According to the heat exchange application and operation, there are various materials.
The common ones are Aluminum, Alloy, Copper, Brass, Nickel, Titanium, Stainless Steel, Carbon Steel, etc, among which the aluminum and alloy are mostly used.
The basic performance for fin tube heat exchange should be with good solder ability and form ability, higher mechanical strength, good corrosion resistance and thermal conductivity. In spite of these, aluminum and alloy are also featured in extension and higher tensile strength increases under lower temperature. Around all world, especially for low temperature and compact heat exchange, they are widely applied.
Let’s see the feature of aluminum
- Low Density
By alloying and heat treatment, it can reach the structural of construction steel. Suitable for various transportation, especially for small vehicle, reducing weight and consumption.
- Good Corrosion Resistance
When under harsh conditions, the materials oxide from aluminum is non-toxic. With aluminum heat exchange, no worries that air or liquid inside will be destructed by oxide after long time.
- Good Thermal Conductivity
Especially suitable for radiating fin, heat transfer evaporator and condenser.
- High Yielding and resistance to die cutting.
It is easy for processing and forming.
As a professional finned tube manufacturer, our leading product is aluminum finned tube. Should you have any interest, please contact us for more.
Fin Tube Ration Affected by Fin Height, Fin Thickness and Fin Pitch
When the fins are root-grounded on the base bare tube, in the case of heat from inside to outside, the heat will be transferred from fin root along fin height. It is also continuously transmitted to the surrounding fluid by convective heat transfer. As a result, the fin temperature gradually decreases along the altitude. This also illustrates that difference between fin temperature and ambient fluid temperature is reducing gradually and the heat change per unit is shrinking. Therefore, the effect of fin surface area on enhanced heat transfer is decreasing. The higher the fin, the contribution of the increased area to heat exchange is smaller.
Generally speaking, as for the high frequency welded fin tube applied in engineering project, when fin height is 15mm, the fin efficiency is about 0.8; when fin height is 20mm, the fin efficiency is decreased to 0.7. Based on this, 15mm is the best height. If fins height above 20mm, the fin efficiency will be very bad, so generally not adopted. However, for the aluminum fin on air cooler, height at 22-25mm are always adopted due to much better heat conductivity coefficient of aluminum than carbon steel.
How will fin pitch affect fin ratio?
Usually smaller pitch can effectively increase fin ratio. While considering the flow gas property and ash deposit , we should pay attention to following factors.
A. Serious heavy ash deposit
Such as electric furnace and converter in steel works and exhaust of industrial cellar furnace, the ash content is heavy. If fin tubes are used for heat exchange, larger fin pitch will be suggested. For example, if pitch above 10mm, it is necessary to add a air discharge and choose an air blower.
B. Occasion with small ash deposit but should also be cared.
Take exhaust on plant boiler and industrial boiler as example, 8mm fin pitch is suitable, but should be designed with self-blowing ability.
C. Occasion with no dust or light dust.
Such as exhaust on burning natural gas equipment or air cooler, fin pitch at 4-6mm is OK. For aluminum air cooler, 3mm as fin pitch is also chosen.
Fin and tube heat exchangers
With careful design, aluminum exceeds copper-based systems on most key performance indexes – and it is less expensive. Today, all-aluminum design has established itself as the reference.
Choosing aluminum alloys
When incorporating aluminum in your product, you need to use the correct alloys for the different components. But choosing a combination of alloys that ensures the highest degree of corrosion performance is challenging. Our competence helps you get the best results possible.
Aluminum meets all design requirements
An all-aluminum fin and tube system can solve all design challenges, with direct cost benefits compared to the alternative with copper tubing:
- No galvanic corrosion between fin and tube
- No formicary corrosion, as aluminum is inherently immune to it
- Can be used in ammonia systems, copper can not
- Heat exchanger manufacturers save 20-25 percent on material costs
- All-aluminum is always easy to recycle
Materials Choice In Heat Exchanger Design: Aluminum vs. Copper
From heat recovery to air coils and refrigeration to power plants, choosing the right material for heat exchangers — particularly with reference to thermal qualities, resistance to sag during brazing and corrosion resistance — is key.
Did you know that the best example of heat exchange in the natural world is as obvious as the nose on your face? Well, technically it is the nose on your face, which warms inhaled air and cools exhaled air. But heat exchanger design depends on much more than an intuitive understanding of biology.
It requires careful consideration of the operating environment, application and, crucially, the properties of the materials used.
Fortunately, choosing materials becomes easier once you have assessed the environment and the application. If the heat exchanger will be operating outdoors, or in a processing plant with corrosive media, then a high corrosion resistance will be a necessity.
How does a shell & tube heat exchanger work?
Likewise, design engineers must consider what fluid will be carried through the exchanger and specify materials accordingly.
For example, it could be critical that a substance remains pure while being passed through a standard shell and tube heat exchanger in a pharmaceutical processing application. In such an environment, the tubes must be made of an inert material, perhaps even an unconventional one that is non-metallic – such as glass.
Generally, the two most commonly selected materials for heat exchangers are aluminum and copper. Both metals have the optimum thermal properties and corrosion resistance to make them ideal choices, with most of the differences being application-specific.
Copper for heat exchangers
The typical thermal conductivity of generic pure copper is 386.00 W/(m·K) at 20°C. This makes copper the most thermally conductive common metal, which, along with its relatively low specific heat — of approximately 0.385 J/(g·°C — underpins its popularity in heat exchangers.
These characteristics do bring with them a slightly elevated price. Most design engineers and product designers consider this one of the biggest deciding factors between copper and aluminium for smaller projects.
However, there are a few practical considerations to consider when using copper. The density of the material, for example, might mean that it is unsuitable for certain applications that require a lightweight heat exchanger.
