Basic Concepts of Thermodynamics The science of Energy

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Abner Stewart
6 years ago
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Thermodynamics Lecture Series Capturing the Lingo Assoc. Prof. Dr. Jaafar Jantan aka DR.

Journeytowards Enrichment and Balanceutilizing Arts and Sciencesin Teaching & Learning Voice: 019-455-1621 email: drjjlanita@hotmail.com; jjnita@salam.uitm.edu.my Website: http://www3.uitm.edu.my/staff/drjj/drjj1.

You do not learn much just sitting in classes listening to teachers, memorizing prepackaged assignments, and spitting out answers.

-Source:"Implementing the Seven Principles: Technology as Lever" by Arthur W. Chickering and Stephen C.

1 Thermodynamics Lecture Series Capturing the Lingo Assoc. Prof. Dr. Jaafar Jantan aka DR. JJ Applied Science Education Research Applied Science, UiTM, Shah Alam Deep Impact Mission: Flyby camera capturing the image when impactor spacecraft collides with Tempel 1 on July 3 rd. Journeytowards Enrichment and Balanceutilizing Arts and Sciencesin Teaching & Learning Voice: drjjlanita@hotmail.com; jjnita@salam.uitm.edu.my Website: 8/10/2005 Education is the kindling of a flame, not the filling of a vessel - Socrates. Learning is not a spectator sport. You do not learn much just sitting in classes listening to teachers, memorizing prepackaged assignments, and spitting out answers. You must talk about what you are learning, write reflectively about it, relate it to past experiences, and apply it to your daily lives. You must make what you learn part of yourselves. -Source:"Implementing the Seven Principles: Technology as Lever" by Arthur W. Chickering and Stephen C. Ehrmann C Learning Objectives/Intended Learning Outcome: At the end of this session, participants should be able to: 1. State, discuss and apply the terminologies used in thermodynamics to daily life. 2. State and identify origins and transformations of the many different forms of energy 3. State and discuss the characteristics and description of changes from and to a system 4. State and discuss the zeroth law of thermo. Basic Concepts of Thermodynamics The science of Energy CHAPTER 1 8/10/2005 C FIGURE 1 5 Some application areas of thermodynamics. Steam Power Plant 1-1

FIGURE 1 13 System, surroundings, and boundary.

and out NO VOLUME CHANGE V initial = V final V = constant W in

transfer E in = E out = 0 A rigid tank An isolated system

2 FIGURE 1 13 System, surroundings, and boundary. FIGURE 1 14 Mass cannot cross the boundaries of a closed system, but energy can Systems Systems Q in Q out Dynamic Energies cross in and out NO VOLUME CHANGE V initial = V final V = constant W in W out NO mass transfer m in = m out = 0 NO dynamic energy transfer E in = E out = 0 A rigid tank An isolated system FIGURE 1 17 A control volume may involve fixed, moving, real, and imaginary boundaries. Open system devices Heat Exchanger Throttle 1-5

3 First Law of Thermodynamics Properties: Temperature Pressure Volume Internal energy Entropy Properties System The system can be either open or closed. The concept of a property still applies. Movable boundary position gone up System System A change has taken place. System expands Classes of properties Extensive MASS, m VOLUME, V ENERGY, E ADDITIVE OVER THE SYSTEM. Classes of properties Intensive TEMPERATURE, T PRESSURE, P DENSITY Specific properties NOT NOT ADDITIVE OVER THE THE SYSTEM. Box with 3 sections after equilibrium Extensive: Total : V = V 1 + V 2 + V 3 E = E 1 + E 2 + E 3 m = m 1 + m 2 + m 3 Intensive: not size independent n = n 1 = n 2 = n 3 = V/m e = e 1 = e 2 = e 3 = E/m T, P States States State A set set of of properties describing the condition of of a system A change in in any property, changes the state of of that system Equilibrium A state of of balance Thermal temperature same at at all all points of of system Mechanical pressure same at at all all points of of system at at all all time Phase mass of of each phase about the same Chemical chemical reaction stop

4 States State postulate Must have 2 independent intensive properties to to specify a state: Pressure & specificinternal internal energy Pressure & specific volume Temperature & specific enthalpy Processes and cycles First Law of Thermodynamics Properties will change indicating change of state FIGURE 1 25 A process between states 1 and 2 and the process path. Mass in Q in Q out System E 1, P 1, T 1, V 1 To E 2, P 2, T 2, V 2 W in W out Mass out 1-6 FIGURE 1 28 The P-V diagram of a compression process. p State 1 Thermodynamic process State 2 V T 1-7

5 Example: Heating water System analysis of the slow heating process: System Boundary Neglect vapor loss T 1 T 1 +dt T 1 +2dT T 2. T 1 T 1 +dt T 1 +2dT T 2 Heat supplied by electricity or combustion. T water T heater Assume no heat losses from sides and bottom. Energy in via electricity or gas combustion System analysis for the water under equilibrium processes: T water T water p S 1 Processes & Equilibrium States Process Path T heater Energy In Heating via an equilibrium process T heater Energy Out Reversed process of slow cooling, which is reversible for the water T S 2 V What is is the state of of the system along the process path? p State 1 Thermodynamic process Process 1 State 2 P 1 State 1 State 2 Thermodynamic cycles Process Path I Process 2 V Process Path II T P 2

