Most of the bikes in India has parallel projections all around its engine. Have you ever wondered why they are present? These projections are known as pin fins and they are seen only in air cooled engines and they play an important role in cooling. An air-cooled engine is cooled by the air by a process called as convection. Which can be natural of forced (using fans). Convection is best explained as keeping a cup of hot milk under a fan cools faster than keeping it in a room having no fan. The heat transfer equation is given by,
Q = hA(T2-T1)
Where,
Q is the amount of heat transferred,
h is the heat transfer coefficient (Constant for a given material with specified conditions)
A is the area under which convective heat transfer takes place.
And T represents the temperature.
From the above conditions, it is evident that there are two ways in increasing the heat temperature as the temperature conditions are fixed h and A can be increased to increase Q. Increasing h involves adding a fan or providing liquid cooling etc which would not be economical for an average middle-class bike. Therefore, people came up with a beautiful solution by increasing the area. This gave birth to pin fins. This increases the area of the convective heat transfer. Pin finds are nothing but a piece of highly conductive material attached to the cylinder by means of extrusion, welding, etc.
When a cup of milk needs to be cooled faster, one might transfer it to a wider cup or a plate which essentially increases the heat transfer area and fins does a similar job.
They basically conduct heat of the engine and sends them to the environment (sink) by convection. Not only in bikes they find application in many places in electronics. Components like IC uses pin-fins to increase the heat transfer indifferent size and shape depending on the needs.
Not only in bikes they find application in many places in electronics. Components like IC uses pin-fins to increase the heat transfer indifferent size and shape depending on the needs.
One thing must be kept in mind is that fins are added in the place where h value is high. For example, if a pipe carrying hot water is to be cooled, the fins are added in the outside (to air).