الفهرس 
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Abstract
Three desalination processes are investigated in this study, the Multistage
flashing (MSF), Multiple effect desalination (MED), Mechanical vapor
compression system (MVC).
Multi-stage flash desalination plants are the major sources of potable
water in the world. This work describes a steady-state mathematical model
developed to analyze the MSF desalination process.
The model accounts for the geometry of the stages, the mechanism of heat
transfer, the variation of the physical properties of water with temperature and
salinity, also the model takes into consideration the role of fouling and its effect
on the plant performance ratio.
Relations between the parameters controlling the product cost to other operating
and design variables are established, such as ”plant performance ratio, specific
flow rate of recirculating brine, top brine temperature, specific heat transfer
area”. These relations are used for studying an existing plant.
The results obtained by the model are compared with data from an existing
plant. There is a good agreement between the calculated results and the plant
data of an existing unit in ”SIDl-KRIR” west Alexandria. The plant under the
study contains 17 recovery and 3 rejection stages.
Also the model results are not only used for design purposes, but also can be
considered a support for the study of different operating conditions such as part
load, this can be achieved by decreasing the recirculated flow rate and/or the top
brine temperature this will result in a variation in the unit performance ratio.
Also decreasing the sea water temperature below the design value will increase
the unit production rate, and increasing in the fouling factor will reduce the plant
production rate.The effect of the process variables on the performance of a Multi-effect
boiling falling film ”forward type” is carried out during this study.
The study includes the effect of number of effects, top brine temperature on the
performance ratio. Also the influence of these factors on the specific heat
transfer area, and the effect of seawater inlet temperature on the performance
ratio are investigated. The effect of top brine temperature on the cooling brine
flow rate is investigated also.
The effect of temperature difference along the effects is studied to indicate the
variation in the performance ratio and the specific heat transfer area by changing
the effect temperature difference.
from this study it is clear that the performance ratio is greatly dependent on the
number of effects and slightly dependent on the top brine temperature.
This work also describes the experimental and mathematical model of the
Mechanical Vapor Compression desalination system, which already exists in the
heat transfer laboratory of the Atomic Energy Authority. This MVC unit has a
capacity of 5 m3/d. The study contains some details of the operational features
of the unit. The work includes a comparison between the data of the unit with
both the theoretical and experimental work.
The experimental and theoretical work indicate that the production rate
increases approximately to 100% by increasing the operating temperature from
70°C to 98°C ”Evaporator designed temperature 70°C”.
Also the increase of the heat transfer coefficient is predicted by increasing the
evaporator temperature.