Why do you not like the mesh that is there? What jumps out at me is that there is no inflation layer which is necessary to capture the sharp gradients within the boundary layer. Also you have a large jump in mesh size from the hex to the tets. You may want to apply some bias to the hex elements so there isn't a big jump. Do you want a conformal mesh between the two mesh types?
Based upon your inquiry I expect you (or your professor) would like hex elements through these tubes. Hex elements will generally require less number of cells and be faster and more accurate for the same number of tet cells. Yes the body is simple enough that you could create a fully hex mesh for it. But it may take you 8 hours to decompose and get the mesh that you want. If you compare this to a tet mesh it may save you 8 hours (likely less) of compute time. But whose time is more valuable, yours or the computer?
I said that it would be possible to create a pure hex mesh, so how would you go about it? The first thing I would do is to remove the rounds as it looks like you only have one element through it anyways. This will help the mesher (and yourself) a lot. Then in ANSYS meshing you can use the multizone method to create a pure hex mesh. Compare the two pictures below. This is for without (upper) and with (lower) rounds. Due to the size of the round the mesh size is shrunk and the result is a huge number of elements (500000+ vs 23000). Also the lower image shows the mesh has some difficulty with the blocking on the several of the tubes and thus would require some babysitting.
 
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