1/13/2015 1 Course Overview MEL170: INTRODUCTION TO MECHANICAL & PRODUCTION ENGINEERING (5 credits; 3-1-2) - 3 hours lecture, 1 hour tutorial and 2 hours practices per week UNIT 1: Thermodynamics. (Thermodynamic laws, internal energy, entropy and enthalpy, properties of steam, use of steam tables etc) – there will be numericals. UNIT 2: Boilers. UNIT 3 and 4: Engines, Turbines and water pumps. UNIT 5, 6, 7, 8, 9 and 10: Manufacturing processes (plant layout, Engineering materials & their properties, Casting, Foundry, metal cutting, Welding etc) LAB WORK: Five experiments from Mechanical course contents (Units 1, 2, 3 and 4) and five from Production course contents (Units 5, 6, 7, 8, 9 and 10). Books • Engineering Thermodynamics by P.K. Nag • Elements of Mechanical Engineering by R. K. Rajput Rajput (Publisher: Laxmi Publications (P) LTD. (Units 2, 3 and 4). • Basics of Mechanical Engineering by Dr. D. S. Kumar, Publisher S.K. Kataria and sons (Units 1, 3 and 4) • Workshop Technology, Vol. 1, Manufacturing Processes by B. S. Raghuwanshi, Publisher Dhanpat Rai & Co. (Units 5 to 10) • Workshop Technology (manufacturing Process) by S. K. Garg (Units 5 to 10) Marks distribution (Total Marks = 200) • Theory (lecture) – 130 Marks 60 Marks for Major Exam Full Syllabus 65 Marks - 20 for Minor 1 - 20 for Minor 2 - 20 (Class Assessment) - 10 for online quiz • Lab. (practical) – 70 Marks 28 marks Lab. report, Lab. behavior etc 14 marks Midterm viva 28 marks Final practical Test Today we will cover • What is thermodynamics. • System and surrounding. • Types of systems (open, closed, isolated). • Laws of thermodynamics. Some of the definitions of thermodynamics: • The science that deals with the interaction between energy and material properties. • The science concerned with the relations between heat and work, and the conversion of one into the other. •It Is the study of energy conversion between heat and mechanical work, and properties of a system.
Transcript
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Course OverviewMEL170: INTRODUCTION TO MECHANICAL & PRODUCTION ENGINEERING
(5 credits; 3-1-2) - 3 hours lecture, 1 hour tutorial and 2 hours practices per week
UNIT 1: Thermodynamics.(Thermodynamic laws, internal energy, entropy and enthalpy, properties ofsteam, use of steam tables etc) – there will be numericals.
UNIT 2: Boilers.
UNIT 3 and 4: Engines, Turbines and water pumps.
UNIT 5, 6, 7, 8, 9 and 10: Manufacturing processes(plant layout, Engineering materials & their properties, Casting, Foundry, metalcutting, Welding etc)
LAB WORK:Five experiments from Mechanical course contents (Units 1, 2, 3 and 4) andfive from Production course contents (Units 5, 6, 7, 8, 9 and 10).
Books• Engineering Thermodynamics by P.K. Nag• Elements of Mechanical Engineering by R. K. Rajput
Thermodynamic SystemsSystem is a definite quantity of matter bounded by some closed surface
(boundary) which is unchanged to the flow of matter. Thermodynamic systemis defined as any prescribed and identifiable collection of matter upon whichattention is focused for investigation. Everything else other than system i.e.,the space and matter external to a system is known as surroundings.
System + Surroundings = Universe
Thermodynamic Systems There are three classes of Thermodynamic Systems: Thermodynamic Systems There are three classes of Thermodynamic Systems:
System
Surrounding
a) Open SystemMatter (mass)
interchange - (Yes)
Energy Interchange – (Yes)
b) Close SystemMatter (mass)
interchange – (No)
Energy Interchange – (Yes)
c) Isolated SystemMatter (mass)
interchange - (No)
Energy Interchange – (No)
Some examples of open, closed and isolated system Some examples of open, closed and isolated systemOpen system examples: moving car ( due to mass transfer
because of exhaust gas), moving bike (because ofexhaust gas), human body (due to mass transferbecause breathing and heat loss because oftemperature difference with environment), cup ofcoffee (heat lost because of high temperature of coffee,mass loss because of vapor)
Closed system examples: light bulb [energy transferbecause of work (electric work) input and heat output],tube light, hot iron rode, AA battery (electric energyoutput but no mass transfer).
