# Types Of Fins | Heat transfer Equation For Fins

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__Introduction of Fins:__

__Introduction of Fins:__

Fins

are the extended surfaces designed to Increase heat transfer rate for a fixed

surface temperature, or lower surface temperature for a fixed heat transfer

rate.

are the extended surfaces designed to Increase heat transfer rate for a fixed

surface temperature, or lower surface temperature for a fixed heat transfer

rate.

__Types of Fins:__Types Of Fins |

__HEAT TRANSFER FROM FINNED SURFACES__

The

rate of heat transfer from a surface at a temperature

surrounding medium at

rate of heat transfer from a surface at a temperature

*Ts*to thesurrounding medium at

*T*infinity is given by Newton’s law of cooling as,Equation of fins |

where.

*As*is

the heat transfer surface area and

*h*is

the convection heat transfer coefficient

temperatures

*Ts*

and*T*infinity are fixed by design considerations,
There

are

existing one with a larger one, but this approach may or may not be practical.

Besides, it may not be adequate.

are

**to increase the***two ways*to increase the rate of heat transfer:*or to increase the*__convection__

heat transfer coefficient hheat transfer coefficient h

*surface area As.*Increasing*h*may require the installation of a pump or fan, or replacing theexisting one with a larger one, but this approach may or may not be practical.

Besides, it may not be adequate.

The

alternative is to increase the

aluminum. Finned surfaces are manufactured by extruding, welding, or wrapping a

thin metal sheet on a surface. Fins enhance heat transfer from a surface by

exposing a larger surface area to convection and radiation.

alternative is to increase the

**by attaching to the surface**__surface area__*extended*

surfacescalledsurfaces

*fins*made of highly conductive materials such asaluminum. Finned surfaces are manufactured by extruding, welding, or wrapping a

thin metal sheet on a surface. Fins enhance heat transfer from a surface by

exposing a larger surface area to convection and radiation.

Finned

surfaces are commonly used in practice to enhance heat transfer, and they often

increase the rate of heat transfer from a surface several fold. The car

radiator shown in Fig. below is an example of a finned surface. The closely

packed thin metal sheets attached to the hot water tubes increase the surface

area for convection and thus the rate of convection heat transfer from the

tubes to the air many times. There are a variety of innovative fin designs

available in the market, and they seem to be limited only by imagination.

surfaces are commonly used in practice to enhance heat transfer, and they often

increase the rate of heat transfer from a surface several fold. The car

radiator shown in Fig. below is an example of a finned surface. The closely

packed thin metal sheets attached to the hot water tubes increase the surface

area for convection and thus the rate of convection heat transfer from the

tubes to the air many times. There are a variety of innovative fin designs

available in the market, and they seem to be limited only by imagination.

Innovation In Fins |

In

the analysis of fins, we consider

the material to remain

the analysis of fins, we consider

*steady*operation with*in the fin, and we assume the thermal conductivity***no heat**

generationgeneration

*k*ofthe material to remain

*constant.*
We

also assume the convection heat transfer coefficient

the

also assume the convection heat transfer coefficient

*h*to be*constant*

and*uniform*over the entire surface of the fin for convenience inthe

*analysis.*
We

recognize that the convection heat transfer coefficient

recognize that the convection heat transfer coefficient

*h*, in general,*varies along the fin as well as its circumference, and its value at a point*

*is a strong function of the*

*fluid motion*at that point.
The value of

lower at the

is surrounded

its motion to the point of

has little contact

resistance to flow.

*h*is usually*much*lower at the

*fin base*than it is at the*fin tip*because the fluidis surrounded

*by solid surfaces near the base, which seriously disrupt*its motion to the point of

**“suffocating”**it, while the fluid near the fin tiphas little contact

*with a solid surface and thus encounters little*resistance to flow.

**Therefore,**

increase in

*adding too many fins on a surface may actually decrease the overall heat*

*transfer when the decrease in*

*h*offsets any gain resulting from theincrease in

*the surface area.*
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