Abstract
The introductory part of this paper offers an overview of approaches to the management of marine fresh water generator and points out the most important factors influencing the processes. The second part deals with operation time and total overhaul time both influenced by evaporation intensity. Comparison and simple calculation are made of several distinct modes of operation assuming days in voyage and hours necessary for overhaul. Next section gives a thermal analysis of the processes, resulting in energy balance equation that could be used as a base for the optimal control system for one single-stage unit. In fact, the suggested control system is based on the energy balance equation that is given in this section. In the fourth part the analysis of the most important operational values is made. The changes recorded on the six-channel plotter are used to evaluate the suggested control system. The paper gives an example of optimal control system for the single stage fresh water generator and suggests further research.
Highlights
The main effects on the distillation process have: heating fluid flow through the evaporator and cooling fluid flow through the condenser, both affected by heat transfer coefficients that are deteriorating with operation hours, the temperature differences between the fluids in those heat exchangers, and the pressure in the vessel
Since there are temperature differences between two fluids both in the evaporator and the condenser, i. e. dT i dT, and that they evap cond represent, together with the respective fluid flows, main heat exchange generators, it is clear the effect of evaporation would be increased, and the intensity of condensation decreased with decrease of the pressure in the vessel
Increasing the vacuum or lowering the absolute pressure in the vessel graphically would mean the line representing saturation temperature would move to the left, resulting in the earlier start of the evaporation but the condensation would be retarded
Summary
The main effects on the distillation process have: heating fluid flow through the evaporator and cooling fluid flow through the condenser, both affected by heat transfer coefficients that are deteriorating with operation hours, the temperature differences between the fluids in those heat exchangers, and the pressure in the vessel. E. dT i dT , and that they evap cond represent, together with the respective fluid flows, main heat exchange generators, it is clear the effect of evaporation would be increased, and the intensity of condensation decreased with decrease of the pressure in the vessel.
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