Isolated system examples: ideal thermos, piece of paper,block of wood.
Laws of Thermodynamics1) Zeroth law 2) 1st law: Energy can never be
created or destroyed or in other words:
Energy added to system = Increase in energy of the system + Energy removed from the system.
3) 2nd law. 4) 3rd law.
If two systems are each equal intemperature to a third, then they areequal in temperature to each other.(This equality of temperature is alsocalled Thermal equilibrium)
AB CIf [T (A) = T (B) and T (A) = T (C)] Then T (B) = T (C)
SystemEnergyAdded
EnergyRemoved
In the following Slides We will discuss later
1st Law: Some more definitions• Heat and work are mutually convertible but since energy
can neither be created nor destroyed, the total energy associated with an energy conversion remains constant.
Joules Experiment (For a Cycle) [Q = W = mC(T2-T1)]C= 4.186 J/(g·0C)
Examples of Systems where heat is converted to work
• Diesel Engine
• Power plant
• Automobile Engines
Examples of devices where High Grade Energy (Work) is converted to heat
1st Law: Some more definitions
Energy change in this system = 0
PMM 1
Converse of PMM 1
Energy change in this system = 0
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• Ist law also implies that there can no machine which would continuously supply mechanical work without some form of energy disappearing simultaneously. Such a fictitious machine is called a perpetual motion machine of first kind (PMM 1). A PMM 1 is impossible.
1st Law: Some more definitions
• The Reverse of above is alsotrue, i.e., there can be nomachine which wouldcontinuously consume workwithout energy change insystem
Energy change in this system = 0
PPM 1
Reverse of PMM 1
Energy change in this system = 0
• Thermal Energy Reservoirs: Any reservoir which is having large amount of heat capacity in such a way that if some amount of heat will be given or Taken, to or from reservoir ,its temperature will be unaffected.
1) Sink 2) Source
2nd Law of thermodynamicsThis law has two parts (1. Clausius statement and 2.
Kelvin-Plank statement). The first considers transfer ofheat between two thermal reservoirs while the secondconsiders the transformation of heat into work.
Clausius Statement – “It is impossible to design a devicewhich is operating on a cycle and transferring heat froma body at lower temperature to a body at a highertemperature, unaided by any external energy”. In otherwords, heat of, itself, cannot flow from a colder to ahotter body.
Kelvin-Plank Statement – It is impossible to construct anengine, which while operating in a cycle and convertingall of the heat interacting with single reservoir toequivalent work output.
Clausius Statement leads to Kelvin-Planks Statement, and vice-versa
Examples illustrating 1st and second law (1)
Examples illustrating 1st and second law (1) Examples illustrating second law (2)
When all the properties of a system have definite values, the system is said to exist at a definite state.
PropertiesProperty = A property of a system is any observable
characteristics of the system. The properties we shall deal with are measurable in terms of numbers and units of
measurements (eg. Pressure, density, temperature etc)
Intensive ExtensiveIntensive properties are independent of the mass in the system, e.g., pressure, temperature, etc.
Extensive properties are related to mass e.g., volume, energy, etc.
When all the properties of a system have definite values, the system is said to exist at a definite state.
Important Properties we are concerned about
• Pressure - Force per unit time.• Temperature • Volume • Specific volume (volume per unit mass).• Density (mass per unit volume).• Entropy - > S• Enthalpy - > (H = U + PV)• Internal Energy - U
Intensive and Extensive PropertiesExtensive Properties Intensive Properties---- P = Pressure (pa, atm, bar etc)----- T = Temperature (K or oC or F)V = Volume (m3) v = Specific volume (m3)/kgM = mass (kg) d = density (kg/m3)S = entropy (J/K) s = specific entropy (J per
Kelvin per kg)H = enthalpy (joules) h = specific enthalpy (j/kg)U = Internal Energy (joules) u = specific internal energy
(j/kg)
State State•State is the condition of the system at an instance of time asdescribed or measured by the properties.•Or in other words each unique condition of a system is calleda state.At a particular state, all properties have fixed values.
•When all the properties of a system have definite values, thesystem is said to exist at a definite state.
