Presentation on theme: "Analysis of First Law of Thermodynamics P M V Subbarao Professor Mechanical Engineering Department A Law of sizing for thermodynamic Equipment….."— Presentation transcript:
Analysis of First Law of Thermodynamics P M V Subbarao Professor Mechanical Engineering Department A Law of sizing for thermodynamic Equipment…..
The First Law of Thermodynamics Cyclic Integral of Heat Cyclic Integral of Work If a control mass undergoes a cyclic process, the cyclic integral of the heat is proportional to the cyclic integral of work.
Need for Analysis of First Law of Thermodynamics Thermoelectric phenomenon discovered by Thomas Seebeck in 1821.
Need for Analysis of First Law of Thermodynamics Nicolaus Ottowas's first occupation was as a traveling salesman selling tea, coffee, and sugar. He soon developed an interest in the new technologies of the day and began experimenting with building four-stroke engines. After meeting Eugen Langen, a technician and owner of a sugar factory, Otto quit his job, and in 1864, the duo started the world's first engine manufacturing company N.A. Otto & Cie (now DEUTZ AG, Köln). In 1867, the pair were awarded a Gold Medal at the Paris World Exhibition for their atmospheric gas engine built a year earlier.
Displacement Work Devices : Spark Ignition Engine A I R Intake Stroke FUEL Ignition Power Stroke Fuel/Air Mixture Compression Stroke Combustion Products Exhaust Stroke Otto was also thinking of developing a cyclic device
Displacement Work Devices : Spark Ignition Engine A I R Intake Stroke FUEL Ignition Power Stroke Fuel/Air Mixture Compression Stroke Combustion Products Exhaust Stroke
Air TC BC Q in Q out Compression Process Const volume heat addition Process Expansion Process Const volume heat rejection Process Otto Cycle Active Part of the Innovation
SI Engine for Propulsion
Analysis of Cycles using First Law
Relating a cycle to Processes
Comparison of Two Cycles
An Universal Characteristic : Independent of Path
Any variable, which is independent of path (process) during a change of state is called as a property. Let this variable be E. E is having units of heat or work and is called as total energy of the system.
First law for a Control Mass during a Process The change in energy of a system during a change of state is numerically equal to the algebraic sum of heat transfer during the process and the work transfer during the process. Remarks: 1.Only change of energy has been defined. 2.Zero Energy has to be expressed with respect to some arbitrary reference! 3.Q and W must be measured in same units.
Further Remarks on Definition of Energy The Energy of a system at any state A is: E a = E ref + E. How to Define zero energy state? One popular definition: Stagnant Liquid at triple point at sea level will have zero energy. Energy is an extensive property. The energy of a system of unit mass is called as specific energy. Specific energy is an intensive property.
Members of the Family of Energy FORMS OF ENERGY All forms of energy fall under two categories Microscopic or Macroscopic and/or Potential Energy or Kinetic Energy. Potential energy is stored energy and the energy by the virtue of state or position. Macro Potential Energy : Gravitational Energy or Strain energy. Micro Potential Energy : Chemical energy and Nuclear energy. Kinetic energy is due to motion (Motive Energy) - the motion of waves, electrons, atoms, molecules and system.
Potential Energy CHEMICAL ENERGY : Chemical energy is the energy stored in the bonds of atoms and molecules. Biomass, petroleum, natural gas, propane and coal are examples of stored chemical energy. NUCLEAR ENERGY : Nuclear energy is the energy stored in the nucleus of an atom - the energy that holds the nucleus together. The energy of nucleus of a uranium and Thorium atoms is an example of nuclear energy. STORED MECHANICAL ENERGY : Stored mechanical energy is energy stored in objects by the application of a force. Compressed springs and stretched rubber bands are examples of stored mechanical energy. GRAVITATIONAL ENERGY : Gravitational energy is the energy of place or position. Water in a reservoir behind a hydropower dam is an example of gravitational potential energy.
Kinetic Energy RADIANT ENERGY : Radiant energy is electromagnetic energy that travels in transverse waves. Radiant energy includes visible light, x-rays, gamma rays and radio waves. Solar energy is an example of radiant energy. THERMAL ENERGY : Thermal energy is the internal energy in substances - the vibration and movement of atoms and molecules within substances. Geothermal energy is an example of thermal energy. MOTION :The movement of objects or substances from one place to another is motion. Wind and hydropower are examples of motion. SOUND : Sound is the movement of energy through substances in longitudinal (compression/rarefaction) waves. ELECTRICAL ENERGY: Electrical energy is the movement of electrons. Lightning and electricity are examples of electrical energy.
Change in Energy During A Process : Control Mass Q - W depends only on the initial and final states and not on the path followed between the two states. Therefore it is the differential of a property of the system. This property is the energy of the mass and is given the symbol E. Thus E = Micro Kinetic energy + Micro potential energy +Macro kinetic energy + Macro potential energy + ….. E = Internal energy +Macro kinetic energy + Macro potential energy + …..
The first law of thermodynamics for a CM during an infinitesimal process
A Simple Process to Increase Macroscopic Kinetic Energy
Can we use Heat Action to Increase Kinetic Energy of A System? Should it be a control mass or Control volume or either of the two?
WINDS WIND ENERGY CLOUDS HYDRO ENERGY VEGETATION CHEMICAL ENERGY OCEAN THERMAL ENERGY SOLAR RADIATION THERMAL WAVE VELOCITY RAINS CO 2 + H 2 O PHTOSYNTHESIS SOLAR ENERGY INCOMING RESOURCE FOSSIL FUEL COAL PETROLEUM NATURAL GAS FOSSILIZATION SUN
The Sun provides 175 million million watts of energy to the Earth’s atmosphere each hour. Of this, approximately 1-2% is converted to wind energy.
Global Wind Patterns
A Process to Utilize Macroscopic Potential Energy