Thermo Chapter 1- Basic Concepts of Thermo - fkm.utm.mymazlan/?download=Thermo Chapter 1- Basic Conc… · 3/24/2009 2 What is thermodynamics ? CHAPTER 1111 Thermodynamics Defined

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CHAPTER CHAPTER CHAPTER CHAPTER CHAPTER CHAPTER CHAPTER CHAPTER 11111111

THERMODYNAMICS

SMJ 2403/SME 1413

INSTRUCTOR: DR. MAZLAN ABDUL WAHID

TEXT: Thermodynamics: An Engineering Approach

( 5/edition ) by Yunus A. Çengel & Michael A. Boles

FACULTY OF MECHANICAL ENGINEERINGUNIVERSITI TEKNOLOGI MALAYSIASKUDAI, JOHOR, MALAYSIA

THERMODYNAMICSBASIC CONCEPTSBASIC CONCEPTSBASIC CONCEPTSBASIC CONCEPTSBASIC CONCEPTSBASIC CONCEPTSBASIC CONCEPTSBASIC CONCEPTS

MAZLAN

Yunus A. Çengel & Michael A. Boles

CHAPTER CHAPTER CHAPTER CHAPTER CHAPTER CHAPTER CHAPTER CHAPTER 11111111Chapter 1Basic Concepts of Thermodynamics

•What is thermodynamics•Applications•Applications•Macroscopic view and microscopic view•Dimensions•Systems: Closed and open system•Properties of a system•State and equilibrium•Process and cycles



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•Process and cycles•Forms of energy•Temperature•Pressure

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CHAPTER CHAPTER CHAPTER CHAPTER CHAPTER CHAPTER CHAPTER CHAPTER 11111111What is thermodynamics ?

Thermodynamics Defined as the science of energy

Greek words:

therme heat

dynamis

power

Greek words:



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power

Today: A subject talking about energy, energy transformation (on home appliances, power generation systems, transportation, etc) and relationship among properties of matter

CHAPTER CHAPTER CHAPTER CHAPTER CHAPTER CHAPTER CHAPTER CHAPTER 11111111Some application areas of thermodynamics



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CHAPTER CHAPTER CHAPTER CHAPTER CHAPTER CHAPTER CHAPTER CHAPTER 11111111More examples of thermodynamic applications



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CHAPTER CHAPTER CHAPTER CHAPTER CHAPTER CHAPTER CHAPTER CHAPTER 11111111Thermodynamic approachMacroscopic and Microscopic view

Looking the system at its molecular level

Observing the system by taking the gross or average effects of many molecules



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In this course we will deal only on the macroscopic view of thermodynamicsClassic Thermodynamics

at its molecular level (Kinetic theory)

average effects of many moleculesClassical Thermodynamics

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CHAPTER CHAPTER CHAPTER CHAPTER CHAPTER CHAPTER CHAPTER CHAPTER 11111111Dimensions and Units

Primary dimensions

Derived or secondary dimensions

Name Length Time Mass Force

Int’l System (SI) Meter Sec Kilogram Newton

(m) (s) (kg) (kg. m/s2)

US (English - Engineering) Foot Sec Pound Mass

Pound Force

(ft) (s) lbm (lbf)

Force, F= ma=(kg)(m/s2)=N, Newton Weight, W=mg with g=9.81 m/s2



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Force, F= ma=(kg)(m/s2)=N, Newton Weight, W=mg with g=9.81 m/s2

In this course SI unit will be used most often

Velocity, V = length/time=(m)/(s)=m/s Work, W=Force*distance=(N)(m)1 Nm = 1 Joule

CHAPTER CHAPTER CHAPTER CHAPTER CHAPTER CHAPTER CHAPTER CHAPTER 11111111Prefixes in SI

Multiple Prefix

1012

109

106

tera, Tgiga, Gmega, M106

103

102

101

10-1

10-2

10-3

mega, Mkilo, khecto, hdeka, dadeci, dcenti, cmilli, m



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10-3

10-6

10-9

10-12

milli, mmicro, µnano, npico, p

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CHAPTER CHAPTER CHAPTER CHAPTER CHAPTER CHAPTER CHAPTER CHAPTER 11111111System, surroundings, and boundary

SURROUNDINGS

The region outside the system

A device or combination of devices containing a quantity of matter

SYSTEM

BOUNDARY



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The real or imaginary surfacethat separates the system from its surroundings.

CHAPTER CHAPTER CHAPTER CHAPTER CHAPTER CHAPTER CHAPTER CHAPTER 11111111Closed and Open Systems

Closed systemor control mass

Mass = fixedEnergy = can flow in and out

Open systemor control volume



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or control volume

Mass = can flow in and outEnergy = can flow in and out

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CHAPTER CHAPTER CHAPTER CHAPTER CHAPTER CHAPTER CHAPTER CHAPTER 11111111Properties of a system

Property – any characteristic of a systeme.g. pressure, p

temperature, Tvolume, V

• Specific Volume ( v = 1/ ρρρρ ) – volume per unit mass of a substance.

