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INTRODUCTION OF THERMODYNAMICS ◦ Thermodynamics & Energy ◦ Closed & Open Systems ◦ Properties of a Systems ◦ State & Equilibrium ◦ Pressure & Temperature ◦ Work, Energy & Heat ◦ Kinetic & Potential Energy ◦ Internal Energy ◦ Specific Heat & Lantern Heat 1
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Objective of this session ◦ Definition of thermodynamics ◦ Introduction to energy conversion 2
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What is “Thermodynamics”? science of energy 3
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The name thermodynamics stems from the Greek words therme (heat) and dynamis (power), which is most descriptive of the early efforts to convert heat into power. 4
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Rub your hands together for 15 seconds. Are your hands warm? Thermal energy
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The study of the effects of work, heat flow, and energy on a system Movement of thermal energy Engineers use thermodynamics in systems ranging from nuclear power plants to electrical components. SYSTEM SURROUNDINGS BOUNDARY
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Thermal Energy is kinetic energy in transit from one object to another due to temperature difference. (Joules) Temperature is the average kinetic energy of particles in an object – not the total amount of kinetic energy particles. (Degrees) Temperature #1Temperature #2 Heat
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ScaleFreezing point of water Boiling point of water Celsius0°C100°C Fahrenheit32°F212°F Kelvin273K373K Matter is made up of molecules in motion (kinetic energy) An increase in temperature increases motion A decrease in temperature decreases motion Absolute Zero occurs when all kinetic energy is removed from a object 0 K = -273° C
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Thermal equilibrium is obtained when touching objects within a system reach the same temperature. When thermal equilibrium is reached, the system loses its ability to do work. Zeroth Law of Thermodynamics: If two systems are separately found to be in thermal equilibrium with a third system, the first two systems are in thermal equilibrium with each other. Object #2 Object #3 Object #1 (Thermometer) Object #2
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The transfer or movement of thermal energy Most common types of transfer Convection Conduction Radiation 100% efficiency is unattainable ALL processes are irreversible
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Power plant 11
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Rocket 12
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Air conditioning 13
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Internal Combustion Engine 14
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Objective of this session ◦ Definition of systems ◦ Familiar with different property definition 15
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Types of systems 1. Closed system (or control mass) 18
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2. Open system (or control volume) 19
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Isolated system 20
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Any characteristic of a system. Some familiar properties are; # pressure P, # temperature T, # volume V, and # mass m 21
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Example of extensive and intensive properties 23
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State: condition of the system characterized by the values of its properties 24
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Process: any change that a system undergoes from one equilibrium state to another. eg: heating water, student entering classroom…. 27
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Quasistatic (quasiequilibrium) process: is a process which proceeds in such a manner that the system remains infinitesimally close to an equilibrium state at all times e.g. room heating up uniformly coffee cooling down uniformly 28 121’1’’ System
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Path: the series of states through which a system passes during a process. 29 State 1 p v State 2 121’1’’ System
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Cycle: System returns to initial state at the end of process(es) 31 p v State 2 12 System 2 System 1 State 1
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◦ Process or cycle efficiency: quality of cycle or process 32
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