Could anyone tell me where can I find, in Europe, a design engineering company able to design pressure vessels and heat echangers according to AD 2000 Merkblatt?
Look for any (U-)stamp holder in Germany through ASME's stamp holder search engine, 95% chance they can also handle AD-2000 PV design.
I think e.g. Schiller Apparatebau GmbH Essen does.