Mechanical Engineering
GATE ME Thermodynamics PYQs
Build your understanding with focused practice from past exam papers.
Questions 31–40 of 58. Imported answers require independent review unless marked reviewed.
Question 24
Open questionMENAT1 markNeeds review
The compressor of a gas turbine plant, operating on an ideal intercooled Brayton cycle, accomplishes an overall compression ratio of 6 in a two-stage compression process. Intercooling is used to cool the air coming out from the first stage to the inlet temperature of the first stage, before its entry to the second stage. Air enters the compressor at 300 K and 100 kPa. If the properties of gas are constant, the intercooling pressure for minimum compressor work is ____________ kPa (round off to 2 decimal places).
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Open questionMEMCQ2 marksNeeds review
One kg of air in a closed system undergoes an irreversible process from an initial state of
bar (absolute) and
, to a final state of
bar (absolute) and
. If the gas constant of air is 287 J/kg.K and the ratio of the specific heats
, then the change in the specific entropy (in J/kg.K) of the air in the process isYour answerChoose one option.
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Air (ideal gas) enters a perfectly insulated compressor at a temperature of 310 K. The pressure ratio of the compressor is 6. Specific heat at constant pressure for air is 1005 J/kg.K and ratio of specific heats at constant pressure and constant volume is 1.4. Assume that specific heats of air are constant. If the isentropic efficiency of the compressor is 85 percent, the difference in enthalpies of air between the exit and the inlet of the compressor is ______ kJ/kg (round off to nearest integer).
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One kg of air, initially at a temperature of 127°C, expands reversibly at a constant pressure until the volume is doubled. If the gas constant of air is 287 J/kg.K, the magnitude of work transfer is ______ kJ (round off to 2 decimal places).
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Air is contained in a frictionless piston-cylinder arrangement as shown in the figure.
The atmospheric pressure is 100 kPa and the initial pressure of air in the cylinder is 105 kPa. The area of piston is 300 cm². Heat is now added and the piston moves slowly from its initial position until it reaches the stops. The spring constant of the linear spring is 12.5 N/mm. Considering the air inside the cylinder as the system, the work interaction is _____ J (round off to the nearest integer).
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For an ideal Rankine cycle operating between pressures of 30 bar and 0.04 bar, the work output from the turbine is 903 kJ/kg and the work input to the feed pump is 3 kJ/kg. The specific steam consumption is ______ kg/kW.h (round off to 2 decimal places).
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The indicated power developed by an engine with compression ratio of 8, is calculated using an air-standard Otto cycle (constant properties). The rate of heat addition is 10 kW. The ratio of specific heats at constant pressure and constant volume is 1.4. The mechanical efficiency of the engine is 80 percent.
The brake power output of the engine is ______ kW (round off to one decimal place).
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During a non-flow thermodynamic process (1-2) executed by a perfect gas, the heat interaction is equal to the work interaction (
) when the process isYour answerChoose one option.
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Open questionMEMCQ1 markNeeds review
For a simple compressible system,
,
,
and
are specific volume, specific entropy, pressure and temperature, respectively. As per Maxwell’s relations,
is equal toYour answerChoose one option.
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Air of mass 1 kg, initially at 300 K and 10 bar, is allowed to expand isothermally till it reaches a pressure of 1 bar. Assuming air as an ideal gas with gas constant of 0.287 kJ/kg.K, the change in entropy of air (in kJ/kg.K, round off to two decimal places) is ______
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