Why do HVAC coils have copper tubes and aluminum fins?

Okay, here’s why we keep hearing that how heat exchangers and coils are made matters so much. It’s getting the real lowdown, no corporate speak, just the skinny you need.

Copper Tube and Aluminum Fins – The HVAC Dream Team

So, you are wondering why you will never encounter a copper tube, aluminum fin evaporative coil in heating, ventilation, and air conditioning (HVAC) or in a heat exchanger application. Here’s the thing: It’s about getting that sweet spot between how efficiently heat moves and how much it costs you. Those materials are so popular because they get that balance just right for a ton of applications.

Understanding the Players: Tubes and Fins

In any coil or heat exchanger, two main parts are doing the heavy lifting: the tubes, and the fins. The tubes act as the main highway for your hot or cold fluid, the primary surface. The real MVPs in the surface area department when it comes to fins, however, are the fins themselves as the secondary surface. Here’s the clincher: it’s the fins that account for a huge chunk of the heat transfer – to the tune of 65% 70%. The tubes process the remaining 30% to 35%. It seems a little odd that the “secondary” part is doing the bulk of the work, right? But consider how many fins are crammed onto those tubes — many times more surface area than the tubes have alone. For this entire contraption to come off, that bond between the fins and the tubes, formed in the expansion process, has to be strong. Without that strong connection, the fins can’t work properly.

Copper Tubes: The Heavy Hitter (And The Expensive One)

Copper for the tubes, you say? For good reasons, it is often the go-to metal for the tubes.

Copper Tube Pros:

• Thermal Champion: Copper is simply better at moving thermal than aluminum. It is characterized by a higher heat transfer coefficient, an important factor to keep equipment from getting too hot and failing.
• Hardcore Material: Copper is tough. It boasts a tensile strength that is higher — by about 40% — than aluminum’s. That means it’s less likely to get damaged or break. In addition, it has less thermal expansion.
• Fix It Friendly: If a copper tube gets dinged out in the field, it’s often easy to fix and it doesn’t cost an arm and a leg to do it. You can frequently fix it without having to rip out the entire coil.

Copper Tube Cons:

• Copper costs more: Copper prices have skyrocketed, occasionally running for over three times per ton what aluminum does.
• Material Matters: For most applications, you need more copper than you do aluminum.
• Corrosion chomps: Copper isn’t entirely corrosion-proof. It can encounter problems: such as Formicary corrosion and galvanic corrosion which meet aluminum fins. Well, protective coatings and regular cleaning can help keep this at bay.

Aluminum Fins: The Budget Bauble

Now for the fins, aluminum is the final answer. It is the favorite for fins as it combines effectiveness with cost-effectiveness.

Aluminum Fin Pros:

• Budget Friend: Aluminum is much more affordable than copper. It’s a big victory, considering fins cover so much surface area.
• Featherlight: It’s not as heavy as copper.
• Shaping It is Easy: Aluminum is less stiff than copper (increasing ease of manufacturing) and is lighter by weight so you need less.
• Fair Heat Transfer: Aluminum isn’t as efficient as copper, but it’s not terrible at moving heat.
• At least Some Corrosion Protection: For example, aluminum does have oxidation defense copper does not have, so aluminum is very resistant to Formicary corrosion. And because it contains only one material, a coil (all aluminum or all steel) is less susceptible to galvanic corrosion.

Aluminum Fin Cons:

• No Heat King: Not as good a conductor of heat as copper.
• Handle with Care: Aluminum is weaker and more brittle.
• Repair Headache: So an aluminum tube gets a dent in it, and it’s a different story. It is a slow process that requires special materials, takes a long time and that contractors often can’t even do on site. You’re typically going to replace the entire coil.
• Cleaning Can Be a Straight-Up Headache: Aluminum coils tend to be lightweight and fragile, so manufacturers will sometimes put them in heavier cabinets for protection, and that makes cleaning them a BEAR. This can ding their longevity over the long term.

The Dream Team Combo: Balancing the Books and the BTUs

Well, you take those high quality, long-lasting copper tubes, and combine them with the affordable and lightweight aluminum fins. This combination is frequently mentioned as providing the best heat transfer for the money for a ton of applications. It takes advantage of copper where its excellent heat transfer and strength are paramount (in the tubes, where the fluid travels, and the expansion occurs) and aluminum where a large surface area can be used economically (in the fins). It’s sort of like buying a performance car with fuel economy: You get the muscle of the thing without wringing your wallet over the all-in.

The Nuts and Bolts: Rust, Strength, and Keeping Things Together

Let’s explore these metals and address a few common concerns about mixing them.

Corrosion Watch: If you are combining copper tubes and aluminum fins, you should be watching for corrosion.

• Formicary Corrosion: This can be a problem.
• Galvanic Corrosion: This occurs with the contact of two dissimilar metals such as copper and aluminum or copper and galvanized steel in the presence of an electrolyte such as water.

Good maintenance, protective coatings, and routine cleaning are your friends in this one.

Who’s Tougher? On longevity, copper generally comes out ahead. Its greater tensile strength and lower thermal expansion result in lower likelihood of damage or breakage, compared with aluminum.

Repair Rundown: This is where the copper definitely has the metal on aluminum.

• Copper Tube Coils: If one coil ends up leaking or being damaged, field repairs are simple and cheap. You almost never have to replace the entire coil.
• Aluminum Tube Coils: An aluminum tube can be as wicked as headaches. Repairs are hard, require special stuff, just take forever, and can perhaps not be performed on site. This is why replacing the coil is usually the only viable choice. That is a big deal for life span and maintenance costs!

