Objective 01: Heat Engines Flashcards
What is one of the most important applications of thermodynamics?
Heat Engines
What does a Heat Engine do?
Converts Heat energy to Mechanical energy
What are the 3 main elements of a Heat Engine?
- Source of high temperature heat input
- Cyclic process that acts on a working fluid
- Low temperature heat sink
How do Heat Engines usually obtain a source of high temperature heat input?
Combustion of a fuel
What do Heat Engines use Working Fluids for?
To produce work
Why do Heat Engines require a low temperature heat sink?
To reject heat to
Can a Heat Engine operate in reverse?
Yes
What are 3 examples of a Heat Engine working in reverse?
- Refrigeration Device
- Air Conditioner
- Heat Pump
How do Heat Engines convert energy from heat to mechanical work?
The alternate supply and rejection of heat to and from the working fluid in the engine cylinder
How do Heat Engines maintain work output?
Repeatedly supplying and rejecting heat to and from the working fluid
Is there a relationship between the quantities of heat involved and the amount of work produced?
Yes
To engage in the cyclical process, what must Working Fluids be capable of at the end of each cycle?
Returning to their original state
What is the work performed by Heat Engines equivalent to?
The difference between the heat supplied and the heat rejected
What are the 5 types of Heat Engines according to the Thermodynamic Cycle they use?
- Carnot Cycle
- Rankine Cycle
- Otto Cycle
- Diesel Cycle
- Brayton Cycle
Carnot Cycle
Theoretical thermodynamic cycle with the highest possible efficiency
What is the Rankine Cycle applicable to?
Steam Plants
What is the Otto Cycle applicable to?
Spark Ignition Engines
What is the Diesel Cycle applicable to?
Compression Ignition (Diesel) Engines
What is the Brayton Cycle applicable to?
Gas Turbines
What are the 2 types of Heat Engines according to the nature of the Working Fluid?
- Gas Cycle
2. Vapour Cycle
What is the main Working Fluid used by the Gas Cycle?
Air
How does the Gas Cycle work?
- Fuel is combusted with atmospheric air
- Heat of combustion heats and expands the air
- The available energy in the air is used to perform work
- The air and combustion products are released to atmosphere
Which Thermodynamic Cycles are Gas Cycles?
- Otto
- Diesel
- Brayton
What is special about the Brayton Cycle as a Gas Cycle?
It is the only gas cycle that is not restricted to using only air as the Working Fluid
What is the Working Fluid used by the Vapour Cycle?
Condensable Vapour which is in the liquid phase during part of the cycle
What is the most common Working Fluid used by the Vapour Cycle?
Steam
Which Thermodynamic Cycle is a Vapour Cycle?
Rankine Cycle
Is a refrigeration cycle considered to be a Vapour Cycle?
Yes