Aluminum VS. Copper-Brass Radiator: Construction Differences

Aluminum Copper-Brass Construction – So far in our journey through the topic of aluminum vs. copper-brass radiators, we’ve explored how a radiator transfers heat from the coolant to the air. Now we’ll take a look at the differences in how aluminum and copper-brass radiators are built.

In our previous segment, Aluminum VS. Copper-Brass: The Great Debate, we noted that a radiator can perform best when it is built with wide tubes and enough fins per inch (FPI) to maximize surface area without adversely affecting air flow. That being said, your average radiator contains either two, three, or four rows of tubes, which may seem contrary to the ideal radiator setup. Why the different numbers of tubes? It primarily comes down to the strength of the materials.

Strength Difference of Aluminum and Copper-Brass
The brass tubes used in a typical radiator are 1/2 inch in width where as typical aluminum tubes are 1 inch wide (and can be made wider). If wider tubes are better, why not make brass tubes wider? Simply put, the copper-brass tubes are so soft that when you make them wider you have to increase the thickness of the tube walls to the point where the radiator core will weigh almost three times more than normal. Why does the thickness have to be increased? Your cooling system becomes pressurized, as it heats up, to help raise the boiling point of the coolant and allow it to absorb additional heat from the engine. Copper-brass can’t handle the additional pressure in larger tubes without the thicker walls. So a wider tube means a thicker wall and significant weight gain for copper-brass. On the other hand, aluminum tubes can be made wider, have thicker walls, yet weigh significantly less than the copper-brass equivalent (anywhere from 40% to 60% lighter). And as we discussed before, wider tubes allow more surface contact with the fins which improves the radiator’s cooling ability.

Standard aluminum radiator cores are made with only two rows of 1 inch tubes, but the equivalent copper-brass radiator core has to be made with four rows of tubes since it is restricted to the smaller tube. Given that you have to leave some space between tubes for air flow considerations, the four row copper-brass radiator will also be thicker than the two row aluminum radiator.

You may be saying to yourself, “All this is fine and great, but I know copper conducts heat better than aluminum.” It is a fact that, of the two metals, copper has the better heat conductivity rating. It would be nice if we could just leave it at that, but that’s not the end of the discussion. A copper-brass radiator is not made solely of copper, which creates a complication in the heat transfer process.

Heat Transfer Ability of Aluminum and Copper-Brass
Between the two types of radiators, an aluminum alloy radiator is a more uniform metal construction than a copper-brass radiator. This is due to how the radiator core and headers are assembled.

brazed copper-brass radiators

brazed copper-brass radiators

Aluminum cores and headers are fused together in a process known as brazing, resulting in a uniform unit.Copper-brass cores and headers are combined using solder, which is made of different metals.
The aluminum brazing process produces an all aluminum unit giving it a uniform ability to conduct heat. (As a quick side note, there are some companies who build aluminum radiators using epoxy, but we here at C, G, & J Inc. don’t use epoxy since it won’t hold up as well as a brazed unit.) By comparison, the solder used to join copper-brass is usually a lead/tin solder, which does not transfer heat as well as the copper-brass. This effectively insulates areas of the copper-brass radiator and slows the heat transfer process.

There have been attempts to create a brazing process for copper-brass, but they have all been too expensive to be practical. That leaves us with an all aluminum two row radiator and a copper-brass/lead and tin soldered four row radiator. Why is the number of rows important? Take a closer look at these pictures of aluminum and copper-brass cores that we used in our previous discussion.

Since the wider aluminum tubes provider greater surface contact with the fins, it can conduct heat more efficiently than the copper-brass. The brass tubes and copper fins have significantly less contact between them due to the spacing between and curved edges of the tubes. So while copper may conduct heat better than aluminum, both the solder used in its construction and the decreased surface contact with the fins reduces the radiator’s ability to transfer heat. When you combine all of these factors together, the end result is that both a two row aluminum radiator and a four row copper-brass radiator have about the same cooling ability.

One advantage aluminum does have is that it can do this without being as thick. Keep in mind that as a radiator core grows thicker, air flow through the core becomes more difficult. A radiator can’t cool an engine if there is no air flow, and air (like any fluid) is always going to follow the path of least resistance. Regardless of the material used, a thicker radiator is always more difficult to pass air through.

Aluminum Copper-Brass Construction – Before we wrap up this segment of our Aluminum VS. Copper-Brass discussion, let’s review the facts about the construction differences between the two:

Aluminum Construction
Stronger metal
Pure Aluminum metal has less heat transfer capability
Core and headers are brazed as one solid piece, allowing uniform heat transfer
Wider tubes provide better contact with fins for better heat transfer
Core is thinner, allowing better air flow
Lower weight
Copper-Brass Construction
Weaker metal
Pure Copper metal has better heat transfer capability
Core and headers are soldered together, reducing heat transfer capability
Smaller tubes means less contact with fins and reduces heat transfer
Core is thicker, which can impede air flow
Weighs more
If a radiator could be constructed from all copper-brass with no solder and wider tubes, its cooling ability would be way beyond the aluminum equivalent; however, weight would still be a major issue. As it stands, equivalent aluminum and copper-brass radiators will provide similar cooling capability with the aluminum radiator being both thinner and lighter. This is far from the end of our discussion; however, as there are still a number of other factors to take look at. Up next is each type of radiators susceptibility to corrosion.

Aluminum VS. Copper-Brass Discussion Points
Use the links below to follow the discussion or jump ahead. While the purpose of a radiator is straight forward, some of the manufacturing and servicing considerations are not. If you found this discussion helpful, please share it with others.

Copper Rods & Profile

Design Requirements for Copper Decoration

Rectangular Brass Tubes for Ornament

How to Clean Brass with Vinegar and Other Products Found in Your Home

Properties and Uses of Brass Metal

70/30 Copper Nickel Tube

ETP Copper Tubes

DHP Copper Tubes