Most conventional thermal desalination systems use horizontal or vertical tube arrays or parallel-plate structures in evaporation and condensation units. Desalination is usually carried out in coupled heat and mass transfer processes which easily lead to scaling on heat transfer structures and limit the desalination performance. This paper presents an innovative desalination system that performs falling film evaporation with separated heat and mass transfer processes using highly compact multi-finned structures. The system was developed and tested in simulated operating condition to study both the transient and steady-state performance and the influence of the operating temperature and feed seawater flow rate on fresh water yield. Experiment results show noticeable improvement in fresh water yield per unit heat exchange volume and demonstrate the capability of the system to produce fresh water at an operating temperature as low as 36°C. The separation of heat exchange and evaporation enables further enhancement on both processes, which cannot be easily achieved in conventional designs with coupled heat and mass transfer processes.