CWT–04
Booklet No.:
Booklet Series:
03092014
Thermodynamics
(Mechanical Engineering)
A
Student Name:
Roll Number:
Duration: 90 Minutes
PAPER
MAXIMUM MARKS: 60
INSTRUCTIONS
1.
IMMEDIATELY AFTER THE COMMENCEMENT OF THE EXAMINATION, YOU SHOULD CHECK THAT THIS TEST BOOKLET
DOES NOT HAVE ANY UNPRINTED OR TORN OR MISSING PAGES OR ITEMS ETC. IF SO, GET IT REPLACED BY A
COMPLETE TEST BOOKLET.
2.
This Test Booklet contains 30 questions. Each question comprises four responses (answers). You will select the
response which you want to mark on the Answer Sheet. In case you feel that there is more than one correct
response, mark the response which you consider the best. In any case, choose ONLY ONE response for each item.
3.
You have to mark all your response ONLY on the separate Answer Sheet provided.
4.
All items carry equal marks.
5.
Before you proceed to mark in the Answer Sheet the response to various items in the Test Booklet, you have to fill
in some particulars in the Answer Sheet as per instructions.
6.
Each questions 2 marks and 2/3 negative mark is assigned for the wrong answer.
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P h ( 0 1 1 ) - 2 6 1 9 4 8 6 9 , C e l l : 9 8 7 3 0 0 0 9 0 3 , 9 8 7 3 6 6 4 4 2 7 : E - ma i l : q h e n g i n e e r z o n e @ g ma i l . c o m
Thermodynamics (ME)
(1.)
A new temperature scale in degree N is to be defined. The boiling and freezing
on this scale are 400°N and 100°N respectively. What will be reading on new
scale corresponding to 60°C?
(a.) 120°N
(b.) 180°N
(c.) 220°N
(d.) 280°N
Ans: d
(2.)
In the free expansion of a gas between two equilibrium states, the work transfer
involved(a.) Can be calculated by joining the two states on P-V coordinates by any path
and estimating the area below
(b.) Can be calculated by joining the two states by a quasi-static path and then
finding the area below
(c.) Is zero
(d.) Is equal to heat generated by friction during expansion
Ans: c
(3.)
An engine cylinder has a piston of area 0.12 m3 and contains gas at a pressure
of 1.5 MPa. The gas expands according to a process which is represented by a
straight-line on a P-V diagram. The final pressure is 0.15 MPa. Calculate the
work done by the gas on the piston of the stroke is 0.30 m.
(a.) 42.5 kJ
(b.) 29.7 kJ
(c.) 36.2 kJ
(d.) 50.0 kJ
Ans: b
(4.)
Two ideal heat engine cycles represented by the figure. Assume VQ = QR, PQ =
QS and UP = PR = RT. It the work interaction for the rectangular cycle (WVUR)
is 48 Nm, then the work interaction for the cycle PST is-
(a.) 12 Nm
2
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Thermodynamics (ME)
(b.) 24 Nm
(c.) 26 Nm
(d.) 36 Nm
Ans: b
(5.)
In a cyclic heat engine operating between a source temperature of 600°C and a
sink temperature of 20°C, the least rate of heat rejection per kW net output of
the engine is(a.) 0.460 kW
(b.) 0.505 kW
(c.) 0.846 kW
(d.) 0.256 kW
Ans: b
(6.)
The thermal efficiency of the hypothetical heat engine cycle shown in figure is-
(a.) 0.5
(b.) 0.45
(c.) 0.35
(d.) 0.25
Ans: d
(7.)
Heat flows between two reservoir having temperature 1000 K and 500 K,
respectively. It the entropy change of cold reservoir is 10 kJ/K, then what is the
entropy change for the hot reservoir?
(a.) –10 kJ/K
(b.) –5 kJ/K
(c.) 5 kJ/K
(d.) 10 kJ/K
Ans: b
(8.)
The Gibbs-free energy function is a property comprising(a.) Pressure, volume and temperature
(b.) Enthalpy, temperature and entropy
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Thermodynamics (ME)
(c.) Temperature, pressure and enthalpy
(d.) Volume, enthalpy and entropy
Ans: b
(9.)
A milk chilling unit can remove heat from the milk at the rate of 41.87 MJ/h.
Heat leaks into the milk from the surroundings at an average rate of 4.187 M,
4.187 MJ/h. Find the time require for cooling a batch of 500 Kg of milk from
45°C to 5°C. Take the Cp of milk to be 4.187 kJ/kgK.
(a.) 2 h, 13 min
(b.) 4 hr, 26 min
(c.) 6 hr, 20 min
(d.) None of these
Ans: a
(10.)
A mass of 8 kg gas expands within a flexible container. So that the P-V
relationship is of the form PV1.2 = constant. The initial pressure is 100 kPa and
the initial volume is 1m3. The final pressure is 5 kPa. If specific internal energy
of the gas decreases by 40 kJ/kg. Find the heat transfer in magnitude and
direction
(a.) 2500 kJ
(b.) 2612.5 kJ
(c.) 2792.5 kJ
(d.) 3012.20 kJ
Ans: b
(11.)
A cyclic process ABC is show on a V-T diagram in figure. The same process on a
P-V-diagram will be represented as-
(a.)
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Thermodynamics (ME)
(b.)
(c.)
(d.)
Ans: d
(12.)
a 

