1. Babaria Institute of
Technology
Mchanical-1-A

2. Concept
• Introduction of 1st law of thermodynamics.
• Limitation of 1st law of thermodynamics.
• Introduction to 2nd law of thermodynamics.
• Kelvin-plank statement
• Clausius statement
• Equivalence of Kelvin-plank and Clausius statement
• PPM 2
• Carnot cycle and Carnot heat engine
• conclusion

3. • The 1st law of thermodynamics states that a
certain energy flow takes place when a system
under goes a process or change of state.
• δW=δQ
• But , it does not give any information on whether
that process or change of state is possible or not.

4. • Work is completely converted in to heat or heat is
completely converted into work.
(δW = δQ and δQ=δW)
• Potential energy can be transformed into kinetic
energy or kinetic energy can be transformed into
Potential energy.
(PE→KE and KE→PE)
• Heat flows from hot to cold or from cold to hot.
(Th → Tl and Tl → Th)
• Gas expands from high pressure to low pressure or
from low pressure to high pressure .

5. • Heat is not completely converted into work.(Q ˃ W)
• kinetic energy can not be transformed into
Potential energy.(KE ≠> PE)
• Heat flow from cold to hot is not possible.(Tl ≠> Th)
• Gas expands from low pressure to high pressure is
not possible.

6. • 1st law does not help to predict whether the
certain process is possible or not.
• A process can be proceed in particular direction
only , but 1st law does not gives information
about direction.
• 1st law not provides sufficient condition for
certain process to take place.

7. Heat can not flow itself from cold body to hot body.
• The 2nd law of thermodynamics is also used to
determine the theoretical limits for the
performance of mostly used in engineering
systems like heat engines and refrigerators.

8. • It is system that supply or absorb finite amount
of heat without any change in its temperature.

9. • Heat engine is a system that converts heat into work or
mechanical energy .
• It absorb heat at higher temp body and rejects at
lower tem body.
• It is work producing device.
Ex – power plant (it operates on a
complete cycle)

10. Process -
1. they receive heat from a high-temperature source.
2. they convert part of this heat to work.
3. they reject the remaining waste heat
to a low temperature sink atmosphere.
4. they operate on a cycle.

11. • For a heat engine the efficiency is the ratio of
net work done and the heat supplied.
th
net out
in
in out
in
out
in
W
Q
Q Q
Q
Q
Q



 
,
1
where,
W W W
Q Q
net out out in
in net
,  


12. • A device that transfers heat from a low
temperature medium to a high
temperature is the heat pump.
• Refrigerator operates exactly like heat
pump , but difference is that heat pump
maintain heated space at high
temperature reservoir and refrigerator
maintain heated space at low
temperature reservoir.
• They are work consuming device

15.  It is impossible to construct a heat engine that
operates on cycle to receive heat from single
reservoir and produce equivalent amount of
work.
 It implies that it is impossible to build a heat
engine that has 100% thermal efficiency .

16.  It is impossible to construct a device as heat
pump that operates in a cycle and produces no
effect other then the transfer of heat from a
lower temp body to higher temp body.
 Heat can not itself flow from colder body to
hater body.

17.  It can be shown that the violation of one
statement leads to a violation of the other
statement, i.e. they are equivalent.
1. Violation of Kelvin-plank statement leading
to violation of Clausius statement .
2. Violation of Clausius statement leading to violation
of Kelvin-plank statement .

20. • It is against the Kevin-Planck statement: it is
impossible to build an 100% heat engine.
Violate the Second Law of Thermodynamics

21. Any questions ?