chapter one: Introduction to Thermodynamics

chapter one: Introduction to Thermodynamics
Definition and Introduction to Thermodynamics.

1. Thermodynamics

2. Unit I Introduction

3. Thermodynamics can be defined as the science of energy . Energy can be viewed as the ability to cause changes The name thermodynamics stems from the Greek words therme (heat) and dynamis (power), which is most descriptive of the early efforts to convert heat into power . Today the same name is broadly interpreted to include all aspects of energy and energy transformations , including power generation, refrigeration , and relationships among the properties of matter. Introduction

4. One of the most fundamental laws of nature is the conservation of energy principle . It simply states that during an interaction , energy can change from one form to another but the total amount of energy remains constant . That is, energy cannot be created or destroyed  

5. A rock falling off a cliff , for example, picks up speed as a result of its potential energy being converted to kinetic energy

6. A person who has a greater energy input (food) than energy output (exercise) will gain weight (store energy in the form of fat), and a person who has a smaller energy input than output will lose weight

7. Thermodynamics emerge as a science after the construction of the first successful atmospheric steam engines in England by Thomas Savery in 1697 and Thomas Newcomen in 1712. These engines were very slow and inefficient, but they opened the way for the development of a new science. History of Thermodynamics

8. William Thompson 1824-1907 1st Baron Kelvin (or Lord Kelvin) Was the first that uses the term THERMODYNAMICS In 1849 The Thermodynamics is a Science. As every science, has it’s own studied subject: THE TRANSFORMATION OF ENERGY FORMS LIKE HEAT AND WORK; AND RELATIONSHIP AMONG PHYSICAL PROPERTIES OF SUBSTANCES And it’s own Laws: Four Laws

9. The first and second laws of thermodynamics emerged simultaneously in the 1850s , primarily out of the works of William Rankine , Rudolph Clausius , and Lord Kelvin (formerly William Thomson). The first thermodynamic textbook was written in 1859 by William Rankine , a professor at the University of Glasgow . …

10. Any substance consists of a large number of particles called molecules . The properties of the substance naturally depend on the behaviour of these particles . There are two approaches to study the thermodynamic properties of substances; Macroscopic Approach Microscopic Approach The macroscopic approach to the study of thermodynamics does not require a knowledge of the behaviour of individual particles and it is called classical thermodynamics . It provides a direct and easy way to the solution of engineering problems . Example: Reading pressure using pressure gauge A more elaborate approach, based on the average behaviour of large groups of individual particles , is called statistical(microscopic) thermodynamics. Example: Analysis of pressure from momentum of individual molecules Macroscopic and Microscopic Viewpoint

11. All activities in nature involve some interaction between energy and matter ; thus , it is hard to imagine an area that does not relate to thermodynamics in some manner The application of the thermodynamic laws and principles are found in all fields of energy technology , notably in Application Area Steam And Nuclear Power Plants , Internal Combustion (IC)Engines , Gas Turbines , Air Conditioning , Refrigerators , Gas Dynamics , Jet Propulsion , Compressors , Chemical Process Plants And Direct Conversion Devices .

12. 12 Applications of Thermodynamics Power plants The human body Air-conditioning systems Airplanes Car radiators Refrigeration systems

13. A system is defined as a quantity of matter or a region in space chosen for study . The mass or region outside the system is called the surroundings. The real or imaginary surface that separates the system from its surroundings is called the boundary. The boundary of a system can be fixed or movable . Systems and Control Volumes Note that the boundary is the contact surface shared by both the system and the surroundings. Mathematically speaking, the boundary has zero thickness, and thus  it can neither contain any mass nor occupy any volume in space

14. System is classified in to three C A B CLOSED OPEN ISOLATED

15. The closed system is a system of fixed mass. There is no mass transfer across the system boundary. There may be energy transfer into and out of the system. a lso known as a control mass A certain quantity of fluid in a cylinder bounded by piston constitutes a closed system. Closed System

16. The open system is one in which matter crosses the boundary of the system . There may be energy transfer also. Also known as a control volume Most of the engineering devices are open system. E.g Air Compressor, Water Heater, turbine, nozzle, … Open System

17. The boundaries of a control volume are called a control surface , and they can be real or imaginary. In the case of a nozzle , the inner surface of the nozzle forms the real part of the boundary , and the entrance and exit areas form the imaginary part , since there are no physical surfaces there . A control volume can be fixed in size and shape, as in the case of a nozzle , or it may involve a moving boundary as in the piston . A control volume can also involve heat and work interactions just as a closed system, in addition to mass interaction.

