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