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Radiators: How to Keep Your Cool Part 1
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When the dog days of summer roll around, you’ll be quick to think of the radiator in the nose of your car. If you’ve added horsepower over the winter, there’s added pressure: More horsepower equals more heat. And with that comes the need for cooling system attention. One trip to a local car show or drag strip in the heat of the summer with an inadequate cooling system will make you wish you had paid more attention to that heat producer under the hood.
Fair enough. It’s no secret that a high performance engine produces heat - and a bunch of it. Roughly one-half of the total heat energy produced by the engine is transferred back to the cooling system. In a conventional liquid-cooled application, the heat energy moves into the radiator and is then "radiated" back into the atmosphere. Taking this one step further, the liquid cooling system in your car operates very simply. As the coolant (to keep things simple, let's use plain water as an example) temperature approaches 212 degrees F, air pressure begins to build. Since the radiator is closed (with a cap), pressure is allowed to build from within with no opportunity to escape. This air pressure actually expands, which in turn allows the water to reach a temperature higher than 212 degrees F before boiling. As the air pressure increases, so does the boiling point of the water. Basically, this is an efficient system that works well in passenger car applications, but if the coolant temperature continues to increase (without leveling off), the internal pressure will become too great for the radiator cap to handle. What happens next is pretty simple: Your car boils over.
Above, you can see a stock copper brass radiator used to cool a 140 HP, 230 cubic inch 6-cylinder car with zero options. Don’t expect it to cool even a mildly modified V8 engine combination.
The radiator in such a system is a huge tank that allows large amounts of hot coolant to come in contact with an equally large amount of cool (hopefully) air. The coolant is first forced into the radiator side tank (upper tank, if you’re thinking of the old fashioned non-cross flow system). From this point, the coolant makes its way through rows of very small copper or aluminum tubes, finally returning to the adjoining side tank, where it is returned to the engine. While the coolant marches through the tiny tubes, it is cooled by air flowing over and alongside the tubes. The primary purpose of the "fins" contained within the core (and surrounding the little tubes) is to direct airflow into the proper area of the radiator; however, there are also secondary reasons for the fins, as you’ll soon see. FYI, the most common core construction is the tube-fin or the ribbon-cellular design.
Fin count plays an important role in cooling. As a rule of thumb, a radiator will normally have between eight and fourteen fins per inch. When the fin count number is increased, the radiator can "radiate" more heat to both the surface airflow and the surrounding air.
When it comes to rad construction material, what’s the better choice for your car - copper or aluminum? That's a good question. Most recently, Detroit has embraced aluminum as the radiator material of choice. There’s a reason for this, aside from considerable vehicle mass reduction (aluminum radiators, on average, can be as much as 1/3 lighter than an equivalent copper-brass radiator) - and that’s cooling capability.
Certainly, the choice of copper is a good one for radiators. It has better heat dissipating properties than aluminum. But according to DeWitts Radiators, there are a couple of caveats: For example, the primary source of cooling in any radiator is the tubes. Heat dissipates from the coolant through the tube walls. This heat is then transferred to the fins that are in contact with the tubes. In turn, this provides a secondary source of cooling. As air passes through the fins, the heat is carried away. Radiator manufacturers know that wider tubes are more efficient because there is more "tube to fin" contact. That improved tube-to-fin contact is what removes heat. In a typical modern aluminum radiator, the "tube-to fin" contact surface area is increased by 20% over an identically sized copper/brass unit – part of this is due to the fact the fins are both wider and closer together with a shorter fin height than a copper radiator.
But that’s not the end of it. DeWitts also points out that while copper has better thermal conductive properties than aluminum, older copper radiators are made up of (4) four different materials, not just copper. The copper tubes are bonded to the fin with solder (lead) and that has very poor heat transfer properties. The tanks are made of brass and the side channels are steel.
It should be no surprise to anyone reading this that the radiator business is competitive. There are a lot of fancy words used to describe the technology, and as you might have guessed, some of them aren’t exactly correct. In our next issue, we’ll dig into some of the misinformation out there regarding aluminum radiators. You might be surprised when the hype is debunked. It’s interesting! Watch for it!
