This project was prepared for the Israel Electric Corporation. The IEC plans the construction of a new power station with wet purification of exhaust gases. A power station's stack is the main source of additional thermal and chemical pollution of the environment. As a rule, the stack emits droplets of a liquid which is an aggregate of all the toxic acid substances accumulated in the waste gases after wet purification. The IEC requires the stack contractors to construct a 1 : 20 model of the stack in order to reveal the most important factors that determine the emission of pollutants. By that, the IEC will set up specifications for the Rutenberg B power plant.

The objectives of the project were to analyze all the processes that take place in a real stack. They include condensation on the stack walls and in the flow, droplet sedimentation, entrainment and re-entrainment in the wall film as well as the film's instability and drag-up. The analysis of the processes involves hydrodynamics (mainly Navier-Stokes equations), heat transfer, surface tension, gas-liquid interaction and saturation. The problem is that of a free boundary. The flow may be laminar or turbulent. The problem pivotal to the project is whether the droplets condensed in the stack and emitted with the exhaust gas will reach the ground, creating a pollution situation called "acid rain", or evaporate above it. This depends on their size determined by the thickness of the wall film and its drag-up. The resulting system of equations is extremely complex. We could, however, analyze the system and infer that, in case of a constant temperature gradient across the film, d = O ( x^1/3 ), where d is the thickness of the film and x is the height of the stack. If the heat flux is kept constant, then d = O ( x ^1/4 ). Other equations are expected to be derived.

It is not clear whether exact quantitative estimates will be possible. The establishment of the essential qualitative behavior will enable the use of similarity analysis when passing from the model to the real stack. The analysis of the processes in the stack involved setting up more than 20 formulae, equations and functional dependences. Some of these were derived by a mixture of analytical and empirical tools. It is doubtful whether it is possible to compute the critical controlling parameters. After the model is constructed it will be possible, by the developed theory, to use the measured parameters in order to fix them for the real stack.

The study resulted in qualitative analysis on the basis of which the IEC established specifications for the wet stack of the Rutenberg-B power station in Ashkelon. After a contractor is chosen, he will have to be in contact with the Institute for Industrial Mathematics.