GATE XE topic:second-law-thermodynamics PYQs & Answers

Questions 1–10 of 43. Imported answers require independent review unless marked reviewed.

A house looses heat at a rate of 150 MJ per hour. The temperature outside the house is −3 °C. The minimum power (in kW) required to maintain the temperature inside the house at 25 °C using a heat pump is ____________ (rounded off to two decimal places).

You can attempt this question now. Sign in to view the answer key, explanations and discussion.Log in to check answer

M kg of a liquid at a temperature

is mixed with M kg of the same liquid at another temperature

in an isolated tank at constant pressure. The mass specific heat capacity at constant pressure of the liquid is

, which is a constant. The total entropy change in the process is

Your answerChoose one option.

You can attempt this question now. Sign in to view the answer key, explanations and discussion.Log in to check answer

A rigid spherical solid ball at 100 °C is cooled slowly to 200 °C in a surrounding air at 25 °C. The density, specific heat capacity, and diameter of the ball are 800 kg/m³, 500 J/kg-K, and 10 mm; respectively. Assuming that the cooling process is quasi-equilibrium, the entropy generated (in J/K) in the process is ____________ (rounded off to two decimal places).

You can attempt this question now. Sign in to view the answer key, explanations and discussion.Log in to check answer

The inlet and outlet temperatures of the flowing fluid during a steady state flow process are the same as that of the surroundings. If the changes in kinetic and potential energies are neglected, the maximum power that can be obtained is equal to

Your answerChoose one option.

the rate of increase in enthalpy of the flowing fluid

the rate of decrease in Helmholtz energy of the flowing fluid

the rate of decrease in Gibbs free energy of the flowing fluid

the rate of decrease in internal energy of the flowing fluid

You can attempt this question now. Sign in to view the answer key, explanations and discussion.Log in to check answer

Let

and

denote the absolute temperatures of high and low temperature reservoirs, respectively. The coefficient of performance of a reversible refrigerator operating between these two reservoirs is

Your answerChoose one option.

You can attempt this question now. Sign in to view the answer key, explanations and discussion.Log in to check answer

A heat engine having thermal efficiency of 40% receives heat from a source at 600 K and rejects heat to a sink at 300 K. The second-law efficiency (in %) of this engine is __________ (answer in integer).

You can attempt this question now. Sign in to view the answer key, explanations and discussion.Log in to check answer

Air enters a air dryer at 22 °C and 100 kPa with a velocity of 3.7 m/s, and leaves the dryer at 83 °C and 100 kPa with a velocity of 9.1 m/s. The exit area of the dryer is 18.7 cm

, and the ambient temperature is 22 °C. The air is an ideal gas with gas constant

= 0.287 kJ/kg-K and isobaric specific heat

= 1.005 kJ/kg-K. If the change in potential energy is neglected, the second law efficiency (in %) of the dryer is __________ (rounded off to one decimal place).

You can attempt this question now. Sign in to view the answer key, explanations and discussion.Log in to check answer

Two Carnot heat engines (E1 and E2) are operating in series as shown in figure. Engine E1 receives heat from a reservoir at

K and does work

. Engine E2 receives heat from an intermediate reservoir at

, does work

and rejects the rest to a reservoir at

K. Both the engines have identical thermal efficiencies.

Diagram for Engineering Sciences question 107

The temperature T (in K) of the intermediate reservoir is __________ (answer in integer).

You can attempt this question now. Sign in to view the answer key, explanations and discussion.Log in to check answer

In a piston cylinder assembly, one kmol of an ideal gas is compressed from an initial state of 200 kPa and 400 K to a final state of 1 MPa and 400 K. If the surroundings are at 400 K, the minimum amount of work (in kJ/kmol) required for the compression process is __________ (rounded off to two decimal places).

Use: Universal gas constant (

) = 8.314 kJ/kmol-K

You can attempt this question now. Sign in to view the answer key, explanations and discussion.Log in to check answer

A heat source at temperature

transfers the same amount of heat to a sink under the following situations:

Case A: Sink is at temperature

Case B: Sink is at temperature

, which one of the following statements is TRUE?

Your answerChoose one option.

The reversibility is the same, and the entropy generation is greater than zero for Cases A and B

Case B is less reversible with the entropy generation greater than zero

Case B is more reversible with the entropy generation greater than zero

Case B is more reversible with the entropy generation equal to zero

You can attempt this question now. Sign in to view the answer key, explanations and discussion.Log in to check answer

GATE XE topic:second-law-thermodynamics PYQs

How to practice topic:second-law-thermodynamics

Question 95

Question 98

Question 106

Question 91

Question 93

Question 95

Question 105

Question 107

Question 109

Question 88