What is a fin tube heat exchanger? Heat exchangers heat or cool buildings, improve the efficiency of engines and machines. Refrigerators and air conditioners use heat exchangers to cool elements; radiators use them to warm environments. It&#;s all about controlling heat energy &#; either removing it or adding it, depending on the goal and function. 

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At Energy Transfer, we manufacture fin tubes, as well as enhanced surface and formed and dimpled tubes, for tube fin and tubular heat exchangers. We sell both to original equipment manufacturers as well as people looking to repair existing heat exchangers.

When it comes to building or repairing a tube fin or tubular heat exchanger, how do you determine which tube is right for your heat exchanger? Which one will provide the best thermal solution? What do you need to know to ensure superior heat transfer capability?

It pays to do your homework. Thoroughly researching a manufacturer&#;s product offerings and capabilities invariably results in a more suitable fin tube to meet your goals and ambitions. 

Energy Transfer manufactures a diverse range of fin tube pipes to serve a variety of heat exchanger needs. All options are on the table. We&#;re ready to meet any need &#; turn your vision into a reality of superior performance. 

This guide will walk you through the selection process of how to choose the optimal finned tube for your heat exchanger. [/vc_column_text][/vc_column][/vc_row][vc_row][vc_column][vc_column_text]

What is a Fin Tube Heat Exchanger?

[/vc_column_text][vc_empty_space][/vc_column][/vc_row][vc_row][vc_column width=&#;1/2&#;][vc_column_text]By definition, a heat exchanger is a device used to transfer thermal energy between two or more fluids &#; it allows heat from a liquid or gas fluid to pass to a second liquid or gas without the two fluids mixing together or coming into direct contact. 

The objective of a heat exchanger may be to recover or reject heat, or to sterilize, pasteurize, fractionalize, distill, crystallize, or control a fluid or process fluid.[/vc_column_text][/vc_column][vc_column width=&#;1/2&#;][vc_single_image image=&#;&#; img_size=&#;full&#; alignment=&#;center&#; style=&#;vc_box_border_circle&#; border_color=&#;black&#;][/vc_column][/vc_row][vc_row][vc_column][vc_empty_space][vc_column_text]Tubular heat exchangers consist of small tubes located within a cylindrical shell. These finned pipes are positioned within a cylinder as a bundle, allowing various gases or liquids to circulate in a process of heat exchange that either warms or cools an element.

One fluid or gas flows through a set of metal tubes while a second fluid or gas passes through a surrounding sealed shell. The fluids can flow in the same direction (a parallel flow) or opposite directions (counterflow or counter-current), or at right angles (crossflow). 

To increase heat transfer capabilities, fin tube pipes can either have fins that are applied as a second material (as is the case of applied fin tubes), or raised out of the material of the tube itself (such as low fin, medium-high fin, and high finned tubes).

For tubular heat exchangers where there are no fins but just a smooth tube, the tubes can have enhanced surface or formed dimples to mitigate flow and increase heat exchange capabilities.

Conventional Tube-Fin heat exchangers are most commonly used in gas-to-liquid applications.  Round fins on the outside of the tube are used on the gas side of the heat exchanger to increase surface area.  The liquid side of the heat exchanger consists of a tube bundle of Finned Tubes supported by a sheet metal frame with common headers on each end of the bundle.[/vc_column_text][vc_empty_space][vc_column_text]

Determining Required Heat Transfer for Finned Tubes

The first step is to determine how much heat transfer is required and how much heat transfer surface you&#;ll need. This will help decide which type of fin tube pipe is the optimal thermal solution, including necessary fin surface requirements and the ideal material. What fin tube geometry is required in order to accomplish your vision?

You also should determine the necessary rate of flow, which will affect the required diameter of the fin tube. This is affected by tube size. 

• How much pressure drop is needed? 

• What size of hydraulic diameter is required?

• What is the flow length of each fluid side of the heat exchanger?

• What is the minimum free flow area?

• What do you need in the frontal area? 

• What is the flow length of each fluid side of the heat exchanger?

Heat transfer can be improved by increasing the number of tubes or by increasing the length of the finned tubes.

These factors are all measured by heat transfer calculation software that boils down the necessary physics of the tube through well defined computed science. You can then determine if you&#;ll need a smooth tube, a formed and dimpled tube, or a finned tube to achieve the required heat exchange capabilities. [/vc_column_text][vc_empty_space][vc_single_image image=&#;&#; img_size=&#;full&#; alignment=&#;center&#; style=&#;vc_box_shadow_circle&#;][vc_empty_space][/vc_column][/vc_row][vc_row][vc_column][vc_column_text]

How to Optimize Heat Transfer Performance

The potential heat transfer you can achieve is baked into the thermal properties of the fin pipes themselves. The amount of heat transfer can be controlled through surface dimension: fin count, the length of tube, and enhanced or formed and dimpled tube shapes. 

