Thermodynamics - 2 - Mechanical Engineering MCQ

A system undergoes a change of state during which 80 kJ of heat is transferred to it and it does 60 kj of work. The system is brought back to its original state through a process during which 100 kj of heat is transferred to it. The work done by the system is

The internal energy of a certain system is a function of temperature alone and is given by the formula E = 25 + 0.25^t kJ
If this system executes a process for which the work done by it per degree temperature increase is

 the heat interaction per degree temperature increase in kJ is

The air with enthalpy of 100 kJ/kg is compressed by an air compressor to a pressure and temperature at which its enthalpy becomes 200 kJ/kg. The loss of heat is 40 kJ/kg from the compressor as the air passes through it. Neglecting the change in kinetic and potential energies, the power required for an air mass flow of 0.5 kg/s is

The cyclic integral of (SQ — 6W) for a process is

Suppose 0.70 kg/s of air enters the compressor with a specific enthalpy of 290 kJ/kg and leaves it with specific enthalpy 450 kJ/kg. Velocities at inlet and exit are 6 m/s and 2 m/s, respectively. Assuming adiabatic process, what is power input to the compressor?

In a throttling process, which one of the following parameters remain constant?

A refrigerating machine working on reversed Carnot cycle takes out 2 kW per minute of heat from the system while between temperature limits of 300 K and 200 K. COP and power consumption of the cycle will be respectively

A reversible engine operates between temperatures T₁ and T₂. The energy rejected by this engine is received by a second reversible engine at temperature T₂ and rejected to a reservoir at temperature T₃. If the efficiencies of the engines are the same then the relationship between T₁, T₂ and T₃ is given by

A Carnot engine operates between 327° C and 27° C. If the engine produces 300 kJ of work, what is the entiopy change during head addition?

The relation

ds = dQ/T

where s represents entropy, Q represents heat and T represents temperature (absolute), holds good in which one of the following processes?

An inventor says that his new concept of an engine, while working between temperature limits of 27° C and 327° C rejects 45% of heat absorbed from the source. His engine is then equivalent to which one of the following engines?

Three engines A, B and C operating on Carnot cycle use working substances as argon, oxygen and air, respectively. Which will have higher efficiency?

A series of combination of two Carnot engines operate between the temperatures of 180° C and 20°C. If the engine produces equal amount of work, then what is the intermediate temperature?

An engine working on Carnot cycle rejects 40% of absorbed heat from the source, while the sink temperature is maintained at 27°C, then what is the source temperature?

A reversible heat engine rejects 50% of the heat supplied during a cycle of operation. If this engine is reversed and operates as a heat pump, then what is its coefficient of performance?

When the lower temperature is fixed, COP of a refrigerating machine can be improved by

The heat absorbed or rejected during a polytropic process is equal to