Explanation: Fins are provided to a heat exchanger surface to augment the heat transfer by increasing the surface area exposed to the surroundings.

The fin temperature effectiveness or fin efficiency is defined as the ratio of the actual heat transfer rate through the fin base divided by the maximum possible heat transfer rate through the fin base, which can be obtained if the entire fin is at base temperature (i.e., its material thermal conductivity is infinite).

10a-d shows that the fin efficiency decreases monotonically (for different thermal conductivity and at a constant heat transfer coefficient) with increasing thermogeo- metric parameter. Also, it shows the variation of fin efficiency with thermogeometric in longitudinal convecting fin with insu- lated tip.

The results show that (a) the greater the value of heat transfer coefficient of convection h, the smaller the efficiency fin and effectiveness fins (b) In circumstances of unsteady state, the efficiency and effectivity influenced by the value of density, specific heat, heat transfer coefficient of conduction and …

The effectiveness of a fin will be maximum in an environment with free convection. Explanation: The fin temperature is also known as the fin effectiveness. Thus it is defined as the ratio of the actual amount of the heat transfered to the to the divided base temperature in the serve.

Factors affecting fin effectiveness

1. P.Kh.Ac should be greater than unity if the rate of heat transfer from the primary surface is to be improved.
2. If the ratio of P and Ac is increased , the effectiveness of fin is improved.
3. Use of fin will be more effective with materials of large thermal conductivities.

It is essential to evaluate the performance of fins to achieve high heat transfer rate or minimum weight etc. Fin effectiveness, fin efficiency and total efficiency are some methods used for performance evaluation of fins. This quantity is more often used to determine the heat flow when variable area fins are used.

in this equation is equal to the surface area of the fin. The fin efficiency will always be less than one, as assuming the temperature throughout the fin is at the base temperature would increase the heat transfer rate.

The use of fins is most effective in applications involving low convection heat transfer coefficient. Thus, the use of fins is more easily justified when the medium is a gas instead of a liquid and the heat transfer is by natural convection instead of by forced convection.

An ideal fin is the one whose temperature is equal to temperature of the surface. This is possible only if the thermal conductivity of fin material is infinitely high. The effectiveness of an actual fin material is always lower than an ideal fin.

Increasing the length of a fin decreases its efficiency but increases its effectiveness.

Application of Finned Tubed in Industries Finned tubes heat exchangers can be applied in various household as well as industrial machineries. Car radiator also used finned tube heat exchangers which cools the hot water in the tubes when air passes through it. This is a crossflow process.

The fins enhance the heat transfer rate from a surface by exposing larger surface area to convection. The fins are used on the surface where the heat transfer Coefficient is very low. Total heat produced by the combustion of charge in the engine cylinder may not convert into useful power at the crankshaft.

• Fish Fins. Fins are one of the most distinctive features of a fish and appear in several different forms.
• Dorsal Fins.
• Tail Fin or Caudal fin.
• Ventral or Pelvic Fins.
• Anal Fin.
• Pectoral Fin.
• Finlets or Scutes.

if the fin has the thickest point forward it improves its ability to handle higher angles of attack, at the cost of some drag, but it can be made thinner because of this angle of attack capability.

How effective a fin can enhance heat transfer is characterized by the fin effectiveness f: Ratio of fin heat transfer and the heat transfer without the fin. For an adiabatic fin: Conclusion: It is preferred to use thin and closely spaced (to increase the total number) fins.

The purpose is to investigate the effects of longitudinal parabolic perforations on the fin parameters such as temperature distribution, effectiveness and efficiency in which the fin surface is cooled by natural convection and radiation. Different concavity levels are considered to form parabolic perforations.

Extended surfaces or fins are generally used to enhance convective heat transfer rate between a solid and the surrounding fluid.

1) Constant Area Straight Fin 2) Variable Area Straight Fin 3) Pin Fin 4) Annular Fin

• Constant Area Straight Fin.
• Variable Area Straight Fin.
• Pin Fin.
• Annular Fin.

Fins typically function as foils that produce lift or thrust, or provide the ability to steer or stabilize motion while traveling in water, air, or other fluids. Fins are also used to increase surface areas for heat transfer purposes, or simply as ornamentation. Fins first evolved on fish as a means of locomotion.

We observe from the table that heat transfer from a fin increases with mL almost linearly at first, but the curve reaches a plateau later and reaches a value for the infinitely long fin at about mL=5. Therefore, a fin whose length is L=m/5 can be considered to be an infinitely long fin.

The overall heat transfer coefficient, or U-value, refers to how well heat is conducted through over a series of resistant mediums. Its units are the W/(m2°C) [Btu/(hr-ft2°F)].

Heat transfer coefficient depends on both the thermal properties of a medium, the hydrodynamic characteristics of its flow, and the hydrodynamic and thermal boundary conditions. The dependence of the Nu and St numbers on the Re and Pr numbers plays an essential role in heat transfer by forced convection.