Heat transfer is also affected by the thermal conductivity of the metals used to make the fin tubes. Copper fin tubes, for example, are nearly twice as conductive as aluminum fin tubes, and nearly 6 times the thermal conductivity of steel fin tubes. Copper finned tubes are more than 25 times the conductivity of stainless steel finned tubes.

Material corrosiveness or acidity is also a determining factor in material selection, depending on the nature of the gas or fluid that will flow through the heat exchanger. 

Choosing the Right Material

When choosing materials, you naturally face 2 concerns:

1. Availability of Materials

2. Cost of Materials 

Is the material going to be readily available or will it take time to get? How will this affect manufacturing deadlines?

What is the cost of each material? These are precious materials with an inherent value based on fair market prices. Copper fin pipe will generally cost more than aluminum, but it maintains the best heat transfer among common alloys. Copper&#;s chemical properties are ideal for many heat exchanger applications &#; it&#;s easily formed and can be readily enhanced for heat exchanges.

Ask yourself:

• Are the desired heat exchange properties and corrosion advantages worth the cost? 

• Can the materials be accessed within an acceptable time frame? 

Thermal solution advantages must be weighed against cost and material procurement concerns to determine the best path forward.[/vc_column_text][vc_empty_space][vc_single_image image=&#;&#; img_size=&#;full&#; alignment=&#;center&#; style=&#;vc_box_border_circle&#; border_color=&#;black&#;][vc_empty_space][vc_column_text]

Proactive Material Procurement in the Age of COVID-19

The cost of materials is naturally affected by the metals market &#; which can ebb and flow even in normal times. But in the headwinds of COVID-19, it&#;s a perfect storm.

The pandemic has had a radical impact on the tube mill industry and its ability to respond to demand. Many mills have limited production of certain materials; some mills have stopped production completely. 

To navigate these challenges, we&#;ve had to be more thorough in our planning of material procurement. We need to think further ahead and be more proactive in future planning needs.

To optimally meet material needs as we accommodate the challenges of today&#;s &#;new normal,&#; flattening demand is essential. 

Anything you can do to ensure consistency and avoid spikes or drops in demand will result in a smoother procurement process. Fluctuations in demand prove challenging, but consistency can be planned and optimally accommodated. This will result in a smoother, streamlined manufacturing process that&#;s more predictable with fewer hiccups. 

By planning for consistency, you&#;ll stay ahead of demand &#; and maintain an even flow of the fin tubes you need.[/vc_column_text][vc_empty_space][vc_column_text]

Our Unsurpassed Variety in Fin Tube Potential

There is a wide range of fin tubes, enhanced surface tubes, and formed and dimpled tubes available to accommodate an eclectic array of challenges and functions. 

Energy Transfer just happens to have some of the largest varieties of finned tubes on the market. And because of our versatile market position, we can accommodate nearly every style of heat exchanger design and fin tube application you can come up with.

To optimize the heat transfer capabilities of your heat exchanger, take some time to learn what we have available. Take a close look at our product pages, our sales brochure, and the engineering dimensions outlined in detail. [/vc_column_text][vc_row_inner][vc_column_inner width=&#;1/2&#;][vc_single_image image=&#;&#; img_size=&#;full&#; alignment=&#;center&#;][/vc_column_inner][vc_column_inner width=&#;1/2&#;][vc_column_text]After all, creativity is largely fueled by option availability. You can either look at the different finned tube products we have available and pick one &#; or you can learn about our capabilities and come up with your own configuration based on existing products.

Having that information will streamline the selection process for which products will work best. It will also give you a rich understanding of our full potential &#; and help to leverage the advantages of Energy Transfer&#;s superior performance.[/vc_column_text][/vc_column_inner][/vc_row_inner][/vc_column][/vc_row][vc_row][vc_column][vc_column_text]Once you&#;ve taken a detailed look at what finned tubes we have available, talk to one of our sales engineers to see what&#;s truly possible.

The beauty of variety is unleashed potential. That&#;s the advantage of working with a highly qualified company with a rich diversity in product offerings. Energy Transfer has the tooling, mechanical engineers, and development teams ready on hand to make your vision a reality &#; whatever form that might take.[/vc_column_text][vc_empty_space][vc_separator color=&#;black&#; border_width=&#;3&#;][vc_empty_space][vc_column_text]

Have a question about fin tubes? We&#;re happy to help! Schedule a FREE consultation!

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Want to build a seamless fin tube? Our FREE GUIDE tells you everything you need to know. Download yours today![/vc_column_text][vc_empty_space][/vc_column][/vc_row][vc_row][vc_column][vc_column_text] [/vc_column_text][/vc_column][/vc_row]

Heat Exchanger Finned Tube - 8 types you should know about

In a previous article we focused on problems such as corrosion, erosion and thermal fatigue in the tubes of Shell & Tube heat exchangers.