18. Mass in Mass out Boundaries SYSTEM Surroundings

19. The Isolated system is one in which there is no interaction between the system and the surrounding. It is of fixed mass and energy , and there is no mass and energy transfer across the system boundary. Isolated System ISOLATED E = Constant System Isolated boundaries Environment

20. Any characteristic of a system is called a property . Pressure, Temperature, Volume, Mass , Viscosity, Thermal Conductivity… Properties are the coordinates to describe the state of a system. Properties are considered to be either Intensive or Extensive Intensive properties are those that are independent of the mass of a system , such as temperature , pressure, and density. Extensive properties are those whose values depend on the size—or extent—of the system . Total mass, total volume, and total momentum are some examples of extensive properties Properties of A system

21. To determine whether a property is intensive or extensive is to divide the system into two equal parts with an imaginary partition , as shown in figure. Each part will have the same value of intensive properties as the original system, but half the value of the extensive properties .

22. Generally , uppercase letters are used to denote extensive properties ( with mass m being a major exception ), and lowercase letters are used for intensive properties ( with pressure P and temperature T being the obvious exceptions ). Extensive properties per unit mass are called specific properties . Some examples of specific properties are specific volume ( v = V / m ) and specific total energy ( e = E/m ).

23. What is Equilibrium? State and Equilibrium

24. Equilibrium Is State Of Balance (Absence of potential to create a change which makes the state to remain as it is.)

25. With a system not undergoing any change, all the properties can be measured or calculated throughout the entire system, which gives us a set of properties that completely describes the condition , or the state , of the system . At a given state, all the properties of a system have fixed values . If the value of even one property changes ,  the state will change to a different one

26. Thermodynamics deals with equilibrium states . The word equilibrium implies a state of balance . In an equilibrium state there are no unbalanced potentials (or driving forces) within the system . A system in equilibrium experiences no changes when it is isolated from its surroundings. There are many types of equilibrium , and a system is not in thermodynamic equilibrium unless the conditions of all the relevant types of equilibrium are satisfied.

27. Types of Equilibrium Thermal Equilibrium  Mechanical Equilibrium  Phase Equilibrium  Chemical Equilibrium  No Unbalanced Force No Temperature Variation No Change in Chemical Composition (No chemical Reaction) No Unbalanced mass across multiple phase

28. Even though the state of a system is described by its properties, It is not necessary to specify all the properties in order to fix a state . Once a sufficient number of properties are specified, the rest of the properties assume certain values automatically . The number of properties required to fix the state of a system is given by the state postulate: The state of a simple compressible system is completely specified by two independent , intensive properties . State Postulate

29. State Principle : The particular state of any Thermodynamic system will be determined knowing two independent properties . It means that the knowledge of two independent properties lead to determine the others properties of the system that characterize in that state.

30. The state postulate requires that the two properties specified be independent to fix the state . Two properties are independent if one property can be varied while the other one is held constant . Temperature and Specific Volume , for example, are always independent properties , and together they can fix the state of a simple compressible system. Temperature and Pressure , however, are independent properties for single-phase systems, but are dependent properties for multiphase systems.

31. Any operation in which one or more of the properties of a system changes is called a change of state . The succession of states passed through during a change of state is called the path of the change of state . When the path is completely specified , the change of state is called a process . Process

32. A thermodynamic cycle is defined as series of state of changes such that the final state is identical with the initial state . A system consisting of a single phase is called homogeneous system , while a system consisting of more than one phase is known as a heterogeneous system .

33. Phase: Quantity of matter that is homogenous through in both chemical composition and physical structure Homogeneity in physical structure means that the matter is all solid, liquid or vapor . One system can contain more than one phase, and Chemical homogeneity means that the chemical composition of the system is invariable

34. Quasi-static or Quasi-Equilibrium Process When a process proceeds in such a manner that the system remains infinitesimally close to an equilibrium state at all times . It can be viewed as a sufficiently slow process that allows the system to adjust itself internally so that properties in one part of the system do not change any faster than those at other parts .

35. If the piston is moved slowly , the molecules will have sufficient time to redistribute and there will not be a molecule pileup in front of the piston. As a result , the pressure inside the cylinder will always be nearly uniform and will rise at the same rate at all locations . Since equilibrium is maintained at all times , this is a quasi-equilibrium process .

