https://www.indiabix.com/_files/images/data-interpretation/common/15-sym-cparen-h1.gif"></td></tr><tr><td style="text-align: center;">dt</td><td style="text-align: center;">T</td></tr></table>

Discussion

75.	A Carnot cycle is having an efficiency of 0.75. If the temperature of the high temperature reservoir is 727 C. What is the temperature of low temperature reservoir?
A.	23 C
B.	23 C
C.	0 C
D.	250 C
Answer» C. 0 C

Discussion

76.	A gas is heat ed in a duct as it flows over a resistance heater. Consider a 101 kW electric heat ing syst em. The gas ent ers the heat ing section of the duct at 100 kPa and 27 C with a volume flow rate of 15 m /s. If heat is lost from the gas in the duct to the surroundings at a rate of 51 kW, the exit temperature of the gas is (Assume constant pressure, ideal gas, negligible change in kinetic and potential energies and constant specific heat: C
A.	37 C
B.	76 C
C.	53 C
D.	32 C
Answer» E.

Discussion

77.	The exit area of the nozzle in cm is
A.	90.1
B.	56.3
C.	4.4
D.	12.9
Answer» E.

Discussion

78.	Work is done on an adiabatic system due to which its velocity changes from 10 m/s to 20 m/s, elevation increases by 20 m and temperature increases by 1 K. The mass of the system is 10 kg. cv = 100 J/(kgK) and gravitational acceleration is 10 m/s . If there is no change in any other component of the energy of the system, the magnitude of total work done (in kJ) on the system is ______.
A.	4.5 kJ.
B.	5.5 kJ.
C.	6.4 kJ.
D.	6.5 kJ.
Answer» B. 5.5 kJ.

Discussion

79.	Steam enters a turbine at 30 bar, 300 C (u = 2750 kJ/kg, h = 2993 kJ/kg) and exits the turbine as saturated liquid at 15 kPa (u = 225 kJ/kg, h = 226 kJ/kg). Heat loss to the surrounding is 50 kJ/kg of steam flowing through the turbine. Neglecting changes in kinetic energy and potential energy, the work output of the turbine (in kJ/kg of steam) is______.
A.	1417 kJ/kg
B.	2717 kJ/kg
C.	2728 kJ/kg
D.	2564 kJ/kg
Answer» C. 2728 kJ/kg

Discussion

80.	Steam enters a well insulated turbine and expands isentropically throughout. At an intermediate pressure, 20 percent of the mass is extracted for process heating and the remaining steam expands isentropically to 9 kPa.
A.	125MW
B.	125.56 MW
C.	129.56 MW
D.	525.56 MW
Answer» C. 129.56 MW

Discussion

81.	The thermal efficiency of an air-standard Brayton cycle in terms of pressure ratio r
A.	<table><tr><td rowspan="2"> 1 </td><td style="border-bottom:1px solid #000000;vertical-align:bottom;padding-bottom:2px;"><center>1</center></td></tr><tr><td style="text-align: center;">r<sub> </sub><sup> -1</sup></td></tr></table>
B.	<table><tr><td rowspan="2"> 1 </td><td style="border-bottom:1px solid #000000;vertical-align:bottom;padding-bottom:2px;"><center>1</center></td></tr><tr><td style="text-align: center;">r<sub> </sub><sup> </sup></td></tr></table>
C.	<table><tr><td rowspan="2"> 1 </td><td style="border-bottom:1px solid #000000;vertical-align:bottom;padding-bottom:2px;"><center>1</center></td></tr><tr><td style="text-align: center;">(r<sub> </sub>)<sup>1/<sub> </sub></sup></td></tr></table>
D.	<table><tr><td rowspan="2"> 1 </td><td style="border-bottom:1px solid #000000;vertical-align:bottom;padding-bottom:2px;"><center>1</center></td></tr><tr><td style="text-align: center;">r<sub> </sub><sup> -1/<sub> </sub></sup></td></tr></table>
Answer» E.

