1. Prof. Sunil D. Bagade 1PROF. SUNIL BAGADE

2. Thermodynamics  Engineering is nothing but a problem solving tools based on the knowledge of science and mathematics  Thermodynamics is science which deals with energy and its transformations  It is the science of the relations between heat, Work and the properties of the systems  The word thermodynamics comes from two Greek words thermo (heat) and dynamics (work) 2PROF. SUNIL BAGADE

3. Examples of energy transformations were the study of thermodynamics is useful  Thermal energy producing systems like boilers, heat exchangers etc  Power producing devices like Internal combustion engines, steam turbine, gas turbine etc  Power absorbing devices like compressors, pumps etc The science of thermodynamics is based on four laws known as zeroth, first, second and third law of thermodynamics This law based on observations and does not have mathematical proof 3PROF. SUNIL BAGADE

4. Classical thermodynamics and Statistical thermodynamics  Classical thermodynamics uses macroscopic approach while statistical thermodynamics uses microscopic approach for analysis  In statistical thermodynamics the average behavior of large groups of individual molecules is considered  Classical thermodynamics approach does not require knowledge of behavior of individual molecules  In our study we use classical thermodynamics approach which is direct and easy way to the solution 4PROF. SUNIL BAGADE

5. Thermodynamic System  A thermodynamic system is defined as quality of matter or region in space chosen for thermodynamic study  The thermodynamic system is analogous to the free body diagram to which we apply the laws of mechanics, (i.e. Newton’s Laws of Motion)  The system is a macroscopically identifiable collection of matter on which we focus our attention(e.g.: the water kettle or the aircraft engine) 5PROF. SUNIL BAGADE

6.  The mass or region outside the thermodynamic system is called as surroundings  The real or imaginary surface that separates the system from its surroundings is called the system boundary, It can be fixed or movable  The system and surrounding together is called as universe Universe = System + Surroundings 6PROF. SUNIL BAGADE

7. Classification of Thermodynamics Systems  Closed System - It is defined as the system with fixed mass and where only energy crosses system boundary  It is also known as control mass  We do permit heat and work to enter or leave but not mass 7PROF. SUNIL BAGADE

8. Open System  It is defined as the system in which not only mass but also energy crosses system boundary PROF. SUNIL BAGADE8

9.  It is also known as control Volume  A surface that confines the control volume is called control surface  Control surface is nothing but system boundary  Most of the engineering devices are open system (examples - water heater, car radiator, turbine, compressor, and boiler) PROF. SUNIL BAGADE9

10. Isolated System  It is defined as a neither system where neither mass nor energy crosses its boundaries  An universe can be considered to be an isolated system  Thermos Flask can be considered to be an isolated system PROF. SUNIL BAGADE10

11. Choice of the System and Boundaries Are at Our Convenience  We must choose the system for each and every problem we work on, so as to obtain best possible information on how it behaves  In some cases the choice of the system will be obvious and in some cases not so obvious  Important: you must be clear in defining what constitutes your system and make that choice explicit to anyone else who may be reviewing your work (e.g.: In the exam paper or to your supervisor in the work place later) PROF. SUNIL BAGADE11

12.  The boundaries may be real physical surfaces or they may be imaginary for the convenience of analysis  e.g.: If the air in this room is the system, the floor, ceiling and walls constitutes real boundaries  The plane at the open doorway constitutes an imaginary boundary PROF. SUNIL BAGADE12

13. Units and Dimensions  The fundamental dimensions are the time, length, mass and force  A unit is standard by which a dimensions is to be measured  S. I. system is used PROF. SUNIL BAGADE13

14. Time  The fundamental unit of time is second (s)  It is defined as 1/886400 part of mean solar day PROF. SUNIL BAGADE14

15. Length  The fundamental unit of length is meter (m)  It is distance between two marks on a platinum-Iridium rod at 0 0 C, kept in a vault at International Bureau of weights and measures at Sevres, France PROF. SUNIL BAGADE15

16. Mass  The fundamental unit of mass is the kilogram (kg)  It is defined as the mass of lump of platinum iridium also kept at International Bureau of weights and measures at Sevres, France PROF. SUNIL BAGADE16