36. When a gas in a piston-cylinder device is compressed suddenly , the molecules near the face of the piston will not have enough time to escape and they will have to pile up in a small region in front of the piston , thus creating a high-pressure region there .  Because of this pressure difference, the system can no longer be said to be in equilibrium , and this makes the entire process nonquasi equilibrium.

37. WHY Quasi-equilibrium process ? First , they are easy to analyze ; Second work-producing devices deliver the most work when they operate on quasi-equilibrium processes. Therefore, quasi-equilibrium processes serve as standards to which actual processes can be compared. A non quasi-equilibrium process is denoted by a dashed line between the initial and final states instead of a solid line .

38. Steady implies no change with time . The opposite of steady is unsteady, or transient . Uniform , however, implies no change with location over a specified region . Steady Flow Process

39. Processes involving such devices can be represented reasonably well by a somewhat idealized process, called the steady-flow process ,  which can be defined as a process during which a fluid flows through a control volume steadily. That is , the fluid properties can change from point to point within the control volume, but at any fixed point they remain the same during the entire process . Therefore, the volume V , the mass m , and the total energy content E of the control volume remain constant during a steady flow process.

40. DIMENSIONS AND UNITS Any physical property can be characterized by dimensions. The magnitudes assigned to the dimensions are called units. Some basic dimensions such as mass m , length L , time t , and temperature T are selected as primary or fundamental dimensions , while others such as velocity V , energy E , and volume V are expressed in terms of the primary dimensions and are called secondary dimensions , or derived dimensions.

41. Derived Units used in Thermodynamics FORCE UNIT: newton (N) PRESSURE UNIT: PASCAL Work Unit: Joule (J)

42. Factor Prefix Symbol Factor Prefix Symbol 10 12 Tera T 10 -2 centi c 10 9 Giga G 10 -3 mili m 10 6 Mega M 10 -6 micro  10 3 Kilo k 10 -9 nano n 10 2 Hecto h 10 -12 pico p PREFIXES

43. English Units System vs Metric (SI) System Mass : Pound mass ( lbm ) Length: Foot ( ft ) Time: Second (s) Temperature: Rankine ( o R ) Metric Simple & Logical Various units are related based on decimal r/ nship Is being used for scientific and engineering work in indurialized nations including England English Units System Has no apparent systematic numerical base Various units are related to each other rather arbitrarily Confusing & difficult to learn Used in US

44. Dimensions SI English Unit System Mass Kilogram(kg) Pound mass ( lbm ) Length Meter (m) Foot ( ft ) Time Second (s) Second (s) Temperature Kelvin (K) Rankine ( o R ) 1lbm = 0.45359 kg 1ft = 0.3048 m

45. Force English Unit: Pound Force ( lbf ) Is defined as the force required to accelerate a mass of one pound mass at a rate of 32.174 feet per second squared English Unit for Work

46. Some equivalences between the International Unit System and the English Units System

47. Others Units used for Heat BTU.- British Thermal Unit : It is the quantity of heat required to increase the temperature of 1 pound mass of water in one Fahrenheit at 68 o F Cal.-Calorie : It is the quantity of heat required to increase the temperature of 1 gram of water in one degree Celsius at 14.5 o C kcal.-Kilo calorie: It is the quantity of heat required to increase the temperature of 1 kilogram of water in one degree Celsius at 14.5 o C

48. Conversions Factors

49. 1.5 Some Basic Properties of Thermodynamics Density:  ( kg/m 3 ), ( lbm /ft 3 ) Is the inverse of the specific volume, is the mass per unit volume. Specific Volume: v (m 3 /kg ), (ft 3 / lbm ). Is defined as volume per unit mass .

50. Specific Gravity The Specific Gravity - SG - is a dimensionless unit defined as the ratio of density of the material to the density of water at a specified temperature. Can be expressed as the density of a substance relative to the known density of the other, usually the density of water at 4 o C. It is widely used in the Oil Industry.

51. Pressure Pressure is the force exerted by the fluid per unit of area . The Thermodynamic Property is the Absolute Pressure measured relative to absolute zero pressure . As the pressure is a primary property it can be measured. The instrument used to measure the pressure is a manometer. A manometer measures a gage pressure, or vacuum not the absolute pressure .

