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Unformatted text preview: ENME320 1 Definitions Thermodynamics: Science of energy and entropy Science that deals with heat , work , and related substances properties Macroscopic versus Microscopic point of view: 1. Microscopic point of view: the molecular constitution of matter is taken into consideration Statistical Thermodynamics: using probability theory, the average behavior of large groups of individual particles is taken into account ENME320 2 Definitions 2. Macroscopic point of view: this approach does not require a knowledge of the nature and elements of matter Classical Thermodynamics: we deal with average or gross effects of many molecules. In this course we study classical thermodynamics Continuum: with this assumption, the substances are treated as being continuous, disregarding the action of individual molecules (Cont.) ENME320 3 Dimensional Homogeneity Every term in an equation must be dimensionally homogenous c b a = + Identical dimension z y x = Identical dimension Example: a m F . = [M] [L/t 2 ] [ML/t 2 ] ENME320 4 Closed, Open, and Isolated Systems Thermodynamic system : a quantity of matter or a region in space chosen for study Surroundings : the mass or region outside the system Boundary : the real or imaginary surface that separates the system from its surroundings boundary does not have any volume or mass System Surroundings System boundary ENME320 5 Closed, Open, and Isolated Systems (cont.) Open system (or control volume): A properly selected and welldefined region in space separated from surroundings by a control surface Closed system (or control mass): A fixed amount of mass selected to be studied Control Volume Energy Yes Mass Yes Control surface ENME320 6 Closed, Open, and Isolated Systems A open system can exchange both mass and energy with its surroundings A closed system can only exchange energy with its surroundings For both open and closed systems, the boundary can be fixed or movable Gas M=const. Closed system (fixed boundary) Gas M=const. Closed system (movable boundary) Open system (fixed boundary) Gas Open system (movable boundary) (Cont.) ENME320 7 The selection of the system is somewhat arbitrary, but the proper choice make the analysis much easier The thermodynamic relations that are applicable to closed and open systems are different. Therefore, it is extremely important that we recognize the type of system we have before we start analyzing it Closed, Open, and Isolated Systems (Cont.) ENME320 8 Isolated system: A system which does not interact with its surroundings. Energy (in the forms of work and heat) and mass can not cross the boundaries of an isolated system A system and its surroundings comprise an isolated system System Surroundings Isolated system Closed, Open, and Isolated Systems (cont.) ENME320 9 Properties of A System P h a s e : That is a quantity of matter that is homogenous throughout, (i.e....
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This homework help was uploaded on 04/17/2008 for the course ENME 000 taught by Professor Staff during the Spring '08 term at Maryland.
 Spring '08
 staff

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