Fin tube

A fin tube is a tube that has small fins around the outside surface.

These fins act as a filter and a mechanism to transfer heat from the material inside the tube to the outside space or vice versa. Fin tubes are used in applications that require a transfer of heat from a hot fluid to a colder fluid through the tube's wall.

Sunny Steel provide a wide range of fin tubes are used in heat exchangers (air, water and chemically cooled)
for various industries such as petroleum, petrochemical, steel, power generation and many more.

The advantages of finned tubes

Transferring heat from a hot fluid into a colder fluid through a tube wall is the reason many of us use finned tubes. But you may ask, what is the major advantage of using a finned tube? Why can’t you just use a regular tube to make this transfer? Well you can but the rate will be much slower.

By not using a finned tube the outside surface area is not significantly greater than the inside surface area. Because of that, the fluid with the lowest heat transfer coefficient will dictate the overall heat transfer rate. When the heat transfer coefficient of the fluid inside the tube is several times larger than that of the fluid outside the tube the overall heat transfer rate can be greatly improved by increasing the outside surface area of the tube.


Finned tubes increase outside the surface area. By having a finned tube in place, it increases the overall heat transfer rate. This then decreases the total number of tubes required for a given application which then also reduces overall equipment size and can in the long-run decrease the cost of the project. In many application cases, one finned tube replaces six or more bare tubes at less than 1/3 the cost and 1/4 the volume.

For applications that involve the transfer of heat from a hot fluid to a colder fluid through a tube wall, fin tubes are used. Usually, for an air heat exchanger, where one of the fluids is air or some other gas, the air side heat transfer coefficient will be much lower, so additional heat transfer surface area or a fin tube exchanger is very useful. The overall pattern flow of a finned tube exchanger is often crossflow, however, it can also be parallel flow or counterflow.

Fins are used to increase the effective surface area of heat exchanger tubing. Furthermore, finned tubes are used when the heat transfer coefficient on the outside of the tubes is appreciably lower than that on the inside. In other words, heat transferred from liquid to gas, vapor to gas, such as steam to air heat exchanger, and thermic fluid to air heat exchanger.

The rate at which such heat transfer can occur depends on three factors – [1] the temperature difference between the two fluids; [2] the heat transfer coefficient between each of the fluids and the tube wall; and [3] the surface area to which each fluid is exposed.

Finned tubes are used because they help:

Increase Heat Transfer Rate:

A finned tube exchanger typically has tubes with fins attached to the outside. Usually, there will be some liquid flowing through the inside of the tubes and air or some other gas flowing outside the tubes, where the additional heat transfer surface area due to the finned tube increases the heat transfer rate. In a crossflow fin tube exchanger, the fins will typically be radial fins and they’ll either be circular or square in shape.

Improve Heat Transfer Coefficient:

By not using a finned tube, the outside surface area is not significantly greater than the inside surface area. Because of this, the fluid with the lowest heat transfer coefficient will dictate the overall heat transfer rate. When the heat transfer coefficient of the fluid inside the tube is several times larger than that of the fluid outside the tube, the overall heat transfer rate can be greatly improved by increasing the outside surface area of the tube.

Increase Outside Surface Area:

By having a finned tube in place, it increases the overall heat transfer rate. Finned tubes increase the outside surface area. This decreases the total number of tubes required for a given application which then also reduces overall equipment size and can in the long-run decrease the cost of the project.

Finned tube heat exchangers are used in a variety of applications, and more so as industrial heat exchangers. An air heat exchanger like the evaporator coil in an air conditioning unit is typically a fin tube exchanger. Another common fin tube air heat exchanger is the car radiator. The purpose of the car radiator is to cool the hot water in the tubes with the air passing through the crossflow. On the contrary, the air conditioner evaporator coil has the purpose of cooling the air passing through it. The finned tubes that are manufactured at Kainon Boilers, use high grade carbon steel, stainless steel, copper, brass, and aluminum. Our finned tube exchangers are designed to meet the specific duty condition, temperature and pressure of the fluids.

Fin tube reference

Carbon steel fins are available on carbon, stainless steel, or copper tube. Please call for a specific size if not listed

Type Description Base tube
O.D. (mm)
Fin specification (mm)
Fin pitch Fin height Fin thick
Embedded G-type fin tueb 16-63 2.1-5 <17 ~0.4
Extruded Single metal combined metal 8-51 1.6-10 <17 0.2-0.4
Low fin tube t-type fin tube 10-38 0.6-2 <1.6 ~0.3
Bamboo tube corrugated tube 16-51 8-30 <2.5 /
Wound l/kl/ll type fin tube 16-63 2.1-5 <17 ~0.4
String String fin tube 25-38 2.1-3.5 <20 0.2-0.5
U-type U-type tube 16-38 / / /
Welding HF-welding fin tube 16-219 3-25 5-30 0.8-3
H/HH type fin tube 25-63 8-30 <200 1.5-3.5
Studed fin tube 25-219 8-30 5-35 φ5-20

According to user needs, we can produce all kinds of steel strip winding finned tube and steel aluminum composite finned tube.

Materials

Carbon steel fins are available on carbon, stainless steel, or copper tube. Please call for a specific size if not listed

We offer you a broad portfolio of materials and can expand our offering at any time to meet your specific needs regarding thermal conductivity, mechanical properties, or corrosion resistance.

  • Base tube: Carbon steel, Stainless steel, Copper, Cupro Nickel, Aluminium, Alloy Steel
  • Fin: Carbon steel, Stainless steel, Copper, Aluminium
  • Rings: Carbon steel, Aluminium, Hot dip galvanizing

Fintube FAQs

We are a pretty proactive bunch. So, while we do charge a small fee per design to cover our costs, we absorb these costs when it is for a regular customer or where we are working jointly on a project. We also refund the fees in case it is followed by an order.

