There is a rectangular fin attached to a heat exchanger with a base temperature of 350K. The fin has uniform properties and experiencesa uniform heat generation. It also experiences heat transfer with the surroundings through convection and radiation. Dies the fin experience 1D or 2D conduction?
To have it be 1D, you'd have to have the fin have a temperature that depends only on its distance from the heat exchanger. That's unrealistic, the edges will be at lower temperatures. So it will be 2D.
The radiation is approximately 1D for a very thin fin. The 2D nature comes from convection; the velocity of the air (close to the surface) near the edges will be faster than the velocity of air near the center of the fin.