In a Vander wall’s equation  P  2  V  b   RT (R = universal gas constant)

V 
the unit of ‘b’ is(a.) m3/mole
(b.) Liter/mole °C
(c.) Kg-liter/mole
(d.) Dimensionless
Ans: a
(13.)
A fluid flowing along a pipe line undergoes a throttling process from 10 bar to 1
bar in passing through a partially open value. Before throttling, the specific
volume of the fluid is 0.5 m3/kg and after throttling is 2.0 m3/kg. What is the
change in specific internal energy during the throttling process(a.) Zero
(b.) 100 kJ/kg
(c.) 200 kJ/kg
(d.) 300 kJ/kg
Ans: d
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Thermodynamics (ME)
(14.)
According to the Maxwell’s relation, which of the following is correct?
 V 
 S 
(a.) 
  

 T P
 P T
 S 
 P 
(b.) 
 

 V T  T V
 P 
 S 
(c.) 
 

 T V  V T
(d.) All of the above
Ans: c
(15.)
For a steady-flow process from state 1 to 2, enthalpy changes from h1 = 400
kJ/kg to h2 = 100 kJ/kg and entropy changes from S1 = 1.1 kJ/kg-k to S2 = 0.7
kJ/kg-K. Surrounding environmental temperature is 300 K. Neglect changes in
kinetic and potential energy. The change in availability of the system is(a.) 100 kJ/kg
(b.) 200 kJ/kg
(c.) 220 kJ/kg
(d.) 180 kJ/kg
Ans: d
(16.)
Which one of the following statements is not correct?
(a.) Change in entropy during a reversible adiabatic process is zero
(b.) Entropy increases with additional of heat
(c.) Throttling is a constant entropy expansion process
(d.) Change in entropy when a gas is heated under constant pressure given by
S 2  S1  m C P log e
T2
T1
Ans: c
(17.)
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 heater is ____
(a.) 14556 J/k
(b.) –11858 J/k
(c.) 15534 J/k
(d.) 12877 J/k
Ans: b
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Thermodynamics (ME)
(18.)
One reversible heat engine operates between 1600 and T2K, and another
reversible heat engine operates between T2K and 400 K. If both the engine have
the same heat input and output, then the temperature T2 must be equal to(a.) 1000 K
(b.) 800 K
(c.) 600 K
(d.) 200 K
Ans: b
(19.)
Consider the following statements:
The definition of1. Temperature is due to Zeroth law of thermodynamics
2. Entropy is due to first law of thermodynamics
3. Internal energy is due to second law of thermodynamics
4. Reversibility is due to Kelvin-Plank’s statements
Which of the following is/are correct(a.) 1, 2 and 3
(b.) 1, 3 and 4
(c.) 1 alone
(d.) 2 lone
Ans: c
(20.)
An adiabatic vessel contains 2 kg of water at 25°C, by paddle wheel work
transfer, the temperature of water is increases to 30°C. If the specific heat of
water is assumed constant at 4.187 kJ/kgK. Find the entropy change of the
universe
(a.) 0.13934 kJ/K
(b.) 0.19236 kJ/K
(c.) 2.3624 kJ/K
(d.) 0.50568 kJ/K
Ans: a
(21.)
A mass of 1.5 kg of air is compressed in a quasi-static process from 0.1 MPa to
0.7 MPa for which Pv = constant. The initial density of air is 1.16 kg/m3. Find
the work done by the piston to compress the air(a.) 321.72 kJ
(b.) 251.63 kJ
(c.) 225 kJ
(d.) 417.2 kJ
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Thermodynamics (ME)
Ans: b
(22.)
Thermodynamic work is the product of(a.) Two extensive properties
(b.) Two intensive properties