Can you assist with the design for my application?

Absolutely, we can.

Applied Fin Tube

Applied Fin Tube is made with strip wrapped under tension around the base of the tube. Fins are welded to the base tube at the strip ends.

Fin material N° fins per meter Strip thickness Production capacity
All type of material From 50 to 500 From 0,4mm. to 0,5mm. More than 500 meters per day
Tube material Tube thickness O.D. tube Lenght available
All type of material 1,00mm. minimum From 10,00mm. to 200,00mm. All lenghts up to 8 Meters

Why do Pin fin tubes weigh less than L type fin tubes?

Pin Fin tubes are made from wire. Being cylindrical, wire has a larger area per unit of weight than the strip used in L type fin tubes. Also, due to the looped nature of the wire, less material is put on the tube than in the case of L fins. Consequently, the surface area of fins per meter of tubes is also less. However due to the superior turbulence created by the looped wire the actual heat transfer per meter of tube is significantly higher than in the case of L Type Fin Tubes. All of this together contributes to the weight differential between wire wound fin tubes and L Type Fin Tubes. In the case of similar metals, it is weighing half and in the case of Aluminium L fin vs. Steel wire fin they weigh about the same. The higher performance S5 pin fin tubes have an airside heat transfer performance per meter of tube that is 250% of the L type fin tubes.

Can Sunny Steel supply my fin tubes?

Yes. A lot of our customer choose to supply their own pipes or tubes, however, a lot of customers ask us to supply them and we are happy to accommodate! We stock various sizes and if we don’t have what you need we can bring it in from one of our many suppliers. If you would like us to include the pipe or tube material in your order, please indicate that when you request a QUOTE.

High Frequency Resistance Welding

A continuous helical fin is attached to the base tube by high frequency electric resistance welding in order to give an efficient and thermally reliable bond. Fins can be either solid or serrated (segmented). The weld produced in this process is a true forge, blacksmith weld. This type of weld is comprised of a fusion between two portions of parent metal without the introduction of a filler material. The weld is simply produced by heating the interfaces to be joined to a plastic state and applying pressure.

Used in boilers, furnaces and fired heaters for efficient heat recovery.

Uses of finned tubes

The main uses for high frequency welded finned tubes are in the heat recovery associated with boilers for power generation and in furnace applications for the petrochemical industry.

Tube bending:

Our finning machines are equipped with online single or duplex cold bending equipment that can manipulate both ends of tubes in a single operation, thus ensuring exact alignment of the ends.

Do we stock fin tubes?

We do not. Our market lends itself to customer designed products, each special in itself. The number of combinations of diameter, overall length, materials and fin specs are too vast. Sunny Steel builds each finned product to each customers needs.

What are finned tubes used for?

Finned tubes are the main components of heat exchangers. They are a series of tubes where fins have been added on the outside to increase the contact area with the outside fluid, to exchange heat and between the fluid inside the tube and the fluid outside the tube. Finned tubes are elongated aluminium cladded carbon steel flat tubes with brazed aluminium fins.

The rate at which such heat transfer can occur depends on three factors:

(1) the temperature difference between the two fluids;

(2) the heat transfer coefficient between each of the fluids and the tube wall; and

(3) the surface area to which each fluid is exposed. In the case of a bare (unfinned) tubes, where the outside surface area is not significantly greater than the inside surface area, the fluid with the lowest heat transfer coefficient will dictate the overall heat transfer rate. When the heat transfer coefficient of the fluid inside the tube is several times larger than that of fluid outside the tube (for example steam inside and oil outside), the overall heat transfer rate can be greatly improved by increasing the outside surface of the tube. In mathematical terms, the product of heat transfer coefficient for the outside fluid multiplied by the outside surface area is made to more closely match the product of the inside fluid heat transfer coefficient multiplied by the inside surface area.

Production Technique & Applications

We offer multiple fin styles, all with different specs and operative requirements.

"G" fin

G fin tube

Fin strip is wound & embedded on a groove and securely locked by closing the groove with the base tube metal. This ensures maximum heat transfer at high temperatures.
Max. operating temp. 450ºC

“Crimped” Fin

This fin type is a non taper fin wrapped under tension around the base tube. The finning process results in a crimp forming at the foot of the fin. Fin is then welded to the base tube at the strip ends. Max. operating. temp. 250ºC

"KL" fin

After application the fin foot is knurled into the corresponding knurling on the base tube thereby enhancing the bond between the fin and tube resulting in improved heat transfer characteristics. Max. operating. temp. 260ºC

“LL” Fin

LL fin tube

Manufactured in the same way as the ‘L’ fin type except that the fin foot is overlapped to completely enclose the base tube thereby giving excellent corrosion resistance. This type of tube is often used as an alternative to the more expensive extruded type fin in corrosive environments. Max. operating. temp. 180ºC

"L" fin

The strip material is subjected to controlled deformation under tension giving the optimum contact pressure of the foot of the fin onto the base tube thus maximizing the heat transfer properties. The foot of the fin considerably enhances the corrosion protection of the base tube. Max. operating. temp. 150ºC

“Extruded” Fin

This fin type is formed from a bi-metallic tube consisting of an aluminium outer tube and an inner tube of almost any material. The fin is formed by rolling material from the outside of the exterior tube to give an integral fin with excellent heat transfer properties and longevity. Extruded fin offers excellent corrosion protection of the base tube. Max. operating. temp. 280ºC



Fitting specification, Standard and identification

There are different varieties of pipe fittings made of various materials and available in various shapes and sizes.



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