GATE XE topic:first-law-thermodynamics PYQs & Answers — Page 3

Questions 21–30 of 38. Imported answers require independent review unless marked reviewed.

Two air streams of mass flow rates

and

enter a mixing chamber and exit after perfect mixing. The corresponding temperatures of the inlet streams are

and

, respectively. Heat loss rate from the mixing chamber to the surrounding is

. Assume that the process is steady, specific heat capacity is constant, and air behaves as an ideal gas. Identify the correct expression for the final exit temperature

after mixing. The mass specific heat capacities of the gas at constant volume and constant pressure are

and

, respectively. Neglect the bulk kinetic and potential energies of the streams.

Your answerChoose one option.

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Air having a mass flow rate of 2 kg/s enters a diffuser at 100 kPa and 30°C, with a velocity of 200 m/s. Exit area of the diffuser is 400 cm² while the exit temperature of the air is 45°C. The rate of heat loss from the diffuser to the surrounding is 8 kJ/s. The pressure at the diffuser exit is __________ kPa (2 decimal places).

For air, the characteristic gas constant is 287 J/(kgK) and specific heat capacity at constant pressure is 1005 J/(kgK). Assume air to be an ideal gas and the flow in the diffuser is steady.

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A mixture of air and water vapour enters a steady-flow adiabatic saturator at 50°C and 100 kPa. It leaves the saturator in a completely saturated state at temperature of 25°C and pressure of 100 kPa. Liquid water enters the saturator at 25°C. If air is considered to be an ideal gas, with constant specific heat capacity, the relative humidity of the air entering the saturator is __________ % (1 decimal place).

Use the following data:

at 25°C

kJ/kg,

kPa

at 50°C

kJ/kg,

kPa

Specific heat capacity of air at constant pressure

kJ/(kgK)

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Air at a pressure of 1 MPa and 300 K is flowing in a pipe. An insulated evacuated rigid tank is connected to this pipe through an insulated valve. The volume of the tank is 1 m³. The valve is opened and the tank is filled with air until the pressure in the tank is 1 MPa. Subsequently, the valve is closed. Consider air to be an ideal gas and neglect bulk kinetic and potential energy. The final temperature of air in the tank is __________ K (1 decimal place).

Specific heat capacity of air at constant pressure

kJ/(kgK) and characteristic gas constant for air = 0.287 kJ/(kgK)

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A frictionless piston cylinder device contains 1 kg of an ideal gas. The gas is compressed according to Pv¹·³ = constant (P is pressure and v is mass specific volume), from 100 kPa, 250 K, till it reaches a temperature of 500 K. The heat transfer from the piston cylinder device to its surroundings is __________ kJ (2 decimal places).

The characteristic gas constant is 287 J/(kg K) and the ratio of specific heat capacities is 1.4.

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Carbon dioxide (CO

) enters an adiabatic rigid nozzle steady at 1 MPa and 500 °C with a mass flow rate of 1.5 kg/s. The inlet area of the nozzle is 40 cm

and the exit velocity is 10 times of that at the inlet. If CO

can be considered as an ideal gas with gas constant of 0.19 kJ/kg.K and the ratio of specific heats of 1.29, the exit temperature (in K) (rounded off to 1 decimal place) is ________.

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A closed system containing 8 kg of gas undergoes an expansion process following the relation

. The initial and final pressures are 1 MPa and 5 kPa, respectively, while the initial volume is 1 m

. If the specific internal energy of the gas decreases by 40 kJ/kg during the process, the heat transfer (in kJ) associated with the process (rounded off to 1 decimal place) is ________.

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A piston-cylinder system has an initial volume of 0.1 m

and contains an ideal gas (

) at 1.5 bar and 298 K. The piston is moved to compress the gas until the pressure and temperature reach 10 bar and 423 K respectively. During this process, 20 kJ of work is done on the gas. The magnitude of heat transfer (kJ) during this process is

Your answerChoose one option.

134.8

36.2

8.2

3.8

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A rigid, adiabatic container has two parts (A) and (B) separated by a piston. Initially, part (A) is filled with 1 kg of an ideal gas (

J/kg.K,

J/kg.K) at 1 bar, 600 K. The part (B) is filled with 1 kg of the same ideal gas at 2 bar, 400 K. The piston is now removed. In the final state, the pressure (bar, rounded off to two decimal places) will be _____________.

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The statement which is NOT a consequence of the first law of thermodynamics is (A) Heat is a path function (B) Energy is a property of a system (C) Energy of an isolated system is not conserved (D) A perpetual motion machine of the first kind is not possible

Your answerChoose one option.

Heat is a path function

Energy is a property of a system

Energy of an isolated system is not conserved

A perpetual motion machine of the first kind is not possible

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GATE XE topic:first-law-thermodynamics PYQs

Question 3

Question 14

Question 16

Question 17

Question 19

Question 17

Question 18

Question 12

Question 21

Question 3