Discussion

82.	For a spark ignition engine, the equivalence ratio ( ) of mixture entering the combustion chamber has values
A.	< 1 for idling and > 1 for peak power conditions
B.	> 1 for both idling and peak power conditions
C.	> 1 for idling and < 1 for peak power conditions
D.	< 1 for both idling and peak power conditions
Answer» C. > 1 for idling and < 1 for peak power conditions

Discussion

83.	The silencer of an internal combustion engine
A.	reduces noise
B.	decrease break specific fuel consumption (BSFC)
C.	increase BSFC
D.	has no effect on its efficiency
Answer» B. decrease break specific fuel consumption (BSFC)

Discussion

84.	In order to burn 1 kilogram of CH
A.	3
B.	4
C.	5
D.	6
Answer» C. 5

Discussion

85.	For reversible adiabatic compression in a steady flow process, the work transfer per unit mass is
A.	pdv
B.	vdp
C.	Tds
D.	sdT
Answer» C. Tds

Discussion

86.	For an ideal gas with constant properties undergoing a quasi-static process, which one of the following represents the change of entropy ( s) from state 1 to 2?
A.	<table><tr><td rowspan="2">ds = c<sub>p</sub>ln</td><td rowspan="2"></td><td style="border-bottom:1px solid #000000;vertical-align:bottom;padding-bottom:2px;"><center>T<sub>2</sub></center></td><td rowspan="2">- R ln<br></td><td style="border-bottom:1px solid #000000;vertical-align:bottom;padding-bottom:2px;"><center>P<sub>2</sub></center></td><td rowspan="2"></td></tr><td align="center">T<sub>1</sub></td><td align="center">P<sub>1</sub></td></table>
B.	<table><tr><td rowspan="2">ds = c<sub>p</sub>ln</td><td rowspan="2"></td><td style="border-bottom:1px solid #000000;vertical-align:bottom;padding-bottom:2px;"><center>T<sub>2</sub></center></td><td rowspan="2">- R ln<br></td><td style="border-bottom:1px solid #000000;vertical-align:bottom;padding-bottom:2px;"><center>P<sub>2</sub></center></td><td rowspan="2"></td></tr><td align="center">T<sub>2</sub></td><td align="center">P<sub>2</sub></td></table>
C.	<table><tr><td rowspan="2">ds = c<sub>p</sub>ln</td><td rowspan="2"></td><td style="border-bottom:1px solid #000000;vertical-align:bottom;padding-bottom:2px;"><center>T<sub>1</sub></center></td><td rowspan="2">- R ln<br></td><td style="border-bottom:1px solid #000000;vertical-align:bottom;padding-bottom:2px;"><center>P<sub>2</sub></center></td><td rowspan="2"></td></tr><td align="center">T<sub>2</sub></td><td align="center">P<sub>1</sub></td></table>
D.	<table><tr><td rowspan="2">ds = c<sub>p</sub>ln</td><td rowspan="2"></td><td style="border-bottom:1px solid #000000;vertical-align:bottom;padding-bottom:2px;"><center>T<sub>2</sub></center></td><td rowspan="2">+ R ln<br></td><td style="border-bottom:1px solid #000000;vertical-align:bottom;padding-bottom:2px;"><center>P<sub>2</sub></center></td><td rowspan="2"></td></tr><td align="center">T<sub>1</sub></td><td align="center">P<sub>1</sub></td></table>
Answer» B. <table><tr><td rowspan="2">ds = c<sub>p</sub>ln</td><td rowspan="2"></td><td style="border-bottom:1px solid #000000;vertical-align:bottom;padding-bottom:2px;"><center>T<sub>2</sub></center></td><td rowspan="2">- R ln<br></td><td style="border-bottom:1px solid #000000;vertical-align:bottom;padding-bottom:2px;"><center>P<sub>2</sub></center></td><td rowspan="2"></td></tr><td align="center">T<sub>2</sub></td><td align="center">P<sub>2</sub></td></table>

Discussion

87.	Air of mass 1 kg. initially at 300 K and 10 bar, is allowed to expand isothermally till it reaches a pressure of 1 bar. Assuming air as an ideal gas with gas constant of 0.287 kJ/kg K, the change in entropy of air (in kJ/kg K, round off to two decimal places) is _________.
A.	0.66 kJ/kg K
B.	1.66 kJ/kg K
C.	0.33 kJ/kg K
D.	- 1.66 kJ/kg K
Answer» B. 1.66 kJ/kg K

