FUNDAMENTAL OF THERMODYNAMICS ( MEG 201) DR. GBEMINIYI M. SOBAMOWO

1. LECTURE NOTES FUNDAMENTAL OF THERMODYNAMICS ( MEG 201) DR. GBEMINIYI M. SOBAMOWO Department of Mechanical Engineering Faculty of Engineering University of Lagos Nigeria

2. LECTURE 1 BASIC CONCEPTS OF THERMODYNAMICS

3. BRIEF HISTORY OF THERMODYNAMICS The principles of thermodynamics have been in existence since the creation of the universe. The emergence of the principle occured when Thomas Savery in 1697 and Thomas Newcomen in 1712 first successful constructed atmospheric steam engines in England . The inefficiency of the engine pave way for the development of a new science. This development led to the simultaneous uprising of the first and second laws of thermodynamics in 1850s, primarily out of the works of William Rankine, Rudolph Clausius, and Lord Kelvin (formerly William Thomson). Lord Kelvin who is generally referred to as the father of thermodynamics, first used term thermodynamics in his publication in 1849. And such term was concreted through the first thermodynamic textbook written in 1859 by William Rankine, a professor at the University of Glasgow.

4. WHAT IS THERMODYNAMICS ? The word thermodynamics was derived from the two Greek words THERME which means heat and DYNAMIS which means power. It is most descriptive of the early efforts to convert heat into power. It is now broadly interpreted to include all aspects of energy and energy transformations, such as power generation, refrigeration, and relationships among the properties of heat, work and properties of a system. Its study includes two approaches, namely Classical and Statistical thermodynamics. The Classical thermodynamics is concerned primarily with the macroscopic behaviour of matter. It addresses the gross characteristics of large aggregations of molecules and not the behaviour of individual molecules While Statistical thermodynamicsis deals with the microscopic behaviour of matter in transforming work and heat with the methods of statistics in determining quantities of interest. The microstructure of matter is studied in kinetic theory and statistical mechanics (including quantum thermodynamics).

5. APPLICATION OF THERMODYNAMICS The application of thermodynamics is quite enormous. Indeed, it could be seen in all activities in nature involving some interaction between energy and matter. Drawing from the pool of various applications of thermodynamics, we presented the following examples; electric or gas range, the heating and air-conditioning systems, the refrigerator, the humidifier, the pressure cooker, the water heater, the shower, the iron, and even the computer and the TV, design and analysis of automotive engines, rockets, jet engines, and conventional or nuclear power plants, solar collectors, and the design of vehicles from ordinary cars to airplanes.

6. Some Other areas of APPLICATION OF THERMODYNAMICS Also, the principles of thermodynamics and other engineering sciences, such as fluid mechanics and heat and mass transfer has been used by engineers to model, analyze and design things intended to meet human needs. Various applications of these thermodynamic principles help in the design of

7. pictorial views of some areas of APPLICATION OF THERMODYNAMICS

8. pictorial views of some areas of APPLICATION OF THERMODYNAMICS

9. THERMODYNAMICS SYSTEM An important step in any engineering analysis is to describe precisely what is being studied. In a thermodynamic analysis, the system is the subject of the investigation. It is whatever we want to study. It can also be defined as a specified quantity of matter and/or a region that can be separated from everything else by a well-defined surface or 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 control surface or system boundary. This control surface may be movable or fixed. A system of fixed mass is referred to as a control mass or as a closed system. When there is flow of mass through the control surface, the system is called a control volume, or open system. An isolated system is a closed system that does not interact in any way with its surroundings.

