Thermodynamics Mechanical previous year questions with answer
Ques 31 Gate 2020 Set-2
If a reversed Carnot cycle operates between the temperature limits of 27°C and –3°C, then the ratio of the COP of a refrigerator to that of a heat pump (COP of refrigerator/ COP of heat pump) based on the cycle is __________ (round off to 2 decimal places).
0.89-0.91 is the correct answer.
Ques 32 Gate 2019 Set-1
During a non-flow thermodynamic process (1-2) executed by a perfect gas, the heat interaction is equal to the work interaction (Q1-2 = W1-2) when the process is
Ques 33 GATE 2017 SET-2
A mass m of a perfect gas at pressure p1 and volume V1 undergoes an isothermal process. The final pressure is p2 and volume is V2. The work done on the system is considered positive. If R is the gas constant and T is the temperature, then the work done in the process is
Ques 34 GATE 2017 SET-2
If a mass of moist air contained in a closed metallic vessel is heated, then its
Ques 35 GATE 2017 SET-2
In the Rankine cycle for a steam power plant the turbine entry and exit enthalpies are 2803 kJ/kg and 1800 kJ/kg, respectively. The enthalpies of water at pump entry and exit are 121 kJ/kg and 124 kJ/kg, respectively. The specific steam consumption (in kg/kW.h) of the cycle is ________.
3.6 is the correct answer.
Ques 36 GATE 2017 SET-2
A calorically perfect gas (specific heat at constant pressure 1000 J/kg.K) enters and leaves a gas turbine with the same velocity. The temperatures of the gas at turbine entry and exit are 1100 K and 400 K, respectively. The power produced is 4.6 MW and heat escapes at the rate of 300 kJ/s through the turbine casing. The mass flow rate of the gas (in kg/s) through the turbine is
Ques 37 GATE 2017 SET-2
One kg of an ideal gas (gas constant R = 287 J/kg.K) undergoes an irreversible process from state-1 (1 bar, 300 K) to state-2 (2 bar, 300 K). The change in specific entropy (s2 - s1) of the gas (in J/kg.K) in the process is ________.
-198.9 is the correct answer.
Ques 38 GATE 2017 SET-2
The volume and temperature of air (assumed to be an ideal gas) in a closed vessel is 2.87 m3 and 300 K, respectively. The gauge pressure indicated by a manometer fitted to the wall of the vessel is 0.5 bar. If the gas constant of air is R = 287 J/kg.K and the atmospheric pressure is 1 bar, the mass of air (in kg) in the vessel is
Ques 39 GATE 2017 SET-1
The molar specific heat at constant volume of an ideal gas is equal to 2.5 times the universal gas constant (8.314 J/mol.K). When the temperature increases by 100 K, the change in molar specific enthalpy is ________ J/mol.
2909.9 is the correct answer.
Ques 40 GATE 2017 SET-1
A heat pump absorbs 10 kW of heat from outside environment at 250 K while absorbing 15 kW of work. It delivers the heat to a room that must be kept warm at 300 K. The Coefficient of Performance (COP) of the heat pump is ________.
1.67 is the correct answer.