GATE XE format:nat PYQs & Answers — Page 11

Questions 101–110 of 668. Imported answers require independent review unless marked reviewed.

Topic practice 668 questionsPage 11 of 67

A heat engine having thermal efficiency of 40% receives heat from a source at 600 K and rejects heat to a sink at 300 K. The second-law efficiency (in %) of this engine is __________ (answer in integer).

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A rigid tank of 300 litre capacity contains 3 kg of oxygen (molar mass = 32 kg/kmol) at 25 °C. If oxygen behaves as an ideal gas, the pressure (in kPa) inside the tank is __________ (rounded off to two decimal places).

Use: Universal gas constant (Rᵤ) = 8.314 kJ/kmol-K

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A piston-cylinder arrangement contains an ideal gas mixture of 4 kg of hydrogen and 13 kg of nitrogen at 250 K and atmospheric pressure. On heat addition, the mixture expands at constant pressure until the temperature rises to 350 K. The average isobaric specific heats (

) for hydrogen and nitrogen are 14.239 kJ/kg-K and 1.040 kJ/kg-K, respectively. The amount of heat (in MJ) added to the cylinder is __________________ (rounded off to three decimal places).

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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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Air at 101 kPa, 15 °C and 50% relative humidity is first heated to 20 °C in a heating coil, and then humidified by spraying water on it. In the final state, the air has temperature of 25 °C and relative humidity of 85%. The amount of water sprayed (in gm per kg of dry air is _________________ (rounded off to two decimal places).

Use the following data:

The saturation pressure of water at 15 °C = 1.7057 kPa

The saturation pressure of water at 25 °C = 3.1698 kPa

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A stream of superheated steam (2 MPa, 300 °C) mixes with another stream of superheated steam (2 MPa, 400 °C) through a steady-state adiabatic process. The flow rates of the streams are 3 kg/min and 2 kg/min, respectively. This mixture then expands in an adiabatic nozzle to a saturated mixture with a quality of 0.77 and 1 kPa. Neglect the velocity at the nozzle entrance and the change in potential energies. The velocity at the nozzle exit (in m/s) is __________ (rounded off to two decimal places).

Use the following data:

At 2 MPa, 300 °C: Specific enthalpy of superheated steam = 3024.2 kJ/kg

At 2 MPa, 400 °C: Specific enthalpy of superheated steam = 3248.4 kJ/kg

At 1 kPa: Specific enthalpy of saturated water = 29.3 kJ/kg

At 1 kPa: Specific enthalpy of saturated vapour = 2513.7 kJ/kg

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A piston-cylinder assembly having 250 mm diameter contains 0.01 kg of water vapor at 1 MPa and 200 °C. The specific volume of the vapor is 0.20602 m

/kg. The system expands as per the relation

= constant, where p is pressure and V is volume. If the final pressure is 0.35 MPa, the value of the exponent (n) is __________ (rounded off to two decimal places).

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Air enters a air dryer at 22 °C and 100 kPa with a velocity of 3.7 m/s, and leaves the dryer at 83 °C and 100 kPa with a velocity of 9.1 m/s. The exit area of the dryer is 18.7 cm

, and the ambient temperature is 22 °C. The air is an ideal gas with gas constant

= 0.287 kJ/kg-K and isobaric specific heat

= 1.005 kJ/kg-K. If the change in potential energy is neglected, the second law efficiency (in %) of the dryer is __________ (rounded off to one decimal place).

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A steam boiler contains saturated water vapour at 200 °C. After a certain period, the temperature of the boiler drops to 110 °C. Assume that all the valves of the boiler are closed and the energy is lost as heat to the surroundings. The ratio of mass of liquid to the mass of vapour is ____________ (rounded off to two decimal places).

Saturated volume of vapor phase at 200 °C = 0.127 m

/kg

Saturated volume of vapor phase at 110 °C = 1.210 m

/kg

Saturated volume of liquid phase at 110 °C = 0.001 m

/kg

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Two Carnot heat engines (E1 and E2) are operating in series as shown in figure. Engine E1 receives heat from a reservoir at

K and does work

. Engine E2 receives heat from an intermediate reservoir at

, does work

and rejects the rest to a reservoir at

K. Both the engines have identical thermal efficiencies.

Diagram for Engineering Sciences question 107

The temperature T (in K) of the intermediate reservoir is __________ (answer in integer).

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GATE XE format:nat PYQs

Question 95

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Question 100

Question 101

Question 102

Question 103

Question 104

Question 105

Question 106

Question 107