Thermodynamics Chapter 1

Introduction to Thermodynamics

• Thermodynamics is the science of energy
• Energy is the ability to cause changes
• The name "thermodynamics" stems from the Greek words "therme" (heat) and "dynamis" (power)

Laws of Thermodynamics

• The first law of thermodynamics: energy cannot be created or destroyed, only converted from one form to another
• The second law of thermodynamics: energy has quality as well as quantity, and actual processes occur in the direction of decreasing quality of energy

Systems and Control Volumes

• 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
• Closed system (control mass): a fixed amount of mass, and no mass can cross its boundary
• Open system (control volume): a properly selected region in space that involves mass flow

Properties

• Property: any characteristic of a system
• Intensive properties: independent of the mass of a system (e.g., temperature, pressure, density)
• Extensive properties: dependent on the size or extent of the system
• Specific properties: extensive properties per unit mass
• Continuum idealization: treating a substance as a continuous, homogeneous matter with no holes or gaps

State and Equilibrium

• Thermodynamics deals with equilibrium states
• Equilibrium: a state of balance
• Thermal equilibrium: the temperature is the same throughout the entire system
• Mechanical equilibrium: no change in pressure at any point of the system with time
• Phase equilibrium: a system involves two phases and the mass of each phase reaches an equilibrium level and stays there
• Chemical equilibrium: the chemical composition of a system does not change with time

Processes and Cycles

• Process: any change that a system undergoes from one equilibrium state to another
• Path: the series of states through which a system passes during a process
• Quasistatic or quasi-equilibrium process: a process that proceeds in such a manner that the system remains infinitesimally close to an equilibrium state at all times
• Isothermal process: a process during which the temperature remains constant
• Isobaric process: a process during which the pressure remains constant
• Isochoric (or isometric) process: a process during which the specific volume remains constant
• Cycle: a process during which the initial and final states are identical

Temperature and the Zeroth Law of Thermodynamics

• Temperature: a measure of the thermal motion of molecules
• Zeroth law of thermodynamics: if two bodies are in thermal equilibrium with a third body, they are also in thermal equilibrium with each other
• Temperature scales: Celsius, Fahrenheit, Kelvin, and Rankine

Pressure

• Pressure: a normal force exerted by a fluid per unit area
• Absolute pressure: the actual pressure at a given position
• Gage pressure: the difference between the absolute pressure and the local atmospheric pressure
• Vacuum pressures: pressures below atmospheric pressure
• Pascal's law: the pressure applied to a confined fluid increases the pressure throughout by the same amount

Measurement of Pressure

• Manometer: a device used to measure small and moderate pressure differences
• Bourdon tube: a type of pressure transducer
• Piezoelectric transducers: use the principle that an electric potential is generated in a crystalline substance when it is subjected to mechanical pressure

Atmospheric Pressure and Barometers

• Atmospheric pressure: the pressure exerted by the atmosphere on the surface of the Earth
• Barometer: a device used to measure atmospheric pressure
• Standard atmosphere: a unit of pressure defined as the pressure produced by a column of mercury 760 mm in height at 0°C### Thermodynamics and Energy
• Application areas of thermodynamics include energy conversion, power generation, and transportation systems
• Importance of dimensions and units in thermodynamics, including SI and English units
• Dimensional homogeneity and unity conversion ratios in thermodynamics

Systems and Control Volumes

• A system is a quantity of matter or a region in space where a process takes place
• A control volume is a fixed region in space where energy and mass balances are applied
• Properties of a system include density and specific gravity
• State and equilibrium of a system

Temperature and the Zeroth Law of Thermodynamics

• Temperature scales, including Celsius, Fahrenheit, and Kelvin
• The zeroth law of thermodynamics states that if two systems are in thermal equilibrium with a third system, they are also in thermal equilibrium with each other

Energy and Energy Transfer

• Forms of energy include thermal, mechanical, kinetic, potential, electric, magnetic, chemical, and nuclear
• Energy can be transferred as heat, work, and mass
• The first law of thermodynamics states that energy cannot be created or destroyed, only converted from one form to another

