Meshing
 

I've made a cylinder and after I mesh it and click initialize solution, it looks like this:
http://i.imgur.com/gCRtkGx.png.

The front part (not shown in the picure) is mostly green, however the back side looks like that.

Is there something wrong? Looking at the temperature fields in a scalar scene everything looks as one would expect, however the backside have lots of black lines, like this:
http://i.imgur.com/eVp2r6m.png.

I do not think there is any problem. Sometimes it is because of graphics of the computer. Also, if you have used Surface remesher, it may happen. To see if it is because of the Remesher, you can go to Representation and delete Import. Just if do not like to remove the imported surface mesh, do not save the file.