Applications of Power and Refrigeration Cycles: Thermodynamics for Engineers

Question 1

Which component is NOT typically found in a refrigeration cycle?

Accepted Answer

Turbine

Answer

Compressor

Answer

Evaporator

Answer

Condenser

Question 2

The efficiency of a power cycle is commonly measured using which metric?

Accepted Answer

Thermal efficiency

Answer

Carnot efficiency

Answer

Refrigeration efficiency

Answer

Mechanical efficiency

Question 3

In a Carnot cycle, the isothermal processes are characterized as:

Accepted Answer

Isothermal and isentropic

Answer

Adiabatic and isentropic

Answer

Isochoric and isobaric

Answer

Isochoric and adiabatic

Question 4

Which refrigerant among the following has a significant ozone depletion potential (ODP)?

Accepted Answer

R-22

Answer

R-134a

Answer

R-407C

Answer

R-600a

Question 5

The expansion valve in a refrigeration cycle serves the primary purpose of:

Accepted Answer

Reducing the refrigerant pressure

Answer

Raising the refrigerant temperature

Answer

Changing the refrigerant from liquid to gas

Answer

Removing impurities from the refrigerant

Question 6

A notable characteristic of a turbojet engine is its:

Accepted Answer

High thrust-to-weight ratio

Answer

Low fuel consumption

Answer

Ability to generate electricity

Answer

Suitability for long-distance flights

Question 7

The Rankine cycle is commonly applied in:

Accepted Answer

Power plants

Answer

Refrigeration systems

Answer

Air conditioning systems

Question 8

The ideal gas law can be used to determine:

Accepted Answer

The pressure, volume, and temperature of a gas

Answer

The specific heat capacity of a gas

Question 9

The exergy of a system represents its:

Accepted Answer

Available energy

Answer

Potential energy

Question 10

Which of the following factors does NOT affect the efficiency of a Carnot cycle?

Accepted Answer

Type of working fluid used

Answer

Temperature of heat source

Answer

Temperature of heat sink

Answer

Pressure ratio of the cycle

Question 11

The specific heat ratio for an ideal gas is:

Accepted Answer

The ratio of the specific heat at constant pressure to the specific heat at constant volume

Answer

The ratio of the specific heat at constant volume to the specific heat at constant pressure

Answer

The ratio of the heat capacity at constant pressure to the heat capacity at constant volume

Answer

The ratio of the heat capacity at constant volume to the heat capacity at constant pressure

Question 12

Identify the component NOT present in a power cycle:

Accepted Answer

Evaporator

Answer

Boiler

Answer

Condenser

Answer

Turbine

Question 13

For a gas turbine engine, which cycle is employed?

Accepted Answer

Brayton cycle

Answer

Rankine cycle

Answer

Carnot cycle

Answer

Otto cycle

Question 14

The efficiency of a refrigeration cycle is quantified using:

Accepted Answer

Coefficient of performance

Answer

Specific cooling capacity

Answer

Refrigerating effect

Answer

Thermal conductivity

Question 15

Which industry commonly utilizes vapor compression refrigeration cycles?

Accepted Answer

Food processing

Answer

Chemical manufacturing

Answer

Automotive

Answer

Aerospace

Question 16

In a Carnot cycle operating between temperatures T1 and T2, the ideal efficiency is given by:

Accepted Answer

1 - (T1/T2)

Answer

(T1 - T2)/T1

Answer

T1/(T1 - T2)

Answer

T2/(T2 - T1)

Question 17

Which refrigerant has a significant ozone depletion potential?

Accepted Answer

R-22

Answer

R-410A

Answer

R-32

Answer

R-134a

Question 18

In a refrigeration cycle, the evaporator serves the purpose of:

Accepted Answer

Absorbing heat from the surroundings

Answer

Releasing heat to the surroundings

Answer

Compressing the refrigerant

Answer

Expanding the refrigerant

Question 19

Which cycle is employed in steam power plants?

Accepted Answer

Rankine cycle

Answer

Brayton cycle

Answer

Otto cycle

Answer

Diesel cycle

Question 20

Define the specific heat ratio of a gas:

Accepted Answer

Ratio of specific heat at constant pressure to specific heat at constant volume

Answer

Ratio of specific heat at constant volume to specific heat at constant pressure

Answer

Sum of specific heats at constant pressure and constant volume

Answer

Difference between specific heats at constant pressure and constant volume

Question 21

In a refrigeration cycle, the Coefficient of Performance (COP) is defined as the ratio of:

Accepted Answer

Cooling effect produced to the work input

Answer

Work input to the cooling effect produced

Answer

Cooling effect produced to the heat rejected

Answer

Heat rejected to the cooling effect produced

Question 22

In a vapor compression refrigeration system, the primary function of the condenser is to:

Accepted Answer

Remove heat from the refrigerant

Answer

Compress the refrigerant

Answer

Expand the refrigerant

Answer

Regenerate the refrigerant

Question 23

In a boiler system, what is the primary purpose of an economizer?