10. CLOSED AND OPEN SYSTEMs Systems may be considered to be closed or open, depending on whether a fixed mass or a fixed volume in space is chosen for study. A closed system (also known as a control mass) consists of a fixed amount of mass, and no mass can cross its boundary. In such a system, no mass can enter or leave a closed system but energy, in the form of heat or work, can cross the boundary; and the volume of a closed system does not have to be fixed. This means that, the same collection of matter resides within the boundary of the system throughout the period of observation. However, if mass and energy are allowed to cross the boundary such system is called anopen system, or a control volume. Examples of such system are mass flow through compressor, turbine, or nozzle.The boundaries of a control volume are called a control surface, and they can be real or imaginary. A system of special case that neither mass nor energy is allowed to cross the boundary is called an isolated system. Such system has no interaction whatsoever with its surrounding. In general, very few real life applications qualify as isolated systems.

11. PICTORIAL VIEWs OF CLOSED AND OPEN SYSTEMS

12. MACROSCOPIC AND MICROSCOPIC VIEWS OF THERMODYNAMICS Systems can be studied from a macroscopic or a microscopic point of view. The macroscopic approach to thermodynamics is concerned with the gross or overall behaviour. This is sometimes called classical thermodynamics. No model of the structure of matter at the molecular, atomic, and subatomic levels is directly used in classical thermodynamics. Although the behaviour of systems is affected by molecular structure, classical thermodynamics allows important aspects of system behaviour to be evaluated from observations of the overall system. The microscopic approach to thermodynamics, known as statistical thermodynamics, is concerned directly with the structure of matter. The objective of statistical thermodynamics is to characterize by statistical means the average behaviour of the particles making up a system of interest and relate this information to the observed macroscopic behaviour of the system. For applications involving lasers, plasmas, high-speed gas flows, chemical kinetics, very low temperatures (cryogenics), and others, the methods of statistical thermodynamics are essential. Moreover, the microscopic approach is instrumental in developing certain data, for example, ideal gas specific heats For the great majority of engineering applications, classical thermodynamics not only provides a considerably more direct approach for analysis and design but also requires far fewer mathematical complications. For these reasons the macroscopic viewpoint is the one adopted in this course. When it serves to promote understanding, however, concepts are interpreted from the microscopic point of view.

13. THERMODYNAMICS STATE AND PROPERTY Thermodynamic State and Thermodynamic Property The particular condition of a system at any instant of time is called its state. In order to describe a system and predict its behaviour, we require the knowledge of its properties and how those properties are related.The state of a system at a given instant of time is described by its properties . A Propertyis any quantity whose numerical value depends on the state but not the history of the system. It could also be defined as a macroscopic characteristic of a system such as mass, volume, energy, pressure, and temperature to which a numerical value can be assigned at a given time without the knowledge of the previous behaviour (history) of the system. The value of a property is determined in principle by some type of physical operation or test and this property could be extensive and intensive in nature. If a system exhibits the same values of its properties at two different times, it is in the same state at these times. i.e if none of its properties changes with time, the system is said to be at a steady state otherwise, it is in an unsteady state.

14. EXTENSIVE AND INTENSIVE Properties OF THERMODYNAMIC SYSTEM Extensive properties depend on the size , mass or extent of the system. Volume, mass, energy, momentum and entropy are examples of extensive properties. A property is called extensive if its value for an overall system is the sum of its values for the parts into which the system is divided. Mass, volume, energy, and several other properties introduced later are extensive. Extensive properties depend on the size or extent of a system. The extensive properties of a system can change with time, and many thermodynamic analyses consist mainly of carefully accounting for changes in extensive properties such as mass and energy as a system interacts with its surroundings. Intensive properties are independent of the size, mass or extent of the system. Intensive properties are not additive in the sense previously considered. Their values may vary from place to place within the system at any moment. Thus, intensive properties may be functions of both position and time, whereas extensive properties vary at most with time. Pressure, temperature, specific volume and density are examples of intensive properties. When an extensive property is reported on a unit mass or a unit mole basis, it is called a specificproperty.

