I am currently working on a small personal project. It is a small under-water generator/ motor so the setup is as follows. The generator and gearbox are mounted on steel struts within an air-tight nacelle of sorts which is cylindrical and made of steel. The nacelle is submerged in cold water which will be flowing past. I am trying to calculate the heat within the nacelle and what natural cooling will occur knowing only material properties, dimensions and generator and gearbox losses. I am struggling to generally work out how to go forward and work out the temperatures over time. Any help would be great.