Thermodynamics - Ch. 1 Introduction and Basic Concepts
Pascal (Pa)
1 Pa = 1 N/m^2
Barometer
A device that measure atmospheric pressure.
Pressure
A normal force exerted by a fluid per unit area.
Steady-Flow Process
A process during which a fluid a fluid flows through a control volume steadily.
Isobaric Process
A process during which the pressure remains constant.
Isochoric (Isometric) Process
A process during which the specific volume remains constant.
Isothermal Process
A process during which the temperature remains constant.
Cycle
A system is said to have undergone a cycle if it returns to its initial state at the end of the process.
Process
Any change that a system undergoes from one equilibrium state to another.
Property
Any characteristic of a system. i.e. pressure P, temperature T, volume V, and mass m.
Extensive Properties
Are those whose values depend on the size-or extent-of the system. Total mass, total volume, and total momentum are some examples of extensive properties.
Statistical Thermodynamics
Based on the average behavior of large groups of individual particles.
Open System (Control Volume)
Both mass and energy can cross the boundary.
Manometer
Commonly used to measure small and moderate pressure differences. A manometer consists of a glass or plastic U-tube containing one or more fluids such as mercury, water alcohol, or oil.
Bourdon Tube
Consists of a bent, coiled, or twisted hollow metal tube whose end is closed and connected to a dial indicator needle.
Closed System (Control Mass)
Consists of a fixed amount of mass, and no mass can cross its boundary. Energy in the form of heat or work can cross.
Conservation of Energy Principle
During an interaction, energy can change from one form to another but the total amount of energy remains constant. i.e. Energy cannot be created or destroyed.
Second Law of Thermodynamics
Energy has quality as well as quantity, and actual processes occur in the direction of decreasing quality of energy. i.e. Hot coffee cup in a cool room.
calorie (cal)
Energy required to raise the temperature of 1 g of water at 14.5C by 1C.
British Thermal Unit (Btu)
Energy required to raise the temperature of 1 lbm of water at 68F by 1F.
Specific Properties
Extensive properties per unit mass such as specific volume (v = V/m) and specific total energy (e = E/m).
Continuum
Homogeneous matter with no holes.
Phase Equilibrium
If a system involves two phases, it is in phase equilibrium when the mass of each phase reaches an equilibrium level and stays there.
Intensive Properties
Independent of the mass of a system, such as temperature, pressure, and density.
Classical Thermodynamics
Macroscopic approach to the study of thermodynamics that does not require a knowledge of the behavior of individual particles.
Isolated System
Mass and energy are not allowed to cross the boundary of the system.
Density
Mass per unit volume. p=m/V (kg/m^3)
Thermodynamic Temperature Scale
SI=Kelvin scale. English=Rankine scale.
Path
Series of states through which a system passes during a process.
State
Set of properties that completely describes the condition of the system.
Equilibrium
State of balance. In an equilibrium state there are no unbalanced potential within the system.
Zeroth Law of Thermodynamics
States that if two bodies are in thermal equilibrium with a third body, they are also in thermal equilibrium with each other. (Two bodies are in thermal equilibrium if both have the same temperature reading even if they are not in contact.)
Absolute Pressure
The actual pressure at a given position.
First Law of Thermodynamics
The first law of thermodynamics is a version of the law of conservation of energy, adapted for thermodynamic systems. The law of conservation of energy states that the total energy of an isolated system is constant; energy can be transformed from one form to another, but cannot be created or destroyed. Energy is a thermodynamic property.
Surrounding
The mass or region outside the system.
Boundary
The real or imaginary surface that separates the system from its surroundings. Boundary of a system can be fixed or movable.
State Postulate
The state of a simple compressible system is completely specified by two independent, intensive properties.
Watt (W)
Time rate of change for energy in joule per second (J/s).
Independent
Two properties are independent if one property can be varied while the other one is held constant.
Joule
Unit for work. 1 J = 1 N*m
Quasi-Static (Quasi-Equilibrium) Process
When a process proceeds in such a manner that the system remains infinitesimally close to an equilibrium state at all times.
Chemical Equilibrum
When its chemical composition does not change with time, that is, no chemical reaction occurs.
Simple Compressible System
When the system is absent of electrical, magnetic, gravitational, motion, and surface effects.
Thermal Equilibrium
When the temperature throughout an entire system is the same.
Mechanical Equilibrium
When there is no change in pressure at any point of the system with time.
Specific Volume
v=V/m=1/ps
