What are the types of fins in heat transfer?

What are the types of fins in heat transfer?

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.

What is pin fin in heat transfer?

Pin-fin arrays are a common geometry used to increase the internal heat transfer in the trailing edge region of a turbine vane. A pin-fin array is a series of short cylinders which span the cooling flow passage. They increase the internal surface area and the flow passage turbulence.

How do you increase fin effectiveness?

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.

What is the effectiveness of fin?

An effectiveness of indicates that the fin actually acts as insulation, slowing down the heat transfer from the surface. This situation can occur when fins made of low thermal conductivity materials are used. An effectiveness of indicates that the fins are enhancing heat transfer from the surface, as they should.

Can Fin effectiveness be less than 1?

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.

What does value of fin effectiveness is 1 mean?

1. For effectiveness εf =1 indicates that the addition of the fin to the surface does not affect heat transfer at all. In other word, the heat transfer to the fin through the base area Aw is equal to the heat transferred from the same area Aw to the surrounding medium.

Under what conditions can we neglect heat transfer from the fin tip?

If the fin is too long, the temperature of the fin tip will approach the surrounding temperature and we can neglect heat transfer from the fin tip. Also, if the surface area of the fin tip is very small compared to the total surface area of the fin, heat transfer from the tip can again be neglected.

What is an ideal fin?

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.

What is infinitely long fin?

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.

What is the effect of thermal conductivity of fin effectiveness?

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.

What is the fin effectiveness under what conditions are fins most effective?

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.

Which is having highest thermal conductivity?

Diamond

Which type of design of fins is more effective?

So, plate 5 will give the most effective fin type with a lower weight, surface area, size; and as a result minimum cost and maximum efficiency.

What is unsteady state heat transfer?

If the temperature at any given point of a body changes with time, unsteady state heat transfer occurs. 2. Thermal diffusivity is a measure of the ability of a material to transfer thermal energy by conduction compared to the ability of the material to store thermal energy.

What is the difference between steady state and unsteady state heat transfer?

Steady-state and unsteady-state processes describe the time interval that a process occurs over. Steady-state refers to the time where the variable of interest doesn’t change. Unsteady-state is when the variable of interest changes over time.

What does thermal conductivity mean?

Thermal conductivity can be defined as the rate at which heat is transferred by conduction through a unit cross-section area of a material, when a temperature gradient exits perpendicular to the area.

What is meant by a semi infinite solid?

A semi-infinite solid is an idealized body that has a single plane surface and extends to infinity in all directions except one. If a sudden change is imposed to this surface, transient one-dimensional conduction will occur within the solid.

Under what conditions can a plane wall be treated as a semi-infinite medium?

A thick wall can be modeled as a semi-infinite medium if all we are interested in is the variation of temperature in the region near one of the surfaces, and the other surface is too far to have any impact on the region of interest during the time of observation.

What is the law of thermal conductivity?

Fourier’s law of thermal conduction (also known as the law of heat conduction) states that the rate at which heat is transferred through a material is proportional to the negative of the temperature gradient and is also proportional to the area through which the heat flows.

What influences thermal conductivity?

Thermal conductivity is a material property. It will not differ with the dimensions of a material, but it is dependent on the temperature, the density and the moisture content of the material. The thermal conductivity of a material depends on its temperature, density and moisture content.

Does thermal conductivity depend on temperature?

The effect of temperature on thermal conductivity is different for metals and nonmetals. In metals, heat conductivity is primarily due to free electrons. In alloys the change in electrical conductivity is usually smaller and thus thermal conductivity increases with temperature, often proportionally to temperature.

Why does thermal conductivity increase with temperature?

As temperature increases, both number of free electrons and lattice vibrations increase. Thus the thermal conductivity of the metal is expected to increase. In gases, molecular collisions increase with the increase in temperature. Thus, the thermal conductivity of a gas increases with increase in temperature.

Why does thermal conductivity of water increase with temperature?

Same happens when we heat water, as the temperature increases the water expands making atoms move more freely enabling to transfer heat at increased speed (the resistance between atom decreaed) so the thermal conductivity increase with increase temprature.

What temperature does thermal conductivity of water start to fall?

The thermal conductivity exhibits a sharp drop in the temperature interval from the melting point (550 K) up to 650 K. At higher temperatures the thermal conductivity exhibits almost no temperature dependence.

How does temperature affect solid?

Temperature has a direct effect on whether a substance exists as a solid, liquid or gas. Generally, increasing the temperature turns solids into liquids and liquids into gases; reducing it turns gases into liquids and liquids into solids.

What happens when a material is heated?

when a material is heated it expands when you provide energy i.e heat to a substance it’s particles try to get free from intermolecular forces so due to expand of particles it tries to expand.

Which form of water has the highest thermal conductivity?

ice

Which material has least thermal conductivity?

Thermal Conductivity [BTU/(hr·ft⋅°F)] As you can see, out of the more common metals, copper and aluminum have the highest thermal conductivity while steel and bronze have the lowest.

What type of material makes the best insulator?

Plastic, rubber, wood, and ceramics are good insulators. These are often used to make kitchen utensils, such as saucepan handles, to stop heat from flowing up to burn the cook’s hand. Plastic coating is also used to cover most electrical wires in appliances. Air is also a good insulator of heat.