Accepted Answer

Pre-heat the feedwater

Answer

Increase the temperature of the flue gases

Answer

Reduce the pressure of the steam

Answer

Condense the steam

Question 24

In refrigeration systems, the ideal vapor compression cycle is known as:

Accepted Answer

Carnot cycle

Answer

Rankine cycle

Answer

Brayton cycle

Answer

Otto cycle

Question 25

Which of the following is not commonly used as a refrigerant in air conditioning systems?

Accepted Answer

Ammonia

Answer

R-134a

Answer

R-410A

Answer

R-600a

Question 26

In a gas turbine cycle, what is the primary purpose of a regenerative heat exchanger?

Accepted Answer

Enhance cycle efficiency

Answer

Reduce turbine inlet temperature

Answer

Increase compressor work

Answer

Lower exhaust gas temperature

Question 27

Which refrigerant type has the highest ozone depletion potential (ODP)?

Accepted Answer

Chlorofluorocarbons (CFCs)

Answer

Hydrofluorocarbons (HFCs)

Answer

Hydrochlorofluorocarbons (HCFCs)

Answer

Natural refrigerants (e.g., ammonia, CO2)

Question 28

What is exergy, and why is it crucial in assessing the performance of power cycles?

Accepted Answer

Exergy is the maximum work obtainable from a system, considering its state and surroundings.

Answer

Exergy is energy transferable between systems without losses.

Answer

Exergy applies only to closed systems.

Answer

Exergy analysis is irrelevant to power cycles, as it focuses solely on energy efficiency.

Question 29

Describe the key factors that influence the efficiency of a refrigeration cycle and explain how they can be optimized for improved performance.

Accepted Answer

Type of refrigerant and its thermodynamic properties

Accepted Answer

Design and performance of the condenser and evaporator

Accepted Answer

Refrigerant charge volume and its impact on system performance

Accepted Answer

Type of expansion device and its role in refrigerant flow control

Question 30

In a gas turbine power plant, what is the primary purpose of the compressor?

Accepted Answer

Increase the pressure and temperature of the working fluid

Answer

Expand the working fluid

Answer

Reduce the pressure of the working fluid

Question 31

Which of the following is NOT a common refrigerant used in refrigeration systems?

Accepted Answer

Propane

Answer

R-134a

Answer

R-410A

Answer

Ammonia

Question 32

What is the primary function of a condenser in a refrigeration cycle?

Accepted Answer

Reject heat from the system

Answer

Absorb heat from the system

Answer

Expand the refrigerant

Answer

Compress the refrigerant

Question 33

What is an advantage of using a supercritical fluid as a working fluid in a power cycle?

Accepted Answer

Higher thermal efficiency

Answer

Lower operating pressure

Answer

Simplified plant design

Answer

Reduced cooling requirements

Question 34

Which of the following is an application of a power cycle?

Accepted Answer

Driving a car

Answer

Cooling food

Answer

Air conditioning

Answer

Freezing water

Question 35

In a refrigeration cycle, heat is absorbed from where?

Accepted Answer

Refrigerated space

Answer

Condenser

Answer

Compressor

Answer

Expansion valve

Question 36

The most widely used refrigerant in domestic refrigerators is:

Accepted Answer

R134a

Answer

R410a

Answer

R22

Answer

R600a

Question 37

Which type of power cycle is employed in steam turbines?

Accepted Answer

Rankine cycle

Answer

Diesel cycle

Answer

Brayton cycle

Answer

Otto cycle

Question 38

The main function of an evaporator in a refrigeration cycle is to:

Accepted Answer

Absorb heat from the refrigerated space

Answer

Condense the refrigerant

Answer

Compress the refrigerant

Answer

Control the refrigerant flow

Question 39

Which of the following is a benefit of using natural refrigerants in refrigeration cycles?

Accepted Answer

Low global warming potential

Answer

High compressor efficiency

Answer

Improved heat transfer performance

Answer

Reduced system pressure

Question 40

The thermal efficiency of a power cycle is defined as the:

Accepted Answer

Ratio of work output to heat input

Answer

Ratio of heat input to work output

Answer

Ratio of heat rejected to work input

Answer

Ratio of work output to heat rejected

Question 41

In a refrigeration system, the condenser is typically located:

Accepted Answer

Outside the refrigerated space

Answer

Inside the refrigerated space

Answer

Adjacent to the expansion valve

Answer

Between the compressor and evaporator