heat energy transfer
Heat as one of forms of energy can be transferred from one point to another, through three ways. They are by conduction, convention and Radiation.
Heat transfer by conduction:
this is a process by which heat is passed along a metal object from one point to another. In this process heat is being transferred from a particle of higher temperature to the one of lower temperature without the movement of heated particles itself.
Conductors: it is an substance that can transfer heat or electric current by conduction. Example of conductors are, metals like copper, silver and many more.
We also have bad or poor conductor, they are wood, cloths, glass, air, cork asbestos etc. this bad or poor conductor, conduct neither electric current nor heat.
Applications of good conductor:
- Cooking utensils are made of metal so that heat is conducted easily and quickly through them.
- In the past Humphy davy’s lamp made use of high conductivity power of metal.
Applications of poor conductors:
- Roof or air conditioned rooms or heated rooms should be properly insulated, so that heat from the surrounding will not get into the house.
- In cold countries, loose clothing keeps the wearer warmer than tight clothing because air trapped between the clothing layers does not conduct heat away from the body easily.
Heat transfer by convention:
This is the process by which heat energy is transferred in liquid of fluid by actual movement of heated molecule of particles.
Application of heat transfer by conventions
- Land and sea breeze
- House ventilation
Land and sea breeze
This is a process by which hot air move from land to atmosphere during the day , and cold air from move from sea to the land during the day also. But in the night sea being good absorber of heat has become hotter than the land, so hot air from sea move to land and cold air from the land move to sea. This process is what we call land and sea breeze.
Ventilation of room
Our rooms can be ventilated by convention, for example if you light a candle, put it at one end of your room opposite your door, the air around the fire will get heated and found it way out the room through the window while fresh air from the door move in, to replace the hot air . If this continues, the fresh, cool and more dense air also continue to come into the room through door, thereby leaving the room ventilated.
Heat transfer by radiation
Radiation is the process by which heat is transferred from its source to a body without heating up the intervention medium. The heat from sun reaches the earth by Radiation. Radiation unlike conduction and convention need no material medium for it propagation, this means that radiation moves through a vacuum. ( Empty space )
Shining surface or good radiators are poor emitter of radiation and also poor absorber of radiation. A black surface or bad conductor is good emitter and absorber of radiation.
Practical application of heat transfer by radiation
- A house can be made cooler during hot weather by using a shining roof and painting the walls with light colors.
- It is not advisable to wear dark cloth during sunny day because it can cause more heat to the wearer.