This document provides an overview of thermodynamics and the first law. It discusses key concepts like state, path, cycle, boundary work, heat transfer, internal energy, and enthalpy. Several thermodynamic processes are defined including isothermal, isobaric, isochoric, and adiabatic. Joule's experiment is described which proved that energy is a property of the system. The first law of thermodynamics is introduced as the quantitative expression of the law of conservation of energy as it applies to thermodynamic processes.

1. THERMODYNAMICS
Feel the heat ….
Unit – 1 Basic concept and first law
ASHISH MISHRA
ASSISTANT PROFESSOR,
DEPARTMENT OF MECHANICAL ENGG
MUIT, LUCKNOW

2. Objective
discuss energyconservationprinciple andmodeof energy transfer
describe theboundaryworkfor variousthermodynamic processes
define the first law of thermodynamics (cyclic process and process,
enthalpy mechanical equivalent of heat (Joules constant), PMM-I,
specific heat, internalenergyand enthalpy.
explain abouttheJoules experimentandinternalenergy.
prove thatenergy is propertyof system.
create thedifference betweentwospecificheat
determine theinternalenergyandenthalpyfor solid, liquid and gas.

3. 3
THERMODYNAMICS
THERMODYNAMICS
ENGINEERING-BRANCH OF SCIENCE- ENVIRONMENT
THERMODYNAMICS = THERMAL+ DYNAMICS
(HEAT) (POWER)
HEAT – Kind of energy transfer- Temp. difference
POWER- Capable to work
THERMODYNAMICS- Science of energy and energy transfer

4. CONSERVATION OF MASSPRINCIPLE
• The conservation of mass principle states the following:
• Net mass transfer to or from a system during a process is
equal to the net change in the total mass of the system
during that process

5. CONSERVATION OF MASSPRINCIPLE
min= total massenterin tosystem
mout= total massleave from system
Dmsystem= netchange of masswithin system

6. Some application areas of thermodynamics.
6

7. TYES OF HEAT TRANSFER AND WORK TRANSFER

8. BASIC CONCEPT OF THERMODYNAMICS
• Science which deals with energy transfer and
its effect on physical properties of substances.
8

9. 9
• Macroscopic or Classical Approach:
• It is not concerned with the behavior of
individual molecules.
• These effects can be perceived by human senses
or measured by instruments
Eg: pressure, temperature
• Microscopic or Statistical Approach:
• Based on the average behavior of large groups
of individual particles.
• the effect of molecular motion is Considered.

10. SYSTEMS AND CONTROL VOLUMES
•
•
•
•
•
A system is defined as a quantity of matter or a region in space chosen for
study.
Surroundings: The mass or region outside the system boundary.
Boundary: The real or imaginary surface that separates the system from its
surroundings.
The boundary of a system can be fixed or movable.
Systems may be considered to be closed or open.
10

11. 11
Thermodynamic System and Types
• A specified region in which transfer of mass / energy
takes place is called system.
• To a thermodynamic system two ‘things’ may be
added/removed:
➢energy (heat, work) matter (mass)
CLASSIFICATION OF THERMODYNAMIC SYSTEM
•
•
•
•
•
Closed or Non-flow
Open or Flow
Isolated
Homogeneous
Hetrogeneous

12. Closed System (Control Mass)
• No mass can cross system boundary
• Energy may cross system boundary
12

13. Open System/Control Volume
• Mass may cross system boundary (control
surface)
• Energy may cross system boundary
13

14. Isolated System
• No interaction between the system and the
surroundings.
• Neither mass nor energy can cross the
boundry.
• This is purely a theoretical system.
14

15. 15

16. Homogeneous and Hetrogeneous
system
• Homogeneous system:
• System exists in single phase.
• Heterogeneous system:
• System exists in more than one phase.
16

