THERMODYNAMICS MODULE 1 Introduction Thermodynamics is a branch of physics that deals with the laws governing the energy and work of a system, which may be described as the exchange of heat energy to and from other forms of energy within a given system. • Careful study of these concept is essential for good understanding of topics in thermodynamics. • specifically, it defines macroscopic variables, such as internal energy, entropy, and pressure. History The history of thermodynamics as a scientific discipline generally begins with Otto von Guericke who, in 1650, built and designed the world's first vacuum pump and demonstrated a vacuum using his Magdeburg hemispheres. Magdeburg hemispheres Shortly after, the physicist and chemist Robert Boyle had learned of Guericke's designs and, in coordination with the scientist Robert Hooke, built an air pump in 1656. Using this pump, Boyle and Hooke noticed a correlation between pressure, tempe rature, and volume. In time, they formulated Boyle's Law. Based on these concepts, an associate of Boyle's named Denis Papin built a steam digester, which was a closed vessel with a tightly fitting lid that confined steam until a high pressure was generated. The first thermodynamic textbook was written in 1859 by William Rankine. The first and second laws of thermodynamics emerged simultaneously in the 1850s, primarily out of the works of William Rankine, Rudolf Clausius, and William Thomson (Lord Kelvin). Etymology The components of the word thermo- dynamic are derived from the Greek words therme meaning "heat," and dynamics meaning “power”. The term thermo-dynamic was first used in January 1849 by William Thomson, later Lord Kelvin, in the phrase a perfect thermo-dynamic engine to describe Sadi Carnot's heat engine. In April 1849, Thomson added an appendix to his paper and used the term thermodynamic in the phrase the object of a thermodynamic engine. Definition It can be define as the study of energy, energy transformations and its relation to matter. The analysis of thermal systems is achieved through the application of the governing conservation equations, namely Conservation of Mass, Conservation of Energy. In other words, it’s science which deals with the energies possesed by gases and vapours, that includes the conservation of these energies in terms of heat and mechanical work and their relation with properties of system. CHAPTER 1: FUNDAMENTALS OF POWER PLANT ENGINEERING PART 1A: THERMODYNAMICS THERMODYNAMICS is a branch of physical sciences that treats especially phenomena of energy and the related properties of matter, especially of the laws of transformation of heat into other forms of energy and vice-versa. TEMPERATURE AND PRESSURE TEMPERATURE is an indication or degree of hotness and coldness and therefore a measure of intensity of heat. THE SIX TEMPERATURE SCALES 1. Celsius or Centigrade 2. Fahrenheit 3. Kelvin 4. Rankine 5. Reamur 6. Ligem ABSOLUTE TEMPERATURE – is the temperature measured from absolute zero. ABSOLUTE ZERO – Is the temperature at which the molecules stop moving. RELATION BETWEEN TEMPERATURE SCALES: where: R = Rankine (absolute temp. scale; English) K = Kelvin (absolute temp scale; SI) TEMPERATURE INTERVAL – is the difference between two temperature readings from the same scale, and the change in temperature through which the body is heated. T – absolute temperature t - normal temperature THE TEMPEARATURE INTERVAL/CHANGE: NOTE: 1 degree Celsius = 9/5 degree Fahrenheit and degree is to be written after the scale to indicate that it is temperature change. ISOLATED SYSTEM – is a system in which neither mass nor energy cross the boundaries and it is not influenced by the surroundings. (heat and mass is not include) INTENSIVE PROPERTY – size independent EXTENSIVE PROPERTY – size does matter (example: mass, volume, total energy) NONFLOW PROCESS – is a process that takes place in a closed system. EXAMPLE: Compressor STEADY FLOW PROCESS – is a process that takes place in an open system in which the quantity of matter within the system is constant. EXAMPLE: Turbine NON-FLOW WORK – is the work in a non-flow process THE ABSOLUTE PRESSURE AND GAGE PRESSURE: Absolute pressure – is the true pressure measured above a perfect vacuum. Gage Pressure – is the pressure measured from the level of atmospheric pressure by most pressure recording instrument like pressure gage and open-ended manometer. Atmospheric Pressure – is the pressure obtained from barometric reading. where: STEADY FLOW WORK – is the work in a steady flow process. where: P = pressure V = volume LAW OF CONVERSATION OF MASS NOTE: THERMODYNAMIC SYSTEM AND SURROUNDINGS: SYSTEM – is the term given to the collection of matter under consideration enclosed within a boundary SURROUNDING – is the region outside the boundary or the space and matter external to a system. CLOSED SYSTEM – is a system in which there is no transfer of matter across the boundary. (control mass, have only heat enter) OPEN SYSTEM – is a system in which there is a flow of matter through the boundary. (control volume, have mass and hear) STEADY FLOW SYSTEM HEAT and ENTROPY: HEAT – is a form of energy associated with the kinetic random motion of large number of molecules. Sensible heat – is the heat needed to change the temperature of the body without changing its phase. Latent Heat – is the heat needed by the body to change its phase without changing its temperature Latent Heat of Fusion – solid to fusion Latent Heat of Vaporization – liquid to gas ENTROPY – is the measure of the randomness of the molecules of a substance ENTHALPY AND INTERNAL ENERGY ENTHALPY – is the heat energy transferred to a substance at a constant pressure process. INTERNAL ENERGY – is the energy stored within the body. It is the sum of the kinetic energies of all its constituent plus the sum of all the potential energies of interaction among these particles. FIRST LAW OF THERMODYNAMICS Heat is a form of energy, and as what all other forms of energy is subject to, it follows the law of conservation of energy. It means “Heat energy also cannot be created nor destroyed and can only be transferred to one form or another” APPLICATION OF THIS LAW: The disco, a type of rock but in scientists this rock contains an energy that produce heat energy when it undergoes a complete combustion. Actually, some power plant utilizes this coal to generate