Basic Concept of Thermodynamics
Exam Duration: 45 Mins Total Questions : 30
Match List I with List II and select the correct answer using the codes given below the lists.
List I | List II |
P.Work done in a polytropic process | 1.\(-\int { vdp } \) |
Q. Work done in steady flow process | 2.Zero |
R. Heat-transfer in a reversiole adiabatic process | 3. \(\frac { { p }_{ 1 }{ V }_{ 1 }-{ p }_{ 2 }{ V }_{ 2 } }{ \gamma -1 } \) |
S. Work done in an isentropic process | 4.\(\frac { { p }_{ 1 }{ V }_{ 1 }-{ p }_{ 2 }{ V }_{ 2 } }{ n-1 } \) |
- (a)
P Q R S 4 1 3 2 - (b)
P Q R S 1 4 2 3 - (c)
P Q R S 4 1 2 3 - (d)
P Q R S 1 2 3 4
The heat transfer Q, the work done Wand the change in internal energy U are all zero in the case of
- (a)
(a) a rigid vessel containing steam at 150 'C left in the atmosphere which is at 25 oC
- (b)
1kg of gas contained in an insulated cylinder expanding as the piston moves slowly outwards
- (c)
a rigid vessel containing ammonia gas connected through a valve to an evacuated rigid vessel, the vessel, the valve and the connecting pipes being well insulated and the valve being opened and after a time, condition through the two vessels becoming uniform
- (d)
1 kg of air flowing adiabatically from the atmosphere into a previously evacuated bottle
When a system is taken from state A to state B along the path A-C-B, 180 kJ of the heat flows into the system and it does 130 kJ of work (as shown in the figure below).
How much heat will flow into the system along the. path A-D-B, if the work done by it along the path is 40 kJ?
- (a)
40 kJ
- (b)
60 kJ
- (c)
90 kJ
- (d)
135 kJ
The diagram shown in the figure represents reversible compression of air on the p- V coordinates. The work of compression needed a centrifugal compressor is equal to the area
- (a)
ABDE-ABC
- (b)
ABDE
- (c)
ABFG
- (d)
ABFG-ABC
Match List I (Process) with List II (Index n in pvn = C) and select the correct answer using the codes given below the lists.
List I | List II |
P. Adiabatic | 1. n = infinity |
Q. Isothermal | 2. n = Cp/cv |
R. Constant pressure | 3. n = 1 |
S. Constant volume | 4. n = Cp/ Cv- 1 |
5. n = zero |
- (a)
P Q R S 2 3 5 4 - (b)
P Q R S 2 3 5 1 - (c)
P Q R S 3 2 1 5 - (d)
P Q R S 2 5 3 1
Consider the following statements:
1. The first law of thermodynamics is a law of conservation of energy.
2. Perpetual motion machine of the first kind converts energy into equivalent work.
3. A closed system does not exchange work of energy with its surroundings.
4. The second law of thermodynamics stipulates the law of conservation of energy and entropy.
Which of these statements are correct?
- (a)
1 and 4
- (b)
2 and 4
- (c)
2, 3 and 4
- (d)
1,2 and 3
The heat absorbed or rejected during a polytropic process is equal to
- (a)
\({ \left( \frac { \gamma -n }{ \gamma -1 } \right) }^{ 1/2 }\)x work done
- (b)
\(\left( \frac { \gamma -n }{ \gamma -1 } \right) \)x work done
- (c)
\(\left( \frac { \gamma -n }{ \gamma -1 } \right) \)x work done
- (d)
\({ \left( \frac { \gamma -n }{ \gamma -1 } \right) }^{ 2 }\)x work done
In a steady flow adiabatic turbine, the changes in the internal energy, enthalpy, kinetic energy and potential energy of the working fluid from inlet to exit are - 100 kJ/kg, -140 kJ/kg, -10 kJ/kg and zero respectively. Which one of the following gives the amount of work developed by the turbine
- (a)
100 kJ/kg
- (b)
110 kJ/kg
- (c)
140 kJ/kg
- (d)
150 kJ/kg
"A closed system undergoes a process 1-2 for which 'the values of 01.2 and W1-2 are +20 kJ and +50 kJ, respectively. If the system is returned to state 1 and Q2-1 is -10 kJ, what is the value of the work W2-1?