17. THERMODYNAMIC PROPERTIES
•
•
•
•
•
•
•
•
•
•
•
MASS – quantity of matter
WEIGHT - force exerted on a body by gravity
VOLUME – space occupied by matter
SPECIFIC VOLUME – volume per unit mass
SPECIFIC WEIGHT – weight per unit volume
DENSITY – mass per volume of substance
TEMPERATURE – degree of hotness or coldness
PRESSURE - force exerted per unit area
SPECIFIC HEAT – energy required to raise or lower temp.
of substance about 1 k or 1°C
INTERNAL ENERGY – energy contain within system
WORK – kind of energy transfer – acting force- flow
direction
HEAT- kind of energy transfer – temp difference•
• ENTHALPY – total energy of the system (I.E + F.W) 13

18. INTENSIVE or EXTENSIVE PROPERTY
• Intensive properties: The
property which is
independent of the mass of
a system, such as
temperature, pressure, and
and specificdensity
volume.
• Extensive properties: The
property which depends up
on the mass of a system,
such as volume, internal
energy and enthalpy.
18

19. TYPES OFWORK

20. DENSITY AND SPECIFIC GRAVITY
Specific gravity:
The ratio of the density of a substance to the density of some
standard substance at a specified temperature
Density
Density is mass per unit volume; specific volume is volume per unit mass.
Specific weight:
The weight of a unit volume of a substance.
Specific volume
20

21. PRESSURE
The normal stress (or “pressure”) on the feet of a chubby
person is much greater than on the feet of a slim person.
Pressure: A normal force exerted
by a fluid per unit area
68 kg 136 kg
Afeet=300cm2
0.23 kgf/cm2 0.46 kgf/cm2
P=68/300=0.23 kgf/cm2
21

22. •
•
•
Absolute pressure: The actual pressure at a given position. It is
measured relative to absolute vacuum (i.e., absolute zero pressure).
Gage pressure: The difference between the absolute pressure and
the local atmospheric pressure. Most pressure-measuring devices are
calibrated to read zero in the atmosphere, and so they indicate gage
pressure.
Vacuum pressures: Pressures below atmospheric pressure.
22

23. 23
Specific Heat Capacity
• Quantity of heat required to raise the
temperature of unit mass of the material
through one degree celsius.
• Specific Heat at constant pressure( Cp)
• Specific Heat at constant volume (Cv)
•
•
Cp=1.003 kJ/kg-K
Cv= 0.71 kJ/kg-K for air.
UNIVERSAL RU = Cp - Cv

24. STATE, PROCESSES AND CYCLES
State:
It is the condition of a system as
defined by the values of all its
properties.
It gives a complete description of
the system
Process:
Any change
undergoes
that a system
from one
equilibrium state to another.
STATE1- T1,P1,V1
STATE 2- T2,P2,V2
PROCESS - 1 2
24

25. STATE AND EQUILIBRIUM
• State:
• It is the condition of
•the system namely
temperature, pressure,
density, composition,.
• Equilibrium:
• In an equilibrium state there are no unbalanced
potentials (or driving forces) within the system.
A system at two different states
25

26. STATE AND EQUILIBRIUM
• Thermal Equilibrium:
The temperature is the
same throughout the
entire system.
• Mechanical equilibrium:
There is no change in
pressure at any point
of the system with
time.
22
A closed system reaching thermal
equilibrium.
.

27. 27
STATE AND EQUILIBRIUM(Con…)
• Phase equilibrium:
• A system which is having two phases and
when the mass of each phase reaches an
equilibrium level.
• Chemical equilibrium:
• The chemical composition of a system does
not change with time, that is, no chemical
reactions occur.