17. Force  The fundamental unit of force is Newton (N)  It is defined by Newtons second law, force is directly proportional to the product of mass and acceleration F  m. a F = 1/g c m. a  Where F = force, m= mass, a= acceleration, g c = proportionality constant  In S I units g c = 1  Thus F = m. a PROF. SUNIL BAGADE17

18. Weight  Weight of body is the force exerted on its mass due to gravity  The mass of body remains constant but value of weight is changing from place to place due to different gravitational force F = m. g  Where g= gravitational acceleration  Unit of weight is N PROF. SUNIL BAGADE18

19. Density (  )  The density of a system is ratio of mass to the volume  Unit of density is kg/m 3 PROF. SUNIL BAGADE19

20. Specific Weight (w)  It is the weight per unit volume  Unit of specific weight is N/m 3 PROF. SUNIL BAGADE20

21. Specific Volume (v)  It is the volume per unit mass  Unit of specific volume is m 3 /kg PROF. SUNIL BAGADE21

22. Specific Gravity  Specific gravity of a substance is defined as the ratio of density of substance to the density of standard substance PROF. SUNIL BAGADE22

23. Pressure (p)  It is defined as force exerted normal to the unit area  Atmospheric pressure - pressure exerted by atm. air  Gauge pressure – pressure measured by gauge such as Burdon pressure gauge or manometers (greater than atm. pressure)  Vacuum pressure - pressure measured by vacuum gauge (less than atm. pressure) PROF. SUNIL BAGADE23

24.  Absolute pressure – The pressure measured from absolute zero level pressure is called as absolute pressure OR PROF. SUNIL BAGADE24

25. Properties of a system  Any measurable characteristic of a system is called a property  Some familiar properties include mass, volume, pressure, temperature, density etc PROF. SUNIL BAGADE25

26. Classification of Properties  Intensive properties-Properties which are independent of mass of the system like temperature, pressure and density are called intensive properties  Extensive Properties-Properties which depend on the size or extend of the system like total mass, total volume etc are called extensive properties  If mass is increased, the value of extensive property also increases (upper case letters as the symbols)  Extensive properties per unit mass are specific properties.Example Specific volume(volume per unit mass)  Specific properties are intensive properties PROF. SUNIL BAGADE26

27.  The number of properties necessary to define a system depends upon the complexity of the system  If system is in equilibrium state requires only two properties for defining  But if system contains more than one phase requires more than two properties for defining  The minimum properties required to describe the system are called independent properties whereas the rest of other properties are dependent properties PROF. SUNIL BAGADE27

28.  Some of the system properties cam be measured in reference to some other defined state, called datum state  This datum can be arbitrarily defined or can be fixed by third law of thermodynamics but it can also be fixed anywhere depending upon our convenience  The such properties involve relationship between the system and surroundings and are called extrinsic properties (like enthalpy, entropy, kinetic energy, potential energy, internal energy etc)  On the other hand there are other properties like pressure, temperature, volume etc arise from particular characteristics of mass within system boundaries and are called intrinsic properties PROF. SUNIL BAGADE28

29. Thermodynamic State  It is the condition of a system as defined by the values of all its properties OR  Thermodynamic State is defined as a condition of a system described by properties  It gives a complete description of the system  Any operation in which one or more properties of a system change is called a change of state PROF. SUNIL BAGADE29

30.  For example a system can be said to be in a state 1 if its properties are pressure P 1, Temperature T 1 and Volume V 1. Similarly a system will be at state 2 with properties P 2, T2 and V 2 PROF. SUNIL BAGADE30

31. Phase  It is a quantity of mass that is homogeneous throughout in chemical composition and physical structure  e.g. solid, liquid, vapour, gas  Phase consisting of more than one phase is known as heterogeneous system.  e.g. mixture of oil and water PROF. SUNIL BAGADE31

32. Thermodynamic Equilibrium  A system is in thermodynamic equilibrium if there are no unbalanced potentials or driving potentials within the system or between system and surroundings  Equilibrium generally requires all properties to be uniform throughout the system  The system reaches in thermodynamic equilibrium when mechanical, thermal and chemical equilibrium is achieved. Properties of system are same in thermodynamic equilibrium PROF. SUNIL BAGADE32

33. Thermal Equilibrium  A system is in thermal equilibrium if the temperature is same throughout the system  In thermal equilibrium there is no temperature difference throughout the system PROF. SUNIL BAGADE33

