What component is responsible for collecting heat from the coolant and transferring it to the air?

The component responsible for collecting heat from the coolant and transferring it to the air is the fins. In cooling systems, particularly in vehicles, fins are often part of a heat exchanger, such as a radiator. They increase the surface area available for heat exchange, allowing the warmth from the coolant flowing through the radiator to dissipate into the air more effectively. As air passes over these fins, it absorbs the heat, thus cooling the coolant before it circulates back into the engine. This process is vital for maintaining optimal operating temperatures and preventing overheating in engines. Fins enhance the cooling efficiency by promoting better airflow and heat transfer.

The other components listed have different roles: the water pump circulates the coolant, the thermostat regulates the flow based on temperature, and the expansion tank accommodates the coolant as it expands and contracts, but none of these directly collect and transfer heat to the air.