28. Thermodynamic Cycle
• Path: The series of states
through which a system
passes during a process. To
describe
completely,
a process
one should
specify the initial and final
states,
• Cycle: A number of
processes in sequence
bring back the system to
the original condition.
28

29. BOUNDARY WORK
The work associated with a moving
boundary is called boundary work
Therefore, the expansion and compression
work is often called moving boundary work, or
simply boundary work (Fig.). Some call it the P
dVwork.
The moving boundary work associated with real engines or
compressors cannot be determined exactly from a thermodynamic
analysis alone because the piston usually moves at very high
speeds, making it difficult for the gas inside to maintain
equilibrium. Then the states through which the system passes
during the process cannot be specified, and no process path can be
drawn. Work, being a path function, cannot be determined
analytically without a knowledge of the path. Therefore, it is
determined by direct measurements in real engines or compressors

30. BoundaryWork
In this section, we analyse the moving boundary work for a
quasi-equilibrium process, a process during which the system remains
nearly in equilibrium at all times. A quasi- equilibrium process,
also called a quasistatic process, is closely approximated by real
engines,especiallywhenthepistonmovesatlowvelocities.
Under identical conditions, the work output of the engines is
found to be a maximum, and the work input to the compressors
to be a minimum when quasi-equilibrium processes are used in
place of nonquasi-equilibriumprocesses.

31. Boundary Work

32. Boundary Work

33. Boundary Work

34. Boundary Work

35. Quasistatic or quasi-equilibrium
process
• Reversible process is a succession of
equilibrium states and infinite slowness is its
characteristic feature.
• Work done w = ∫ pdv
35

36. BOUNDARYWORK FORVARIOUS THERMODYNAMIC
PROCESS

37. BOUNDARYWORK FORVARIOUS THERMODYNAMIC
PROCESS

38. BOUNDARYWORK FORVARIOUS THERMODYNAMIC
PROCESS

39. BOUNDARYWORK FORVARIOUS THERMODYNAMIC
PROCESS

40. BOUNDARYWORK FORVARIOUS THERMODYNAMIC
PROCESS

41. BOUNDARYWORK FORVARIOUS THERMODYNAMIC
PROCESS

42. BOUNDARYWORK FORVARIOUS THERMODYNAMIC
PROCESS

43. BOUNDARYWORK FORVARIOUS THERMODYNAMIC
PROCESS

44. BOUNDARYWORK FORVARIOUS THERMODYNAMIC
PROCESS

45. BOUNDARYWORK FORVARIOUS THERMODYNAMIC
PROCESS

46. BOUNDARYWORK FORVARIOUS THERMODYNAMIC
PROCESS

47. BOUNDARYWORK FORVARIOUS THERMODYNAMIC
PROCESS

48. Thermodynamic Work
• positive work is done by a
system when the sole effect
external to the system could
be reduced to the rise of a
weight.
• Unit of work is N-m or Joule.
• Work flow into the system is
negative
• Work flow out of the system
is positive
48

49. Thermodynamic Heat
transferred without
transfer between the
• Energy
mass
system
due
and the surroundings
to
temperature
difference in
between the
system and the surroundings.
• The unit of heat is Joule or kilo
Joule
• Heat flow into the system is
positive
• Heat flow out of the system is
negative
49

50. 50
Energy and Forms of Energy
• Energy:
• Capacity to do work
• Forms of Energy:
•
•
Stored Energy
Energy in transition form

51. 51
Stored Energy(Con…)
• Internal Energy(U):It is sum of kinetic energies
of individual atoms or molecules, that kinetic
energy occurred by external heat supplied to
the system it will converted to work.
• Sum energy always stored in the system (U)
not fully converted to work.
• Change in internal energy =mcv(T2-T1) kJ

52. 52
Enthalpy(H)
• Internal energy and pressure volume product.
• H=u+pv
• Change in enthalpy= mcp(T2-T1) kJ
• Where m=mass in kg
• cp=sp.heat at const.pressure in kJ/kg
• (T2-T1)= temp. difference in K

53. 53
Stored Energy(Con…)
• Kinetic Energy: Energy possessed by a body by
virtue of its motion.
• Change in K.E.=1/2 m(c2-c1) N-m.2 2
• Flow Energy: Energy required to make the
flow of the system in and out of the device.
• Change in F.E.=( p2v2-p1v1) N-m

54. 54
PATH and POINT FUNCTION
• If cyclic integral of a variable is not equal to
zero, then the variable is said to be a path
function.
• If cyclic integral of a variable is equal to zero,
then the variable is said to be a point
function.

