GATE XE Thermodynamic Cycles PYQs & Answers — Page 2

Questions 11–20 of 37. Imported answers require independent review unless marked reviewed.

Consider the following data from a Brayton cycle.

Enthalpy at inlet to turbine: 1400 kJ/kg

Enthalpy at exit of turbine: 880 kJ/kg

Enthalpy at exit of compressor: 600 kJ/kg

On adding a regenerator of effectiveness equal to 0.8, the absolute value of percentage change in heat addition is ________ (rounded off to the nearest integer).

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If an ideal air-standard Otto cycle and an ideal air-standard Diesel cycle operate on the same compression ratio, then the relation between the thermal efficiencies (

) of the cycles is

Your answerChoose one option.

and

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An ideal Diesel cycle has a compression ratio of 20 and cut-off ratio of 1.5. At the beginning of the compression stroke, air is at 100 kPa, 300 K. Use the cold-air-standard assumptions with property value

kJ/kg-K. Assume

. For this cycle, the net work output per unit mass is

Your answerChoose one option.

335 kJ/kg

395 kJ/kg

500 kJ/kg

165 kJ/kg

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Consider a spark ignition engine which operates on an ideal air-standard Otto cycle. It uses a fuel which produces 44 MJ/kg of heat in the engine. If the engine requires 40 mg of fuel to produce 1 kJ of work output, then the compression ratio of the Otto cycle is ______ (rounded off to two decimal places).

For the entire cycle, use

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A refrigerator operates on an ideal vapor compression cycle between the pressure limits of 140 kPa and 800 kPa. The working fluid is the refrigerant R-134a. The refrigerant enters the compressor as saturated vapor at 140 kPa and exits at 800 kPa and 60 °C. It leaves the condenser as a saturated liquid at 800 kPa. The coefficient of performance (COP) of the refrigerator is ______ (rounded off to two decimal places).

Use the following property data for R-134a:

At 140 kPa:

kJ/kg,

kJ/kg

At 800 kPa:

kJ/kg,

kJ/kg

At 800 kPa and 60 °C:

kJ/kg

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A steam power plant operates on a simple ideal Rankine cycle. The condenser pressure is 10 kPa and the boiler pressure is 5 MPa. The steam enters the turbine at 600 °C. Mass flow rate of the steam is 50 kg/s. Neglecting the pump work, the net power output of the plant is ______ MW (rounded off to one decimal place).

Use the following property data for water:

At 10 kPa:

kJ/kg,

kJ/kg

kJ/kg-K,

kJ/kg-K

At 5 MPa and 600 °C:

kJ/kg,

kJ/kg-K

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An air standard Diesel cycle consists of four processes: 1-2 (isentropic compression), 2-3 (constant pressure heat addition), 3-4 (isentropic expansion) and 4-1 (constant volume heat rejection).

is the temperature (in K) attained at the end of isentropic expansion (3-4) before constant volume heat rejection. The constant volume heat rejection process (4-1) is replaced by a constant pressure heat rejection process (4a-1) such that

is the temperature (in K) reached at the end of isentropic expansion (3-4a), and the state point 1 remains the same. Then

Your answerChoose one option.

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Gas in a cylinder-piston device expands from state 1

to state 2

. The expansion process is polytropic, i.e.,

. Assuming the ideal gas behaviour, the expression for the work done,

by the system is given by

Your answerChoose one option.

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A steam power plant operates on Rankine cycle. At certain operating condition of the plant, there is a reduction of 20% net work output (kJ/kg) as compared to 100% capacity. This reduction will cause the specific steam consumption (kg/kJ) to increase by ______ % (in integer).

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An ideal Brayton cycle operates between maximum and minimum temperatures of

and

, respectively. For constant values of

and

, the pressure ratio (

) for maximum work output is

(

is the specific heat ratio of air)

Your answerChoose one option.

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GATE XE Thermodynamic Cycles PYQs

Question 103

Question 91

Question 98

Question 104

Question 105

Question 106

Question 89

Question 90

Question 95

Question 102