The Orbital Tube Evaporator (OTE) was inspired 10 years ago by the emerging technology of the horizontal tube evaporator (HTE). Recent market share (1985–June 1986) of H.T.E. for large land based systems is an impressive growth of 10% from its all time total of 3% (3.3 to 1) as against 48% from 28% (1.7 to 1) for all types of membrane systems and the declining position of 42% from 64.5% for the industrial standby, the multi-stage Flush (MSF) type. (Table II) In either the multi-effect boiling (MEB) or the vapor compression (VC) system configurations, O.T.E. plays essentially the same role as the HTE or the Vertical Tube Evaporator (VTE), but with much higher heat transfer coefficient, higher output purity without the need of demister and less tendency to scaling or fouling. Several engineering models were developed to substantiate its various performances and to simplify the mechanical design for practical application. The superior features of the OTE are derived from an inertially coupled whip rod revolving inside each tube to spread the fluid into thin and uniform film to fascilitate the heat transfer, while allowing the main stream of the throughput to flow down the tube freely. This division of the heat transfer and the mass transfer of the fluid permits the reduction of the dwelling time and assures an even temperature distribution of the fluid quite similar to the wiper evaporators, but without their troublesome seals and mechanical drive mechanism inside the evaporation chamber. The excellent showing of the HTE in the desalination market provides a strong encouragement for further development and adaptation of the OTE for desalination systems of various sizes and configurations. In addition, OTE may also be used for the production of pure water for pharmaceutical or electronic chip manufacture, or for the distillation of other kinds of fluids. Furthermore, OTE as a concentrator can be more cost effective than either the wiper type or the falling film type for a number of applications. Since the OTE is quite simple in system configuration, a successful field test in any one of the above applications would facilitate its adaptation to other systems.