Problem in Meshing a tube in tube Helical HX
 

I have been modelling an tube in tube helical coil heat exchanger with hot fluid at inner tube and cold fluid at outter tube.Since it involves both solid and fluid zones the meshing seems difficult and doesn't match well.

I have meshed the model and obtained 556856 nodes and 383435 elements but while analysing i cant get the proper results.

Is there any specific kind of meshing needed to be done for these kind of problems kindly suggest me a solution