What are extended surfaces in heat transfer?

What are extended surfaces in heat transfer?

Extended surfaces have fins attached to the primary surface on one side of a two-fluid or a multifluid heat exchanger. Fins can be of a variety of geometry—plain, wavy or interrupted—and can be attached to the inside, outside or to both sides of circular, flat or oval tubes, or parting sheets.

How can extended surface affects heat transfer?

Extended surface or fins are used to increases the heat transfer due to increase surface area of cross section in which convection process occur. The fin material should have high thermal conductivity and minimize temperature variation from base to top.

What is the purpose of using an extended surface for heat transfer?

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

What is meant by one-dimensional heat conduction?

We shall consider steady one-dimensional heat conduction. By steady we mean that temperatures are constant with time; as the result, the heat flow is also constant with time. By one dimensional we mean that temperature is a function of a single dimension or spatial coordinate.

Where do you find the application of extended surface heat transfer?

A BRIEF OVERVIEW OF APPLICATION OF EXTENDED SURFACES (FINS) FOR ENHANCEMENT OF HEAT TRANSFER. Extended Surfaces (Fins) are widely used in the engineering field for enhancement of heat transfer rate by increasing surface area with additional material attachment.

Is heat transfer steady or transient?

The heat flow rate keeps changing, and the cause of the varying rates of heat transfer can be either fluctuating temperature differences over the medium or changes in properties of the medium. In the physical world, heat transfer starts as transient and then reaches a steady-state until thermal equilibrium is reached.

What is the effectiveness of fin?

2 Fin Efficiency and Surface Effectiveness. Fin efficiency is defined as the ratio of actual heat flow of the fin to that which would be obtained with a fin of constant temperature uniformly equal to the base surface temperature, that is, one with infinite thermal conductivity.

Which is the case of steady-state heat transfer?

Under Steady-state conditions, the temperature within the system does not change with time. Conversely, under unsteady state conditions, the temperature within the system does vary with time.

What is steady-state heat transfer?

Steady-state heat transfer can be a conduction, convection, or radiation process. Steady-state heat transfer can be described in terms of the temperature as the variable; the temperature of the system remains constant over time in steady-state heat transfer after thermal equilibrium is attained.

Which one of the following is correct fins are used to increase the heat transfer from a surface by?

Explanation: The surface area exposed to the surroundings is frequently increased by the attachment of protrusions to the surfaces, and the arrangement provides a means by which heat transfer rate can be improved. Explanation: Option b is also known as annular fins.

How do you increase heat transfer area?

In single-phase heat transfer processes, three options are available to increase the heat transfer rate. One of them is the choice of smaller free flow sectional area for increased fluid velocity bringing about a reduction of the thickness of the laminar sublayer.

How to calculate heat dissipation from an extended surface?

Equations 5.4 and 5.5 provide a general form of the energy equation for one-dimensional heat dissipation from an extended surface. For a given fin, the parameter m is constant provided the convective film coefficient h is constant over the entire surface and the thermal conductivity k is constant within the considered temperature range.

How is heat dissipation improved in thermal engineering?

In many engineering situations, means are often sought to improve heat dissipation from a surface to its surroundings. The Newton-Rikhman relation Q = hA (t – t a) reveals that the convective heat flow can be enhanced by increasing the film coefficient h, the surface area A and the temperature difference (f – t a ).

How are protrusions used to increase heat transfer?

The surface area exposed to the surroundings is frequently increased by the attachment of protrusions to the surfaces, and the arrangement provides a means by which heat transfer rate can be substantially improved. The protrusions are called fins or spines, and these extensions can take a variety of forms.

How is heat transfer from a fin to a surface?

(ii) The fin is losing heat at the tip, i.e., the heat conducted to the fin at x = l equals the heat convected from the end to the surroundings- At the tip of fin, the cross-sectional area for heat conduction A c equals the surface area A g from which the convective heat transport occurs.