Mechanical Gate Subject

Aptitude and Reasoning Engineering Mathematics Engineering Mechanics Manufacturing Thermodynamics Industrial Engineering Material Science Vibrations Machine Theory Heat Transfer Strength of Material

Thermodynamics Mechanical previous year questions with answer

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Ques 11 GATE 2025

A thermodynamically closed system contains 1 kg of hydrogen. The system undergoes a reversible polytropic process with polytropic index 1.3. The work output during the process is 400 kJ. During the process, hydrogen behaves as an ideal gas with constant specific heats. The absolute value of heat transfer during the process is ______ kJ (rounded off to 1 decimal place).
Specific heat of hydrogen at constant pressure =14.56 kJ kg^-1K^-1
Specific heat of hydrogen at constant volume =10.4 kJ kg^-1K^-1

Ques 12 GATE 2025

A heat pump, operating in reversed Carnot cycle, maintains a steady air temperature of 300 K inside an auditorium. The heat pump receives heat from the ambient air. The ambient air temperature is 280 K. Heat loss from the auditorium is 15 kW. The power consumption of the heat pump is ______ kW (rounded off to 2 decimal places).

Ques 13 GATE 2024

A furnace can supply heat steadily at 1200 K at a rate of 24000 kJ/min. The maximum amount of power (in kW) that can be produced by using the heat supplied by this furnace in an environment at 300 K is

300

150

18000

Ques 14 GATE 2024

Which one of the following statements regarding a Rankine cycle is FALSE?

Superheating the steam in the boiler increases the cycle efficiency.

The pressure at the turbine outlet depends on the condenser temperature.

Cycle efficiency increases as condenser pressure decreases.

Cycle efficiency increases as boiler pressure decreases.

Ques 15 GATE 2024

Consider an air-standard Brayton cycle with adiabatic compressor and turbine, and a regenerator, as shown in the figure. Air enters the compressor at 100 kPa and 300 K and exits the compressor at 600 kPa and 550 K. The air exits the combustion chamber at 1250 K and exits the adiabatic turbine at 100 kPa and 800 K. The exhaust air from the turbine is used to preheat the air in the regenerator. The exhaust air exits the regenerator (state 6) at 600 K. There is no pressure drop across the regenerator and the combustion chamber. Also, there is no heat loss from the regenerator to the surroundings. The ratio of specific heats at constant pressure and volume is c_p / c_v = 1.4. The thermal efficiency of the cycle is % __________. (answer in integer).

46 is the correct answer.

Ques 16 GATE 2024

A piston-cylinder arrangement shown in the figure has a stop located 2 m above the base. The cylinder initially contains air at 140 kPa and 350 o C and the piston is resting in equilibrium at a position which is 1 m above the stops. The system is now cooled to the ambient temperature of 25 o C. Consider air to be an ideal gas with a value of gas constant R = 0.287 k J / ( k g. K ). The absolute value of specific work done during the process is ______.(rounded off to 1 decimal place)

141.0 is the correct answer.

Ques 17 GATE 2024

A heat pump (H.P.) is driven by the work output of a heat engine (H.E.) as shown in the figure. The heat engine extracts 150 kJ of heat from the source at 1000 Κ. The heat pump absorbs heat from the ambient at 280 K and delivers heat to the room which is maintained at 300 K. Considering the combined system to be ideal, the total amount of heat delivered to the room together by the heat engine and heat pump is __________ kJ (answer in integer).

171 is the correct answer.

Ques 18 GATE 2023

Consider a mixture of two ideal gases, X and Y, with molar masses M'_X = 10 kg/kmol and M'_Y = 20 kg/kmol, respectively, in a container. The total pressure in the container is 100 kPa, the total volume of the container is 10 m3 and the temperature of the contents of the container is 300 K. If the mass of gas-X in the container is 2 kg, then the mass of gas-Y in the container is ____ kg.
(Rounded off to one decimal place)
Assume that the universal gas constant is 8314 J kmol^-1K^-1.

1.6 is the correct answer.

Ques 19 GATE 2023

A heat engine extracts heat (QH) from a thermal reservoir at a temperature of 1000 K and rejects heat (QL) to a thermal reservoir at a temperature of 100 K, while producing work (W). Which one of the combinations of [QH QI and W] given is allowed?

QH=2000 J QL=500 J W=1000 J

QH=2000 J QL=750 J W=1250 J

QH=6000 J QL=500 J, W=5500J

QH=6000 J QL=600 J, W=5500J

Ques 20 GATE 2023

Which one of the following statements is FALSE?

For an ideal gas, the enthalpy is independent of pressure.

For a real gas going through an adiabatic reversible process, the process equation is given by PVγ= constant, where P is the pressure, V is the volume and y is the ratio of the specific heats of the gas at constant pressure and constant volume.

For an ideal gas undergoing a reversible polytropic process PV^1.5 = constant, the equation connecting the pressure, volume and temperature of the gas at any point along the process is P/R = mT/V, where R is the gas constant and m is the mass of the gas.

Any real gas behaves as an ideal gas at sufficiently low pressure or sufficiently high temperature.