ME 311 Chapter 1 lecture

ME 311 Chapter 1 lecture - Chapter 1 INTRODUCTION AND BASIC...

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Chapter 1 INTRODUCTION AND BASIC CONCEPTS
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2 Objectives Identify the unique vocabulary associated with thermodynamics through the precise definition of basic concepts to form a sound foundation for the development of the principles of thermodynamics. Review the metric SI and the English unit systems. Explain the basic concepts of thermodynamics such as system, state, state postulate, equilibrium, process, and cycle. Review concepts of temperature, temperature scales, pressure, and absolute and gage pressure. Introduce an intuitive systematic problem-solving technique.
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THERMODYNAMICS AND ENERGY Thermodynamics : The science of energy. Energy : The ability to cause changes. The first law of thermodynamics: Conservation of energy Energy is a thermodynamic property. 3 Energy cannot be created or destroyed; it can only change forms (the first law).
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The second law of thermodynamics: It asserts that energy has quality as well as quantity , and actual processes occur in the direction of decreasing quality of energy. Classical thermodynamics : A macroscopic approach – Provides a direct and easy way to solve engineering problems Statistical thermodynamics : A microscopic approach based on the average behavior of large groups of individual particles. 4 Heat flows in the direction of decreasing temperature.
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Application Areas of Thermodynamics 5
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IMPORTANCE OF DIMENSIONS AND UNITS Dimensions . Units . Primary or fundamental dimensions others such as velocity V , energy E , Pressure P, and volume V are expressed in terms of the primary dimensions and are called secondary dimensions , or derived dimensions . Metric SI system : A simple and logical system based on a decimal relationship between the various units. English system : It has no apparent systematic numerical base, and various units in this system are related to each other rather arbitrarily. 7
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Some SI and English Units 8 Work (Energy) = Force × Distance 1 J = 1 N·m 1 cal = 4.1868 J 1 Btu = 1.0551 kJ
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Unity Conversion Ratios 9 All nonprimary units (secondary units) can be formed by combinations of primary units . Force units, for example, can be expressed as They can also be expressed more conveniently as unity conversion ratios as Unity conversion ratios can be inserted into any calculation to convert units. Dimensional homogeneity All equations must be dimensionally homogeneous – i.e. all the terms in an equation must have the same unit
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SYSTEMS AND CONTROL VOLUMES System : A quantity of matter or a region in space chosen for study. Surroundings
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ME 311 Chapter 1 lecture - Chapter 1 INTRODUCTION AND BASIC...

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