Well, looking at your tube I can only say that you have to work on your mesh modelling techniques. I guess you modelled it with boolean subtract? I see many long triangular face which almost always give bad result when rendering. I also see some overlapping faces, not sure how you created them.
Ok, let me help you build an easy basic smooth tube.
- in topview, create a circle (space->add->mesh->circle->ok)
- Extrude the circle but don’t move the points (press E->Region->RMB)
You have now create an extra circle of points on top of the first one.
- Scale the new circle (press S and move mouse to scale)
- Go to frontview and select all the vertices (press A twice)
- Extrude Region to create a basic tube
- Select all vertices and press Ctr-A, to Recalculate Normals Outside. (To see the normals on your model press F9 in edit mode and click on Draw Normals in the right MeshTool window.)
- Now you can set smooth and… voila, a basic smooth tube.
That’s it. Two last tips:
- Don’t use Boolean modelling if you don’t have to.
- Watch out for long triangular faces which may give bad results