GATE XE discipline:engineering-sciences PYQs & Answers — Page 30

Questions 291–300 of 1772. Imported answers require independent review unless marked reviewed.

A tank of 4 m

contains an ideal gas mixture of 60% hydrogen and 40% nitrogen by volume at 100 kPa and 300 K. Nitrogen is added to the tank such that the composition changes to 50% nitrogen by volume, with a final temperature of 300 K. The amount of nitrogen (in kmol) to be added is __________ (rounded off to three decimal places).

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

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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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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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For a pure substance that expands on freezing, which of the following statement(s) is/are CORRECT

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

Temperature of the liquid phase can be lower than the temperature at the triple point

Critical pressure is equal to the pressure at the triple point

Highest pressure at which the vapour phase can exist is the pressure at the triple point

Highest temperature at which solid-liquid phase change can happen is the temperature at the triple point

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Consider a gas obeying the relation

, where b and R are constants. Which of the following statement(s) is/are CORRECT about the specific heat capacity at constant pressure?

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

It is independent of temperature

It is a function of pressure

It is a function of temperature

It is independent of both specific volume and pressure

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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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GATE XE discipline:engineering-sciences PYQs

Question 94

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