Heat Engines, Refrigerators and Carnot Principles - Second Law of Thermodynamics - Engineering Sciences Previous Year Questions

1

2007 · Engineering Sciences · Second Law of Thermodynamics · Heat Engines, Refrigerators and Carnot Principles

Engineering Sciences (XE) 2007

A reversible heat engine receives heat inputs of 300 kJ and 200 kJ from two thermal reservoirs at 1000 K and 800 K, respectively. The engine rejects heat Q to a reservoir at 300 K.
The value of Q is

A

65 kJ

B

165 kJ

C

100 kJ

D

265 kJ

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2

2008 · Engineering Sciences · Second Law of Thermodynamics · Heat Engines, Refrigerators and Carnot Principles

Engineering Sciences (XE) 2008

The COP of a Carnot heat pump operating between \( -3^\circ C \) and \( 27^\circ C \) is

A

10

B

0.1

C

9.0

D

1.0

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3

2008 · Engineering Sciences · Second Law of Thermodynamics · Heat Engines, Refrigerators and Carnot Principles

Engineering Sciences (XE) 2008

A Carnot engine having efficiency η = 0.5 drives a Carnot refrigerator with COP = 4. The energy absorbed by the refrigerator from the cold body for each kJ of energy absorbed from the source by the Carnot engine is

A

2 kJ

B

2.4 kJ

C

3 kJ

D

4 kJ

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4

2008 · Engineering Sciences · Second Law of Thermodynamics · Heat Engines, Refrigerators and Carnot Principles

Engineering Sciences (XE) 2008

It is proposed that the solar energy be used to heat a large collector plate. The energy in turn be transferred as heat to a fluid within a heat engine, and the engine would reject energy as heat to the atmosphere. Experiments indicate that 0.5 kW/m² of energy can be collected at the operating temperature of the plate and the maximum efficiency of the engine is 0.2. The minimum collector area that would be required for a plant to produce 1 kW of useful shaft power is

A

1 m²

B

10 m²

C

100 m²

D

1000 m²

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5

2008 · Engineering Sciences · Second Law of Thermodynamics · Heat Engines, Refrigerators and Carnot Principles

Engineering Sciences (XE) 2008

A reversible engine operates between temperatures T₁ = 1000 K and T₂ = 400 K. The engine drives a refrigerator which operates between T₂ = 400 K and T₃ = 200 K. The energy transfer to the engine is 2000 kJ and the net work output of the combined engine and refrigerator is 300 kJ. The energy transferred to the refrigerant is

A

9 kJ

B

90 kJ

C

900 kJ

D

9000 kJ

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6

2008 · Engineering Sciences · Second Law of Thermodynamics · Heat Engines, Refrigerators and Carnot Principles

Engineering Sciences (XE) 2008

A reversible heat engine in a satellite operates between a hot reservoir at temperature T₁ and a radiating panel at temperature T₂. Radiation from the panel is proportional to the area A and T⁴. The constant of proportionality is the Stefan-Boltzmann constant σ. The ratio of the work output W to the temperature difference (T₁ - T₂) is

A

σAT

B

σAT²

C

σAT₃

D

σAT₄

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7

2008 · Engineering Sciences · Second Law of Thermodynamics · Heat Engines, Refrigerators and Carnot Principles

Engineering Sciences (XE) 2008

A heat engine operates between three reservoirs: R_1 at 550 K, R_2 at 450 K and R_3 at 350 K. For every cycle, the engine accepts 100 kJ from R_1 and rejects 60 kJ into R_2 and 30 kJ into R_3. The engine efficiency is

A

0.10

B

0.20

C

0.30

D

can not be defined

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8

2009 · Engineering Sciences · Second Law of Thermodynamics · Heat Engines, Refrigerators and Carnot Principles

Engineering Sciences (XE) 2009

A Carnot refrigerator operating between -1 °C and 33 °C has a cooling capacity of 1.6 kW. The power consumed by the refrigerator is

A

160 W

B

178 W

C

200 W

D

1.8 kW

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9

2009 · Engineering Sciences · Second Law of Thermodynamics · Heat Engines, Refrigerators and Carnot Principles

Engineering Sciences (XE) 2009

An engine reversibly receives 1200 J of heat at 900 K. After rejecting heat to the ambient at 300 K, it develops 600 J of work. The irreversibility in joules is equal to

A

600

B

400

C

200

D

zero

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10

2009 · Engineering Sciences · Second Law of Thermodynamics · Heat Engines, Refrigerators and Carnot Principles

Engineering Sciences (XE) 2009

A heat engine $E_1$ operates between an infinite reservoir at 800 °C and a body $B$. The temperature of the body $B$ remains constant at 350 °C. Heat transferred to the engine $E_1$ is 900 kJ and the work output is 200 kJ. Another engine $E_2$ operates between the body $B$ and the atmosphere at 27 °C. Heat rejected to the atmosphere is 350 kJ. The thermal efficiency of the engine $E_2$ is

A

0.39

B

0.5

C

0.61

D

0.635

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11

2010 · Engineering Sciences · Second Law of Thermodynamics · Heat Engines, Refrigerators and Carnot Principles

Engineering Sciences (XE) 2010

A heat pump, which operates in a cycle, extracts heat energy from the cold reservoir and supplies the same amount of energy to the hot reservoir. Which of the following statements holds for this process?

