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Extruded finned tubes are bimetallic tubes whose outer aluminium surface is finned by cold plastic deformation.
There are two major types of finned tubes available with us, single metal tubes (also called mono metallic fin tube) and Bimetallic tube.

The former uses of drilled fins, Copper fins, Aluminum fins, and Copper Nickel fins alone.The later has a core tube on the inside made of harder material. In this case, the outer tube is rolled onto the core tube in order to provide for a tight bond and good thermal contact between the two tubes.

What is a fin tube?

Generally, tubes equipped with surface enhancing devices, such as fins or grooves, are used where heat exchange is required between two fluids whose ability to transmit calories is very far apart. For a water / air exchange, for example, the local exchange coefficient on the water side is much higher than that on the air side. Thus, fins are added to the surface in contact with air in order to increase the density of the heat flux between the two fluids.
Being the only interface between the hot and cold source, the extruded finned
tube is at the heart of heat transfer. Its quality plays a key role in the ability of an exchanger to efficiently transfer thermal energy between the two fluids. More
precisely, the way in which the fin is secured to the tube affects the efficiency of
the exchanger in the short, medium and long term.
Indeed, studies have shown that the main cause of the loss of efficiency of an
exchanger is due to a loss of quality of the fin attachment to the tube. Indeed, after a few thermal cycle, a gap between the fins and the tubes occurs due to
thermal expansion and vibrations. Galvanic corrosion between the two materials is also negatively affecting the tube-to-fin bond.

XTRUDED ALUMINUM FINS
Extruded aluminum finned tubes, also called “integral finned tubes”, are
formed from the parent metal of a thick tubular aluminum sleeve into which the fluid handling tube has been inserted. There is no restriction concerning the fluid handling tube material (it can be copper, copper nickel, stainless steel, titanium, duplex, etc.). The cold working of the fins in the finning process gives
exceptional mechanical resistance to the fins (strong fin, highly resistant to atmospheric corrosion, etc.). The pressure required to extrude fins from the aluminum sleeve creates an excellent “pressure bond” between the two materials.
Furthermore, the aluminum fin material completely encloses the metal of the
tube and consequently there is no risk of galvanic corrosion at the fin root (between tube and fin). All these advantages guarantee the most stable performance over time of all other fin types,Heat exchangers, cooper fin tube exchanger.
In some heat exchange solution, it might use if fin tube cover to protect the heat exchanger from particles of the air.

PERFORMANCE - THE BENEFITS OF EXTRUDED ALUMINUM

The performance degradation of a heat exchanger is essentially due to two phenomenon which occurs over time :

  • Increased fouling resistance due to impurity accumulation contained in both fluids.
  • Increased thermal resistance at the fin tubing, aluminum fins, fin pipe, bond due to thermal cycling dilatation of the materials and to corrosion at the fin base or root. These factors creates a loss of contact or bond pressure in between the fins and the tube.

HOW TO PREVENT LOSS OF PERFORMANCE?

  • Fouling impact on heat exchanger performance can be reduced by an internal and external cleaning on a regular basis.
  • There is No remedial solution (except tube replacement) for correcting performance degradation due to increased tube-to-fin resistance but this
  • can be prevented by using aluminum extruded finned tubes.

EXTRUDED FIN TUBE (BIMETALLIC FIN TUBE):-

The Extruded Fin Tube also known as Bimetallic grilled Tube is one of the most preferred finning processes for various applications.

The fin tube products are manufactured by Extruding the Finned aluminum Tube which is made to Fit with close tolerance over the Base Tube.

The Extrusion takes place on a Continuous Fin Extruder with Three Tooling rolls and extrusion takes place at high pressures in the range of 1200 psi. Because of the cold working process, the Bond between the Tube and fin is flawless and hence gives excellent Heat Transfer Efficiency. At the same time the mechanical strength of the fins is also enhanced drastically.

These tube and fin find application in AIR FIN COOLERS, DRIERS, RADIATORS etc. and are preferred in Industries like Food and Agriculture, Power Plants, Chemical Industries, Steel Plants, Chiller Plants etc.

Properties of Extruded Fin Tubes (Bimetallic Fin Tube):-

  1. Manufacturing Process:- Cold Extrusion
  2. Fin To Tube Bond:- Excellent
  3. Heat Transfer Efficiency:- Excellent
  4. Mechanical Resistance:- Excellent (Hence can be frequently cleaned with high pressure jets unlike other fin tubes. Thereby reducing down time and increasing overall life)
  5. Corrosion Protection:- Gives excellent corrosion protection to the base tube since it entirely covers the base tube (except bare ends).
  6. Temperature Range:- Upto Maximum 300 Deg C

1) What is Fin Tubes?
Fin Tubes or Finned Tubes are a type of heat exchanger tubes. They are used mainly in an air-cooled type heat exchanger where the exchange of heat takes place between gas flowing on the Fins and the fluid flowing inside the Fin Tubes. The main purpose is to increase the surface area to facilitate more exchange of heat between the medium and the air.