(a) Initial state before heating (b) Final state after heating
12
2
1
ttdt � ³ It means that t to be property, dt is an exact differential. Change in property =
State 1 State 2
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Thermodynamics EquilibriumA system is said to be in thermodynamic equilibrium if properties of thesystem are same at all points and do not change with time.
Thermodynamics Equilibrium
A system is said to be in thermodynamic equilibrium if properties of thesystem are same at all points and do not change with time.
P1,T1,ρ1,s1….Properties
Location (a) State 1
(time = t1)
Location (b)
Location (c)
P2,T2,ρ2,s2….Properties
Location (a) Location
(b)
Location (c)
State 2 (time = t2)
Thermodynamic Equilibrium
¾Properties do not change with time
¾Properties are same at all the points/locations
¾Properties are same at all the points/locations
¾Properties do not change with time
A system is said to be in thermodynamic equilibrium if properties of thesystem are same at all points and do not change with time.
P1,T1,ρ1,s1….Properties
Location (a) State 1
(time = t1)
Location (b)
Location (c)
P1 at Location (a) = P1 at Location (b) = P1 at Location (c) T1 at Location (a) = T1 at Location (b) = T1 at Location (c) ρ1 at Location (a) = ρ1 at Location (b) = ρ1 at Location (c) s1 at Location (a) = s1 at Location (b) = s1 at Location (c) Etc …
P2,T2,ρ2,s2….Properties
Location (a) Location
(b)
Location (c)
P2 at Location (a) = P2 at Location (b) = P2 at Location (c) T2 at Location (a) = T2 at Location (b) = T2 at Location (c) ρ2 at Location (a) = ρ2 at Location (b) = ρ2 at Location (c) s2 at Location (a) = s2 at Location (b) = s2 at Location (c) Etc …
State 2 (time = t2)
¾Properties are same at all the points/locations
¾Properties are same at all the points/locations
P1 at Location (a) = P2 at Location (a) P1 at Location (b) = P2 at Location (b) P1 at Location (c) = P2 at Location (c)
T1 at Location (a) = T2 at Location (a) T1 at Location (b) = T2 at Location (b) T1 at Location (c) = T2 at Location (c) etc ….
Thermodynamic Equilibrium
Thermodynamic Equilibrium: Existence of thermodynamics equilibriumimplies existence of following three equilibriums.
P1,T1,ρ1,s1….Properties
Location (a) State 1
(time = t1)
Location (b)
Location (c)
P2,T2,ρ2,s2….Properties
Location (a) Location
(b)
Location (c)
State 2 (time = t2)
Thermodynamic Equilibrium: A system is said to be in thermodynamicequilibrium if properties of the system are same at all points and do not change withtime. Existence of thermodynamics equilibrium implies existence of following threeequilibriums.
P1,T1,ρ1,s1….Properties
Location (a) State 1
(time = t1)
Location (b)
Location (c)
P2,T2,ρ2,s2….Properties
Location (a) Location
(b)
Location (c)
State 2 (time = t2)
¾Thermal Equilibrium:[Temperature does not change with time and locations]
¾Chemical Equilibrium: If chemical concentration of the systemis same at all the points of the system and does not change with time.
¾Mechanical Equilibrium:[Pressure does not change with time and locations]
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�Pressure of the system is same at all the points/locations9P1 at Location (a) = P1 at Location (b)9P2 at Location (a) = P2 at Location (b))� Pressure does not change with time9P1 at Location (a) = P2 at Location (a) 9P1 at Location (b) = P2 at Location (b)
�Temperature of the system is same at all the points/locations9T1 at Location (a) = T1 at Location (b)9T2 at Location (a) = T2 at Location (b)� Temperature does not change with time9T1 at Location (a) = T2 at Location (a) 9T1 at Location (b) = T2 at Location (b)
Thermodynamic Equilibrium: A system is said to be in thermodynamicequilibrium if properties of the system are same at all points and do not change withtime. Existence of thermodynamics equilibrium implies existence of following threeequilibriums.
P1,T1,ρ1,s1….Properties
Location (a) State 1
(time = t1)
Location (b)
Location (c)
P2,T2,ρ2,s2….Properties
Location (a) Location
(b)
Location (c)
State 2 (time = t2)
¾Thermal Equilibrium:[Temperature does not change with time and locations]
¾Chemical Equilibrium: If chemical concentration of the systemis same at all the points of the system and does not change with time.