- (a)
+20kJ
- (b)
-40 kJ
- (c)
-80 kJ
- (d)
+40 kJ
A fluid flowing alonq a pipe line undergoes a throttling process from 10 bar to 1 bar is passing through a partially open valve. Before throttling, the specific volume of the fluid is 0.5 m3/kg and after throttling is 2.0 m3/kg. The change in specific internal energy during the throttling process is
- (a)
zero
- (b)
100 kJ/kg
- (c)
200 kJ/kg
- (d)
300 kJ/kg
The internal energy of certain system is a function of temperature alone and is given by the formula E = 25 + 0.25 t kJ. If this system executes a process for which the work done by it per degree temperature increase is 0.75 kN-m, the heat interaction per degree temperature increase, in kJ is
- (a)
-1.00
- (b)
-0.50
- (c)
0.50
- (d)
1.00
A tank containing air is stirred by a paddle wheel. The work input to the paddle wheel is 9000 kJ and the heat transferred to the surrounding from the tank is 3000 kJ. The external work done by the system is
- (a)
zero
- (b)
3000 kJ
- (c)
6000 kJ
- (d)
9000 kJ
A system while undergoing a cycle A-8-C-D-A has the values of heat and work transfers as given in the table.
Process | Q(in kJ/min) | W(in kJ/min) |
A-B | +687 | +474 |
B-C | -269 | 0 |
C-D | -199 | -180 |
D-A | +75 | 0 |
The power developed in kW is nearly
- (a)
4.9
- (b)
24.5
- (c)
49
- (d)
98
Gas from a cylinder of compressed helium is used to inflate an inelastic flexible balloon, originally folded completely flat, to a volume 0.6 m3. If the barometer reads 760 mm Hg, then amount of work done upon the atmosphere by the balloon
- (a)
60.795 kJ
- (b)
- 60.795 kJ
- (c)
zero
- (d)
Cannot be determined
In an internal combustion engine, during the compression stroke the heat rejected to the cooling water is 50 kJ/kg and the work input is 100 kJ/kg. The change in internal energy of the working fluid is
- (a)
zero
- (b)
50 kJ/kg, gain
- (c)
50 kJ/kg, loss
- (d)
100 kJ/kg, loss
0.3 kg of nitrogen gas at 1 bar and 40°C is contained in a cylinder. The piston is moved compressing nitrogen until the pressure becomes 10 bar and temperature becomes 160OC.The work done during the process is 30 kJ. The heat transferred from the nitrogen to the surroundings If Cv for nitrogen = 0.75 kJ/kg-K
- (a)
3 kJ
- (b)
-3 kJ
- (c)
3 J
- (d)
-3 J
A closed cylinder of 0.25 m diameter is fitted with a frictionless piston. The piston is retained in position by a catch in the cylinder wall and the volume on one side of the piston contains air at a pressure of 750 kN/m2. The volume on the other side of the piston is evacuated. A spring is mounted coaxially with the cylinder in this evacuated space to give a force" of 120 N on the piston in this position. The catch is released and the piston travels along the cylinder until it comes to rest after a stroke of 1.2 m. The piston is then held in its position of maximum travel. The spring force increases linearly with the piston displacement to a final value of 5 kN. The work done by the compressed air on the piston is
- (a)
3.07 J
- (b)
-3.07 J
- (c)
-3.072 kJ
- (d)
3.072 kJ
A cylinder containing the air comprises the system. Cycle is completed in following two process:
82000 N-m of work is done by the piston on the air during compression stroke and 45 kJ of heat are rejected to the surroundings.
- (a)
63 J
- (b)
63 kJ
- (c)
36 J
- (d)
36 kJ
An imaginary engine receives heat and does work on a slowly moving piston at such rates that the cycle of operation can be represented as a circle 10 cm in diameter on a p-V diagram on which 1 cm = 300 kPa and 1 cm = 0.1 m3/kg. Work is done by each kg of working fluid for each cycle of operation is
- (a)
2.356 kJ/kg
- (b)
23.562 kJ/kg
- (c)
2356.2 kJ/kg
- (d)
235.62 kJ/kg
A gas undergoes a thermodynamic cycle consisting of three processes beginning at an initial state, where P1 = 1 bar, V1 = 1.5 m3 and U1 = 512 kJ. The processes are as-
For process 1-2; compression with pV = constant
to P2 = 2 bar, U2 = 690 kJ
For process 2-3; W2-3 = 0, 02.3 = -150 kJ
For process 3-1: W3-1 = +50 kJ (neglecting PE and KE changes.)