electrical energy for what we called as electricity . They feed this coal into a boiler furnace and with an assistance of oxygen and a little heat this creates a combustion in a form of heat of energy. The heat energy will transfer its energy to water above it making it into a steam. The steam will rotate a turbine and that’s a mechanical energy. This turbine will detect a generator which converts that energy into electrical energy. SECOND LAW OF THERMODYNAMICS The major of second law: Clausius Statement - it is impossible for any system in such a way that the sole result would be and energy transfer by heat from a cooler to a hotter body. Kelvin-Planck Statement - it is impossible for any system to operate in a thermodynamic cycle and deliver a net amount of energy by work to its surroundings while receiving energy by heat transfer from a single reservoir. Entropy Statement - it is impossible for any system to operate in a way that entropy is destroyed To make it easy we make two easier statement: High to Low For any process a natural flow will always be from higher energy value to lower energy value Example: Coffee, the temperature of coffee is higher than its cup and as what it says higher energy value. The temperature of coffee transferred to the cup which is cooler lower energy value. That is why, the cup gets hotter. Compressed gas in a balloon, if you open a small hole in a balloon that is the outside air enters the balloon no instead the gas in the balloon goes outside transfers its pressure to the outside air because the gas in balloon has higher pressure than the outside air a tank of water connected to an empty tank with valve in the middle. When open the valve, it happens that the tank level is lowered transferring its level to the empty tank. Topic being discussed in the classroom, that transfer of ideas comes from the professor which has more ideas to its students which is lower ideas. Salary from employer to employee. Perfect is Impossible For every real world process there will always be losses. Example: It means you cannot convert all of your car’s fuel into mechanical energy which can rotate your car’s wheels proof is the gases you see on the car muffler. Try bouncing a ball by first throwing it up to the air see that as the number of buttons increases the level of bounce decreases because of the loss of energy which is transferred to the ground. Our foods that is our source of energy. We can see the losses through our sweat urine and solid waste. THIRD LAW OF THERMODYNAMICS “as temperature approaches absolute zero, the entropy of a system approaches a constant minimum” ENTROPY measure of disorder and randomness of a system Example: Bottle of carbonated drink, when you share it you will see bubbles forming at the top surface and when you open it, the bottle of coke explodes and forms a lot of bubbles. That is entropy. The bottle coke at rest have a very low entropy, but the moment you share it, you have introduce kinetic energy in the molecules inside the bottle, increasing the disorder and randomness of the molecules. “When a pure crystal is cooled approaching absolute zero. It becomes highly organized/entropy approaches to zero.” - it means that any substance with temperature greater than absolute zero must have positive amount of entropy. It indicates that a material or substance requires certain amount of energy to raise their temperature this is called SPECIFIC HEAT CAPACITY. The energy requirement of one kilogram substance to raise its temperature by one Kelvin. Example: It will take more time to warm a wooden glass than an aluminum glass because aluminum is a better conductor than wood. Find how much energy is required? If A is thermo equilibrium to B, A is also thermo equilibrium in another body of C, thus B is thermo equilibrium to C. A=B=C. Bodes reaching thermal equilibrium means that there is already no heat transfer. Because these bodies have same amount of heat. Example FUN FACTS: Did you know that researchers discovered an object which eventually reached a point where it can’t get any colder this is PIN ICE. In which its atomic magnetic moments remain random on its absolute zero. This makes it hold properties that most things than such as magnetic balls. ZEROTH LAW OF THERMODYNAMICS “If two thermodynamic systems are each in thermal equilibrium with a third, then they are in thermal equilibrium with each other. You place a fresh meat in refrigerator, the next morning you assume that meat already reached the thermal equilibrium with the refrigerator because basically heat will flow if is exposed in unbalanced system. Measure the temperature of room, you got 27 degree Celsius, according to zero law of thermodynamics you can assume that your room and the other things in your room have the same temperature of 27 degree Celsius. This law is fundamentally applied in our thermometers. As we put thermometer in a hotter body, as the temperature increases the mercury expands and increases in the tube. The change of height of mercury in the thermometer indicates the change in temperature. BOYLE’S LAW • • • • it is concerned in pressure and volume. it is formulated by the famous scientist Robert Boyle in 1662. this law relates the expansion and compression of the gas at constant temperature. he has a J shaped tube, with a shorted end closed, and long end open. He put mercury in the tube and determines the volume of trapped gas, when he poured some more mercury he found out the volume of trapped gas decreases while the change in height increases. Which indicates the pressure also increases. He find out that volume is inversely proportional to pressure. CHARLE’S LAW • • • it is concerned in volume and temperature. it is formulated by the famous scientist Jacque Charles less than two centuries of Boyle’s law in 1800. this law describes how gases will expand when heated in his experiment, he prepared a test tube with drop air under a small mercury plug. It was immersed in water but with heating coil for heating and cooled with ice. Upon changing the temperature the volume of the gas dropped in the test also changes. Having all the data he then found out that volume and pressure in the graph. NOTE: Malaking tulong sana itong notes na ito. PADAYON!! FUTURE ELECTRICAL ENGINEER GOODLUCK sa ating MIDTERM EXAMINATION. FIGHTING para sa PANGARAP. STAY SAFE ALWAYS GODBLESS US ALL.