¾Mechanical Equilibrium:[Pressure does not change with time and locations]
Quasi-Equilibrium Process
Quasi-Equilibrium Process
A process during which the system only deviatesfrom equilibrium by an infinitesimal amount.
Path, State and Cycle
Pres
sure
(Pa)
Volume
(a)
(c)(d) (e)
(f)
(b)
Path, State and Cycle
• State : When all the properties of a system have definite values, the system is said to exist at a definite
• Path: The succession of states passed through during a change of state is called the path
• Cycle: A thermodynamic cycle is defined as a series of state changes such that the final state is identical with the initial state.
Pres
sure
(Pa)
Volume
(a)
(c)(d) (e)
(f)
(b)
Path, State and Cycle
• State : When all the properties of a system have definite values, the system is said to exist at a definite state. (a, b, c, d, e and f are examples of states)
• Path: The succession of states passed through during a change of state is called the path
• Cycle: A thermodynamic cycle is defined as a series of state changes such that the final state is identical with the initial state.
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Pres
sure
(Pa)
Volume
(a)
(c)(d) (e)
(f)
(b)
Path, State and Cycle
• State : When all the properties of a system have definite values, the system is said to exist at a definite state. (a, b, c, d, e and f are examples of states)
• Path: The succession of states passed through during a change of state is called the path
• Cycle: A thermodynamic cycle is defined as a series of state changes such that the final state is identical with the initial state.
Pres
sure
(Pa)
Volume
(a)
(c)(d) (e)
(f)
(b)
Path, State and Cycle
• State : When all the properties of a system have definite values, the system is said to exist at a definite state. (a, b, c, d, e and f are examples of states)
• Path: The succession of states passed through during a change of state is called the path
• Cycle: A thermodynamic cycleis defined as a series of state changes such that the final state is identical with the initial state.
Pres
sure
(Pa)
Volume
(a)
(c)(d) (e)
(f)
(b)
Path, State and Cycle
• State : When all the properties of a system have definite values, the system is said to exist at a definite state. (a, b, c, d, e and f are examples of states)
• Path: The succession of states passed through during a change of state is called the path
• Cycle: A thermodynamic cycleis defined as a series of state changes such that the final state is identical with the initial state.
Pres
sure
(Pa)
Volume
(a)
(c)(d) (e)
(f)
(b)
Process When the path is completely specified, the change of state is called a process i.e. the system is then said to have gone through a process. Process is a path of the successive equilibrium states through which the system passes when it changes its position from one state to another. It is mainly used to define the general characteristics of a path
(a)
(c)(d) (e)
(f)
(b)
T (d
egre
e C)
Volume
Pres
sure
(Pa)
Volume
(a)
(c)(d) (e)
(f)
(b)
Constant Temperature (isothermal) – (c to e)
(a)
(c)(d) (e)
(f)
(b)
T (d
egre
e C)
Volume
Constant Pressure (isobaric) – (c to e)
Process When the path is completely specified, the change of state is called aprocess i.e. the system is then said to have gone through a process. Process is apath of the successive equilibrium states through which the system passes when itchanges its position from one state to another. Its is many used to define the generalcharacteristics of a path
Pres
sure
(Pa)
Volume
(a)
(c)(d) (e)
(f)
(b)
Constant Temperature (isothermal) – (c to e)
(a)
(c)(d) (e)
(f)
(b)
T (d
egre
e C)
Volume
Constant Pressure (isobaric) – (c to e)
Cons
tant
Vol
ume
(isoc
horic
)
Process When the path is completely specified, the change of state is called aprocess i.e. the system is then said to have gone through a process. Process is apath of the successive equilibrium states through which the system passes when itchanges its position from one state to another. Its is many used to define the generalcharacteristics of a path
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Tem
pera
ture
s
T (d
egre
e C)
h
Isentropic (constant entropy) process
Isenthalpic (constant enthalpy) process
Process When the path is completely specified, the change of state is called aprocess i.e. the system is then said to have gone through a process. Process is apath of the successive equilibrium states through which the system passes when itchanges its position from one state to another. Its is many used to define the generalcharacteristics of a path
Tem
pera
ture
s
T (d
egre
e C)
h
Isentropic (constant entropy) process
Isenthalpic (constant enthalpy) process
Process When the path is completely specified, the change of state is called aprocess i.e. the system is then said to have gone through a process. Process is apath of the successive equilibrium states through which the system passes when itchanges its position from one state to another. Its is many used to define the generalcharacteristics of a path
Some more examples of processesAdiabatic process is when heat transfer to and from the system is zero.