Heat transfer Q1-2 is
- (a)
zero
- (b)
7.403 kJ
- (c)
74.03 kJ
- (d)
22 kJ
A gas undergoes a thermodynamic cycle consisting of three processes beginning at an initial state, where P1 = 1 bar, V1 = 1.5 m3 and U1 = 512 kJ. The processes are as-
For process 1-2; compression with pV = constant
to P2 = 2 bar, U2 = 690 kJ
For process 2-3; W2-3 = 0, 02.3 = -150 kJ
For process 3-1: W3-1 = +50 kJ (neglecting PE and KE changes.)
Heat transfer Q3-2 is
- (a)
zero
- (b)
22 kJ
- (c)
74.03 kJ
- (d)
540 kJ
A container is divided into compartments by a partition. The container is completely insulated so that there is no heat transfer. One portion contains gas at temperature T1 and pressure P1 while the other portion also has the same gas but at temperature T2 and pressure P2. If partition is removed
- (a)
\(\delta \)Q=0, \(\delta \)W\(\neq \) 0
- (b)
\(\delta \)W=0, \(\delta \)U=0
- (c)
\(\delta \)Q\(\neq \)0, \(\delta \)W\(\neq \)0
- (d)
\(\delta \)W=0, \(\delta \)U \(\neq \)0
A blower handles 1kg/s of air at 20°C and consumes a power of 15 kW. The inlet and outlet velocities of air are 100 m/s and 150 m/s respectively. The exit air temperature, assume adiabatic conditions, (take Cp of air = 1.005 kJ/kg-K) is
- (a)
28.7 K
- (b)
28.7°C
- (c)
8.75°C
- (d)
301.83oC
In a turbine unit, the gases flow through the turbine is 15 kg/s and the power developed by the turbine is 12000 kW. The enthalpies of gases at the inlet and outlet are 1260 kJ/kg and 400 kJ/kg respectively and the velocity of gases at the inlet and outlet are 50 m/s and 110 m/s respectively
The rate at which heat is rejected to the turbine,
- (a)
828 W
- (b)
8.28 kW
- (c)
55.2 kW
- (d)
828 kW
At the inlet to a certain nozzle, the enthalpy of the fluid passing is 3000 kJ/kg and the 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
The velocity at exists from the nozzle
- (a)
702.05 m/s
- (b)
891.79 m/s
- (c)
692.53 m/s
- (d)
543.76 m/s
At the inlet to a certain nozzle, the enthalpy of the fluid passing is 3000 kJ/kg and the 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
If the inlet area is 0.1 m2 and the specific volume at inlet is 0.187 m3/kg, find the mass flow rate
- (a)
0.32 kg/s
- (b)
0.26 kg/s
- (c)
26.05 kg/s
- (d)
32.1 kg/s
At the inlet to a certain nozzle, the enthalpy of the fluid passing is 3000 kJ/kg and the 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
If the specific volume at the nozzle exit is 0.498 m3/kg, find the exit area of the nozzle
- (a)
6.04 m2
- (b)
7.91 m2
- (c)
8.02 m2
- (d)
0.023 m2
In oil cooler, oil flows steadily through a tube submerged in a steady stream of cooling water. Under steady flow conditions, the oil enters at 90°C and leaves at 30 °C, while the water enters at 25°C and leaves at 70°C. The enthalpy of oil at tOC is given by h = 1.68 t + 10.5 x 10-4 t2 kJ/kg The cooling water flow required for cooling 2.78 kg/s of oil is
- (a)
2.7 kg/s
- (b)
1.6 kg/s
- (c)
0.7 kg/s
- (d)
3.2 kg/s
An electric storage battery which can exchange heat goes through a complete cycle of two processes. In proces 1-2, 2.8 kW -h of electrical work flow into the battery while 732 kJ of heat flow out to the atmosphere. During process 2-1, 2.4 kW-h of work flow out of the battery. The heat transfer in process 2-1 is
- (a)
-708 kJ
- (b)
+ 708 kJ
- (c)
zero
- (d)
Cannot be determined
Joule-Thomson coefficient is defined as
- (a)
\({ \left( \frac { \partial T }{ \partial p } \right) }_{ n }\)
- (b)
\({ \left( \frac { \partial h }{ \partial p } \right) }_{ T }\)
- (c)
\({ \left( \frac { \partial h }{ \partial T } \right) }_{ p }\)
- (d)
\({ \left( \frac { \partial p }{ \partial T } \right) }_{ h }\)