15. THERMODYNAMICS STATE AND PROPERTies

16. THERMODYNAMIC PROCESS, PATH AND CYCLE Any change that a system undergoes from one equilibrium state to another is called a process, i.e When any property of a system changes in value there is a change in state, and the system is said to undergo a process. The series of states through which a system passes while undergoing a change from one state to another is called thermodynamic path. When a process proceeds in such a manner that the system remains infinitesimally close to an equilibrium state at all times, it is called a quasi-static, or quasi-equilibrium, process. A path is identifiable only when a quasi-equilibrium is taking place. This quasi-equilibrium process 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. When a system in a given initial state goes through a sequence of processes and finally returns to its initial state, it is said to have undergone a cycle.The initial and the final states are identical i.e at the conclusion of a cycle all properties have the same values they had at the beginning. Consequently, over the cycle the system experiences no net change of state.

17. AIR-CONDITIONING SYSTEM IS AN EXAMPLE OF SYSTEM WHERE THERMODYNAMIC CYCLE OCCURS

18. REFRIGERATION SYSTEM IS AN EXAMPLE OF SYSTEM WHERE THERMODYNAMIC CYCLE OCCURS

19. Internal combustion engine IS AN EXAMPLE OF SYSTEM WHERE THERMODYNAMIC CYCLE OCCURS

20. Reversible AND IRREVERSIBLE processes A process is said to be reversible if it is possible for its effects to be eradicated in the sense that there is some way by which both the system and its surroundings can be exactly restored to their respective initial states. A process is irreversible if there is no way to undo it. That is, there is no means by which the system and its surroundings can be exactly restored to their respective initial states. Irreversibilities could be internal and external. Internal irreversibilities are those that occur within the system, while external irreversibilities are those that occur within the surroundings, normally the immediate surroundings. There are many effects whose presence during a process renders it irreversible. These include, but are not limited to, the following: heat transfer through a finite temperature difference; unrestrained expansion of a gas or liquid to a lower pressure; spontaneous chemical reaction; mixing of matter at different compositions or states; friction (sliding friction as well as friction in the flow of fluids); electric current flow through a resistance; magnetization or polarization with hysteresis; and inelastic deformation.

21. PHASE AND PURE SUBSTANCE The term phase refers to a quantity of matter that is homogeneous throughout in both chemical composition and physical structure. Homogeneity in physical structure means that the matter is all solid, or all liquid , or all vapour (or, equivalently, all gas). A system can contain one or more phases. For example, a system of liquid water and water vapour (steam) contains two phases. A pure substance is the one that is uniform and invariable in chemical composition. A pure substance can exist in more than one phase, but its chemical composition must be the same in each phase.For example, if liquid water and water vapour form a system with two phases, the system can be regarded as a pure substance because each phase has the same composition. A uniform mixture of gases can be regarded as a pure substance provided it remains a gas and does not react chemically. A system consisting of air can be regarded as a pure substance as long as it is a mixture of gases; but if a liquid phase should form on cooling, the liquid would have a different composition from the gas phase, and the system would no longer be considered a pure substance. The nature of phases that coexist in equilibrium is addressed by the phase rule

22. THERMODYNAMIC EQUILIBRIUM Classical thermodynamics places primary emphasis on equilibrium states and changes from one equilibrium state to another. Thus, the concept of equilibrium is fundamental. In mechanics, equilibrium means a condition of balance maintained by an equality of opposing forces. In thermodynamics, the concept is more far-reaching, including not only a balance of forces but also a balance of other influences. Each kind of influence refers to a particular aspect of thermodynamic, or complete, equilibrium. Accordingly, several types of equilibrium must exist individually to fulfill the condition of complete equilibrium; among these are thermal, mechanical, phase, and chemical equilibrium. Thermal equilibrium refers to an equality of temperature, Mechanical equilibrium to an equality of pressure, and Phase equilibrium to an equality of chemical potentials (Multi-component Systems). Chemical equilibrium is also established in terms of chemical potentials (Reaction Equilibrium). For complete equilibrium, the several types of equilibrium must exist individually. To test if a system is in thermodynamic equilibrium, when such system is isolated, if it cannot interact with its surroundings; however, its state can change as a consequence of spontaneous events occurring internally as its intensive properties, such as temperature and pressure, tend toward uniform values. When all such changes cease, the system is in equilibrium at the moment it was isolated .