34. Mechanical Equilibrium  A system is in mechanical equilibrium if the pressure is same throughout the system  In mechanical equilibrium there is no pressure difference throughout the system PROF. SUNIL BAGADE34

35. Chemical Equilibrium  A system is in chemical equilibrium if its chemical composition is same throughout the system  In chemical equilibrium no chemical reactions occur throughout the system PROF. SUNIL BAGADE35

36. Electrical Equilibrium  A system is said to be in state of electrical equilibrium if there exists an uniformity of electrical potential throughout the system PROF. SUNIL BAGADE36

37.  Between the system and surroundings, if there is no difference in  Thermodynamic equilibrium implies all those together  A system in thermodynamic equilibrium does not deliver anything PROF. SUNIL BAGADE37

38. Path and Process  Any change that a system undergoes from one equilibrium state to another is called a thermodynamic process  The series of states through which a system passes during a process is known as process path of the process PROF. SUNIL BAGADE38

39. Types of Processes  As a matter of rule we allow one of the properties to remain a constant during a process  Construe as many processes as we can (with a different property kept constant during each of them) -Isothermal (T) -Isobaric (p) -Isochoric(v) -Isentropic(s) -Isenthalpic(h) -Adiabatic (no heat addition or removal PROF. SUNIL BAGADE39

40. Quasi-static Processes  A process during which the system remains infinitesimally close to an equilibrium state at all times, it is called a quasi-static, or quasi-equilibrium, process PROF. SUNIL BAGADE40

41.  A quasi-static process is one in which The deviation from thermodynamic equilibrium is Infinitesimal All states of the system passes through are equilibrium states If we remove the weights slowly one by one the pressure of the gas will displace the piston gradually. It is quasi-static On the other hand if we remove all the weights at once the piston will be kicked up by the gas pressure.(This is unrestrained expansion) but we don’t consider that the work is done - because it is not in a sustained manner In both cases the systems have undergone a change of state Another eg: if a person climbs down a ladder from roof to ground, it is a quasistatic process. On the other hand if he jumps then it is not a quasistatic process PROF. SUNIL BAGADE41

42. Flow and Non-flow process  Flow processes happen in open or flow systems while non-flow processes occur in closed systems Non-FlowFlow PROF. SUNIL BAGADE42

43. Steady Flow Process  A flow process can be steady flow process if during a process, properties of system does not change with time  A large number of engineering devices operate for long periods of time under the same conditions, and they are classified as steady-flow devices PROF. SUNIL BAGADE43

44. Reversible Process  A process is reversible if the system passes through a continuous series of equilibrium states  A process is called reversible process if the initial state together with all energies transferred during process can be completely restored in both system and surroundings PROF. SUNIL BAGADE44

45. Irreversible Process  A process is irreversible if a system passes through a sequence of non- equilibrium states  It will not restore the original state PROF. SUNIL BAGADE45 1

46. Thermodynamic cycle  A system is said to have undergone a thermodynamic cycle if it returns to its initial state at the end of the processes  This means the initial state and final state in a thermodynamic cycle are same PROF. SUNIL BAGADE46

47. Temperature  Temperature is a measure of “hotness” or “coldness”  It can be sensed and with words like freezing cold, cold, warm, hot, and red-hot  However, we cannot assign numerical values to temperatures based on our sensations alone  Furthermore, our senses may be misleading  A metal chair, for example, will feel much colder than a wooden one even when both are at the same temperature  So temperature scale is necessary  The zeroth law of thermodynamics forms the basis of temperature measurement PROF. SUNIL BAGADE47

48. 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  The temperature measurement is done 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 PROF. SUNIL BAGADE48

49.  If A is thermal equilibrium with B, and B is in thermal equilibrium with C then A and C are in thermal equilibrium with each other PROF. SUNIL BAGADE49

50. Explanation of Zeroth Law  Let us say T A, T B and T C are the temperatures of A,B and C respectively  A and C are in thermal equilibrium T A = T C  B and C are in thermal equilibrium T B = T C  Consequence of ‘0’th law A and B will also be in thermal equilibrium T A = T B Looks very logical All temperature measurements are based on this LAW. PROF. SUNIL BAGADE50