When the dog days of summer roll around, you’ll be quick to think of the radiator in the nose of your car. If you’ve added horsepower over the winter, there’s added pressure: More horsepower equals more heat. And with that comes the need for cooling system attention. One trip to a local car show or drag strip in the heat of the summer with an inadequate cooling system will make you wish you had paid more attention to that heat producer under the hood.
Fair enough. It’s no secret that a high performance engine produces heat - and a bunch of it. Roughly one-half of the total heat energy produced by the engine is transferred back to the cooling system. In a conventional liquid-cooled application, the heat energy moves into the radiator and is then "radiated" back into the atmosphere. Taking this one step further, the liquid cooling system in your car operates very simply. As the coolant (to keep things simple, let's use plain water as an example) temperature approaches 212 degrees F, air pressure begins to build. Since the radiator is closed (with a cap), pressure is allowed to build from within with no opportunity to escape. This air pressure actually expands, which in turn allows the water to reach a temperature higher than 212 degrees F before boiling. As the air pressure increases, so does the boiling point of the water. Basically, this is an efficient system that works well in passenger car applications, but if the coolant temperature continues to increase (without leveling off), the internal pressure will become too great for the radiator cap to handle. What happens next is pretty simple: Your car boils over.
Above, you can see a stock copper brass radiator used to cool a 140 HP, 230 cubic inch 6-cylinder car with zero options. Don’t expect it to cool even a mildly modified V8 engine combination.
The radiator in such a system is a huge tank that allows large amounts of hot coolant to come in contact with an equally large amount of cool (hopefully) air. The coolant is first forced into the radiator side tank (upper tank, if you’re thinking of the old fashioned non-cross flow system). From this point, the coolant makes its way through rows of very small copper or aluminum tubes, finally returning to the adjoining side tank, where it is returned to the engine. While the coolant marches through the tiny tubes, it is cooled by air flowing over and alongside the tubes. The primary purpose of the "fins" contained within the core (and surrounding the little tubes) is to direct airflow into the proper area of the radiator; however, there are also secondary reasons for the fins, as you’ll soon see. FYI, the most common core construction is the tube-fin or the ribbon-cellular design.
Fin count plays an important role in cooling. As a rule of thumb, a radiator will normally have between eight and fourteen fins per inch. When the fin count number is increased, the radiator can "radiate" more heat to both the surface airflow and the surrounding air.
When it comes to rad construction material, what’s the better choice for your car - copper or aluminum? That's a good question. Most recently, Detroit has embraced aluminum as the radiator material of choice. There’s a reason for this, aside from considerable vehicle mass reduction (aluminum radiators, on average, can be as much as 1/3 lighter than an equivalent copper-brass radiator) - and that’s cooling capability.
Certainly, the choice of copper is a good one for radiators. It has better heat dissipating properties than aluminum. But according to DeWitts Radiators, there are a couple of caveats: For example, the primary source of cooling in any radiator is the tubes. Heat dissipates from the coolant through the tube walls. This heat is then transferred to the fins that are in contact with the tubes. In turn, this provides a secondary source of cooling. As air passes through the fins, the heat is carried away. Radiator manufacturers know that wider tubes are more efficient because there is more "tube to fin" contact. That improved tube-to-fin contact is what removes heat. In a typical modern aluminum radiator, the "tube-to fin" contact surface area is increased by 20% over an identically sized copper/brass unit – part of this is due to the fact the fins are both wider and closer together with a shorter fin height than a copper radiator.
But that’s not the end of it. DeWitts also points out that while copper has better thermal conductive properties than aluminum, older copper radiators are made up of (4) four different materials, not just copper. The copper tubes are bonded to the fin with solder (lead) and that has very poor heat transfer properties. The tanks are made of brass and the side channels are steel.
It should be no surprise to anyone reading this that the radiator business is competitive. There are a lot of fancy words used to describe the technology, and as you might have guessed, some of them aren’t exactly correct. In our next issue, we’ll dig into some of the misinformation out there regarding aluminum radiators. You might be surprised when the hype is debunked. It’s interesting! Watch for it!
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