No abstract

a b s t r a c tThe paper deals with the work of the single-stage vacuum fresh water plant usually used on board cargo ships, namely with the influence of the thermodynamics process and of the technological arrangement on the performances. The distillation method has been well known since the ancient civilization, but there is still room for the improvement of the process depending on the selected criterion. Furthermore, the arrangement of the plant, including all control and regulation elements, has an impact on the process running and, after all, on the quality and quantity of the generated distillate as well as on the price of the installation. As a conclusion, a simple mathematical analysis has pointed to the key parameters that have to be monitored during the work as well as to the possible optimal control system, as it has been proved by simulating the work and registering the changes in the stated parameters during variable working conditions. The result of the paper could lead to a simpler and cheaper governing system, to the better quality of the distillate and more operating hours of the equipment.

ABSTRACT

The reliability of composite system (series, parallel) is improved by (i) reduction method, and by (ii) cold duplication, considering the system's survival functions. Then these reliability improvement methods are compared mentioning that the hot duplication method was studied recently by Pogány et al. [8].In this companion article to [8], related survival equivalence functions and pointwise survival equivalence factors are derived in all cases when the components lifetime distribution follow the gamma-Weibull distribution introduced recently by Leipnik and Pearce, and studied intensively by Nadarajah and Kotz, then by Pogány and Saxena.

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.