Slide 1Slide 2INTRODUCTIONFORMS OF ENERGYSlide 5Slide 6Slide 7Some Physical Insight to Internal EnergySlide 9More on Nuclear EnergyMechanical EnergySlide 12Slide 13ENERGY TRANSFER BY HEATSlide 15Historical Background on HeatENERGY TRANSFER BY WORKSlide 18Electrical WorkMECHANICAL FORMS OF WORKShaft WorkSpring WorkWork Done on Elastic Solid BarsWork Done to Raise or to Accelerate a BodyTHE FIRST LAW OF THERMODYNAMICSSlide 26Slide 27Energy BalanceEnergy Change of a System, EsystemMechanisms of Energy Transfer, Ein and EoutSlide 31ENERGY CONVERSION EFFICIENCIESSlide 33Slide 34Slide 35Slide 36Slide 37Efficiencies of Mechanical and Electrical DevicesSlide 39ENERGY AND ENVIRONMENTSlide 41Ozone and SmogSlide 43Acid RainSlide 45The Greenhouse Effect: Global Warming and Climate ChangeSlide 47Slide 48SummaryCHAPTER 2 ENERGY, ENERGY TRANSFER, AND GENERAL ENERGY ANALYSISLecture slides byMehmet KanogluCopyright © The McGraw-Hill Education. Permission required for reproduction or display.Thermodynamics: An Engineering Approach 8th EditionYunus A. Çengel, Michael A. BolesMcGraw-Hill, 20152Objectives•Introduce the concept of energy and define its various forms.•Discuss the nature of internal energy.•Define the concept of heat and the terminology associated with energy transfer by heat.•Discuss the three mechanisms of heat transfer: conduction, convection, and radiation.•Define the concept of work, including electrical work and several forms of mechanical work. •Introduce the first law of thermodynamics, energy balances, and mechanisms of energy transfer to or from a system. •Determine that a fluid flowing across a control surface of a control volume carries energy across the control surface in addition to any energy transfer across the control surface that may be in the form of heat and/or work.•Define energy conversion efficiencies. •Discuss the implications of energy conversion on the environment.3INTRODUCTION•If we take the entire room—including the air and the refrigerator (or fan)—as the system, which is an adiabatic closed system since the room is well-sealed and well-insulated, the only energy interaction involved is the electrical energy crossing the system boundary and entering the room. •As a result of the conversion of electric energy consumed by the device to heat, the room temperature will rise.A refrigerator operating with its door open in a well-sealed and well-insulated roomA fan running in a well-sealed and well-insulated room will raise the temperature of air in the room.4FORMS OF ENERGY•Energy can exist in numerous forms such as thermal, mechanical, kinetic, potential, electric, magnetic, chemical, and nuclear, and their sum constitutes the total energy, E of a system. •Thermodynamics deals only with the change of the total energy. •Macroscopic forms of energy: Those a system possesses as a whole with respect to some outside reference frame, such as kinetic and potential energies.•Microscopic forms of energy: Those related to the molecular structure of a system and the degree of the molecular activity.•Internal energy, U: The sum of all the microscopic forms of energy.•Kinetic energy, KE: The energy that a system possesses as a result of its motion relative to some reference frame.•Potential energy, PE: The energy that a system possesses as a result of its elevation in a gravitational field.56Total energy of a systemEnergy of a system per unit massPotential energy per unit massKinetic energy per unit massPotential energyTotal energy per unit massKinetic energyMass flow rateEnergy flow rate78Some Physical Insight to Internal EnergySensible energy: The portion of the internal energy of a system associated with the kinetic energies of the molecules.Latent energy: The internal energy associated with the phase of a system.Chemical energy: The internal energy associated with the atomic bonds in a molecule.Nuclear energy: The tremendous amount of energy associated with the strong bonds within the nucleus of the atom itself.Internal = Sensible + Latent + Chemical + NuclearThermal = Sensible + Latent9•The total energy of a system, can be contained or stored in a system, and thus can be viewed as the static forms of energy. •The forms of energy not stored in a system can be viewed as the dynamic forms of energy or as energy interactions.•The dynamic forms of energy are recognized at the system boundary as they cross it, and they represent the energy gained or lost by a system during a process. •The only two forms of energy interactions associated with a closed system are heat transfer and work. •The difference between heat transfer and work: An energy interaction is heat transfer if its driving force is a temperature difference. Otherwise it is work.10More on Nuclear Energy•The best known fission reaction involves the split of the uranium atom (the U-235 isotope) into other elements and is commonly used to generate electricity in nuclear power plants (440 of them in 2004, generating 363,000 MW worldwide), to power nuclear submarines and aircraft carriers, and even to power spacecraft as well as building nuclear bombs.•Nuclear energy by fusion is released when two small nuclei combine into a larger one.•The uncontrolled fusion reaction was achieved in the early 1950s, but all the efforts since then to achieve controlled fusion by massive lasers, powerful magnetic fields, and electric currents to generate power have failed.11Mechanical EnergyMechanical energy: The form of energy that can be converted to mechanical work completely and directly by an ideal mechanical device such as an ideal turbine. Kinetic and potential energies: The familiar forms of mechanical energy.Mechanical energy of a flowing fluid per unit massRate of mechanical energy of a flowing fluidMechanical energy change of a fluid during incompressible flow per unit massRate of mechanical energy change of a fluid during incompressible flow121314ENERGY TRANSFER BY HEATHeat: The form of energy that is transferred between two systems (or a system and its surroundings) by virtue of a temperature difference.15Heat transfer per unit massAmount of heat transfer when heat transfer rate changes with timeAmount of heat transfer when heat transfer rate is constant16Historical Background on Heat•Kinetic theory: Treats molecules as tiny balls that are in motion and thus possess kinetic energy. •Heat: The energy associated with the random motion of atoms and