# chap 2 - EML 3100 EML 3100 Fall 2010 2010 Instructor : Dr....

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ML 3100 EML 3100 all 2010 Fall 2010 Instructor : Dr. J. N. Chung

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HAPTER CHAPTER Some Concepts and efinitions Definitions
§ 2.1 Thermodynamic System and the Control Volume System –Defining the domain of analysis A thermodynamic system is a designated part of the universe, enclosed by a system boundary , that we select for analysis. Everything that is not inside yy g the system boundary is considered to be e rroundings r vironment the surroundings or environment . efining the territory of analysis which is your system Defining the territory of analysis which is your system

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ystem and Surroundings System and Surroundings niverse = System +Surroundings Universe System +Surroundings d i Surroundings System ystem Boundary System Boundary
§ 2.1 System and the Control Volume Boundary (control surface) : a real or imaginary surface that separates the system from its surroundings. The boundary of a system can be fixed or movable . It can change shape or size. Surrounding : the mass or region outside the system. It is so large such that its state and conditions (pressure and temperature) do not ange with time. change with time.

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§ 2.1 Closed and Open Systems Isolated system : neither mass nor energy can cross the boundary . Closed system (or control mass): fixed amount of mass; energy can cross the boundary ; e.g., balloon, cold beer can, etc. Open system (or control volume ): both mass and energy can cross the boundary (control volume) ; e.g., a boiling kettle, …
Controlled Mass Mass cannot cross the boundaries of a closed system, but nergy can. Cold Coke a Can energy can. in a Can Heat into the can

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Open System
Control Volume Analysis of a Piston Engine Moving boundary Coolant Mass transfer – mass in and out during intake and exhaust Energy transfer – work done and gain by the system during Power and exhaust. Also heat transfer to the coolant that flows around the cylinder.

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2.2 Macroscopic vs. microscopic viewpoints. .. 2.5 cm 3 gas container has 10 20 atoms AIR 2.5 cm 2.5 cm A collection of atoms within a container, each with a unique velocity.
Energy in a microscopic description Temperature ? AIR umber of molecules = N Kinetic Energy of a single molecule, 2 1 2 ii i em V Number of molecules = N Total kinetic Energy = N e N i e 1 i i e N 1 i Average Kinetic Energy of the gas Volume = Gas volume temperature, T, is proportional to the Average Kinetic Energy of the gas Volume

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More insight on the temperature implication ince N Since 1 , i i e T e N total number of molecules N  ,t a n / So T e proportional cons t Q total thermal energy N N W N W  / ) m W e ,, (/ ) , molecule QN em NW m Qm W e W w e i ght o f a molecules ) ( /) molecule molecule W T (1 / )(1 / ) , 1/ () molecule olecule W T Q mCT C W , molecule ref ref Q mC T T T zero Kelvin 
Force in a microscopic description Pressure ?

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## This note was uploaded on 09/27/2011 for the course EML 3100 taught by Professor Sherif during the Fall '08 term at University of Florida.

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chap 2 - EML 3100 EML 3100 Fall 2010 2010 Instructor : Dr....

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