GATE XE concept:specific-heats PYQs & Answers

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concept:specific-heats

Attempt a question, record the concept and assumptions, then check the available answer. Rework mistakes after revising the relevant concepts. Topic tags can overlap; review the question context.

Questions 1–10 of 14. Imported answers require independent review unless marked reviewed.

Topic practice 14 questionsPage 1 of 2

In a mixing chamber hot water enters at a temperature of 80 °C with a flow rate of 0.5 kg/s. From another entry, cold water enters the chamber at 20 °C. The desired temperature after mixing at the exit of the chamber is 40 °C. There is no water leakage and the mixing happens at adiabatic conditions. Assume the specific heat capacity of water is 4.2 kJ/kg-K. For a steady state operation, the mass flow rate (in kg/s) of the cold-water stream is

Your answerChoose one option.

2.0

1.5

1.0

0.5

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An adiabatic rigid and impermeable tank of volume

contains air at 800 kPa and 70 °C. The air is allowed to leave the tank until the pressure is one-fourth of its original value. During the process, the air in the tank is maintained at 70 °C using an electrical heater. Assume that the air behaves as an ideal gas having gas constant and ratio of specific heat capacities as 287 J/kg-K and 1.4, respectively. The total electrical energy (in MJ) supplied by the heater is ____________ (rounded off to two decimal places).

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Two kg of a gas is compressed in a process. Pressure (P) and mass specific volume (v) of the gas during the process follows:

. The temperature of the gas before and after compression is 300 K and 600 K, respectively. Assume that the gas behaves as an ideal gas with gas constant and ratio of specific heat capacities equal to 287 J/kg-K and 1.4, respectively. The heat rejected (in kJ) during the process is ____________ (rounded off to two decimal places).

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A rigid insulated tank containing an ideal gas at 300 K and 1 bar is being filled from an external pressurized line supplying the same gas at 300 K and 10 bar. When the mass of gas inside the tank has doubled, its temperature (in K) is ________ (rounded off to the nearest integer).

Assume ratio of specific heats to be constant for this process and equal to 1.4.

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Air in a closed system undergoes a thermodynamic process from an initial temperature of 300 K to the final temperature of 400 K. The specific heat of air at constant volume,

varies linearly with the temperature,

(in K) as

Change in the specific internal energy of the air in the system is ______ kJ/kg (round off to 2 decimal places).

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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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Two air streams of mass flow rates

and

enter a mixing chamber and exit after perfect mixing. The corresponding temperatures of the inlet streams are

and

, respectively. Heat loss rate from the mixing chamber to the surrounding is

. Assume that the process is steady, specific heat capacity is constant, and air behaves as an ideal gas. Identify the correct expression for the final exit temperature

after mixing. The mass specific heat capacities of the gas at constant volume and constant pressure are

and

, respectively. Neglect the bulk kinetic and potential energies of the streams.

Your answerChoose one option.

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Air having a mass flow rate of 2 kg/s enters a diffuser at 100 kPa and 30°C, with a velocity of 200 m/s. Exit area of the diffuser is 400 cm² while the exit temperature of the air is 45°C. The rate of heat loss from the diffuser to the surrounding is 8 kJ/s. The pressure at the diffuser exit is __________ kPa (2 decimal places).

For air, the characteristic gas constant is 287 J/(kgK) and specific heat capacity at constant pressure is 1005 J/(kgK). Assume air to be an ideal gas and the flow in the diffuser is steady.

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A mixture of air and water vapour enters a steady-flow adiabatic saturator at 50°C and 100 kPa. It leaves the saturator in a completely saturated state at temperature of 25°C and pressure of 100 kPa. Liquid water enters the saturator at 25°C. If air is considered to be an ideal gas, with constant specific heat capacity, the relative humidity of the air entering the saturator is __________ % (1 decimal place).

Use the following data:

at 25°C

kJ/kg,

kPa

at 50°C

kJ/kg,

kPa

Specific heat capacity of air at constant pressure

kJ/(kgK)

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Air at a pressure of 1 MPa and 300 K is flowing in a pipe. An insulated evacuated rigid tank is connected to this pipe through an insulated valve. The volume of the tank is 1 m³. The valve is opened and the tank is filled with air until the pressure in the tank is 1 MPa. Subsequently, the valve is closed. Consider air to be an ideal gas and neglect bulk kinetic and potential energy. The final temperature of air in the tank is __________ K (1 decimal place).

Specific heat capacity of air at constant pressure

kJ/(kgK) and characteristic gas constant for air = 0.287 kJ/(kgK)

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GATE XE concept:specific-heats PYQs

How to practice concept:specific-heats

Question 90

Question 101

Question 102

Question 108

Question 93

Question 103

Question 3

Question 14

Question 16

Question 17