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Introduction
This refers to the energy flow from a hotter material towards a cooler one because of the temperature difference. It involves the conversion and the exchange of energy between two systems. When a physical metal that is hot is dipped into cold water, then we experience an energy flow from hot to cold .Normally heat is transferred between two physical bodies at different temperature levels, Heat transfer occurs in three modes namely conduction, convection and radiation.
Convection
It refers to the mode through which the transfer of heat is done through a liquid or gas that is caused by the motion of molecular. Through convection the currents in liquids or gases that are arising from the changes in temperatures are utilized.
Conduction
It is refered to the movement of heat a molecule to a molecule in other words transmission of heat through a conductor. If a rod is heated the temperatures will tend to go up causing the molecules of the of the rod that has been hitted to vibrate more powerfully and a result of the vibration energy is passed to the next materials through a process known as collision.
Radiation
This refers to the transfer of heat using the invisible infra-red rays, It does not require any medium to transfer the heat, transfer of heat through a vacuum can be done through radiation. When the rays fall on a material some of them are absorbed while other rays are reflected away ,The hotter object on which some of the rays fall emits more radiation than the other one. However we also learn that the black surfaces are good absorbers and emitters while the shiny surfaces are poor emitters.
Differences between the free and forced convection
- Free convection-It is a type of convection on where the fluid flow is only because of its solidity difference due to the temperature variation. A good example of this is the boiling of water.
- Forced convection-It is a mode of heat where some external source of heat like a blower,fan,pump,or mixer is used to cause the motion of the fluid i.e.air
Solving convection problems
When solving convection problems, one should have the following tips:
If the velocity of the fluid is mentioned in the problem, you can straight away do the calculation for forced convection.
If the velocity of the fluid is negligible, then it is free convection
However, forced convection involves fluid motion as well as conduction. It increases the convective transfer rate. Rate of heat transfer in forced convection depends on the velocity of air. The greater the velocity of air the the greater the transfer of heat through convection .It also occurs in electronics cooling by adding a fan or a blower, when active cooling is improvised by the use of technologies the fluid flow is likely to rise during the process of convection.
Principles used the heat transferring process can be used in the preservation o temperature and it also plays a great role in increasing and decreasing of temperature under so many situations that might arise.
Applications of Heat Transfer
Efficient utilization of energy is the main objective in the amount of energy that is needed in the cooling and the heating process,Through the use of architecture the air currents may lead to causing structural damage, so if we implement improvements on the insulators and also seal the leaks then an energy audit will help us to assess this progress or initiative
Heat transfer also plays a greater role in the monitoring of our climate,Restructuring of the climate involves removal of the toxic gases such as caborn dioxide because it determines the radiative balance on the atmosphere. It also reduces the greenhouse effect since this effect involves the thermal radiation from the earth surface that had already been absorbed by the greenhouse gases and is re-radiated towards all directions
It also applicable in the cooling techniques especially in the case of evaporative cooling
that occurs when the vapor of a liquid is added to the surrounding environment. Energy required in the evaporation of water is usually extracted from the surrounding which is usually in a form of heat that is later converted into the heat of solidification, when the temperatures are not at bar the higher the evaporative cooling impact.
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