Thermodynamics Flashcards
What is the origin of the energy conservation equation used in flow systems?
The first law of thermodynamics.
What does the first law of thermodynamics state?
The first law of thermodynamics states that the heat energy entering a closed system can either increase the temperature (increase U) or be used to perform work (increase W) on the surroundings.
What does the second law of thermodynamics state in terms of entropy?
- The entropy of the environment always increases in real processes.
What does the second law of thermodynamics state in terms of working fluid?
A substance can be brought back to its original state without increasing the entropy of the environment only in a reversible system.
What does the second law of thermodynamics state in terms of equipment?
A machine that returns the working fluid to its original state requires a heat sink.
What does the second law of thermodynamics say in terms of heat transfer in cycles?
It is impossible for a system working in a complete cycle to accomplish, as its sole effect, the transfer of heat from a body at a given temperature to a body at a higher temperature.
What is an adiabatic process?
One in which there is no heat flow.
What is an isentropic process?
No heat flow and is reversible.
What does the Carnot cycle depend and not depend on?
It depends on the source and sink temperatures; not the working fluid.
What are heat cycles usually defined by?
Working substance; high and low-temperature reservoirs; the means of working on the system, and removing energy from the system.
What is the thermal efficiency of a power cycle?
Defined as the ratio of useful work output to the supplied input energy.
What does the maximum work obtained from a cycle depend on
Local environment temperature.
What type of process can obtain maximum work output?
Reversible process.
What is process irreversibility?
The difference between the maximum and actual work output.
Which processes in the Carnot cycle are reversible?
All of them.