• Density ( ρρρρ = m/V) ) ) ) – mass per unit volume of a substance.

mass, m

Intensive properties– independent of size (p, T, ρ)ρ)ρ)ρ)



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Extensive properties– depend on size or extent of the system (m, V, E – total energy)


Pressure– the normal force exerted by a fluid on its containment vessel. For a fluid at rest, the pressure is the same in all directions.

δA

δFP n

δA'δA→→→→==== lim

area smallest the ===='δA



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continuum a considered be can that

area smallest the ===='δA

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CHAPTER CHAPTER CHAPTER CHAPTER CHAPTER CHAPTER CHAPTER CHAPTER 11111111Gage pressure– the pressure measured relative to atmospheric pressure.

Atmospheric pressurePgag

Vacuum pressurethe pressure measured relative to atmospheric pressure P

Pvac

Pgage

Patm

Pabs = Patm +Pgage



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pressurePabs = Patm – Pvac

Patm m

CHAPTER CHAPTER CHAPTER CHAPTER CHAPTER CHAPTER CHAPTER CHAPTER 11111111Atmospheric pressure - Barometer



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Patm = ρρρρgh

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CHAPTER CHAPTER CHAPTER CHAPTER CHAPTER CHAPTER CHAPTER CHAPTER 11111111The Manometer Patm

P2 = Patm + ρρρρgh



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P1 = P2

density of fluid h


Pressure Measurement – Manometers

gHPPPgHP

APgAHAPAPmgAP

FF

B

B

B

BB updown

ρρρρ====−−−−====ρρρρ++++

====ρρρρ++++====++++

====

0

0

0downBF



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gHPgHPPB

ρρρρ====∆∆∆∆ρρρρ====−−−− 0

upBF

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P2 = Patm

P = P

AB



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PA = PBPA = PB

P1 + ρρρρgh1 + ρρρρgh2 = ρρρρgh3 + P2


A piston/cylinder with cross sectional area of 0.01 m2 has a piston mass of 100 kg resting on the stops, as shown in the figure. With an outside atmospheric pressure of 100 kPa, what should the water pressure be to lift the piston?



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Two cylinders are filled with liquid water, ρρρρ = 1000 kg/m3, and connected by a line with a closed valve. A has 100 kg and B has 500 kg of water, their cross-sectional areas are AA = 0.1 m2 and AB = 0.25 m2 and the height h is 1 m. Find the pressure on each side of the valve. The valve is opened and water m. Find the pressure on each side of the valve. The valve is opened and water flows to an equilibrium. Find the final pressure at the valve location.



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Two bodies have an equality of temperature if when they are in thermal contact with each other, we can observe no are in thermal contact with each other, we can observe no changes in their observable properties.

When two bodies have equality of temperature with a third



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When two bodies have equality of temperature with a third body, then they have equality of temperature each other.

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• Temperature Based on the Thermodynamic Behavior of a Substance– freezing and boiling point of water.

Boiling Pt.

• Absolute Temperature Scale–temperature scale independent of the thermodynamic properties of a particular substance.

Freezing Pt.

1527300 .++++==== CK



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Absolute Zero67459

1527300 .

.++++====++++====

FR

CK


Energy



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• MECHANICAL POTENTIAL ENERGY: Exists because of relative positions of two or more objects

MECHANICAL ENERGY

because of relative positions of two or more objects• MECHANICAL KINETIC ENERGY: Exists because

of relative velocities to two or more objects -- energy of motion

• MECHANICAL WORK: Mechanical energy in transition



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transition• When an object has been moved through a distance

against a resisting force (by, of course, an assisting force), mechanical work has been done.


• Intermolecular Potential Energy – energy associated with the force between associated with the force between molecules.

• Molecular Kinetic Energy – energy associated with the translational velocity of individual molecules.

• Intramolecular Energy – energy associated with the molecular and atomic structure.



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structure.

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CHAPTER CHAPTER CHAPTER CHAPTER CHAPTER CHAPTER CHAPTER CHAPTER 11111111Forms of energy

Energy – found in many forms: thermal, mechanical, kinetic, potential, electric, magnetic, chemical, nuclear

Total Energy = Energythermal+ Energymechanical

+ Energykinetic



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• Phase– a quantity of matter that is homogeneous throughout the system or part of the system (gas, liquid, solid).

• States– condition of matter as defined by specific properties i.e.. temperature, pressure, etc.

• Properties– quantities that define the state of matter i.e.. temperature, pressure, etc.

• Intensive Properties– properties that are independent of mass.

• Extensive Properties– properties that vary with the mass being



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• Extensive Properties– properties that vary with the mass being considered.

• Thermodynamic Equilibrium – when all properties of the system are in equilibrium, i.e. not changing with time.

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• Process– a path of successive state through which a system passes.system passes.

• Equilibrium Process – process in which the successive states of the system can be described by the thermodynamic properties of the system.

• Quasi-equilibrium Process– process in which the deviation from thermodynamic equilibrium is infinitesimal.



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• Thermodynamic Cycle – when a system starts at an initial state and undergoes a sequence of changing states and then returns to its initial state.




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Documents

Thermo Chapter 1- Basic Concepts of Thermo - fkm.utm.mymazlan/?download=Thermo Chapter 1- Basic Conc… · 3/24/2009 2 What is thermodynamics ? CHAPTER 1111 Thermodynamics Defined