A couple things, actually.
One. Your mesh, in blender 2.42a, needs to have smooth shading on. Two, your mesh needed to be subdivided at least once(on the z axis, in this case), so the tangent would have something to tangent across.
One other thing. Though it isn’t neccesary, having a closed mesh doesn’t hurt because other-wise it won’t shadow itself properly. If you want to keep it a tube, then just select all the faces and extrude them inwards. (extrude, then to scale them just press s to scale, and then shift+z to toggle scaling off on the z axis so the mesh won’t bevel by accident)
And once that’s done, you can prolly crank the colour and reflectivity back up from black and 0, respectively.
Hope this helps. :]