Some more examples of processesAdiabatic process is when heat transfer to and from the system is zero.
Reversible and Irreversible processes.
Some more examples of processesAdiabatic process is when heat transfer to and from the system is zero.
Reversible and Irreversible processes.
Is one in which both the system and the surroundings can return to their original state
Is one in which both the system and the surroundings cannot return to their original state
Some more examples of processesAdiabatic process is when heat transfer to and from the system is zero.
Reversible and Irreversible processes.
Is one in which both the system and the surroundings can return to their original state
Is one in which both the system and the surroundings cannot return to their original state
Assume all surfaces to be frictionless and assume that air is not causing any resistance.
Assume that friction is present
Eg.
Cyclic process
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Some more examples of processesAdiabatic process is when heat transfer to and from the system is zero.
Reversible and Irreversible processes.
Is one in which both the system and the surroundings can return to their original state
Is one in which both the system and the surroundings cannot return to their original state
Assume all surfaces to be frictionless and assume that air is not causing any resistance.
Assume that friction is present
Eg.
Cyclic process is one in which the end states are identical i.e., the system after undergoing a series of processes returns to its original condition.
Types of EnergiesEnergy: Simple definition is capacity for
For the purpose of Thermodynamics we will only consider these energies
Energies we are consideringWork –
Heat –
Internal Energy –
Energies we are consideringWork (W)- is energy in
transition whose soleeffect external to thesystem can be reducedto rise of weight.
Heat (Q) – Energy transferbecause of temperaturedifference
Internal Energy (U) – Energyassociated with randommotion of molecules andhow they interact.
Enthalpy (H) –
H = U + pV [a combinationthat occurs frequently]
Translational Motion
Rotational Motion
VibrationalMotion
Intramolecular potential Intermolecular potential
¾W & Q are energy in transition, their transfer takes through boundaries and path functions¾U, H, P.E, K.E are energies of the system and they are contained in the system.
(a) Battery (b) Battery with motor
Flow of current from a battery as work. We will consider electricalenergy as work
Sign conventions for change of U, W, H, Q
• W:
• Q :
• H or U.
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Sign conventions for change of U, W, H, Q• W: done by the system is considered positive
work and work done on the system is considered negative.
• Q : Heat added to the system is considered positive. Heat removed from system is considered negative.
• If change in U or H of a system is positive then U or H are said to have increased. If this change is negative then U or H are said to have decreased.
¾W & Q are energy in transition, their transfer takes through boundaries and pathfunctions. Since they are path functions and do not have exact differential, theyare not properties.¾U, H, P.E, K.E are energies of the system and they are contained in thesystem.
Work Done in a Quasistatic Process
Work Done in a Quasistatic Process
(a) Gas executing a quasistatic process (b) P-V diagram
Work done in a quasistatic processδ W = p Adl = p dv
³ 2
1
pdvW = Area Under the curve
If we change path, area will change so the work, therefore work is a path function
Work Done in Contact Pressure (Isobaric) Quasistatic Process
Work Done in Contact Volume (Isochoric) Quasistatic Process
Work Done in Constant Pressure (Isobaric) Quasistatic Process
W12 = ³2
1
p dv = p (v2 – v1)
Work Done in Constant Volume (Isochoric) Quasistatic Process
W12 = ³2
1
p dv = 0
1
21112
1
211
2
111
2
1
112
112
11
ln
ln
constant a is C wherevp = C = pv process, isothermalan For
vvvpW
vvvp
vdvvp
dvvvppdvW
³
³³
Work Done in Constant Temperature (Isothermal) QuasistaticProcess
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Work Done in Polytropic QuasistaticProcess
> @
1
1
1
1
1
constant a is C wherevp = C = pv
process, polytropican For
221112
1122
1111
1222
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nnnn
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nn
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First law of Thermodynamics for a Closed System Executing a Cycle
(b) P-V diagram for a cycle
First law of Thermodynamics for a Closed System Executing a Cycle
³³ WQ GG
P-V diagram for a cycle
First law of Thermodynamics for a Closed System Executing a process
P-V diagram for two cycles
WWQQb
b
a
a
b
b
a
a
GGGG ³³³³ � �1
2
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1
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a
c
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2
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is independent of pathfollowed. It only dependson initial and final state,hence is a property.
