THIN-FILM EVAPORATION IN VAPOR-COMPRESSION STILLS
Abstract
A study is made to explore promising mechanisms of heat transfer which may be used to develop more efficient sea-water distillation units. As a basis of investigation, an extensive research survey of low-temperature- difference boiling heat transfer is briefly summarized, with the conclusion that with the present understanding of ebullition there is little prospect of achieving the desired heat transfer with active boiling. The metal-to-fluid superheat necessary to form a steam bubble with known types and sizes of nucleation sites prevents ebullition except with minimum temperature differences of 8 to 10F between the temperature of the metal wall and the saturation temperature of the fluid. The concept of evaporation from a very thin film without boiling is considered in detail, and two small experiments are reported. It is shown, both theoretically and experimentally, that very high evaporation rates can be obtained with the very thin film technique; methods of maintaining a thin film continuously in a practical vapor-compression still are considered. A single-tube experiment, in which methods of introducing feed water and checking probable scaling problems will be studied, is described as the next phase of this task. (Author)
Document Details
- Document Type
- Technical Report
- Publication Date
- Apr 01, 1965
- Accession Number
- AD0613572
Entities
People
- E. J. Beck
Organizations
- Naval Facilities Engineering Service Center