2) What is Extruded Fin Tubes or Bi-Metallic Fin Tubes?
Extruded Fin Tubes or Bi-Metallic Fin Tubes are a type of fin tubes that have extruded fins from the outer surface. The base tube is made to slide inside an outer tube made of copper or aluminum. Then, this assembly of the inner and outer tube is passed through an automatic extrusion machine. During the extrusion process, the fin is extruded from the outer tube to the desired height, thickness, and density configuration.

3) What is an extruded fin tube made of?
Extruded Fin Tubes or Bi-Metallic Fin Tubes are made of two main components:

  • Base Tube Material:- Carbon Steel/Alloy Steel/Mild Steel/Stainless steel and tubes manufactured by ERW or Seamless Process
  • Fin Material:- Aluminum/Copper

We can supply the Extruded Fin Tubes or Bi-Metallic Fin Tubes in both the combinations. Since this type of fin tube generally incorporates two different types of MOC for base tubes and fin material these are widely known as Bi-Metallic Fin Tubes also.

4) Where are Extruded Fin Tubes used?
Extruded Fin Tubes are mainly used in air fin coolers and different types of air-cooled radiators. They mainly find application in areas where the heat exchanger or the air fin cooler is exposed to a lot of harsh environment. They are preferred in the corrosive atmosphere mainly because of the following benefits:-

  • The outer provides comprehensive protection to the exposed surface of the base tube. It covers it completely throughout the length of the finned area and hence increases the overall life of the equipment.
  • The fins are made by the extrusion process and hence the strength of the fins is much more than other types of fins. This facilitates easy cleaning of the fin tubes, increases the service life, and reduces the time of the equipment.

Main industries in which the Extruded Fin Tubes or Bi-Metallic Fin Tubes find service are Process Chemical Plants, Refineries, Gas Processing Plants, Steel plants, Rice Processing Plants, Power Plants, Fertilizer Manufacturing Plants, etc.

Extruded Fin Tubes which are manufactured by cold rotary extrusion process. The Extruded Fin is formed from an outer aluminum tube with a large wall thickness, which is aligned over an inner base tube. The two tubes are pushed through three arbors with rotating discs that literally squeeze or extrude the aluminum fins up and out of the muff material in a spiral shape in one operation. The process of extrusion hardens the fins and prevents dissimilar metal contacts at the fin root. The exposed external surface is aluminum and there are no minute gaps between adjacent fins where moisture can penetrate. This ensures good efficiency that is expected when using an extended surface for heat transfer. During the finning process a tight mechanical bond is made between the finned aluminum outer tube and inner base tube of the required metal.

Advantages of Extruded Finned Tubes:

  • 100% fin-to-tube bond providing exceptional efficiency and longevity.
  • Excellent corrosion protection on the base tube.
  • Easy to clean with a high-pressure water jet without deforming the fins.
  • As the outer sleeve is continuous No galvanic corrosion between the tube and fins.
  • The bonding of the outer and inner tubes removes the risk of loss of contact with the aluminum due to thermal stress and fins are vibration resistant.
  • Higher heat transfer performance for the life of the unit.
  • Extruded Finned tubes are commonly used in applications with temperature up to 325 °c.

Applications of Extruded Finned Tubes:
Extruded Fin Tubes are widely used in the refinery, petrochemical and chemical industry for:

  • Air-cooled condensers
  • Air-cooled coolers for products
  • Gas coolers
  • Gas heaters

Extruded aluminum fin tubes

Extruded fin tubes  are the centerpiece of nearly all our heat exchangers. Their “double-wall” construction makes them extremely durable and heat-efficient. You can also choose from among several types of tube materials, which allows our heat exchangers to be specifically adapted to a given application. In addition, our extruded fin tubes are designed to prevent corrosion between the fins and tube, unlike fins embedded in the exterior wall of the tube. Used properly, our tubes are entirely suitable for steam coils.

Extruded fin tubes are manufactured by a rotary extrusion process in order to obtain integral fin tubes. We manufacture them by inserting a lining in an aluminum extrusion. The extrusion is radially crushed on the lining, and the excess material is pushed into the shape of spiral fins. The extrusion process solidifies the fins and prevents the galvanic corrosion that would occur if there were two metal alloys exposed to air, as is the case with other types of fins. Compared to other similar products, our fins do not break, nor do they uncoil, and the lining does not come loose, thereby maintaining the heat exchanger’s thermal performance.

