Thermodynamics I Chapter 5 Second Law of Thermodynamics Mohsin Mohd Sies Fakulti Kejuruteraan Mekanikal, Universiti Teknologi Malaysia.

Slides:



Advertisements
Similar presentations
Department of Mechanical Engineering ME 322 – Mechanical Engineering Thermodynamics Lecture 18 Introduction to 2 nd Law and Entropy.
Advertisements

The Second Law of Thermodynamics
Carnot Thermodynamics Professor Lee Carkner Lecture 12.
P V Isotherm, pV = constant = Nk B T Adiabat, pV  = constant v = 10:1:100; t = 100; r = 8.314; gamma = 1.67; p = r*t./v; k = (10^(gamma-1)).*r*t; pa =
Chapter 6 The Second Law of Thermodynamics Study Guide in PowerPoint to accompany Thermodynamics: An Engineering Approach, 5th edition by Yunus.
The Carnot Cycle Physics 313 Professor Lee Carkner Lecture 14.
5 CHAPTER The Second Law of Thermodynamics.
Thermodynamics Lecture Series Applied Sciences Education.
Second Law of Thermodynamics (YAC Ch.5) Identifies the direction of a process. (e.g.: Heat can only spontaneously transfer from a hot object to a cold.
Chapter 6 THE SECOND LAW OF THERMODYNAMICS
Second Law of Thermodynamics Identify the direction of a process. (ex: Heat can only transfer from a hot object to a cold object, not the other around)
EGR 334 Thermodynamics Chapter 5: Sections 1-9
The Second Law of Thermodynamics Chapter 7.  The first law of thermodynamics states that during any cycle that a system undergoes, the cyclic integral.
Thermodynamics I Chapter 6 Entropy Mohsin Mohd Sies Fakulti Kejuruteraan Mekanikal, Universiti Teknologi Malaysia.
Thermodynamics I MECN 4201 Professor: Dr. Omar E. Meza Castillo
THE SECOND LAW OF THERMODYNAMICS
VII. The second low of Thermodynamics
CHAPTER 6 THE SECOND LAW OF THERMODYNAMICS
Limitation of the 1st law of thermodynamics
ENGR 2213 Thermodynamics F. C. Lai School of Aerospace and Mechanical Engineering University of Oklahoma.
ENGR 2213 Thermodynamics F. C. Lai School of Aerospace and Mechanical Engineering University of Oklahoma.
ChemE 260 The 2 nd Law of Thermodynamics April 26, 2005 Dr. William Baratuci Senior Lecturer Chemical Engineering Department University of Washington TCD.
Laws of Thermodynamics Thermal Physics, Lecture 4.
The Second Law of Thermodynamics Chapter 6. The Second Law  The second law of thermodynamics states that processes occur in a certain direction, not.
Lecture Outline Chapter 12 College Physics, 7 th Edition Wilson / Buffa / Lou © 2010 Pearson Education, Inc.
Thermodynamic cycles 2nd law of Thermodynamics Carnot Cycle Lecture 30: 2nd Law of Thermodynamics.
Chapter 7 THE SECOND LAW OF THERMODYNAMICS
PTT 201/4 THERMODYNAMICS SEM 1 (2013/2014) 1. Objectives Introduce the second law of thermodynamics. Identify valid processes as those that satisfy both.
PHY1039 Properties of Matter Heat Engines, Thermodynamic Efficiency, and Carnot Cycles April 30 and May 3, 2012 Lectures 17 and 18.
Chapter 6 THE SECOND LAW OF THERMODYNAMICS
Second Law It is impossible to construct a device which operating in a cycle will produce no effect other than transfer of heat from a cooler to a hotter.