Discussion

88.	An ideal gas undergoes a process from state 1 (T
A.	0.3 kJ/kg-K
B.	0.2 kJ/kg-K
C.	0.4 kJ/kg-K
D.	- 0.3 kJ/kg-K
Answer» B. 0.2 kJ/kg-K

Discussion

89.	The pressure ratio across a gas turbine (for air, specific heat at constant pressure, cp = 1040 J/ kg K and ratio of specific heats = 1.4) is 10. If the inlet temperature to the turbine is 1200 K and the isentropic efficiency is 0.9, the gas temperature at turbine exit is ________K.
A.	679.4 K
B.	675.4 K
C.	689.4 K
D.	669.4 K
Answer» B. 675.4 K

Discussion

90.	A p-V diagram has been obtained from a test on a reciprocating compressor. Which of the following represents that diagram?
A.	<img src="http://images.interviewmania.com/wp-content/uploads/2019/10/77a1.png">
B.	<img src="http://images.interviewmania.com/wp-content/uploads/2019/10/77a2.png">
C.	<img src="http://images.interviewmania.com/wp-content/uploads/2019/10/77a3.png%20">
D.	<img src="http://images.interviewmania.com/wp-content/uploads/2019/10/77a4.png%20">
Answer» E.

Discussion

91.	The following data pertain to a single stage impulse steam turbine: Nozzle angle = 20 Blade velocity = 200 m/s Relative steam velocity at entry = 350 m/s Blade inlet angle = 30 Blade exit angle = 25 If blade friction is neglected the work done per kg steam is
A.	124 kJ
B.	164 kJ
C.	169 kJ
D.	174 kJ
Answer» B. 164 kJ

Discussion

92.	A Curtis stage, Rateau stage and a 50% reaction stage in a steam turbine are examples of
A.	different types of impulse stages
B.	different types of reaction stages
C.	a simple impulse stage, a velocity compounded impulse stage and reaction stage
D.	a.velocity compounded impulse stage, a pressure compounded impulse stage and a reaction stage
Answer» E.

Discussion

93.	In a steam power plant operating on a ideal Rankine cycle, superheated steam enters the turbine at 3 MPa and 350 C. The condenser pressure is 75 kPa. The thermal efficiency of the cycle is ________%. Given data: For saturated liquid, at p = 75 kPa, hf = 384.39 kJ/kg, v
A.	0.26 or 26%
B.	0.25 or 25%
C.	0.27 or 27%
D.	0.36 or 36%
Answer» B. 0.25 or 25%

Discussion

94.	Steam at a velocity of 10 m/s enters the impulse turbine stage with symmetrical blading having blade angle 30 . The enthalpy drop in the stage is 100 kJ. The nozzle angle is 20 . The maximum blade efficiency (in percent) is ____.
A.	88.3 %
B.	87.3 %
C.	88.5 %
D.	87.5 %
Answer» B. 87.3 %

Discussion

95.	A single acting two stage compressor with complete inter cooling delivers air at 16 bar. Assuming an intake state of 1 bar at 15 C, the pressure ratio per stage is
A.	16
B.	8
C.	4
D.	2
Answer» D. 2

Discussion

96.	In the Rankine cycle for a steam power plant the turbine entry and exit enthalpies are 2803 kJ/kg and 1800 kJ/kg, respectively. The enthalpies of water at pump entry and exit are 121 kJ/kg and 124 kJ/kg respectively. The specific steam consumption (in kg/kWh) of the cycle is______.
A.	3.6 kg/kW - h
B.	2.6 kg/kW - h
C.	4.6 kg/kW - h
D.	3.1 kg/kW - h
Answer» B. 2.6 kg/kW - h

Discussion

97.	At the time of starting, idling and low speed operation, the carburettor supplies a mixture which can be termed as
A.	Lean
B.	slightly leaner than stoichiometric
C.	stoichiometric
D.	rich
Answer» E.

