Dear Peteroznewman,nThank you for your quick answer and recommendation.nI was able to do the mesh on the five bodies (water, tubes thicknes, Cavity=air, absorber and glass), in the next images you can have a look to the results.nnThe number of nodes is 4,9 millions, too much for doing Fluent modelling later.nIn the sweep method I select the next options for water and tubes sweep:nAnd in the sweep method for glass, absorber and cavity (air) the next features:nAnd in general mesh size option I have:nnIf I try to increase Sweep element size in tubes and water to 6 mm, for example, I get the following error:patch-conforming tetrahedron mesh failed because of an edge intersection.Any recommendation of what can I do to reduce the number of nodes?n  Thank you in advance,nKind regards,nNaiaran