¾ δQ - δW is denoted by dE¾ E is called stored energy
δQ - δW = dEor δQ = dE + δWQ12 = E2-E1 + W12
Internal Energy and Stored Energy� E is called stored energy, total energy or called asonly energy.� Energy is a property derived from first law ofthermodynamics when applied to a closed systemexecuting a process.� E represents total energy i.e. sum of microscopicenergy and macroscopic energy, which a system possessat a given state.¾ Macroscopic types include Kinetic and potential energy.¾ Microscopic energy includes Chemical energy, nuclearenergy , vibrational energy and electronic energy ofmolecules. This microscopic energy is called internal energy.
ΔE = ΔU + Δ (½ mv2)+ Δ(mgz) = Q - W
Constant Pressure Process
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H = U + p V h = u + pvdH = dU + pdV + Vdp
δQ = dU + pdVdH = δQ + V dp
If p is constant dH = δQ
¾At 00 C, enthalpy is takento be zero.¾In an open system
H = U + pV¾pV is called the flowwork. Flow work is due topressure and moves thefluid in or out of a controlvolume.
¾In throttling process,enthalpy remains constant.
In a constant pressureprocess from state 1 tostate 2, change in enthalpyis equal to heat supplied.
Constant Pressure Process First Law of Thermodynamics Applied to an open system or to a Steady Flow Process
First Lawfor anOpenSystem
First Law of Thermodynamics Applied to an open system or to a Flow Process
. .. .. .
First Lawfor anOpenSystem
E1 = Stored energy entering the control volume = m1 (u1 + ve12/2 + gz1)
E2 = Stored energy leaving the control volume = m2 (u2 + ve22/2 + gz2)
.
..
.
1: Mass Balance2: Energy Balance
W = Entry Displacement Work + Exit Displacement Work + WCV
E1 + m1 p1v1 + Q = E2 + m2 p2v2 + WCV + δEC.V/δt
. .. .. .
E1 = Stored energy entering the control volume = m1 (u1 + ve12/2 + gz1)
E2 = Stored energy leaving the control volume = m2 (u2 + ve22/2 + gz2)
Application of First Law of Thermodynamics applied to a control volume or Applications of Steady Flow Equation.
Steam Turbine
Q = m {(h2 + ve22/2 + gz2) - (h1 + ve1
2/2 + gz1) } + W. . .
Q = m {(h2 + ve22/2 + gz2) - (h1 + ve1
2/2 + gz1) } + W. . .
0 = m (h2 - h1) + W. .W = Wout = m (h1 – h2)
. .
Air Compressor
Win= m (h2 – h1)
..
Pump
Win= m (h2 – h1)
..
Steam Boiler
.
Qin= m (h2 – h1)
..
Q = Qout = m (h1 – h2) . .
• Heat Engine
• Heat Pump
• Refrigerator
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• Heat Engine
• Heat Pump
• Refrigerator
• Heat Engine K
• Heat Engine
1QW
K
soQQW ,21 �
1
21
QQQ �
K
1
21QQ
�
Heat Pump
Refrigerator
POC ..
POC ..
Heat Pump
Refrigerator
WQPOC 1..
W = Q1 – Q2
21
1..QQ
QPOC�
WQPOC 2..
21
2..QQ
QPOC�
Heat Pump
Refrigerator
WQPOC 1..
W = Q1 – Q2
21
1..QQ
QPOC�
WQPOC 2..
21
2..QQ
QPOC�
1.... � HPHP POCPOC
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Perpetual Motion Machine of Second Kind, PMMSK
Perpetual Motion Machine of Second Kind, PMMSK
A system which operates in a cycle and convertsall heat into work and exchanges heat with asingle reservoir is called perpetual motionmachine of second kind, PMMSK.
Q = W
Can not exist asit is violation ofKelvin-Planck’sstatement.
