A system having a reactor for continuous processing of fluid is provided herein. The reactor, in general, includes an outer vessel to accommodate fluids to be processed or used in connection therewith, an inner vessel situated within the outer vessel to serve as an energy exchange surface, and an annular space defined between the outer and inner vessels and along which processing of the fluids can be implemented. The continuous thin film reactor can be used to perform, for example, distillation and evaporation, fluid-fluid or solid-fluid-fluid reactions, organic reactions, cooling, and desalination.