The advantages of extruded aluminum fin tubes are as follows:

  • Easy to clean with a high-pressure water jet without deforming the fins
  • The tube is not mechanically stretched to adhere to the fins
  • Uniform and reliable heat transfer
  • No galvanic corrosion between the tube and fins
  • The fins are vibration resistant
  • Perfectly suited to industrial applications
  • Unequalled quality/price ratio for demanding applications

Extruded Finned Tube

This fin type is formed from a bi-metallic tube consisting of an aluminum 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 produce an integral fin with excellent heat transfer properties and longevity. Extruded fin offers excellent corrosion protection of the base tube and excludes virtually all exposure to any outside fluid.

Aluminum finned carbon steel tubes
Cross-sectional schematic of extruded fin

Extruded finned tubes are used in high temperature conditions and corrosive atmospheric conditions such as:

  • operating temperatures less than 300°C;
  • offshore or other remote applications;
  • heat pipes;
  • dry air coolers for air, gas or oil;
  • air to air heat exchangers for HVAC applications;
  • air dehumidification in air treatment plants and
  • energy recovery in air exhaust system.

EXTRUDED TYPE FINNED TUBE FOR HEAT EXCHANGERS

Short Description:
The processing technology of steel-aluminum Extruded Type Finned Tube is to first process aluminum tube and steel tube into bimetallic composite tube, and then form fins after mechanical cold rolling.

Steel-Aluminum Extruded Type Finned Tube

The processing technology of steel-aluminum Extruded Type Finned Tube is to first process aluminum tube and steel tube into bimetallic composite tube, and then form fins after mechanical cold rolling. The aluminum fins are tightly combined into a bimetallic tube finned tube (composite extruded finned tube)

Steel-aluminum rolled finned tubes are integrally rolled from aluminum tubes, and have the characteristics of no contact thermal resistance, high strength, thermal shock resistance and mechanical shock resistance, good thermal performance, and a considerable expansion heat transfer surface. This finned tube heat exchanger is in front of the tube or around the plate.

Steel-Aluminum Extruded Type Finned Tube Quick Details:
Core tube material:
1. Carbon steel: A179, A192, SA210 Gr A1/C, A106 Gr B
2. Stainless steel: TP304/304L, TP316/TP316L/316Ti, A789 S31803/S2205
3. Copper: UNS12200/UNS14200/UNS70600, CuNi70/30, CuNi 90/10
Fin material:
1. Aluminum (Alu.1100, Alu.1060)
2. Copper.

Fin type: Solid plain
Fin Tube Type: G Type Embedded
Outer diameter (OD): 16mm Min~50.8mm max.
Tube length: up to 18,000 mm.
Fin height: 16.5mm max.
Fin thickness: generally 0.4mm~0.6mm
Fin pitch: 2.1mm minimum (12FPI)
Surface Protection: Both bare ends shall be zinc or aluminum metallized by electrospray arc system coating.
Accessories: Tube support boxes, clamps or spacer boxes (materials: aluminium, zinc and stainless steel).

Additional Info
Payment Terms:T/T, LC
Delivery: 15-30 days after payment
Marking: Standard + Steel Grade + Size + Heat No + Lot No
Package: Iron frame packing boxes and the desiccants are put into each package for continental transportation as well. or as required

Fin Type:
Fins are solid flat or serrated into 12, 16 or 24 segments or according to your design.

Finless part
Both end with appr. 10mm~50mm, there is a gap in the middle (no fin part).
 
Steel-Aluminum Extruded Type Finned Tube with two different materials
Core tube material: carbon steel, low alloy steel, stainless steel, brass, copper, copper-nickel alloy, aluminum bronze, nickel alloy.

Fin material:
1. Aluminum (Alu.1100, Alu.1060)
2. Copper.
3. Steel

Quality Control for Steel-Aluminum Extruded Type Finned Tube
Inspection and Tests Performed
Chemical Composition inspection,
Mechanical Properties Test(Tensile Strength, Yield Strength, Elongation, Flaring, Flattening, Hardness, Impact Test),
Surface and Dimension Test,
No-destructive Test,
Hydrostatic Test.
 
Acceptance Criteria
API Standard 661 (Air-Cooled Heat Exchangers for General Refinery Service) or Delivery Conditions (TDC).
 
Features of Steel-Aluminum Extruded Type Finned Tube
1. High heat transfer performance and small contact thermal resistance;
2. The contact area between the fin and the tube is large, and the fit is tight and reliable;
3. Good corrosion resistance and stable long-term performance;
4. The fins have good rigidity and are not easily deformed.
 
Application of Steel-Aluminum Extruded Type Finned Tube
Steel-Aluminum Extruded Type Finned Tube is widely used in steel, petroleum, chemical, machinery, shipbuilding, power station, hospital and food industries.

There’s another material of Heat exchanger ,such as cooper fin tube exchanger is also a very good heat transmit object in heat exchange filed. Sometime, designer will use the fin tube cover to protect the heat exchanger system from pollution of particles.

Your best solution in Heat Exchange solution!

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