The First Law of Thermodynamics

• The first law is a statement of energy conservation, stating that the energy change of a system is equal to the net heat transfer and work done on the system
• Energy balance equations for a system, including internal, kinetic, and potential energy changes

Energy Conversion Efficiencies

• Efficiency is a measure of how well an energy conversion or transfer process is accomplished
• Examples of energy conversion efficiencies include the efficiency of a water heater and the annual fuel utilization efficiency (AFUE) of space heating systems

Types of Energy

• Mechanical energy: the energy associated with the motion and position of an object
• Thermal energy: the energy associated with the temperature of an object
• Electrical energy: the energy associated with the movement of charged particles
• Nuclear energy: the energy associated with the nucleus of an atom

Heat Transfer

• Heat transfer mechanisms: conduction, convection, and radiation
• Heat transfer equations, including heat transfer rate and heat transfer per unit mass

Work Transfer

• Work transfer mechanisms: mechanical work, electrical work, and magnetic work
• Work transfer equations, including work done per unit mass and power### Energy Conversion Efficiencies
• A generator is a device that converts mechanical energy to electrical energy
• Generator efficiency is the ratio of electrical power output to mechanical power input
• Thermal efficiency of a power plant is the ratio of net electrical power output to rate of fuel energy input
• Overall efficiency of a power plant is the product of the turbine efficiency and generator efficiency

Energy and Environment

• Energy conversion processes often affect the environment and air quality
• Pollutants emitted during fossil fuel combustion cause smog, acid rain, and global warming
• Motor vehicles are the largest source of air pollution
• Energy conversion processes are often accompanied by environmental pollution

Ozone and Smog

• Smog is made up of ground-level ozone (O3), carbon monoxide (CO), particulate matter, and volatile organic compounds (VOCs)
• Ground-level ozone is formed when hydrocarbons (HC) and nitrogen oxides (NOx) react in the presence of sunlight
• Ozone irritates eyes and damages lungs, causing shortness of breath, wheezing, fatigue, headaches, and nausea
• Carbon monoxide is a colorless, odorless, poisonous gas that deprives the body's organs of oxygen

Acid Rain

• Sulfur in fuel reacts with oxygen to form sulfur dioxide (SO2), an air pollutant
• Sulfur oxides and nitric oxides react with water vapor and other chemicals to form sulfuric and nitric acids
• Acid rain is formed when these acids dissolve in suspended water droplets in clouds or fog
• Acid rain affects soil, vegetation, and wildlife, and can also damage buildings and infrastructure

The Greenhouse Effect and Global Warming

• The greenhouse effect occurs when carbon dioxide (CO2), water vapor, and other gases trap heat in the atmosphere
• The main sources of CO2 emissions are fossil fuel combustion, deforestation, and land-use changes
• Global warming can cause severe weather patterns, flooding, and droughts, as well as rising sea levels and loss of wetlands and coastal areas
• Renewable energy sources such as wind and solar power can help minimize global warming

Properties of Pure Substances

• A pure substance has a fixed chemical composition throughout
• Air is considered a pure substance, although it is a mixture of gases
• Nitrogen and gaseous air are pure substances
• A mixture of liquid and gaseous water is a pure substance, but a mixture of liquid and gaseous air is not

Phases of a Pure Substance

• In a solid, molecules are kept at relatively fixed positions by intermolecular forces
• In a liquid, groups of molecules move about each other
• In a gas, molecules move about randomly
• The arrangement of atoms in different phases: solid, liquid, and gas

Phase-Change Processes of Pure Substances

• Compressed liquid: a substance that is not about to vaporize
• Saturated liquid: a liquid that is about to vaporize
• Saturated vapor: a vapor that is about to condense
• Superheated vapor: a vapor that is not about to condense

Thermodynamics: An Engineering Approach

• Thermodynamics is the study of energy and its interactions with matter
• The first law of thermodynamics states that energy cannot be created or destroyed, only converted from one form to another
• The second law of thermodynamics states that the total entropy of an isolated system always increases over time