12:30 AM
M V Rao
SECOND LAW
1. Define Clausius statement.
It is impossible for a self-acting machine working in a cyclic process, to transfer
heat from a body at lower temperature to a body at a higher temperature without
the aid of an external agency.
2. What is Perpetual motion machine of the second kind?
A heat engine, which converts whole of the heat energy into mechanical work is
known as Perpetual motion machine of the second kind.
3. Define Kelvin Planck Statement.
It is impossible to construct a heat engine to produce network in a complete cycle
if it exchanges heat from a single reservoir at single fixed temperature.
4. Define Heat pump.
A heat pump is a device, which is working in a cycle and transfers heat from
lower temperature to higher temperature.
5. Define Heat engine.
Heat engine is a machine, which is used to convert the heat energy into
mechanical work in a cyclic process.
6. What are the assumptions made on heat engine?
1. The source and sink are maintained at constant temperature.
2. The source and sink has infinite heat capacity.
7. State Carnot theorem.
It states that no heat engine operating in a cycle between two constant temperature heat reservoir can be more efficient than a reversible engine operating between the same reservoir.
8. What is meant by reversible process?
A reversible process is one, which is performed in such a way that at the conclusion of process, both system and surroundings may be restored to their initial state, without producing any changes in rest of the universe.
9. What is meant by irreversible process?
The mixing of two substances and combustion also leads to irreversibility. All spontaneous process is irreversible.
10. Explain entropy?
It is an important thermodynamic property of the substance. It is the measure of molecular disorder. It is denoted by S. The measurement of change in entropy for reversible process is obtained by the quantity of heat received or rejected to absolute temperature.
11. What is absolute entropy?
The entropy measured for all perfect crystalline solids at absolute zero temperature is known as absolute entropy.
12. Define availability.
The maximum useful work obtained during a process in which the final condition of the system is the same as that of the surrounding is called availability of the system.
13. Define available energy and unavailable energy.
Available energy is the maximum thermal useful work under ideal condition. The remaining part, which cannot be converted into work, is known as unavailable energy.
14. Explain the term source and sink.
Source is a thermal reservoir, which supplies heat to the system and sink is a thermal reservoir, which takes the heat from the system.
15. What do you understand by the entropy principle?
The entropy of an isolated system can never decrease. It always increases and remains constant only when the process is reversible. This is known as principle of increase in entropy or entropy principle.
16. What are the important characteristics of entropy?
1. If the heat is supplied to the system then the entropy will increase.
2. If the heat is rejected to the system then the entropy will decrease.
3. The entropy is constant for all adiabatic frictionless process.
4. The entropy increases if temperature of heat is lowered without work being done as in throttling process.
5. If the entropy is maximum, then there is a minimum availability for conversion in to work.
6. If the entropy is minimum then there is a maximum availability for conversion into work.
17. What is reversed Carnot heat engine? What are the limitations of carnot cycle?
1. No friction is considered for moving parts of the engine.
2. There should not be any heat loss.
18. Why Rankine cycle is modified?
The work obtained at the end of the expansion is very less. The work is too inadequate to overcome the friction. Therefore the adiabatic expansion is terminated at the point before the end of the expansion in the turbine and pressure decreases suddenly, while the volume remains constant.
19. Name the various vapour power cycle.
Carnot cycle and Rankine cycle.
20. Define efficiency ration.
The ratio of actual cycle efficiency to that of the ideal cycle efficiency is termed as efficiency ratio.
21. Define overall efficiency.
It is the ratio of the mechanical work to the energy supplied in the fuel. It is also defined as the product of combustion efficiency and the cycle efficiency.
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2 comments:
nice
http://studythermodynamics.blogspot.in/
That was really helpful. Thnx
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