23. More notes on actual and quasi-equilibrium processes There is no requirement that a system undergoing an actual process be in equilibrium during the process. Some or all of the intervening states may be non-equilibrium states. For many such processes we are limited to knowing the state before the process occurs and the state after the process is completed. However, even if the intervening states of the system are not known, it is often possible to evaluate certain overall effects that occur during the process. Processes are sometimes modeled as an idealized type of process called a quasi-equilibrium (or quasi-static) process. A quasi-equilibrium process is one in which the departure from thermodynamic equilibrium is at most infinitesimal. All states through which the system passes in a quasi-equilibrium process may be considered equilibrium states. Because non-equilibrium effects are inevitably present during actual processes, systems of engineering interest can at best approach, but never realize, a quasi-equilibrium process. The quasi-equilibrium process concept is instrumental in deducing relationships that exist among the properties of systems at equilibrium

24. LECTURE 2 THERMODYNAMICSQUANTITIES AND UNITS

25. PHYSICAL Quantities and their units IN THERMODYNAMICS When engineering calculations are performed, it is necessary to be concerned with the units of the physical quantities involved. A unit is any specified amount of a quantity by comparison with which any other quantity of the same kind is measured. For example, meters, centimeters, kilometers, feet, inches, and miles are all units of length. Seconds, minutes, and hours are alternative time units. Milligram, gram and kilograms are all units of mass. Because these physical quantities are related by definitions and laws, a relatively small number of physical quantities suffice to conceive of and measure all others. These may be called primary or fundamental dimensions. The others may be measured in terms of the primary dimensions and are called secondary or derived dimensions. The commonly used primary dimensions that suffice for applications in mechanics are mass, length, and time. Additional primary dimensions are required when additional physical phenomena come under consideration. Temperature is included for thermodynamics, and electric current is introduced for applications involving electricity. Once a set of primary dimensions is adopted, a base or fundamental unit for each primary dimension is specified. Units for all other quantities are then derived in terms of the base units

26. Système International d’Unités, (International System of Units, SI Units ) The system of units called SI, takes mass, length, and time as primary dimensions and regards force as secondary. SI is the abbreviation for Système International d’Unités (International System of Units), which is the legally accepted system in most countries. The conventions of the SI are published and controlled by an international treaty organization. The SI base unit for temperature is the kelvin, K. The SI base unit of mass is the kilogram, kg. It is equal to the mass of a particular cylinder of platinum–iridium alloy kept by the International Bureau of Weights and Measures near Paris. The mass standard for the United States is maintained by the National Institute of Standards and Technology. The kilogram is the only base unit still defined relative to a fabricated object. The SI base unit of length is the meter (metre), m, defined as the length of the path traveled by light in a vacuum during a specified time interval. The base unit of time is the second, s. The second is defined as the duration of 9,192,631,770 cycles of the radiation associated with a specified transition of the cesium atom. The SI unit of force, called the newton, is a secondary unit, defined in terms of the base units for mass, length, and time. Newton’s second law of motion states that the net force acting on a body is proportional to the product of the mass and the acceleration. The Newton is defined so that the proportionality constant in the expression is equal to unity. The Newton, N, is the force required to accelerate a mass of 1 kilogram at the rate of 1 meter per second per second.

27. SI units for other physical quantities are also derived in terms of the SI base units. Some of the derived units occur so frequently that they are given special names and symbols, such as the Newton. SI units for quantities pertinent to thermodynamics are given in Table below Since it is frequently necessary to work with extremely large or small values when using the SI unit system, a set of standard prefixes is provided in Table below for simplicity .

