GATE XE concept:enthalpy PYQs & Answers

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Questions 1–4 of 4. Imported answers require independent review unless marked reviewed.

Topic practice 4 questionsPage 1 of 1

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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Steam at 2 MPa and 300 °C steadily enters a nozzle of inlet diameter of 20 cm. Steam leaves the nozzle with a velocity of 300 m/s. The mass flow rate of steam through the nozzle is 10 kg/s. Assume no work interaction and no change in potential energy. If the heat loss from the nozzle per kg of steam is 3 kJ, the exit enthalpy per kg of steam is ______ kJ (rounded off to nearest integer).

Use the following data for steam:

At 2 MPa and 300 °C:

/kg,

kJ/kg

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An insulated rigid tank of volume 10 m³ contains air initially at 1 MPa and 600 K. A valve connected to the tank is opened, and air is allowed to escape until the temperature inside the tank drops to 400 K. The temperature of the discharged air can be approximated as the average of the initial and final temperatures of the air in the tank. Neglect kinetic and potential energies of the discharged air. Assume that air behaves as an ideal gas with constant specific heat so that internal energy

and enthalpy

. Then, the final pressure of the air in the tank is ______ MPa (round off to 2 decimal places).

Assume

kJ/(kg K),

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Superheated steam at 2 bar and 300 °C, with an enthalpy of 3072.1 kJ/kg, enters a horizontal adiabatic nozzle with negligible velocity and leaves at 0.2 bar as saturated vapour with an enthalpy of 2609.9 kJ/kg. Assuming steady flow and neglecting the potential energy changes, the exit velocity (in m/s) of the steam (up to 1 decimal place) is __________.

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GATE XE concept:enthalpy PYQs

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