Thermodynamics I ME 20000
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This 7 page Class Notes was uploaded by Kristopher Beahan on Saturday September 19, 2015. The Class Notes belongs to ME 20000 at Purdue University taught by Staff in Fall. Since its upload, it has received 22 views. For similar materials see /class/207989/me-20000-purdue-university in Mechanical Engineering at Purdue University.
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Date Created: 09/19/15
ME 200 Thermodynamics l Session 2 Fall 2008 rs Course website Class information Prof S H Frankel Class time MWF 10301120AM Of ce ME 165 or Chaffee 125 MWF Email 7 frankelgurdue edu e ankel 5tevengrnail corn Phone 7 765749471507 7 765740476067 Of ce Hou of ce cell F113 E 165 MW 01230 httpengineeringpurdueedumeZOO Research website httpllristrettoecnpurdueedu Outline Course details Chapter 1 Getting started Introductory Concepts and Definitions Using thermodynamics De ning systems Describing systems and their behaviors Measuring mass length time and force Properties Speci cvolume Pressure Temperature Problem solving methodology Course details Course policy Read items 1 4 Textbookwebsite Engineering Thermodynamics HW problems will be collected on Monday s Includes problems from previous M W F Only subset of problems will be graded Graded HWs returned to you usually within 1 week Read items 5 14 Schedule note exam datetimelocation Equation sheet bring to exam Basic Concepts What is thermodynamics Science of energy What is energy Ability to cause changes Thermodynamics from Greek word therme heat amp dynamis power heat to power Key principle is conservation of energy During interaction energy can change from one form to another but total amount of energy remains constant ie energy cannot be created or destroyed Potential energy of weight converted into thermal energy of water Joule apparatus 1 843 Laws AA m First law of thermodynamics A statement of conservation of energy principle Energy is a thermodynamic property tbd quantifies energy Second law of thermodynamics Energy has quality as well as quantity Actual processes occur in direction of decreasing quality of energy Example A cup of hot coffee left on a table eventually cools but a cup of cool coffee left on a table never gets hot by itself degradation of high temperature energy why a degradation es 4257 History Birth of thermodynamics as a science 1697 1712 atmospheric steam engine 1850s William Rankine Rudolf Clasius and Lord Kelvin Rankine first textbook in 1859 First ME 200 student falls asleep in class August 1860 Only two laws how hard a subject can this be Substances consist of large number of particles called molecules Two approaches Classical approach does not require detailed knowledge of molecular motion but a little does not hurt Statistical approach considers molecular motion in detail We shall pursue the classical approach but draw on molecular details for insight eg we will use to understand internal energy entropy and ideal gas aw Application areas Home electricgas range HVAC refrigerator humidifier pressure cooker water heater shower etc Automotive engines rockets jet engines conventional or nuclear power plants Even human body httpwwwrollsrovcecomeducationschoolshow thinqs workiournev02flashhtml Systems Closed and open Thermodynamic system quantity of matter or a region of space chosen for study Mass or region outside system is called surroundings Real or imaginary surface that separates system from surroundings is boundary SURROUNDINGS BOUNDAR Y Boundary may be fixed eg rigid tank or moveable eg pistoncylinder device Closed system control mass Features Fixed amount of mass No mass can cross its boundary Energy in form of heat and work interactions can cross boundary Volume of closed system does not have to be fixed mass NO CLOSED SYSTEM m constant YES Open system control volume Properly selected region of space usually encloses device which involves mass flow ie compressor turbine or nozzle Both mass and energy can cross the boundary of a CV which is called a control surface CS Note Form of thermodynamic relations are different for open and closed systems so it is important to identify what type of system you are considering first to determine proper analysis Imaginary boundary Real boundary E i V U E i 1 Moving CV boundary 1 a nozzle 1 I CV L I I Fixed quot boundary Control volumes IIWquot a A control volume with real and imaginary boundaries 2 A control volume with fixed and moving boundaries Properties of a system Any characteristic of a system is a property ie pressure P temperature T volume V mass m etc Some properties are defined in terms of others ie density is mass per unit volume m 3 p kg m gt V Specific volume Note Pointwise property definitions based on concept of continuum ie spaces between molecules ignored no microscopic holes valid for most applications Intensive vs extensive properties Intensive independent of size of system ie T P or dens y Extensive depend on sizeextent of system ie m V E Does property change when system is divided in half Extensive properties per unit mass are called specific properties and are intensive ie specific volume Extensive 12 value I N Intensive same value State Consider system not undergoing any change measure properties of system this defines state A system at 2 states Equilibrium Thermodynamics deals with equilibrium states Equilibrium implies a balance ie no unbalanced driving forces If isolated from surroundings system remains unchanged Thermal equilibrium implies temperature same throughout eg see below for before and after ll No temperature differentials system temperature can be described by a single number in equilibrium Mechanical no change in pressure Chemical no change In composntlon Thermodynamic all aspects of system in equilibrium Process path Any change system undergoes from one equilibrium state to another is called a process Series of states through which a system passes during a process is called path of process Property A Advantage Only one value for each State 2 property describes entire system eg one value of P T etc State of system represented by processpath single point on plot w properties as coordinates State 1 Path can only be drawn if processes Pr t B Oper y proceed In eqUIIIbrIum manner
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