GATE XE format:nat PYQs & Answers — Page 23

Questions 221–230 of 668. Imported answers require independent review unless marked reviewed.

Topic practice 668 questionsPage 23 of 67

Air at 400 K and 200 kPa is heated at constant pressure to 600 K. Assuming that the internal energy is a function of temperature only, the magnitude of change in internal energy during this process is __________ kJ/kmol (rounded off to one decimal place). Use the following data: Molar specific heat of air at constant volume

(kJ/kmol-K)

where T is temperature in K,

kJ/kmol-K,

kJ/kmol-K

and

kJ/kmol-K

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A piston-cylinder device initially contains 1 m

of air at 200 kPa and 25 °C. Air expands at constant pressure while a heater of 250 W is switched on for 10 minutes. There is a heat loss of 4 kJ during this process. Assuming air as an ideal gas, the final temperature of air is ______ °C (rounded off to one decimal place).

Use the following data for air:

kJ/kg-K,

kJ/kg-K

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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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A rigid tank of 2 m

internal volume contains 5 kg of water as a saturated liquid-vapor mixture at 400 kPa. Half of the mass of the saturated liquid in the tank is drained-off while maintaining constant pressure of 400 kPa in the tank. The final quality of the mixture remaining in the tank is ______ (rounded off to two decimal places).

Use the following data for water:

At 400 kPa:

/kg,

/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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In an air-conditioning system, air enters at 20 °C and 30% relative humidity at a steady rate of 30 m

/min in a humidifier and it is conditioned to 25 °C and 60% relative humidity. Assuming entire process takes place at pressure of 100 kPa, the mass flow rate of the steam added to air in the humidifier is ______ kg/min (rounded off to three decimal places).

Use the following property data:

At 20 °C and 25 °C, saturation pressures of water are 2.3392 kPa and 3.1698 kPa, respectively.

For air,

kJ/kg-K

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An office uses a heat pump to receive 500 kJ/day heat in winter to maintain its temperature at 300 K. The ambient temperature is 280 K. If the COP of the heat pump is 60% of its theoretical maximum value, the ratio of actual work input to the minimum theoretical work input to the heat pump is ______ (rounded off to one decimal place).

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In a liquid-vapor phase change process,

at 100 °C for saturated water is 370 Pa/K. If the resulting change in specific volume

is 1.672 m

/kg, the enthalpy of vaporization (

) will be ______ kJ/kg (in integer).

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GATE XE format:nat PYQs

Question 96

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Question 109