In this month&#;s article, we aim to provide you with an overview of some of the different types of finned tubes (extended surface tubes) you may encounter and the applications or duties they suit.

Fig 1: Large Seven Fan Finned Coil cooler &#; copper tubes with bulleted aluminium fins

Finned tube heat exchangers generally use air to cool or heat fluids such as air, water, oil or gas, or they can be used to capture or recover waste heat. These heat exchangers can used in a broad range of industries including oil & gas, power generation, marine and HVAC&R.

Finned tube heat exchangers have a wide range of applications, a few of which are:

• diesel charge air coolers;
• oil coolers;
• hydrogen coolers;
• waste heat recovery;
• driers;
• air conditioning;
• air heaters;
• steam condensers;
• generator coolers

Finned tube heat exchangers are often used in circumstances where air is the preferred medium for the cooling or heating, particularly where there is limited or poor quality water.

In a finned tube heat exchanger, heat is exchanged between a thermally efficient fluid that transports heat efficiently, such as a liquid which has some viscosity, and a fluid that does not, such as air or gas with little density. On the &#;air side&#;, the tube surface is enhanced by the addition of fins or other elements such as looped wires, designed to increase the surface area of the tube and improve its thermal performance.

Fins can range in height (high-fin to low-fin) and the fins can be either pressure connected to the outer surface of the tube or formed into the tube surface.

Depending on the intended duty and the environment in which they are to operate, finned tubes can be manufactured in numerous designs and incorporate a combination of differing materials for both the tubes and the fins. The types and combinations of tubes and fins is significant, but in this article, we will explore only the more common types.

Are you interested in learning more about Industrial Finned Tube Heat Exchanger? Contact us today to secure an expert consultation!

Fig. 2: Finned Tube Dry Air Cooler

Fin Profile

The profile of the fins has significant effect of the performance of a finned tube heat exchanger.  It is important to ensure each fin has a tight connection on the tube surface to provide maximum thermal conductivity.

The larger the fins and the tighter the fin pitch, the more thermal conductivity is achieved. The trade-off may be an increase in pressure drop which may, in turn, adversely affect performance. A balance between the two opposing functions is vital for effective and optimal thermal performance and equipment function.

Fig. 3: Typical Finned tube schematic with annular fins.
A = fin height; B = fin pitch, C = fin thickness and D = Diameter of

1. Elfin Technology

&#;Elfin&#; finned tubes are used extensively in hydro power generator coolers and have been chosen by hydro power stations such as Snowy Hydro, Hydro Tasmania and Origin Energy, to provide long lasting and reliable cooling of their important generators.

With the Elfin computer-generated technology, each fin strip is mechanically forced over the outside of tube, producing a tight and thermally efficient bond. This process ensures, not only excellent adhesion of the fin to the tube, but the vital inner tube wall is not compromised in any way.

Unlike Elfin tubes, bulleted tube fins are formed by passing a bullet inside the tube to enlarge and force its wall outward into the fins to form a bond with the fins.

Fig. 4: Elfin Technology &#; Titanium Fins and Titanium Tubes. Note the spacer lip on the fin ensuring exact pitch.

As can be seen in Fig. 4 the fins have been precision punched to leave an &#;L&#; shaped lip that ensures exact fin pitch spacing between fins. The computerized punch process can adjust the tube pitch minutely to 0.01mm tolerance to conform with the exacting computer calculations. Elfin finned tubes are produced in blocks which are custom sized to fit the exact duty requirements and dimensions of the heat exchanger.

Bulleting require tubes that are sufficiently thin and ductile to allow for expansion however Elfin technology allows tubes of any wall thickness and material to be used and ensures the inner surface of the tube is not compromised and the strength of both the tubes and the fins is enhanced.

Fig. 5: Hydro Power Generator Cooler Elfin Block Finned Tubes &#; Copper tubes & Aluminium fins

Fig. 6: Elfin Block Gas-liquid Heat Exchanger. Note: Rolled Naval Brass Tube Sheet

Fig. 7: Elfin Block Charge Air Cooler. Note: Rolled Naval Brass Tube Sheet

2. Bulleted Fins

With an external appearance similar to Elfin Finned Tubes, bulleted finned tubes are a common and cost-effective way to attach strip fins to tubes. This is achieved by manually placing the fins over the tubes and pushing or pulling a &#;bullet&#; through the tube (&#;bulleting&#;) to expand the tube wall out into the fins, locking them in place.

Bulleting is commonly used in Fin Coil units found in applications such as HVAC&R and is a cost effective process which requires tubes that are of a material and thickness and sufficiently ductile to enable the tube to be expanded into the fins.

