Elements of Mechanical Engineering PDF

Elements of Mechanical Engineering Prof. Dipesh Patel, Assistant Professor Mechanical Engineering Department  CHAPTER-1 Basic of Thermodynamics Prime mover Natural source of Energy to Mechanical work or useful work (shaft power) Mainly two types: 1. Thermal- Nuclear, Solar & G...

Elements of Mechanical Engineering Prof. Dipesh Patel, Assistant Professor Mechanical Engineering Department  CHAPTER-1 Basic of Thermodynamics Prime mover Natural source of Energy to Mechanical work or useful work (shaft power) Mainly two types: 1. Thermal- Nuclear, Solar & Geothermal Energy 2. Non Thermal- Hydro and Wind energy Examples of prime movers are: Wind turbine, steam turbine, water turbine etc. Source of energy Fuel Heat energy is produced when fuel is burnt. Amount of heat produced by burning of fuel depends upon calorific value of that fuel. Water Energy Water stored at high elevation contains potential energy. Example water stored in dam contains potential energy. Source of energy Atoms (Nuclear Energy ) Heat energy is produced by fission or fusion of atoms. This heat energy is converted into mechanical work by engines. Non-conventional Energy Sources Renewable energy sources include Hydro, solar and wind Energy Terms related to Thermodynamics Terms related to Thermodynamics Terms related to Thermodynamics Pressure: It is the force exerted by system per unit area. Pressure = Force/Area= N/m2 The SI unit of pressure is known as Pascal (Pa) or N/m2, 1 Pa = 1 N/m2 The SI unit of pressure is known as Pascal (Pa) or N/m2, 1 Pa = 1 N/m2  Terms related to Thermodynamics Atmospheric pressure: It is the pressure exerted by atmosphere. The atmospheric pressure varies from place to place. Std atmosphere ,Pressure =101325 Pa at Sea level. Barometer is used to measure atmospheric pressure. Image source : https://www.tes.com Terms related to Thermodynamics Terms related to Thermodynamics Absolute Pressure: = Atmospheric pressure + Gauge pressure Vacuum Pressure: It is define as pressure below atmospheric pressure. A perfect vacuum is obtained when absolute pressure is zero. Gauge Pressure : It is the pressure measured by a pressure gauge. Terms related to Thermodynamics Work: It is defined as force causing the movement of an object Work = Force x Distance moved into direction of force. Unit of work is N∙m or Joule (J) Power: it can be defined as the rate of work done. Power = work done/Time Unit of power is Joule/second is also called as Watt Terms related to Thermodynamics Terms related to Thermodynamics Temperature: The degree of intensity of heat present in a substance or object. SI unit of temperature is Kelvin. It is denoted by the symbol “K” Absolute zero temperature: It is the temperature at which the volume occupied by the gas becomes zero. This is the lowest temperature that can be measured by a gas thermometer Terms related to Thermodynamics Image source : www.google.com/search?q=heat+flow+direction Thermodynamics system A system is defined as a quantity of matter or a region in space chosen for study. Image source : https://www.hkdivedi.com Thermodynamics system Open system :The system in which the transfer of mass as well as energy can take place across its boundary. Closed system: The system in which the transfer of energy takes place across its boundary with the surrounding, but no transfer of mass takes place Image source : https://www.hkdivedi.com Thermodynamics system Isolated system : The system in which neither the transfer of mass nor that of energy can take place across its boundary with the surroundings is termed as an isolated system. Image source : https://www.hkdivedi.com Changes of State The various basics states of substance (Phases) are Solid, Liquid and Vapour. Image source : https://www.hkdivedi.com Definition of Internal Energy and Enthalpy Internal energy: When heat energy is supplied to a body it cannot be totally converted in to work. Mathematically, Q = U + W, where Q is amount of heat, W is work and U is internal energy. Enthalpy: It is a property of thermodynamic system, which is equal to the system's internal energy plus the product of its pressure and volume It is represented by the symbol H. Thermodynamic property Intensive Property: Mass of the system does not have any effect on Intensive property. Examples of Intensive property includes Pressure, Temperature, Density, etc. Extensive Property: Mass of the system effects Extensive property. Examples of Extensive property includes Mass, Volume, Total energy, Enthalpy etc.  Zeroth law of Thermodynamics The two bodies A and B are in thermal equilibrium with a third body C individually then the two bodies A and B shall also be in thermal equilibrium with each other. Image source : https://blog.myrank.co.in  First law of Thermodynamics Energy can neither be created nor destroyed, it can be converted from one form to another and total energy remains same” Change in total Energy = Net energy transferred as heat and work Δ E = Q-W, Where Δ E is summation of various energies like IE,KE & PE Therefore, Δ E = Δ U + Δ KE + Δ PE +......... Now, since in a closed system mass is fixed and there is no elevation and movement, therefore, Δ KE = 0 and Δ PE = 0 , Δ E = Δ U  Second law of Thermodynamics It states that the processes which involves the conversion of heat energy are irreversible. Kelvin‐Planck Statement: It is not possible for any device that operates on a cycle to receive heat from a single reservoir and generate a net amount of work. In other words, thermal efficiency of 100% is not possible in any heat engine. Image source: https://docplayer.com  Second law of Thermodynamics Clausius Statement: It is impossible to construct a device that operates in a cycle and produces no effect other than the transfer of heat from a lower‐temperature body to higher temperature body. In other words, a refrigerator will not operate unless its compressor is driven by an external power source. Image source: https://docplayer.com  References:  Books:  Elements of Mechanical Engineering S.B.Mathur, S. Domkundwar; Dhanpat Rai & Sons Publications.  Basic Mechanical Engineering T. S. Rajan; Wiley Eastern Ltd.  Fundamental of Mechanical Engineering G. S. Sawhney; PHI Publication New Delhi.  Elements of Mechanical Engineering Sadhu Singh; S. Chand Publisher.  Basic Mechanical Engineering P. K. Nag, Kartikeya Tripathi C. B. Pawar Tata McGraw-Hill Education  Basic Mechanical Engineering. Shanmugam_ S. Ravindran - -McGraw-Hill Education  Basic Mechanical Engineering-Pearson Education (2018) , Pravin Kumar  Elements of Mechanical Engineering- P.S.Desai, S.B. Soni; Atul Prakashan References:  Video Links  https://www.youtube.com/watch?v=JK9sENnK_Bk (Thermodynamic system)  https://www.youtube.com/watch?v=IqV5L66EP2E (Kinetic and Potential Energy)  https://www.youtube.com/watch?v=CMUmQRgJAo0 (Phase change and phase change) www.paruluniversity.ac.in