Chapter 18 Second Law of Thermodynamics. Introduction 2 First law → conservation of energy Processes that conserve energy may not occur 400K300K heat.
Second Law of Thermodynamics Heat generally cannot flow spontaneously from a material at lower temperature to a material at higher temperature. The entropy.
Physics 101: Lecture 28, Pg 1 Physics 101: Lecture 28 Thermodynamics II l Today’s lecture will cover Textbook Chapter
Physics 101: Lecture 26, Pg 1 Physics 101: Lecture 26 Thermodynamics II Final.
Thermodynamics II Thermodynamics II. THTH TCTC QHQH QCQC W HEAT ENGINE THTH TCTC QHQH QCQC W REFRIGERATOR system l system taken in closed cycle   U.
Lecture 26: Thermodynamics II l Heat Engines l Refrigerators l Entropy l 2 nd Law of Thermodynamics l Carnot Engines.
Chapter 12 Laws of Thermodynamics. Chapter 12 Objectives Internal energy vs heat Work done on or by a system Adiabatic process 1 st Law of Thermodynamics.
SECOND LAW OF THERMODYNAMICS PREPARED BY, JIGNESH VANPARIYA ( ) DARSHN INSTITUTE OF ENGG. & TECHNOLOGY.
Second law of thermodynamics. The Second Law of Thermodynamics.
L.C. INSTITUTE OF TECHNOLOGY BHANDU. Ch.2  Ch.2 Second Law of Second Law of Thermodynamics Thermodynamics.
Unit 61: Engineering Thermodynamics Lesson 8: Second Law of Thermodynamics.
Unit 61: Engineering Thermodynamics Lesson 9: Carnot Engine Cycles.
Heat Engines A gasoline engine is a form of a heat engine, e.g. a 4-stroke engine INTAKE stroke: the piston descends from the top to the bottom of the.
K.J. INSTITUTE OF ENGINEERING AND TECHNOLOGY FACULTIES :- Santosh Varma Bhavin Sir By :- Parth tavrawala ( ) BRANCH :MECHANICAL B (D2D) Engineering.
Lecture 27Purdue University, Physics 2201 Lecture 27 Thermodynamics II Physics 220.
Chapter 7 THE SECOND LAW OF THERMODYNAMICS
Carnot Cycle Pratik Vasava ( ) Dept. of Mech. Engg., ADIT, New V. V. Nagar.
1 Reversible Processes The second law of thermodynamics state that no heat engine can have an efficiency of 100%. Then one may ask, what is the highest.
2 2 The second law of thermodynamics It will arouse changes while the heat transfers from low temp. substance to high temp. one.
THE SECOND LAW OF THERMODYNAMICS
Chapter 6 THE SECOND LAW OF THERMODYNAMICS
Second Low of Thermodynamics
Chapter: 06 The Second Law.
Chapter 6 THE SECOND LAW OF THERMODYNAMICS
LAXMI INSTITUTE OF TECHNOLOGY
An iso certified institute
– SOLANKI JIGNESH.
REVERSIBLE AND IRREVERSIBLE PROCESSES
Chapter 6 THE SECOND LAW OF THERMODYNAMICS
Chapter 6 THE SECOND LAW OF THERMODYNAMICS
Chapter 6 THE SECOND LAW OF THERMODYNAMICS
THE SECOND LAW OF THERMODYNAMICS
An Engineering Approach Chapter 6 THE SECOND LAW OF THERMODYNAMICS
Z.E. Z.E. Z.E. IE 211 INTRODUCTION TO ENGINEERING THERMODYNAMICS
Second Law of Thermodynamics
Chapter 6 THE SECOND LAW OF THERMODYNAMICS
SECOND LAW OF THERMODYNAMICS
Equivalence of the Two Statements
Chapter 7 THE SECOND LAW OF THERMODYNAMICS
Presentation transcript:

Thermodynamics I Chapter 5 Second Law of Thermodynamics Mohsin Mohd Sies Fakulti Kejuruteraan Mekanikal, Universiti Teknologi Malaysia

Second Law of Thermodynamics (Motivation) Energy has quality apart from quantity. This results in a preferred direction of processes. This preferred direction is described by the 2 nd Law. The 2 nd Law can be understood by practical insights into the workings of heat engines.

2 nd LAW of THERMODYNAMICS 1 st Law – Energy Conservation - amount, quantity 2 nd Law – Direction of process - quality For a process to occur, 1 st and 2 nd Laws must be obeyed Work – High quality energy (100% work can turn into heat) Heat – Low quality energy (not 100% heat can turn into work)

4 Observations A cup of hot coffee does not get hotter in a cooler room. Transferring heat to a wire will not generate electricity. Transferring heat to a paddle wheel will not cause it to rotate. These processes cannot occur even though they are not in violation of the first law.

1.The second law may be used to identify the direction of processes. 2.The second law also asserts that energy has quality as well as quantity. The first law is concerned with the quantity of energy and the transformations of energy from one form to another with no regard to its quality. The second law provides the necessary means to determine the quality as well as the degree of degradation of energy during a process. 3.The second law of thermodynamics is also used in determining the theoretical limits for the performance of commonly used engineering systems, such as heat engines and refrigerators, as well as predicting the degree of completion of chemical reactions. MAJOR USES OF THE SECOND LAW

Heat Reservoir A body which can receive/reject heat without resulting in temperature change Source - reservoir supplies heat (heat leaves reservoir) Sink - reservoir receives heat (heat enters reservoir) Heat Engine A device that converts heat into work Characteristics Receives heat from a heat source at high temperature, T H Only part of the heat is converted into work The rest is rejected to another heat sink at low temperature, T L Engine works in a cycle (continuously)

Examples of Heat Engines

High Temperature Heat Source Low Temperature Heat Sink THTH Heat Engine TLTL W out Q H or Q in Q L or Q out

2 factors limit efficiency Irreversibilities Side effect of heat transfer Irreversibility Friction Electrical resistance Mixing of different substances Free expansion Non-isothermal heat transfer Etc. Irreversible Process Process where the above factors are present

Side Effect of Heat Transfer Heat Transfer Expansion (Work Output) Temperature Increase (Energy Diverted) If the diverted energy is not thrown away, engine temperature will finally reach heat source temperature, causing Q H to stop (since no more delta_T), stopping the engine altogether.

Side Effect of Heat Transfer For the engine to keep operating – Need to cool the engine – Need to reject heat, Q L. Rejected heat Q L, – Cannot be recycled (Q L at T L cannot flow on its own to T H to become heat source again) Efficiency will always be less than 100% (even if there’s no friction and other irreversibilities)

Reversible Process After forward and reverse processes are done (system back to initial state), there is no change on the universe (system and surrounding) Reversible because there is no irreversibilities Internally reversible - irreversibilities assumed to exist only outside the system Externally reversible - irreversibilities assumed to exist only inside the system

Kelvin-Planck Statement (Heat Engine) “It is impossible for a device that works in a cycle (continuously) to receive heat supply from one heat reservoir and produces the same amount of work” Clausius Statement (Heat Pump) “It is impossible to construct a device that works in a cycle which does not produce any other effect except the transfer of an amount of heat from a cold to a hot body” 2 nd Law of Thermodynamics

Refrigerator & Heat Pump (Reversed Heat Engine) -To force heat at T L to flow to T H (work must be supplied) THTH  TLTL QLQL QHQH W in

Refrigerator -To achieve cooling effect by taking away heat (Q L ) from cold space THTH  TLTL QLQL QHQH W in Coefficient of Performance for Refrigerators Cooling Effect or Cooling Load

Heat Pump -To achieve heating effect by supplying heat (Q H ) to hot space using heat from cold surrounding THTH  TLTL QLQL QHQH W in Coefficient of Performance for Heat Pumps Heating Effect

Reversible Heat Engine/Reversed H.E No irreversibilities in the engine (friction etc.) All processes within the cycle are reversible processes (heat transfer done isothermally, etc.) Real Heat Engine -There exist irreversibilities (friction etc.) Reversible vs Real Heat Engines

Carnot Principles THTH TLTL 3 heat engines between the same T H, T L (due to heat rejection requirement)

Thermodynamic Temperature Scale - From Carnot Principle (b)

Maximum Performance General Ideal/Max/Carnot/Reversible

Carnot Cycle (Reversible Heat Engine) 2 isothermal processes (heat transfers) 2 reversible adiabatic processes

Reversed Carnot Cycle (for refrigerators/heat pumps) -Same processes, but reversed direction

25 PERPETUAL-MOTION MACHINES A perpetual-motion machine that violates the first law (PMM1). A perpetual-motion machine that violates the second law of thermodynamics (PMM2). Perpetual-motion machine: Any device that violates the first or the second law. A device that violates the first law (by creating energy) is called a PMM1. A device that violates the second law is called a PMM2. Despite numerous attempts, no perpetual-motion machine is known to have worked. If something sounds too good to be true, it probably is.

Terms Heat Reservoir Source Sink Heat Engine Irreversibility Thermal Efficiency Reversed Heat Engine Coefficient of Performance Carnot Kelvin-Planck, Clausius Heat Pump Refrigerator Perpetual Motion Machine