Hello Mr. Tore,
When the U-Boat is on the surface or schnorchelling...
The hull/sluice valves in the diesel room can provide cooling water for both diesel engines and cooling water to the e-room for the e-motor coolers, e-motor bearings, thrust bearings, e-compressor, and the junkers compressor (if present). The diesel engine's cooling water returns to the sea via the diesel exhaust muffler vents, the header tank, the exhaust muffler exit ports on the Junkers compressor (if present), and the open Starboard hull/sluice valve in the e-room.
When the U-boat is running submerged...
The Port hull/sluice valve is providing the cooling water to all said components in the e-room, and the sea water is returned to the sea via the open Starboard hull/sluice valve in the e-room. I believe this source for cooling water also feeds forward though the diesel engines and some may exit to the sea via the diesel mufflers and the header tank...
MY Question Is...
In all instances; running on the surface, schnorchelling, or submerged - The e-room Starboard hull/sluice valve is open and draining circulated cooling water to the sea. What would be the reason for ever shutting this valve? It looks like components in the e-room require this valve to be open; including the thrust bearings???
Regards,
Don_