1. Manthan Kanani 1400501190282. Ishant Kalra 1400501190273. Pratik Kanani 140050119029

Guided by-Jagruti Shah

• By increasing the surface area in contact with air or providing fins.• By increasing the heat transfer coefficient for the surface.• By increasing the temp of the hot surface or by increasing the temperature difference between hot and cold bodies.

• In many engineering situation, means are often sought to improve heat dissipation from a surface to its surrounding

• Whenever the available surface is found inadequate transfer the required quantity of heat with available temperature drop and convective heat transfer coefficient, extended surfaces or fins are used.

• In many engineering application, large quantities of heat have to be dissipated from small areas.

• The fins increases the effective area of the surface thereby increasing the heat transfer by convection.

• In other words, the shape of fins must be optimized such that the heat transfer density is maximized when the space and the materials used for the finned surfaces are constraints.

• The fins are designed and manufactured in many shapes and forms.

• They manufactured in different geometries, depending upon the practical applications.

• The ribs attached along the length of a tubes are called longitudinal fins.

• The concentric annular disc around a tube are termed as circular or annular fins

• Pin fins or spines are rods protrading from a surface.

Case Tip condition (x=L) Temperature distribution Fin heat transfer rate

A Convection heat transfer

B Adiabatic

C Constant Temperature

D Infinite Fin Length

Fin performance can be described in three different ways.

 1:- The first is fin effectiveness. It is the ratio of the fin heat transfer rate to the heat transfer rate of the object if it had no fin. The formula for this is

where    is the fin cross-sectional area at the base

 2:- Fin performance can also be characterized by fin efficiency. This is the ratio of the fin heat transfer rate to the heat transfer rate of the fin if the entire fin were at the base temperature.

 in this equation is equal to the surface area of the fin

 Fin efficiency will always be less than one

3:- The third way fin performance can be described is with overall surface efficiency.

where    is the total area and    is the sum of the heat transfer rates of all the fins.

Comparison of the different types of extended surfaces using heat transfer/pressure drop as the figure of merit.

from a purely size standpoint, pin fins offer the smallest design for the best heat transfer while straight fins are the most inefficient from a heat transfer and smallest size constraint.

Advantages:By using the fins, heat transfer rate can be increased without any preventive maintenance. It is the cheapest way for increasing the heat transferring rate from the hot bodies.

Disadvantages:We know that the length of fins is directly proportional to the heat transferring rate. But the larger length is may be cause of bending in the fins and also increases the weight of engine. Therefore the overall efficiency will goes to decrease.

• Common applications of finned surfaces are with,

• Cooling of electronics components• Condensors and economisers of thermal

power plants• Dry type cooling towers• Air cooled cylinders of compressors, IC

engines• Evaporators and condensors of

refrigeration and air conditioning system.

• Electric motor and transformers,

Annular Fins

Straight Fins

Splines

Trapazoidal Fins