A

This process violates both the first and the second law

B

This process violates the first law but not the second law

C

This process violates the second law but not the first law

D

This process does not violate both first and second law

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12

2010 · Engineering Sciences · Second Law of Thermodynamics · Heat Engines, Refrigerators and Carnot Principles

Engineering Sciences (XE) 2010

Value of T_f is

A

30 °C

B

42.5 °C

C

47.5 °C

D

50 °C

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13

2011 · Engineering Sciences · Second Law of Thermodynamics · Heat Engines, Refrigerators and Carnot Principles

Engineering Sciences (XE) 2011

A heat pump extracts heat at the rate of 100 kW from a low temperature reservoir and delivers heat at the rate of 160 kW to a high temperature reservoir. The COP of the heat pump is

A

1.60

B

1.67

C

2.60

D

2.67

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14

2011 · Engineering Sciences · Second Law of Thermodynamics · Heat Engines, Refrigerators and Carnot Principles

Engineering Sciences (XE) 2011

The thermal efficiency of a reversible heat engine operating between two thermal reservoirs is \(\eta_{max}\). The coefficient of performance of a reversible refrigeration cycle operating between the same two reservoirs is

A

\(\left(\frac{1}{\eta_{max}}-1\right)\)

B

\(\left(\frac{1}{\eta_{max}}+1\right)\)

C

\(\left(\frac{1}{\eta_{max}}\right)\)

D

\(1-\left(\frac{1}{\eta_{max}}\right)\)

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15

2012 · Engineering Sciences · Second Law of Thermodynamics · Heat Engines, Refrigerators and Carnot Principles

Engineering Sciences (XE) 2012

If \( Q_L \) represents the magnitude of heat transfer from a low temperature reservoir to a cyclic device and \( Q_H \) represents the magnitude of heat transfer from a cyclic device to a high temperature reservoir, then for the same \( Q_L \) and \( Q_H \), the coefficient performance of a refrigerator ( \( COP_R \) ) and the coefficient performance of a heat pump ( \( COP_{HP} \) ) can be related as

A

\(COP_R = 1 - COP_{HP} \)

B

\(COP_{HP} = COP_R + 1 \)

C

\(COP_R . COP_{HP} = 1 \)

D

\(COP_{HP} = COP_R - 1 \)

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16

2012 · Engineering Sciences · Second Law of Thermodynamics · Heat Engines, Refrigerators and Carnot Principles

Engineering Sciences (XE) 2012

Consider two Carnot heat engines A and B operating in series. Engine A receives heat from a reservoir at 1750 K and rejects heat to another reservoir at temperature \( T \). Engine B receives an amount of energy same as that rejected by Engine A from the reservoir at temperature \( T \). Engine B then rejects heat to another reservoir at 320 K. In both cases, the engines produce some amount of work. If the thermal efficiencies of both the engines are the same, then the temperature \( T \) is approximately

A

\(848 \text{ K} \)

B

\(748 \text{ K} \)

C

\(648 \text{ K} \)

D

\(548 \text{ K} \)

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17

2013 · Engineering Sciences · Second Law of Thermodynamics · Heat Engines, Refrigerators and Carnot Principles

Engineering Sciences (XE) 2013

A thermodynamic cycle operates between one source at a temperature of 600 K, another source at a temperature of 300 K and a sink at a temperature T as shown in the figure below
If the First and Second laws of thermodynamics are not violated, what should be the value of T in K?______

Check answer

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18

2014 · Engineering Sciences · Second Law of Thermodynamics · Heat Engines, Refrigerators and Carnot Principles

Engineering Sciences (XE) 2014

The efficiency of a reversible engine operating between two temperatures is 40 %. The COP of a reversible refrigerator operating between the same temperatures is

A

1.5

B

2.5

C

0.4

D

3.5

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19

2014 · Engineering Sciences · Second Law of Thermodynamics · Heat Engines, Refrigerators and Carnot Principles

Engineering Sciences (XE) 2014

A reversible heat engine (E) operates using three thermal reservoirs with temperatures as shown in the following figure. If Q₁=Q₂, the efficiency of the engine is ______.

A

0.25

B

0.125

C

0.625

D

0.75

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20

2016 · Engineering Sciences · Second Law of Thermodynamics · Heat Engines, Refrigerators and Carnot Principles

Engineering Sciences (XE) 2016

The thermal efficiency of a Carnot engine is 0.5. If the temperature of the cold reservoir is 300 K, then the temperature of the hot reservoir is:

A

600 K

B

1200 K

C

900 K

D

450 K

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