The air should flow from the outside to the inside in any case, as the cooler air is in the surroundings than in the enclosure.

For example, the air inside the enclosure is 55°C and is forced through the radiator...

In the working environment there is approx. 23°C

Where is the higher cooling capacity achieved?

Definitely in the ambient air that is drawn in.

One or two additional fans that push air outwards help with the temperatures in the case... but it does not go through a radiator