What are the thin, horizontal baffles that separate the tubes within the radiator core called?

The thin, horizontal baffles that separate the tubes within the radiator core are called fins. Fins are critical components in the radiator's design, as they enhance the surface area for heat exchange. This allows for more efficient cooling of the engine coolant as it flows through the tubes of the radiator. By increasing the area available for heat transfer, fins help dissipate heat into the air more effectively, ensuring that the engine remains within its optimal temperature range.

In the context of the other options, insulation refers to materials used to prevent heat transfer, which is not relevant to the function of the radiator baffles. Tubules could imply small tubes but do not specifically designate the function of separating channels within the radiator. Tie bars refer to structural components that hold different parts of a system together, rather than serving as heat exchange structures in a radiator.