55. Zeroth Law
55
• If two bodies A
equilibrium with
and B are in thermal
a third body C
independently, then these two bodies (A and
B) must be in thermal equilibrium with each
other.
Application: Thermometer

56. CONSERVATION OF MASS PRINCIPLE

57. ENERGY CONSERVATION PRINCIPLE

58. ENERGY CONSERVATION PRINCIPLE

59. The first law of thermodynamics
• Expression of the conservation of energy
principle.
• Statement: If a closed system executes a cyclic
process then net heat transfer is equal to net
work transfer.
• dQ=dW
• Q=W+dU for a process.
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60. The first law of thermodynamics

61. First -Law for Cyclic Process

62. JOULE’SEXPERIMENT

63. JOULE’SEXPERIMENT

64. JOULE’SEXPERIMENT

65. FIRST LAW FROM ENERGY PRINCIPLE

66. First Law for Process (Closed system)

67. JOULE’S EXPERIMENT

68. PROOF: ENERGY IS PROPERTY OF SYSTEM

69. PROOF: ENERGY IS PROPERTY OF SYSTEM

70. EXPANSION OF FIRST LAW

71. INTERNAL ENERGY

72. INTERNAL ENERGY

73. INTERNAL ENERGY

74. Internal Energy is Molecular Energy

75. INTERNAL ENERGY VS. HEAT

76. TEMPERATURE VS. INTERNAL ENERGY

77. Corollary 1 of First Law

78. Corollary 2 of First Law

79. ENTHALPY

80. 80
Laws Of Perfect Gas
•
•
•
1)Boyle’s law- “The absolute pressure of a given mass of
perfect gas varies inversely as its volume, when the
temperature remain constant”.
Mathematically pv = constant (T= const.)
2)Charles law- “The volume of a given mass of a perfect gas
varies directly as its absolute temperature, when the pressure
remains constant”.
Mathematically, V/T = constant (p= const.)
3)Gay-lussac law- “The absolute pressure of a given mass of
a perfect gas varies directly as its absolute temperature when
volume is constant.”
Mathematically, P/T = constant (v= const.)

81. 81
THERMODYNAMIC PROCESS
Here is a brief listing of a few kinds of processes, which we will encounter in TD:
Isothermal process → the process takes place at constant temperature
(e.g. freezing of water to ice at –10C)
Isobaric → constant pressure
(e.g. heating of water in open air→ under atmospheric pressure)
Isochoric → constant volume
(e.g. heating of gas in a sealed metal container)
Reversible process → the system is close to equilibrium at all times (and infinitesimal
alteration of the conditions can restore the universe (system + surrounding) to the original
state.
Irreversible Process: The reversal of the process leaves some trace on the system and its
surroundings.
Cyclic process → the final and initial state are the same. However, q and w need not be zero.
Adiabatic process → dq is zero during the process (no heat is added/removed to/from the
system)

82. 82
Thermodynamics processes
of Perfect Gas1) Const. Volume/ isochoric process:
-Temperature and Pressure will increase
-No change in volume and No work done by gas
-Governed by Gay-Lussac law
2) Const. Pressure/ isobaric process:
- Temperature and volume will increase
- Increase in internal energy
- Governed by Charles law
3) Constant temperature/ isothermal process:
- No change in internal energy
- No change in Temperature
- Governed by Boyles law (p.v = constant)

83. Conti….
4) Adiabatic/ isentropic process:
- No heat leaves or enters the gas Q = 0,
- Temperature of the gas changes
- Change in internal energy is equal to the work done
5) isentropic process:
- Entropy remains constant dS = 0,
- Temperature of the gas changes
- Change in internal energy is equal to the work done
4) Polytropic process:
- It is general law of expansion and compression of the gases.
p.v^n = Constant
5) Free expansion:
-When a fluid Is allowed to expand suddenly into a vacuum chamber
through on orifice of large dimensions.
Q = 0, W = 0, and dU = 0.
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84. Thank you
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