Discussion

98.	In a 3-stage air compressor, the inlet pressure is p1, discharge pressure is p
A.	464.15 kPa
B.	454.15 kPa
C.	474.15 kPa
D.	460.15 kPa
Answer» B. 454.15 kPa

Discussion

99.	The power required by the compressor in kW/ kg of gas flow are is
A.	194.7
B.	243.4
C.	304.3
D.	378.5
Answer» D. 378.5

Discussion

100.	During a Morse test on a 4 cylinder engine, the following measurements of brake power were taken at constant speed. All cylinders firing 3037 kW Number 1 cylinder not firing 2102 kW Number 2 cylinder not firing 2102 kW Number 3 cylinder not firing 2100 kW Number 4 cylinder not firing 2098 kW The mechanical efficiency of the engine is
A.	91.53%
B.	85.07%
C.	81.07%
D.	61.22%
Answer» D. 61.22%

Discussion

Explore topic-wise MCQs in Thermodynamics.

In a gas turbine, hot combustion products with the specific heats cp = 0.98 kJ/kgK, and cv = 0.7538 kJ/kgK enters the turbine at 20 bar, 1500 K and exits at 1 bar. The isentropic efficiency of the turbine is 0.94. The work developed by the turbine per kg of gas flow is

A mixture of ideal gases has the following composition by mass : N2 O2 CO2 60% 30% 10% If the universal gas constant is 8314 J/kmolK, the characteristic gas constant of the mixture (in J/kgK) is _______.

A frictionless piston-cylinder device contains a gas initially at 0.8 MPa and 0.015 m3. It expands quasistatically at constant temperature to a final volume of 0.030 m3. The work output (in kJ) during this process will be

A vessel of volume 1.0 m3 contains a mixture of liquid water and steam in equilibrium at 1.0 bar. Given that 90% of the volume is occupied by the steam, find the fraction of the mixture. Assume at 1.0 bar, vf = 0.001 m3/kg and vg = 1.7 m3/kg.

A piston-cylinder device initially contains 0.4 m3 of air (to be treated as an ideal gas) at 100 kPa and 80 C. The air is now isothermally compressed to 0.1 m3. The work done during this process is ______kJ. (Take the sign convention such that work done on the system is negative)

Alcohols are unsuitable at diesel engine fuels because

Knocking tendency in a Sl engine reduces with increasing

The power output from a spark ignition engine is varied by

In a power plant, water (density = 1000 kg/m ) is pumped from 80 kPa to 3 MPa. The pump has an isentropic efficiency of 0.85. Assuming that the temperature of the water remains the same, the specific work (in kJ/kg) supplied to the pump is

When an ideal gas with constant specific heats is throttled adiabatically, with negligible changes in kinetic and potential energies.

The density of air in kg/m at the nozzle exit is

The current level of the maximum temperature of steam turbine inlet.is much lower than that at gas turbine inlet because

One kilomole of an ideal gas is throttled from an initial pressure of 0.5 MPa to 0.1 MPa. The initial temperature is 300 K. The entropy change of the universe is

Which one of the following modifications of the si mpl e i deal Rank i ne cycl e i ncr eases t he thermal efficiency and reduces the moisture content of the steam at the turbine outlet?

Which of the following statements regarding a Rankine cycle with reheating are TRUE? (i) increase in a average temperature of heat addition (ii) reduction in thermal efficiency (iii) drier steam at the turbine exit

Steam at an initial enthalpy of 100 kJ/kg and inlet velocity of 100 m/s, enters an insulated horizontal nozzle. It leaves the nozzle at 200 m/s. The exit enthalpy (in kJ/kg) is ________

Which among the following relations is/are valid only for reversible process undergone by a pure substance?

The slopes of constant volume and constant pressure lines in the T-s diagram are _______ and _________ respectively.

A Carnot cycle is having an efficiency of 0.75. If the temperature of the high temperature reservoir is 727 C. What is the temperature of low temperature reservoir?

The exit area of the nozzle in cm is

Steam enters a well insulated turbine and expands isentropically throughout. At an intermediate pressure, 20 percent of the mass is extracted for process heating and the remaining steam expands isentropically to 9 kPa.

