THERMODYNAMICS

THERMODYNAMICS

literally means “moving or evolving heat.” The science of thermodynamics is concerned

with heat and its transformation to mechanical

energy.

SYSTEM - object or collection of objects under study. Everything else is referred to as surroundings

The system and the surroundings constitute the universe.

INTERNAL ENERGY- refers to the sum of the kinetics energies of the molecules of a body and the potential energy to intermolecular forces

REVERSIBLE PROCESS – one in which the system and its surroundings can be returned to their initial state before the process occurs

IRREVERSIBLE PROCESS - one in which the system and its surroundings cannot be returned to their initial state before the process occurs. Also known as the natural process.

Laws of Thermodynamics

ZEROTH LAW OF THERMODYNAMICS

A

CB“If object A is in thermal equilibrium with object B and object A is in thermal equilibrium with a third object C, then object B must be in equilibrium with object C”

Thermal Equilibrium- the main concern of the zeroth law, two bodies are said to be in thermal equilibrium if they have the same temperature.

THE FIRST LAW OF THERMODYNAMICS

“When heat is added to a system, some of it remains in the system increasing its internal energy, while the rest leaves the system as the system does work.”

THE SECOND LAW OF THERMODYNAMICS Three versions of the second law of

thermodynamics:

KELVIN-PLANCK STATEMENT – no heat engine can completely convert heat energy to work . In other words, there is no 100% efficient heat engine.

CLAUSIUS STATEMENT – heat flows naturally from hot to cold objects .

ENTROPY STATEMENT – when a reversible process occurs, the total entropy of the universe remains the same. When an irreversible process occurs, the total entropy of the universe increases.

Entropy is an abstract or theoretical quantity. It is used to predict the direction of natural events and to predict whether a given chemical or physical process is possible. If the process is found to be impossible, additional data may tell scientist what can be done to make the process possible.

THE THIRD LAW OF THERMODYNAMICS

“The entropy of a perfect crystal of a substance at the absolute zero temperature is zero.”

Heat Engines

HEAT ENGINES

a device that converts heat energy to

mechanical work

TYPES OF HEAT ENGINES

INTERNAL COMBUSTION ENGINE – burns the fuel inside the engine.

EXTERNAL COMBUSTION ENGINE - burns the fuel outside the engine.

STEAM ENGINES

HERO OF ALEXANDRIA – invented the oldest heat engine since 200 B. C. called Aeolipile in which steam was conducted through pipes from a boiler.

Aeolipile

THOMAS SAVERY – developed the first commercial steam engine in 1968.

Savery Engine

THOMAS NEWCOMEN – came up with a modified engine using steam at atmospheric pressure in 1712.

Newcomen Engine

JAMES WATT – introduced a greatly improved steam engine with a separate condenser in 1769. This invention triggered the so called “Industrial Revolution” and stimulated the inventions of other types of engine.

Watt Steam Engine

The gasoline engine and diesel engine are internal combustion engines. These engines operate on four different stokes: intake, compression, power and exhaust.

GASOLINE AND DIESEL ENGINES

Maximum efficiency is obtained if all processes undergone by the working substance of a heat engine are reversible. This statement is called Carnot principle, named after French engineer Sadi Carnot. The Carnot engine is a hypothetical heat engine undergoing all reversible process.

IDEAL HEAT ENGINE

WHAT YOU SHOULD KNOW:

• You should know that efficiency is a comparison of the useful work energy provided by a machine or system to the work energy applied to the machine or system.

• You should know that the formula for efficiency is: input workefficiency= x 100% output work

• You should know that the parts of a machine or system and how they are connected together will affect the machine's or system's efficiency.

• You should know that other forces such as friction will affect an object's movement.

• You should know that velocity ratio is a comparison of the distance a load moves to the distance travelled by the force needed to move it.

CREATED BY :IV-1 BSU-ARASOF NASUGBU

ANA CONSTANCIA U. CALINGASANBLESSY FAITH CIPE

MICHELLE N. DIONESROZELYN T. MACUTAY

JOSE ANGELO E. BARAL