28. MEASURABLE PROPERTIES IN THERMODYNAMICS Three intensive properties that are particularly important in engineering thermodynamics are specific volume, pressure, and temperature. The specific volume v is defined as the reciprocal of the density, It is the volume per unit mass. Like density, specific volume is an intensive property and may vary from point to point. SI units for density and specific volume are kg/m3 and m3/kg, respectively. However, they are also often expressed, respectively, as g/cm3 and cm3/g. Pressure is defined as force per unit area. Pressure at the point is the same in all directions as long as the fluid is at rest. This is a consequence of the equilibrium of forces acting on an element of volume surrounding the point. However, the pressure can vary from point to point within a fluid at rest; examples are the variation of atmospheric pressure with elevation and the pressure variation with depth in oceans, lakes, and other bodies of water. The SI unit of pressure is pascal. However, in this text it is convenient to work with multiples of the pascal: the kPa, the bar, and the MPa.

29. Pressure as discussed above is called absolute pressure. Although absolute pressures must be used in thermodynamic relations, pressure-measuring devices often indicate the difference between the absolute pressure in a system and the absolute pressure of the atmosphere existing outside the measuring device. The magnitude of the difference is called a gage pressure or a vacuum pressure. The term gage pressure is applied when the pressure in the system is greater than the local atmospheric pressure. When the local atmospheric pressure is greater than the pressure in the system, the term vacuum pressure is used. The relationship among the various ways of expressing pressure measurements is shown in Fig. 1.5.

30. MEASURING TEMPERATURE Like force, a concept of temperature originates with our sense perceptions. It is rooted in the notion of the “hotness” or “coldness” of a body. We use our sense of touch to distinguish hot bodies from cold bodies and to arrange bodies in their order of “hotness,” deciding that 1 is hotter than 2, 2 hotter than 3, and so on. However sensitive the human body may be, we are unable to gauge this quality precisely. Accordingly, thermometers and temperature scales have been devised to measure it. Any body with at least one measurable property that changes as its temperature changes can be used as a thermometer. Such a property is called a thermometric property. The particular substance that exhibits changes in the thermometric property is known as a thermometric substance. A familiar device for temperature measurement is the liquid-in-glass thermometer (a) . The other include Infrared sensing ear thermometer( b) and thermocouple. A good thermometer should posses desirable characteristics of sensitivity, accuracy, reproducibility and fast response.

31. THE ZEROTH LAW OF THERMODYNAMICS The zeroth law of thermodynamics states that if two bodies are in thermal equilibrium with a third body, they are also in thermal equilibrium with each other. This serves as a basis for the validity of temperature measurement. By replacing the third body with a thermometer, the zeroth law can be restated as two bodies are in thermal equilibrium if both have the same temperature reading even if they are not in contact.This law was first formulated and labelled by R. H. Fowler in 1931. As the name suggests, its value as a fundamental physical principle was recognized more than half a century after the formulation of the first and the second laws of thermodynamics. It was named the zeroth law since it should have preceded the first and the second laws of thermodynamics.

32. Thermodynamic temperature scales The common temperature scales used in the SI and in the English system today are the Celsius scale (formerly called the centigrade scale; in 1948 it was renamed after the Swedish astronomer A. Celsius, 1702–1744, who devised it) and the Fahrenheit scale (named after the German instrument maker G. Fahrenheit, 1686–1736). In order to have a temperature scale that is independent of the properties of any substance or substances, a thermodynamic temperature scale in the SI called Kelvin scale, named after Lord Kelvin (1824–1907) was developed. The temperature unit on this scale is the Kelvin, which is designated by K (not °K; the degree symbol was officially dropped from Kelvin in 1967). The English system uses a thermodynamic temperature scale called Rankine scale, named after William Rankine (1820–1872). The temperature unit on this scale is the Rankine, which is designated by R.

