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

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Objective of this session◦Definition of thermodynamics◦Introduction to energy conversion

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What is “Thermodynamics”?

science of energy

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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.

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Rub your hands together for 15 seconds.

Are your hands warm?

Thermal energy

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

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 #1 Temperature #2

Heat

Scale Freezing point of water

Boiling point of water

Celsius 0°C 100°C

Fahrenheit 32°F 212°F

Kelvin 273K 373K

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

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 #2Object #2 Object #3Object #3

Object #1Object #1(Thermometer)(Thermometer)

Object #1Object #1 Object #2Object #2

The transfer or movement of thermal energy

Most common types of transfer

Convection

Conduction

Radiation

100% efficiency is unattainable

ALL processes are irreversible

Power plant

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Rocket

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Air conditioning

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Internal Combustion Engine

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Objective of this session◦Definition of systems◦Familiar with different property definition

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Types of systems1. Closed system (or control mass)

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2. Open system (or control volume)

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Isolated system

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Any characteristic of a system. Some familiar properties are;

# pressure P, # temperature T, # volume V, and # mass m

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Example of extensive and intensive properties

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State: condition of the system characterized by the values of its properties

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Process: any change that a system undergoes from one equilibrium state to another. eg: heating water, student entering classroom….

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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

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12 1’1’’System

Path: the series of states through which a system passes during a process.

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State 1

p

v

State 2

12 1’1’’System

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Cycle: System returns to initial state at the end of process(es)

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p

v

State 2

12System 2

System 1

State 1

◦Process or cycle efficiency: quality of cycle or process

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