|M.Sc Student||Lengel Yoav|
|Subject||Flow Regimes and Heat Transfer in Two Phase Vertical Flow|
|Department||Department of Mechanical Engineering||Supervisor||PROFESSOR EMERITUS Gad Hetsroni (Deceased)|
|Full Thesis text - in Hebrew|
The frequent demand in modern industry to transfer fluids, in large scales, across long distances and during long periods of time, has brought researchers to look for ways to improve these processes. Improvement may be through reduced consumption of energy needed to make the process happen, and by using the qualities of the fluids more efficiently.
Among the methods to do so are: changing the flow characteristics from one phase to two-phase flow, injecting additives to the flow, and the combination of the two. Aiming at the investigation of a common configuration of flow, this research is focused on vertical upward two phase water-air flow with the addition of surface active agents. The additive that was chosen leaves negligible impact on the environment.
The change in the friction factor is manifested by changes in the flow regime maps. The additive has also changed the pressure drop along the pipe in each of the flow regimes. A correlation was proposed in which the connection is made between the flow characteristics and the PDR ( = Pressure Drop Reduction). A qualitative explanation was given for the connection between the presence and concentration of surfactant, and the nature of the pressure signals. The research indicates that the churn flow regime is the most likely to be effected by the addition of the surfactant in the aspect of drag reduction.
The subject of heat transfer was studied by comparing the experimental results to the results previously reached by others, for both single phase and two phase flow.
In order to investigate these issues, an experimental apparatus was built, which included a large scale piping system to assure that developed, steady flow is achieved. It included the use of a fast camera (pictures were taken through a transparent section), and a thermal radiometer that made it possible to get temperature maps.
The influence of the surfactant on the flow qualities was investigated with two concentrations: 100, and 300 [PPM] in which its influence could be best investigated.
As predicted, it was discovered that the surface-active agents reduced the friction of the fluids with the pipe’s walls and thus the ability to remove heat from the fluid was also reduced.