The thermal efficiency of an air-standard Brayton cycle in terms of pressure ratio r

For a spark ignition engine, the equivalence ratio ( ) of mixture entering the combustion chamber has values

The silencer of an internal combustion engine

In order to burn 1 kilogram of CH

For reversible adiabatic compression in a steady flow process, the work transfer per unit mass is

For an ideal gas with constant properties undergoing a quasi-static process, which one of the following represents the change of entropy ( s) from state 1 to 2?

Air of mass 1 kg. initially at 300 K and 10 bar, is allowed to expand isothermally till it reaches a pressure of 1 bar. Assuming air as an ideal gas with gas constant of 0.287 kJ/kg K, the change in entropy of air (in kJ/kg K, round off to two decimal places) is _________.

An ideal gas undergoes a process from state 1 (T

The pressure ratio across a gas turbine (for air, specific heat at constant pressure, cp = 1040 J/ kg K and ratio of specific heats = 1.4) is 10. If the inlet temperature to the turbine is 1200 K and the isentropic efficiency is 0.9, the gas temperature at turbine exit is ________K.

A p-V diagram has been obtained from a test on a reciprocating compressor. Which of the following represents that diagram?

The following data pertain to a single stage impulse steam turbine: Nozzle angle = 20 Blade velocity = 200 m/s Relative steam velocity at entry = 350 m/s Blade inlet angle = 30 Blade exit angle = 25 If blade friction is neglected the work done per kg steam is

A Curtis stage, Rateau stage and a 50% reaction stage in a steam turbine are examples of

In a steam power plant operating on a ideal Rankine cycle, superheated steam enters the turbine at 3 MPa and 350 C. The condenser pressure is 75 kPa. The thermal efficiency of the cycle is ________%. Given data: For saturated liquid, at p = 75 kPa, hf = 384.39 kJ/kg, v

Steam at a velocity of 10 m/s enters the impulse turbine stage with symmetrical blading having blade angle 30 . The enthalpy drop in the stage is 100 kJ. The nozzle angle is 20 . The maximum blade efficiency (in percent) is ____.

A single acting two stage compressor with complete inter cooling delivers air at 16 bar. Assuming an intake state of 1 bar at 15 C, the pressure ratio per stage is

In the Rankine cycle for a steam power plant the turbine entry and exit enthalpies are 2803 kJ/kg and 1800 kJ/kg, respectively. The enthalpies of water at pump entry and exit are 121 kJ/kg and 124 kJ/kg respectively. The specific steam consumption (in kg/kWh) of the cycle is______.

At the time of starting, idling and low speed operation, the carburettor supplies a mixture which can be termed as

In a 3-stage air compressor, the inlet pressure is p1, discharge pressure is p

The power required by the compressor in kW/ kg of gas flow are is

In a gas turbine, hot combustion products with the specific heats c_p = 0.98 kJ/kgK, and c_v = 0.7538 kJ/kgK enters the turbine at 20 bar, 1500 K and exits at 1 bar. The isentropic efficiency of the turbine is 0.94. The work developed by the turbine per kg of gas flow is

A mixture of ideal gases has the following composition by mass :
N₂ O₂ CO₂
60% 30% 10%

If the universal gas constant is 8314 J/kmolK, the characteristic gas constant of the mixture (in J/kgK) is _______.

A frictionless piston-cylinder device contains a gas initially at 0.8 MPa and 0.015 m³. It expands quasistatically at constant temperature to a final volume of 0.030 m³. The work output (in kJ) during this process will be

A vessel of volume 1.0 m³ contains a mixture of liquid water and steam in equilibrium at 1.0 bar. Given that 90% of the volume is occupied by the steam, find the fraction of the mixture. Assume at 1.0 bar, v_f = 0.001 m³/kg and v_g = 1.7 m³/kg.

A piston-cylinder device initially contains 0.4 m³ of air (to be treated as an ideal gas) at 100 kPa and 80 C. The air is now isothermally compressed to 0.1 m³. The work done during this process is ______kJ.
(Take the sign convention such that work done on the system is negative)

The slopes of constant volume and constant pressure lines in the T-s diagram are _ and ___ respectively.