Helical Fins

Round or Helical Fins come in a number of geometries commonly identified by a letter corresponding to the profile of the base of the fin where it connects with the tube.

Fig. 8: Hydrogen Cooler in the process of manufacture.
Helical wound fins &#; CuNi tubes / Cu fins

3. &#;L&#; Finned Tubes

One common type of finned tube is the &#;L&#; fin. Receiving its name from the letter it creates from the cross-sectional view, the &#;L&#; fin relies on maximum surface contact between fin and tube which is ensured by tension-forming a fin strip helically around the base tube.

This type of connection maximizes the heat transfer capacity and enhances the corrosion protection of the tube. The &#;L&#; fin accommodates temperatures between 150 to 170 °C and comes in mainly ductile metals such as aluminum or copper which are capable of withstanding the compression around the base of the fin and allow stretching on the outside during installation.

Fig. 9: Typical Heavy-Duty Dry Air Cooler or Condenser &#; commonly using copper, aluminium or carbon steel tubes with helical aluminium or galvanized fins.
Note the removable bolts in the header box which allow for inspection and cleaning of the tubes.

Fig. 10: Copper finned tubes copper tubes

Fig. 11: Cross-sectional schematic of L fin

4. &#;LL&#; Finned Tube

Manufactured in the same way as the &#;L&#; finned tube, the &#;LL&#; fin has overlapping feet to completely enclose the base tube, resulting in excellent corrosion resistance. The maximum operating temperature is approximately the same as the &#;L&#; fin. This type of fin commonly available in aluminum and copper. The Overlapped &#;L&#; fin design has interlocking fins that are wound together to prevent movement and separation. The fins protect the entire tube and the designation works well for the applications where corrosion is an issue.

Fig. 12: Copper finned carbon steel tubes

Fig. 13: Cross-sectional schematic of &#;LL&#; fin

5. &#;KL&#; Finned Tube

&#;KL&#; Fin Tubes are also called knurled finned tubes. The fin is wrapped around the tube and the foot is rolled into the outer surface of the pre knurled tube and secured at each end. The fins are manufactured from a strip of metal which is machined into an accurately controlled L shape foot, similar to the L type fin, then it is rolled into a taper causing it to curl. The tube surface is knurled by a rotating tool, then the foot of the fin is knurled into the base tube providing a tight bond that optimizes thermal transfer.

Fig. 14: Aluminum finned carbon steel tubes

Fig. 15: Cross-sectional schematic of &#;KL&#; fin

6. &#;G&#; Embedded Finned Tube

The main design feature of Embedded Fin tubes involves the fin being inserted and welded into a helical groove cut into the tubes. G fins can be used in higher temperatures and are very durable. Embedded fins are best suited for use in high thermal cycling or high temperatures and where the fin side will be subjected to regular cleaning. This type of fin comes with a major limitation being the need for a minimum wall thickness of 1.65mm to accommodate the grooves. However, the &#;G&#; type fin can withstand temperatures of up to 400°C and can incorporate carbon steel fins for better conductivity.

Fig. 16: Copper &#;G&#; finned carbon steel tube

Fig. 17: Cross-sectional schematic of &#;G&#; fin

7. 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.

Fig. 19: Aluminum finned carbon steel tubes

Fig. 20: Cross-sectional schematic of extruded fin

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

• operating temperatures up to 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.

8. Wire Finned Tube

Wire loop tube is a high efficiency tube consisting of a series of elongated wire loops enhancing the surface of the tube, spirally wound on to the tube wall and held in position with a binding wire at the base of the loops. The loops and binding wire are then soft-soldered to the tube wall to give a metallic bond between the wire loops and the tube.

The wire loop secondary surface gives these enhanced tubes excellent heat transfer characteristics due to its ability to promote turbulence in the fluid passing over it. Temperatures of up to 250 °C can be applied to this type of finned tube.

Fig. 21: Copper wire loops on carbon steel tube

What next?

There are many variables  to be considered to successfully select and design a finned tube heat exchanger including:

• the duty to be performed;
• type, style and number of tubes required;
• metals best suited for the tubes and the fins;
• type of tube enhancement &#; fins or wire;
• thickness of the tube walls;
• I/D and O/D of the tubes;
• pitch of the fins;
• type and number of fans to provide air flow;
• the environment in which the heat exchanger is to be used and
• the duty it is required to perform

To ensure you get the best finned tube heat exchanger for your needs requires high-end software calculations, experience and technical know-how to bring it all together into a reliable unit that will provide years of efficient and reliable service.

Fluid Dynamics and its highly skilled international partners have many decades of expertise in the design, manufacture and maintenance of finned tube heat exchangers. Get in touch to find out more.

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