6 Example: A steam power cycle. Combustion Products Fuel Steam Turbine Mechanical Energy to Generator Types of Energy Air Pump Heat Exchanger Cooling Water System System Boundary Boundary for for Thermodynamic Thermodynamic Analysis Analysis Dynamic Heat, Q Work, W Energy of of moving mass, E mass mass Crosses in in and out of of system s boundary Types of Energy System Internal, U Kinetic, KE KE Potential, PE PE Changes occuring within system Internal, U Types of Energy Sensible, Relates to to temperature change Latent Relates to to phase change FIGURE 1 32 The various forms of microscopic energies that make up sensible energy. Kinetic Types of Energy Changes with square of of velocity KE = (mv 2 2 )/2, kj; ke ke = v 2 2 /2, /2, kj/kg If If velocity doubles, KE = (m(2v) 2 2 )/2 )/2 = (4mv 2 2 )/2, kj kj If If decrease by by ½, ½, then KE = (m(v/2) 2 2 )/2 )/2 = (mv 2 2 )/8, kj kj 1-8

7 Potential Types of Energy Changes with vertical position, PE PE = mg(y ff -- y i ) ) = i mgh, kj; pe pe = gh, kj/kg If If position above reference point doubles, PE = mg(2h), kj; pe pe = g2h, kj/kg If If decrease by by ½, ½, then PE = mgh/2, kj; pe pe = gh/2, kj/kg APPLICATION OF THE EQUILIBRIUM PRINCIPLE Zeroth Law of Thermodynamics Heat, and Temperature Heat & temperature Temperature & heat... Large body at at constant temperature T 1 1 Large body at at constant temperature T 2 <T 2 <T 1 1 Our sense of the direction of heat flow - from high to low temperature. Temperature and heat are related. T 1 T 1 T 1 T 1 T 2 Caloric definition of temperature T 1 Isolating boundaries T 2 T 2 For metals, high heat flow - diathermal materials. T 2 T 2 For nonmetals, low heat flow - insulating. T 1 > T 2

8 Bring systems into thermal contact and surround with an isolating -- adiabatic -- boundary. T 1 T 2 T 1 T 2 Initial configuration of the closed, combined systems with a diathermal wall between the two. Heat is observed to flow from the subsystem at the higher temperature to that with the lower temperature. T 1,final T 2,final Zeroth Law of Thermodynamics... The final observed state of the total system is that when the temperatures are equal. Heat flow from subsystem 1 to subsystem 2 decreases in time. Thermal equilibrium Demonstration of the Zeroth Law A B Adiabatic T 1 T 2 Diathermal Initial State: T 1 > T 2 T 1,final T 2,final D C D Final State: T 1 = T 2 Two subsystems in equilibrium with a third subsystem

1-11 FIGURE 1 45 P versus T plots of the experimental data obtained from a constant-volume gas thermometer using four different gases at different (but

9 The Zeroth Law FIGURE 1 41 The greenhouse effect on earth. Two systems in thermal equilibrium with a third system are in thermal equilibrium with each other FIGURE 1 45 P versus T plots of the experimental data obtained from a constant-volume gas thermometer using four different gases at different (but low) pressures. FIGURE 1 47 Comparison of temperature scales FIGURE 1 51 Absolute, gage, and vacuum pressures. FIGURE 1 55 The pressure is the same at all points on a horizontal plane in a given fluid regardless of geometry, provided that the points are interconnected by the same fluid

1-16 1-17 FIGURE 1 63 The basic barometer.

the same amount of energy as a 300-W electric

1-18 1-19 FIGURE 1 39 Ground-level ozone, which

and NOx react in the presence of sunlight in hot

FIGURE 1 40 Sulfuric acid and nitric acid are

10 FIGURE 1 57 The basic manometer. FIGURE 1 61 Schematic for Example FIGURE 1 63 The basic barometer. FIGURE 1 75 Some arrangements that supply a room the same amount of energy as a 300-W electric resistance heater FIGURE 1 39 Ground-level ozone, which is the primary component of smog, forms when HC and NOx react in the presence of sunlight in hot calm days. FIGURE 1 40 Sulfuric acid and nitric acid are formed when sulfur oxides and nitric oxides react with water vapor and other chemicals high in the atmosphere in the presence of sunlight

11 FIGURE 1 7 The definition of the force units. 1-2

Read Assgn/Concept Map 2: CHAPTER 2 (Part 2) due by 3:00pm Aug 2 nd.

Read Assgn/Concept Map 2: CHAPTER 2 (Part 2) due by 3:00pm Aug 2 nd. COURSE OUTLINE THERMAL PHYSICS TEXTBOOK Thermodynamics: An Engineering Approach 4 th Edition International Edition By YUNUS A. CENGEL & MICHAEL A. BOLES. Additional materials provided as required. This