52. zero absolute pressure level Atmospheric pressure level Gage pressure Absolute pressure 2 vacuum Absolute pressure2 P atm P abs P m P v P abs

53. Temperature It is a very important Thermodynamic property that is the measure the average kinetic energy of the particles of a substance or body, is a measure of the thermal equilibrium. The temperature difference between two point of the system causes the heat transfer until the equilibrium state is achieved The temperature difference between the system and the environment causes the heat transfer exchange The temperature of an ideal monatomic gas is a measure related to the average kinetic energy of its atoms as they move. In this animation, the size of helium atoms relative to their spacing is shown to scale under 1950 atmospheres of pressure. These room-temperature atoms have a certain, average speed (slowed down here two trillion fold).

54. Zero Law of Thermodynamic If one body is in thermal equilibrium, with a second and is in thermal equilibrium with a third then the second and the third are in thermal equilibrium too. T 1 T 1 A B T 1 A C T 1 If and then T 1 B C T 1

55. Temperature Scales Temperature scale like Celsius and Fahrenheit use the ice point and boiling point of water . Celsius proposed temperatures of o C and100 o C . Fahrenheit scale the ice point and the boiling point of water read about 32 and 212 respectively at standard normal pressure.

56. Absolute Scales Kelvin Scale Rankine Scale

57. Kelvin Scale Where measurements are made in SI units, thermodynamic temperature is measured in kelvins (symbol: K). By international agreement, the unit “kelvin” and its scale are defined by two points: absolute zero , and the triple point of Vienna Standard Mean Ocean Water (water with a specified blend of hydrogen and oxygen isotopes). Absolute zero—the coldest possible temperature—is defined as being precisely 0 K and −273.15  °C . The triple point of water is defined as being precisely 273.16 K and 0.01 °C. This definition does three things:

58. Kelvin Scale This definition does three things : It fixes the magnitude of the kelvin unit as being precisely 1 part in 273.16 parts the difference between absolute zero and the triple point of water . It establishes that one kelvin has precisely the same magnitude as a one-degree increment on the Celsius scale; & It establishes the difference between the two scales’ null points as being precisely 273.15 kelvins (0 K = −273.15 °C and 273.16 K = 0.01 °C ).

59. Rankine Scale William John Macquorn Rankine FRS (5 July 1820 – 24 December 1872) was a Scottish engineer and physicist . He was a founding contributor, with Rudolf Clausius and William Thomson (1st Baron Kelvin), to the science of thermodynamics . Rankine developed a complete theory of the steam engine and indeed of all heat engines. His manuals of engineering science and practice were used for many decades after their publication in the 1850s and 1860s. He published several hundred papers and notes on science and engineering topics, from 1840 onwards, and his interests were extremely varied, including, in his youth, botany , music theory and number theory , and, in his mature years, most major branches of science , mathematics and engineering. He was an enthusiastic amateur singer, pianist and cellist who composed his own humorous songs. He was born in Edinburgh and died in Glasgow

60. Rankine is a thermodynamic (absolute) temperature scale named after the British engineer and physicist William John Macquorn Rankine , who proposed it in 1859 . The symbol is R .Occasionally this is written °R , but as with the Kelvin scale the usage of the degree symbol is incorrect. Zero on both the Kelvin and Rankine scales is absolute zero , but the Rankine degree is defined as equal to one degree Fahrenheit , rather than the one degree Celsius used by the Kelvin scale. A temperature of -459.67 °F is exactly equal to 0 R .

61. Comparison between the scales From Rankine To Rankine Celsius [°C] = ([R] − 491.67) × 5⁄9 [R] = ([°C] + 273.15) × 9⁄5 Fahrenheit [°F] = [R] − 459.67 [R] = [°F] + 459.67 Kelvin [K] = [R] × 5⁄9 [R] = [K] × 9⁄5 For temperature intervals rather than specific temperatures, 1 R = 1 °F = 5 ⁄ 9 °C = 5 ⁄ 9 K

62. Conversion Formulas From Kelvin To Kelvin Celsius [°C] = [K] − 273.15 [K] = [°C] + 273.15 Fahrenheit [°F] = [K] × 9⁄5 − 459.67 [K] = ([°F] + 459.67) × 5⁄9 For temperature intervals rather than specific temperatures, T= 1 K = 1 °C = 1.8 °F = 1.8 °R

63. Temperature measurement The temperature is usually determined by indirect measurement using its effects on substances.