(c.) An intensive property and change in an extensive property
(d.) An extensive property and change in an intensive property
Ans: c
(23.)
A system composed of 2kg of the above expands in a frictionless. Piston and
cylinder machine from an initial state of 1 MPa, 100°C to a final temperature of
30°C. If there is no heat transfer, find the net work for the process
(a.) 212.25 kJ
(b.) 141.72 kJ
(c.) 100.52 kJ
(d.) None of these
Ans: c
(24.)
A heat engine is used to drive a heat pump. The heat transfers from the heat
engine and from the heat pump are used to heat the water circulating through
the radiators of a building. The efficiency of the heat engine is 27% and the COP
of the heat pump is 4. Evaluate the ratio of the heat transfer to the circulating
water to the heat transfer to heat engine
(a.) 2.25
(b.) 1.81
(c.) 5.25
(d.) 3.06
Ans: b
(25.)
When a gas is heated at constant pressure, the percentage of the energy
supplied, which goes at the internal energy of the gas is(a.) More for a diatomic gas than for tri-atomic gas
(b.) Some for mono-atomic, diatomic and tri-atomic gases but less than 100%
(c.) 100% for all gases
(d.) Less than tri-atomic gas than for a diatomic gas.
Ans: a
(26.)
When air is expressed, the enthalpy is increased from 100 to 200 kJ/kg. Heat
lost during this compression is 50 kJ/kg. Neglecting kinetic and potential
energies, the power required for a mass flow of 2 kg/s of air through the
compressor will be-
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Thermodynamics (ME)
(a.) 300 kW
(b.) 200 kW
(c.) 100 kW
(d.) 50 kW
Ans: a
(27.)
Which one of the following pairs best expresses a relationships similar to that
expressed in the pair ‘pressure-volume’ for a thermodynamic system undergoing
a process?
(a.) Enthalpy-Entropy
(b.) Pressure-Enthalpy
(c.) Pressure-Temperature
(d.) Temperature-Entropy
Ans: d
(28.)
A heat reservoir at 900 K is brought into content with the ambient at 300 K for
a short time. During this period 900 kJ of heat is lost by the heat reservoir. The
total loss in availability due to this process is(a.) 9000 kJ
(b.) 6000 kJ
(c.) 18000 kJ
(d.) None of these
Ans: d
(29.)
Which of the following statement is correct?
(a.) The greater the pressure difference in throttling the lesser the irreversibility
(b.) The primary source of internal irreversibility in power is fluid friction is
rotary machines
(c.) The greater the irreversibility, the greater the increase in adiabatic process
(d.) The entropy of the universe is continually on the increase
Ans: a
(30.)
Water is heated at a constant pressure of 0.7 MPa. The boiling point is
164.97°C. The initial temperature of water at 0°C. The latent heat of evaporation
is 2066.3 kJ/kg. Find the increase of entropy of water, if the final state is
steam.
(a.) 6.6967 kJ/kg-K
(b.) 8.2467 kJ/kg-K
(c.) 9.2667 kJ/kg-K
(d.) None of these
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Thermodynamics (ME)
Ans: a
(31.)
Clapeyron equation is used for(a.) Finding specific volume of vapour
(b.) Finding specific volume of liquid
(c.) Finding latent heat of vaporization
(d.) Finding sensible heat
Ans: c
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