unit_4 - Engi2800 (Section I) Engineering Thermodynamics I...

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09/27/09 http://jjl.me.dal.ca/Engi2800 1 J.M. Chuang Dalhousie University Dept. of Mechanical Engineering Last Modified: September 27, 2009 Unit #4 ( Textbook Reference: Ch.4 ) Work and Heat Engi2800 (Section I) Engineering Thermodynamics I
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09/27/09 http://jjl.me.dal.ca/Engi2800 2 Contents First Law of Thermodynamics Definition of Heat Adiabatic Process Isothermal Process Heat Transfer Modes Conduction Convection Radiation Definition of Work Sign Convention of Work Done Evaulation of Work Integral of Work Work is a Function of Path Polytropic Process, Unit of Work Work Done at Moving Boundary of a Simple Compressible System Comparison of Heat and Work
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09/27/09 http://jjl.me.dal.ca/Engi2800 3 First Law of Thermodynamics The 1 st Law of Thermodynamics is called the "Conservation of Energy", i.e. " Energy connot be created or destroyed ". It can only change form. There is no mathematical evidence and there is no evidence against it. Another statement of the 1 st law: During an interaction between a system and its surroundings, Energy can cross the boundary of a closed system in two distinct forms: "Heat and Work". The amount of heat gained by the system The amount of energy lost by the surrounding = System Boundry Heat Work (Energy)
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09/27/09 http://jjl.me.dal.ca/Engi2800 4 Definition of Heat (1) Definition: Heat is the form of energy that is transferred between two systems, or a system and its surroundings. As a result of a temperature difference. Heat is transferred between a system and its surroundings until they are at thermal equilibrium, i.e. same temperature. Heat transfer occurs solely because of between two systems. There is no heat transfer between two systems if Distinct between heat and energy: In Thermodynamics, reference to heat can only be made when there is a transfer of energy due to a termperature difference. Energy is associated with a state Heat is associated with a process. Heat is energy in transition. Once the transition is completed, the energy that was transferred in the form of heat becomes part of the internal energy. System Surrounding ¢ T ¢ T = 0 : Heat T H T L T L
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09/27/09 http://jjl.me.dal.ca/Engi2800 5 Unit of heat = Unit of energy, . Heat to transfer to a system is considered positive. Heat transfered from a system is considered negative. Heat is a path function is recognized as an inexact differential. Amount of heat transfered when a system undergoes a change from state 1 to state 2
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This note was uploaded on 07/15/2010 for the course ENGI 2800 taught by Professor J.chuang during the Winter '09 term at Dalhousie.

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unit_4 - Engi2800 (Section I) Engineering Thermodynamics I...

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