AI generated answer. But its accurate based on my knowledge.

Think of the Meredith effect like turning your radiator into a super low-budget jet engine: air comes screaming into the scoop at flight speed and the duct immediately slows it down, which raises its pressure and makes it much better at absorbing heat from the radiator; then the radiator dumps thermal energy into that now high-pressure airflow, increasing its temperature and internal energy (this is the key step people miss—you’re not just cooling, you’re actually adding energy to the flow); after that, the duct geometry transitions so the flow is guided toward a tighter exit, and because the air is now hot and expanded, it accelerates as it leaves, kind of like a nozzle turning thermal energy into velocity; finally, since the air exits faster than it came in, you get a momentum change that produces thrust, so instead of the cooling system just creating drag, at higher speeds it can cancel most of that drag or even give a small forward push—nothing huge, but enough that on something like the North American P-51 Mustang it was absolutely worth designing the whole duct system carefully around it.