GATE XE Thermodynamic Cycles PYQs & Answers

Questions 1–10 of 37. Imported answers require independent review unless marked reviewed.

Consider an ideal Otto-cycle with cold-air-standard assumptions to be applicable. The temperature of the working fluid at the start and the end of the compression process is 300 K and 750 K, respectively. For the working fluid take the ratio of the specific heat capacities as 1.4. The thermal efficiency (in %) of the cycle is __________________ (rounded off to two decimal places).

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Consider an ideal Rankine cycle with fixed conditions at the turbine inlet. If the condenser pressure is lowered, which of the following statements is/are CORRECT?

Your answerSelect all correct options. You can choose more than one.

Pump work input remains the same.

Moisture content at turbine exit decreases.

Heat rejected in the condenser decreases.

Turbine work output increases.

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Consider an ideal Diesel-cycle with cold-air-standard assumptions to be applicable. The compression ratio is 20 and the cut-off ratio is 1.8. At the end of the compression process, the working fluid is at 1120 K and 6.6 MPa. The ratio of the specific heat capacities is 1.4 for the working fluid. The temperature (in K) at the end of the expansion process is ____________ (rounded off to two decimal places).

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A mixture of helium (He) and nitrogen (N₂) expands in a turbine from 800 kPa to 100 kPa. The mixture composition is 40% He and 60% N₂ by mass. The turbine inlet temperature is 1000 K. The temperature (in K) at the turbine exit is ____________ (rounded off to two decimal places).

Assume:

The process is isentropic. Kinetic and potential energy changes in the process are negligible. He and N₂ behaves as ideal gases. Specific heat capacities are constant.

Use the following data:

Ratio of specific heat capacities for He and N₂ are 1.67 and 1.4, respectively.

Specific heat capacities at constant pressure for He and N₂ are 5.19 kJ/kg-K and 1.04 kJ/kg-K, respectively.

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refers to the ratio of specific heats, the air-standard efficiency of an Otto cycle is

Your answerChoose one option.

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For an ideal gas turbine cycle,

and

are the compressor inlet temperature and turbine inlet temperature respectively. The ratio

is denoted by

and the ratio of specific heats is denoted by

. For any given

, the optimum pressure ratio for the maximum specific work output is

Your answerChoose one option.

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Air in an ideal Diesel cycle is compressed from 3 litre to 0.15 litre. It then expands during a constant pressure heat addition process to 0.3 litre. If the ratio of specific heats,

, the thermal efficiency (in %) of the cycle is ____________ (rounded to one decimal place).

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A power plant operates on a simple ideal Rankine cycle. If superheating is added to this cycle, then which one of the following options is CORRECT?

Your answerChoose one option.

Pump work increases, turbine work output increases, cycle efficiency increases, and moisture content at turbine exit increases

Pump work remains same, turbine work output increases, cycle efficiency increases, and moisture content at turbine exit increases

Pump work remains same, turbine work output increases, cycle efficiency increases, and moisture content at turbine exit decreases

Pump work decreases, turbine work output increases, cycle efficiency increases, and moisture content at turbine exit decreases

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Following data is for an actual vapour compression refrigeration cycle.

Enthalpy at compressor inlet: 246 kJ/kg

Enthalpy at compressor exit: 286 kJ/kg

Heat load on the evaporator: 158 kJ/kg

The enthalpy at the exit of the condenser in kJ/kg is ________ (rounded off to the nearest integer).

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A fixed mass of an ideal gas undergoes two different cycles M and N as shown in the Pressure (

) – Volume (

) diagrams. Based on the information provided, which one of the following statements is always TRUE?

Diagram for Engineering Sciences question 97

Your answerChoose one option.

Heat input in Cycle M is equal to heat input in Cycle N

Heat rejected in Cycle M is equal to heat rejected in Cycle N

Net heat transfer in Cycle M is equal to net heat transfer in Cycle N

Thermal efficiency of Cycle M is equal to thermal efficiency of Cycle N

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GATE XE Thermodynamic Cycles PYQs

How to practice Thermodynamic Cycles

Question 96

Question 100

Question 107

Question 108

Question 92

Question 97

Question 101

Question 92

Question 95

Question 97