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Radiators: Aluminum vs. Brass

2010 March 30
by admin

There is an age-old debate about which material is better to make radiators from:  brass or aluminum. Most people focus on the radiator core design when choosing a radiator - how many tubes, tube size, how many fins per square inch, etc. - but the core is not the only part of the radiator that can cool. The sidetanks hold more of the cooling fluid than the core!

Just about every high-performance vehicle you see in car magazines has an aluminum radiator. So you might assume that aluminum has the best cooling properties. That actually isn't true, and we'd like to share some facts and test data that compare aluminum to brass, and even to composite radiator sidetanks.

Heat rejection is the term for measuring the ability of a material to transfer heat to the air. This is what a radiator's job boils down to: Take engine heat that has been transferred to the engine coolant and transfer it to the atmosphere. Heat rejection is measured by the amount of British Thermal Units (BTU) per hour the system can dissipate. Higher BTU/hour means more heat transfer and better cooling.

Brass radiators came in nearly all vehicles until the '80s. A typical original-equipment brass radiator rejects heat at a rate of about 1,500 BTU/hour. That's pretty good, and this is why brass was chosen as the material for radiators. In the '80s, car manufactures wanted to reduce costs and lower vehicle weight. This led to changing the radiator design to use composite (plastic) tanks with an aluminum core. The plastic tanks transfer about 1,000 BTU/hour; considerably less than the traditional brass construction. Next we come to aluminum radiators. It might surprise you to learn that the typical, smooth aftermarket aluminum radiator tanks dissipate heat at a rate of about only 700 BTU/hour! That's less than half the BTU of brass sidetanks!

When we decided to start engineering our Flex-a-fit radiators, we saw an opportunity to greatly improve heat transfer in the tanks, which is where most of the coolant is in a radiator. We also realized that we could make it easier to mount the radiator, cooling fans and other related components. We make the tanks from extruded aluminum rather than sheet aluminum. The design has cooling fins on the inside of the tank to greatly increase the surface area that contacts the hot engine coolant. Greater contact surface means more heat transfer. On the outside, we use a T-channel design that both adds surface area and provides slots that securely hold fasteners for brackets.

The result from a cooling standpoint is a radiator tank design made from aluminum that transfers over 2,000 BTU/hour! That's 135 percent more efficient than a typical aftermarket aluminum radiator tank and 41 percent more efficient than a brass radiator tank.

You can learn more about Flex-a-fit aluminum radiators by clicking here.

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11 thoughts on “Radiators: Aluminum vs. Brass”

  • Kris
    Kris March 31, 2010 at 12:04 am

    I had no idea that aluminum transfered so much less heat! Why is it so popular?

    • therealcoleq
      therealcoleq March 31, 2010 at 12:11 am

      Aluminum has a few very important advantages. First, it's lighter than brass. This is important in performance cars; especially since it is so far forward in the chassis. Reducing this weight is better for drag racing, road racing and general on-road handling. Second, aluminum is pretty flexible when it comes to fabrication. Finally, most people think it looks good.

  • Chad
    Chad March 31, 2010 at 12:05 am

    What would happen if you added the fins and t-channel to brass sidetanks?

    • therealcoleq
      therealcoleq March 31, 2010 at 12:17 am

      If you could fabricate cooling fins and t-channels from brass, it would outperform the Flex-a-fit in heat transfer. However, this would be very, very time-intensive (read "expensive") to make from brass. Because of the overall difficulty and cost of working in brass, there are very few new radiators made from brass today.

  • Lisa Chissus
    Lisa Chissus March 31, 2010 at 8:58 am

    Cost & weight were definitely factors in our decision to go with aluminum. We also wanted to maximize the durability of these radiators so that they could withstand some of the extreme environments you guys put them through, which is why each tank is hand welded (no epoxy!). Brass tanks would be brazed instead of welded. Dissimilar metals expand and contract differently which can cause leaks.

  • How to Choose the Correct Flex-a-Fit® Radiator « Flex-a-lite Blog May 29, 2010 at 1:56 pm

    [...] tank design that offers additional cooling properties and exceptional flexibility in mounting. See Radiators: Aluminum vs. Brass for more information. There are a few simple steps to go through to see which of our radiators will [...]

  • Patented Radiator Technology « Flex-a-lite Blog August 30, 2010 at 10:49 am

    [...] The patented sidetank design uses internal fins that perform as heat sinks by absorbing heat more quickly from the engine coolant. The external fins increase the surface area threefold to transfer heat more effectively. In fact, these sidetanks transfer 135-percent more efficiently than a typical aftermarket aluminum radiator tank and 41-percent more efficiently than a brass radiator tank. Click here to learn more about the Flex-a-fit design and how its heat-transfer performance compares ... [...]

  • First of 2011 New Products are Shipping « Flex-a-lite Blog March 1, 2011 at 3:26 am

    [...] aftermarket aluminum radiator tank and 41-percent more efficiently than a brass radiator tank. Click here to learn more about the Flex-a-fit design and how its heat-transfer performance compares ... The “T” channel construction also makes mounting accessories such as a transmission cooler or [...]

  • Bill Bisson
    Bill Bisson May 25, 2011 at 8:00 am


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