Here is the same locomotive with and without dynamic brakes. This is the old EMD SD45.
With dynamic brakes:
Without dynamic brakes:
You can clearly see the additional radiators in the center of the long hood on the version with the dynamic brakes. There are a couple of big fans on the top of the hood directly above them as well - you can kind of see them, the big round housings. These things generate a lot of heat. Kind of surprising that, in this day and age, no effort is made to recover that energy.