Chan yeeyi convection

Transfer of Transfer of heat : heat :

ConvectionConvection

Transfer of heat of heatHeat• A form of energy.• Travels from a hotter region to a colder region until both regions are of the same temperature.• Transferred from a warmer to a colder region in three different ways: Conduction

Convection

Radiation

What is convection?ConvectionConvection• The transfer of heat by the circulation of currents

from one region to another in a fluid (liquid or a gas).

• Convection above a hot surface occurs because hot air expands, becomes less dense, and rises.

• Hot water is likewise less dense than cold water and rises, causing convection currents which transport energy.

Examples of convection: Example 1

Heated water in the pot expands and becomes less dense. The warmer water will then rises while the cooler and denser water near the surface descends.Convection currents are formed.

Example 2 Atmospheric convection

Atmospheric convection is a very important part of Earth’s weather.In atmospheric convection, Warm air moves upwards. Cool air falls downwards.

Example 3Coal mines

When a fire was lit up at the bottom,Hot air expands, becomes less dense, and rises. Cooler air from outside the coal mines enter the mines to take the place of the leaving air.Mines were thus ventilated with continuous supply of air.

Natural and forced convectionNatural and forced convectionNatural convection • It is caused by buoyancy forces due to density

differences caused by temperature variations in the fluid.

Eg.

The buoyancy forces caused density differences in the air inside the room thus, convection occurs.

Forced convection• In forced convection, fluid is circulated by a plump or

blower.Eg.

In human circulatory system, a heart is needed to pump the blood to other parts of the body.

• Appliances such as kettles,heaters,air-conditioners and refrigerators make use of convection to heat up or cool down liquids or gases rapidly.

Applications of convection

What are the three different ways of Heat Transfer? Ans :Convection , Conduction & Radiation

What is convection ?

Ans :It is the transfer of heat by the circulation of currents from one region to another in a fluid (liquid or a gas).

What is the function of convection current?

Ans :Convection current transports energy.

What are the two types of convection?

Ans :They are natural convection and forced convection.

Presented By:

Kimbly

Yee Yi

Izzah

Ching Yee

Lavanya

Copyright@ All rights reserved