Heat Exchangers Made with Aluminum Brazing vs. Epoxy
When it comes time to re-core or replace your current charge air cooler, radiator, or oil cooler, the differences in construction can be overwhelming. While some differences are minimal, there is one that can make a huge difference in the performance of your equipment.
Different manufacturers build heat exchangers in different ways. One of the more common practices is to use epoxy in the building process to help seal the tubes and headers in the core. The reason epoxy is used is because certain brazing procedures, such as vacuum brazing, do not produce a complete seal and the epoxy acts as filler. Alternatively, the aluminum brazing process we use completely seals the header and tubes joints producing a stronger, more durable heat exchanger. This process creates a solid aluminum core where metal is brazed directly to metal with no epoxy filler. While both methods bind the pieces together, they produce very different results in a unit’s operating life and performance. Let’s compare these two methods so you can make the best decision about how to spend your money
Brazing and Epoxy Durability Differences
Heat exchangers experience a lot of abuse. The constant cycling from cold to hot to cold again as the equipment is used has the biggest impact on a heat exchanger’s longevity. Keep in mind that the metal in the exchanger will expand and contract during this cycling. This cycling leads to metal fatigue, which is the most common reason for failure, but it also has a significant effect on the binding materials. The concern here is how well does the binding (epoxy or brazing) hold up to the same cycling.
Epoxy and Heat Cycling
Epoxy expands and contracts at a different rate than the metal components it holds together. This can lead to it separating from those components. Needless to say, this separation can cause leaks and lead to damage to both the unit and other parts of the equipment.
Brazing and Heat Cycling
Aluminum brazing has a distinct advantage here. Since the brazing process bonds one metal component to another using a filler metal of a similar material, the entire unit will heat and cool as well as expand and contract evenly. This improves the unit’s ability to withstand the regular cycling it will endure.
Brazing and Epoxy Cooling Differences
A heat exchanger’s ability to cool is most affected by the surface area it has to dissipate heat. The less surface area it has, the less cooling capability it has. This can be affected by a number of different factors, but for the sake of this discussion, we’ll assume we’re using two exchangers of identical builds but one is made using epoxy and the other aluminum brazing.
Epoxy Cooling Capability
While epoxies are engineered to have certain characteristics, including being able to dissipate heat, they simply do not transfer heat as well as metal does. In exchangers made with epoxy, the epoxy will act as an insulator and reduce the unit’s ability to dissipate heat. Every area in the exchanger where there is epoxy effectively reduces the unit’s cooling surface area.
Brazing Cooling Capability
In the case of a brazed heat exchanger, we have an all metal unit with uniform heat dissipation. The binding material used in brazing has the same heat transfer capability as the metal components it connects. This means the unit has the maximum cooling surface area it can have and will outperform a similar exchanger made with epoxy.
Brazing and Epoxy Repair Differences
While repair costs may not be the first thing you think of when comparing different units, it has a significant impact on the over-all cost of operating your equipment. The question you may be tempted to ask is “Which type is least costly to repair?” but that can be misleading. Repair costs may not be limited to just the unit itself. When a heat exchanger fails, it can cause significant damage to other components and drastically increase the cost of equipment repair. A better question to ask is “Which type will cost me more in over-all repairs?”
Epoxy Repair Costs
A lot of people choose heat exchangers made with epoxy because the initial price is cheaper and the replacement or repair cost appears to be cheaper. What is commonly not considered is that these units will require repairs/replacements more often than their brazed counter parts. This goes back to the heat cycling discussed earlier. These heat exchangers are more prone to leaks and failures due to the epoxy separation. When it does begin to leak, you now have additional maintenance costs and are risking damage to the rest of the system.
Brazing Repair Costs
While brazed aluminum heat exchangers may cost a little more upfront, their long lasting durability and cooling performance means less chance of needing repair, a longer period before needing a replacement, and less risk of damage to the equipment. When guaranteed performance is important, aluminum brazed coolers are the way to go.
Summary
Heat exchangers made with epoxy tend to be more appealing at first thanks to their initial lower cost; however, due to the nature of the epoxy separating from the metal as it cycles between hot and cold, their over-all maintenance/replacement cost is higher than aluminum brazed exchangers. Brazed units have better cooling capabilities since they are all metal; where as, epoxy units do not cool as evenly since the epoxy itself does not transfer heat as quickly as the metal. In nearly every situation, we recommend aluminum brazed heat exchangers over epoxy. They will provide the best cooling and durability with the lowest risk of failure.