33. Temperature and its scale A scale of temperature independent of the thermometric substance called a thermodynamic temperature scale. The Kelvin scale, a thermodynamic scale, can be elicited from the second law of thermodynamics . The Celsius temperature scale (also called the centigrade scale) uses the degree Celsius (°C), which has the same magnitude as the Kelvin.Thus, temperature Differences are identical on both scales. However, the zero point on the Celsius scale is shifted to 273.15 K, as shown in the relationship between the Celsius temperature and the Kelvin temperature: FAHRENHEIT SCALE KELVIN SCALE RANKINE SCALE

34. TIME FOR QUESTIONS QUESTION ?

35. LECTURE 3 FIRST LAW OF THERMODYNAMICS

36. THE FIRST LAW OF THERMODYNAMICS The first law of thermodynamics states that when a process undergoes a thermodynamics cycle, the net heat exchange between the system and its surrounding is equal to the net workdone between the system and its surroundings. This actually mean that when energy is exchanged between a system and its surroundings, the final total energy for the universe (system and its surroundings) equals the initial total energy for the universe (system and its surroundings). From the law, it could be concluded therefore that the energy for an isolated system remains constant. Robert Fludd in 1618, proposed a machine which violates this law and the machine is termed Perpetual motion machine of the first kind (PMM1) but this machine has never worked. While the fact that the machine never worked was no proof of the first law of thermodynamics (which was promulgated a little over two centuries later), this fact remains part of the evidence for accepting the law.A major corollary of the first law of thermodynamics is that a PMM1 is impossible.

37. HEAT Heat Closed systems can also interact with their surroundings in a way that cannot be categorized as work, as, for example, a gas (or liquid) contained in a closed vessel undergoing a process while in contact with a flame. The quantity denoted by Q accounts for the amount of energy transferred to a closed system during a process by means other than work. The quantities symbolized by W and Q account for transfers of energy. The terms work and heat denote different means whereby energy is transferred and not what is transferred. Work and heat are not properties, and it is improper to speak of work or heat “contained” in a system. However, to achieve economy of expression in subsequent discussions, W and Q are often referred to simply as work and heat transfer, respectively. Q > 0 heat transfer to the system Q< 0 heat transfer from the system

38. ENERGY AND WORK ENERGY Energy is a fundamental concept of thermodynamics and one of the most significant aspects of engineering analysis. Energy can be stored within systems in various macroscopic forms: kinetic energy, gravitational potential energy, and internal energy. Energy can also be transformed from one form to another and Transferred between systems. For closed systems, energy can be transferred by work and heat transfer. The total amount of energy is conserved in all transformations and transfers. A useful part of energy available in a system is called Exergy while the unuseful part is called Anergy. WORK In thermodynamics, the term work denotes a means for transferring energy. Work is an effect of one system on another that is identified and measured as follows: work is done by a system on its surroundings. Work done by a system is considered positive: W > 0. Work done on a system is considered negative: W < 0. The time rate of doing work, or power, is symbolized by and adheres to the same sign convention.

39. THE second LAW OF THERMODYNAMICS The Second law of thermodynamics was stated in two different statement for two entirely different situations but if one examined critically, they are fundamentally and logically equivalent statement of the same principle. Kelvin-Plank Statement: It is impossible to construct a device that will operate in a cycle and produces no effect other than raising of a weight and the exchange of heat between the device and a single reservoir. John Gamgee in the1880s, proposed an ammonia engine which violates the the Kelvin-Planck Statement and the machine is termed Perpetual motion machine of the second kind (PMM2) but no one has ever got the proposed machine by Gamgee to work. Indeed a major corollary of the Second law of thermodynamics is that a PMM2 is impossible. Clausius Statement: It is impossible to construct a device that will operate in a cycle and produces no effect other than transfer of heat from a low temperature body to a high temperature body. By intuition and experience, this machine is not possible.

40. THE third LAW OF THERMODYNAMICS The Third Law of thermodynamics states that the entropy of a pure substance approaches zero as the temperature of the substance approaches absolute zero temperature. This means that the entropy of a pure substance or perfect crystal is zero at absolute zero temperature. Non-crystalline substances have finite value of entropy at absolute zero temperature because of the level of randomness in their structure. Therefore, a perfect crystal has the maximum degree of order at that temperature. It should be noted that while the Third Law deals with entropy at absolute zero temperature, the Second Law deals with entropy as a property without any consideration given to the base values of this property and the First Law provides information on internal energy.