Furthermore, opper has lower flexibility than aluminium, making it more difficult to form into certain shapes. Because of this, design engineers working on a plate fin exchanger, which is a type of heat exchanger that uses plates and finned chambers to transfer heat between fluids, might find that aluminium is a better fit for the fins.
In addition, it’s important that copper tubes are joined using brazing rather than soldering, as the latter has been known to create a build-up of substances at joints. This means that design engineers should also source copper with a good sagging resistance to reduce deforming during brazing.
SWEP Brazed Plate Heat Exchanger (BPHE) is one of the most efficient ways to transfer heat from one medium to another.
There are some long-term corrosion considerations with copper as well. As the material ages, it can develop verdigris — a thin layer of patina, formed by oxidation over time, that gives the material a green hue.
It’s the same chemical reaction that has made the statue of liberty the iconic green colour it is today. This process typically takes 15 or more years, depending on how the material is maintained and its environment.
Of course, there’s no guarantee that the change in a heat exchanger’s external colour will be as well-received as the statue of liberty’s verdigris, so product designers may choose an alternative to copper to deliver a different aesthetic. In any case, the patina is dielectric and may lead to reduced thermal conductivity as it accumulates.
As a matter of fact, although corrosion resistance is not a natural property of copper, Lebronze Alloys, a leading French manufacturer of high-performance materials, has worked on alloy compositions that provide copper with good oxidation resistance, even when exposed to seawater.
Despite these factors, the thermal conductivity of copper arguably compensates for maintenance considerations with its efficient transference of heat. In some cases, copper’s high comparative thermal conductivity means that a copper tube can conduct heat as effectively as two aluminium pipes.
Aluminium for heat exchangers
For design engineers that require a lighter, thermally efficient material, or are working to a tighter design budget, aluminum is the prime candidate.
Boasting a thermal conductivity of 237 W/(m·K) for pure aluminium or ~160 W/(m·K) for most alloys, aluminium is the third most thermally conductive material and arguably the most cost-effective. Aluminium also offers a specific heat of 0.44 J/(g·°C), making it very nearly as efficient at diffusing heat as copper.
Aluminium is also far more lightweight and flexible than copper, addressing many of the practical issues engineers might encounter with copper. It is far more malleable, so engineers designing a plate-fin exchanger for a gas furnace will find that it is better suited to the intricacies of the fins.
Metallic plate in a heat exchange machine and pump in the food industrial plant.
However, aluminium does typically have lower sag resistance than copper, making it more prone to deformation during the brazing process and after repeated heat cycles.
Fortunately, this can be counteracted by opting to specify an aluminium alloy that has been specifically formulated to bring the metal’s properties closer to that of copper, without significantly increasing the price.
For example, metal supplier Gränges provides aluminium alloy FA6825 H14SR that is suitable for heat exchangers in energy applications. This alloy is fortified with elements such as zinc and manganese to give the alloy a higher tensile strength after brazing. The metal forms large grains during the process, which improve its sag behaviour.
The characteristics of aluminium and copper are very closely matched in terms of suitability for heat exchangers, with the key deciding factor ultimately being the application’s practical requirements.
While the decision may not be as obvious as the nose on your face, design engineers can make it easier by understanding the properties of their materials.
The Features of Aluminum Finned Tube
1. Good Corrosion Resistance
Under serious conditions, the oxide materials from aluminum are non-toxic. For heat exchange, no need to worry that air or liquid inside will be destructed by oxide even for a long time.
2. Low Density
By treatment as alloying or heat, it can be used as the structure of construction steel. Feasible for various transportation, especially for small vehicles to reduce weight and consumption.
3. High Yielding and resistance to die-cutting.
It is easy to process and form.
4. Good Thermal Conductivity
Especially compatible for radiating fin, heat transfer condenser and evaporator.
As a professional finned tube manufacturer, one of our leading products is aluminum finned tube. If you are interested in our products, please do not hesitate to contact us.
Advantages of Aluminum Finned Tube
- Finned tube has compact structure, easy and economical to install. It reduces the joints compared to bare tube, making installation more quickly and cost-saving, reducing the possibility of water leaking at the connection.
Simple for maintenance, you basically don’t need to maintain finned tubes after installation.
- High efficiency, the finned tube is in full contact with the fin and aluminum pipe, the heat dissipation area is more than 7-8 times that of the bare tube, the inside is smoother, and the internal water flow resistance is small.
- Long service life, the high mechanical strength of the combination of fins and pipes. The tensile strength is above 200Mpa.
- Stable heat transfer performance. It has few temperature fluctuations, reduces the high-temperature corrosion and over-temperature damage of the metal surface.
- Widely adaptable for heat exchange between air-air, air-liquid, liquid-liquid and various fluids.
Categories of aluminum finned tube in different process technology and shapes
Applications of Aluminum Finned Tube
- Heat exchanger
- Air conditioner
- Air cooler
- Food processing
- Refrigeration industries
- Industrial boiler
- Gas turbines
- Petrochemical industries
Why Use Aluminum Finned Tube?
Based on the heat exchange application, there are many kinds of materials, and which are Aluminum, Alloy, Copper, Brass, Stainless Steel, Titanium, Carbon Steel, Nickel, etc, while among them, the prominent one is aluminum, and it’s being commonly used.
The fundamental uses of finned tube heat exchange should be with good solderability and better mechanical strength, formability, good corrosion resistance and thermal conductivity. Aside from these, aluminum and alloy also have good advantages as in extension and higher tensile strength increases under lower temperature. All around the world, especially for places where are always at low temperature and compact heat exchange, aluminum finned tubes are widely applied.
Your best solution in heat exchange!