Cooling Basics – Row Quantity vs. Tube Size

In the radiator core, coolant flows through tubes. The tubes are joined together by the fins. More heat can be exchanged when there is more tube-to-fin contact area.

One way to increase the contact area is to use more tubes. This is accomplished by adding another row. Another way is to use larger tubes.

(Image/Summit Racing)

Row Quantity

The number of rows is often referred to as the core number. For example, a 4-row radiator can be called a “4-core” radiator.

Tube Size

The tube size listed is the width of the tube. Wider tubes have more surface area. This means they can dissipate more heat.

How does this affect performance?

In the old days, with copper/brass radiators, more rows meant more cooling. However, it also made the radiator thicker which adds air restriction, making it less efficient. It is also harder on the fan. For mechanical fans, this means more parasitic power loss.

More rows also means the rear tubes are less effective than the front ones. As air flows through the core, it picks up heat. By the time it gets to the back row, it is warmer than when it started. This means less heat can be removed from the rear tubes. As more rows are added, this becomes a bigger issue.

Aluminum radiators have helped to solve these problems. Because aluminum is stronger, the tubes can be wider. This means more contact area without significantly increasing the thickness of the radiator.

For example:

  • A 2-row radiator with 1 in. tubes will have more tube-to-fin contact than a 3-row radiator with 5/8 in. tubes.
    • 2 in. vs. 1 7/8 in.
  • The radiators will be about the same thickness.
  • The 2-row radiator will be less restrictive to airflow.

In this example, the 2-row radiator has more cooling capacity than the 3-row.

This is another in a series of weekly Q&A Mailbag sessions with Summit Racings tech department, in which there are hundreds more. Click here to see them all.