Tube-Tube Heat Exchangers (TTHE) design uses a judicious combination of bends, straight lengths, tube diameter/s, tube material/s, thermal bonding material to enable multi-stream multi-phase heat transfer.
Variation of mass flow rate of fluid stream/s at intermediate stages in a single TTHE is possible.
It offers a double wall vented design which eliminating problem of mixing of fluid streams in case of leakage and offers the flexibility of utilizing different conduit materials that are compatible with the individual fluids.