Where You’ll Notice Them: Common Applications

Look around and you’ll see copper tube and aluminum fin coils and heat exchangers everywhere. They’re super common in:

• HVAC Systems: This is the big one. Consider the coils that are part of air conditioning systems (condenser and evaporator coils, as well as coils for heating or cooling water and steam).
• Refrigerator: Adapters available for different refrigerator systems.
• Power Generation: A key application area.
• Other Industrial Stuff: Gas compression; data centers; food processing; some kinds of military and transit cooling.

Pretty much wherever you need to move heat effectively and price is a consideration, you prolly got these in your cost/benefit posse.

When the Dream Team Is Not Enough: Filling Out a Reality-Based Bench

For most runs copper and aluminum will do fine, but sometimes the operating conditions are just too gnarly. Extreme temperatures, insane pressures or just really corrosive environments can mean you have to look at other materials.

Here’s a quick rundown on some of the alternatives mentioned, why you might choose them and what you give up:

Additional elements such as Molybdenum and Nickel may also be added to stainless alloys to improve corrosion resistance, such as in AL-6XN® and Hastelloy® C-22®.

The End of the Road: Scrapping Copper/Aluminum Coils

All right, now let’s take a detour into the retirement of these coils. Scrapping them is a different story, and really, no matter how I cut them up, getting the copper tubes away from the aluminum fins wasn’t worth the effort. Why?

• Hard Work, Low Pay: Trying to get those aluminum fins off, that’s a bitch. It’s a lot of work, and you don’t get much aluminum for all the copper you used to form the crucible — one pound of aluminum for every 10 pounds of copper, or worse. That cut in scrap value between clean copper and aluminum and leaving them together is just not worth it to most.
• Cuts City: I mean, good luck trying to remove those fins – your hands will be shredded. It’s as though you’re negotiating through many little sharp-edged blades.
• Scrap Category: Some scrap yards will have a separate category for Cu/Al radiators or CuAl coolers. You always trim off any steel ends and sell it as such in that group.
• Separation Attempts: People have attempted various techniques – with tools such as a sawzall, grinder, oscillating saw, or, more controversially, burning the aluminum off (which you know can’t be good for your health). There are machines that pull fins, but generally they are not practical, unless you bought the material super cheap.

Practically everyone who has attempted removing them have the same sentiments, leave it as it is, do not bother scrapping it. Time is money, and the extra cash is not worth your trouble, or the risk of injury.

SUMMARY: SELECTING YOUR HEAT TRANSFER POWERHOUSE

All in all, the copper tube and aluminum fin combination is a great option for a lot of standard heat transfer application, especially, such as HVAC and refrigeration. You get the best of performance with copper’s conductivity and durability, complemented by aluminum’s cost economy per surface area.

But just as how the best tool for a job really depends on the specifics of your use case, the best material set up does too. You should be considering the operating temperature and pressure, whether corrosive chemicals are being run through the unit, how important efficiency is to you and how tight your budget is. Copper tube and aluminum fins are a default for a reason, but it’s never a bad idea to ensure it’s going to meet your needs to a T.

FAQs

What kind of tube did the evaporator use, copper or aluminum?

Most of these coils are made from copper tubes and aluminum fins, and they are built for a long service life. But some manufacturers are now using aluminum both for the tubes in the coils and the fins. When the best material isn’t copper and aluminum Copper tubes with aluminum fins offer many advantages to a variety of industries at Super Radiator Coils (SRC). Capitol Coil & Air frequently offers the two materials together in coils that take advantage of the strengths of both: the copper tubes for excellent heat transfer and the aluminum fins for intensive and efficient air heat transfer.

Is copper tube better than aluminum tube for heat transfer?

yes, for the most part they use copper tubing which is usually easier for heat transfer than the aluminum tubing. Copper – Copper has a higher heat transfer coefficient than Aluminum and is considered ‘better’ because the fins of a heatsink are produced from a single piece of Extrusion. Aluminum, although a good conductor of heat, transfers heat half of what copper does. Due to its thermal conductivity can be a bit less than copper, it can be slightly less effective at moving heat.

Why aluminium fins are used in evaporator and condenser coil?

The addition of aluminum fins on the evaporator and condenser coils principally comes about because aluminum fins provide an effective heat transfer surface in a less expensive manner than similarly functioning copper fins. Copper is great for heat transfer, but prohibitively expensive to use for fins. Fins, called the secondary surface, carry out a large part of heat transfer in coils, ranging up to 65-70% or even 70% because a large area of this surface is compared to the tubular surface. Aluminum fins are widely used in the fins such aluminum fins are of high thermal conductivity, light weight, corrosion resistance and cheap cost. Copper tubes and aluminum fins are an ideal combination for most HCAV coils.

What is the value of scrap AC radiator?

According to the listings, an air conditioner radiator, commonly known as a “cu/al rad” because it is a mixture of copper and aluminum, has a separate category of scrap. We suggests that value is likely about $1.50/lb once the steel ends are cutoff. The sources describe the attempt, and the possible scant payoff, of trying to strip the aluminum fins off of the copper pipe. Some scrap yards will accept the radiators as they are. The aluminum fins are not very heavy, quite light in fact, even as little as 1/10th or lower by weight as compared to the copper pipe, and separating them can be not worth the effort for Kastners for what little extra a few dollars would get them. Removing the fins is hard, can cause cuts, damage your hands, pull down your pants (kidding, of course) or may take power tools such as a circular saw (which is messy), Sharpie, Sawzall, multitool, or channel locks. Burning the fins is cited as an ancient technique, but said to be a lot of work.

What are the 3 common types of copper tube?

The references describe the employment of copper as a material for tubes in heat exchangers. They also refer to copper-nickel (cupronickel) alloys, in particular 90/10 and 70/30 ratios for tubes and fins. But they don’t specify or describe the three well-known types of copper tube that they deliver, which are types K, L, or M.