HEAT ENGINES AND REFRIGERATION

Presented by

Group 1(Class B)

November, 2012

Outline Heat Engines Type of Heat Engines Carnot Cycle Petrol and Diesel Engines Refrigeration Operating principle Method of Refrigeration Recent researches in Heat Engine and

Refrigeration

Heat Engines

Systems that basically converts heat energy to mechanical energy

Harnessing their work done has been the focus of development

Types of Heat Engines

Internal Combustion Heat Engine

External Combustion Heat Engine

The Carnot Cycle Heat engines

cannot convert all the input energy.

The fraction converted is called the thermal efficiency

The maximum possible efficiency of a heat engine is that of a hypothetical (ideal) cycle, called the Carnot Cycle.

Petrol and Diesel Engines Petrol Diesel

η = 1 - 1/(rk-1) re = V1/V3

rc = V1/V2

4-Stroke Engine Induction Stroke Compression

Stroke

4-Stroke Engine Power Stroke Exhaust Stroke

Refrigeration Refrigerator is a reversed

heat engine. Heat is continuously

transferred from the cold space to the hotter surroundings.

This is a violation of the natural law of heat transfer hence energy must be put into the system.

Refrigerators are cyclic devices.

The working fluids are called refrigerants.

Common Application

Operation and Principle

Method of Refrigeration

Cyclic Metho

d

Vapour-compressi

on refrigeratio

n

Vapour-absorption refrigerati

on

Vapour-compres

sion cycle

Ideal vapour compression cycle

Method of Refrigeration

Reverse carnot cycle

Recent Advancement in Refrigeration Operations

Refrigerant decision based on criteria of safety, costs and environment protection

Refrigerant should have excellent thermodynamic properties, high chemical stability and good physical characteristics.

Substances used as refrigerants are: Ammonia refrigeration convinces with top

energy efficiency Using carbon dioxide to save energy and

money

Recent Advancement in Refrigeration Operations

Climate-neutral cooling with hydrocarbons Water refrigeration with up to 25% potential

savings Air: fast refrigeration at low energy costs Double advantage for the environment and

corporate balance sheets