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All the Arabian Gulf States suffer from a shortage of fresh water resources. This deficiency is remedied through the desalination of seawater, mainly by the multi- stage flash (MSF) evaporation technique. The number of MSF distillers in Abu Dhabi is 382, producing a total quantity of 5,465,784 m 3 /d of potable water. It has been reported that these units have a tendency to suffer, at varying degrees, from a variety of corrosion and scaling problems. This paper consists of two sections. The first section describes some of the corrosion problems facing the desalination plants, concentrating mainly on the vapour-side corrosion (VSC) of condenser tubes made of cupronickel alloys, 70/30 and 90/10. The research in this section is necessary because condenser tubes are the part most prone to failure in desalination plants. Almost all of the previous cases of corrosion of condenser tubes reported were focused on water-side corrosion of the tubes. The present paper will discuss two contrasting cases of attack related to both acidic and alkaline corrosion in the vapour side. This is the first such research to be cited anywhere in this field. The second section of the paper will discuss the mechanism of the scale formation reported in the literature, and will present the actual scale formed in desalination plants, which is different from scale formed in the laboratory.

This paper describes a study of fixing light gauge titanium tubes into copper alloy tube sheets by roller expansion. The light gauge titanium tubes of 0.5 mm wall thickness were expanded into copper alloy tube sheets. The expansion procedure was conducted according to the ASME code and the TEMA standard. Fixing of light gauge titanium tubes was as easy as that of copper alloy tubes. Tightness was sufficient, and no leakage was found in the hydraulic test at the joints of the titanium tubes and the copper nickel tube sheet. The data show that the holding strength of the tubes with the tube sheet is in proportion to the t/D of tubes ( t wall thickness, D outside diameter) and to the area expanded. Consequently, it is practical and economical to apply light gauge titanium tubes instead of conventional copper alloy tubes as the evaporator of seawater desalination plants.

The corrosion behavior of 90-10 cupronickel in Arabian Gulf water containing different concentrations of NH4NO3 in ranges of 10−3 to 10−1 M (80–8000 mg/1) has been investigated. 90-10 cupronickel gives a better resistance to corrosion in deaerated water than aerated water. For corrosion-free performance of 90-10 Cu-Ni in Arabian Gulf water, the upper level of ammonia has been determined to be 10−2 M (800 mg/1) and an upper limit for Re to be 6.0 × 104.

Experiments are reported for condensation of steam on horizontal grooved tubes of 1.9 cm diameter with 14.2 grooves/cm (36 tpi Standard American Screw Thread). Three tube wall materials were used: copper, brass and 70–30 cupronickel. The effect of noncondensable gas was investigated for steam-air mixtures in downward forced flow. Heat transfer enhancements of up to a factor of 5.5 were obtained with the brass tube. The deleterious effect of noncondensable gas proved to be no more serious than for smooth tubes. An overhead drip rate of up to ten equivalent tubes caused no significant decrease in heat transfer.

Effects of the shapes of corrugated tubes hd.ch affect heat transfer and pressure drop characteristics were experimentally studied. All heat transfer experiments were conducted with steam at atomospheric pressure condensing on the outside of a horizontally mounted 90–10 cupronickel tube. Tube side pressure drop was measured under isothermal cold flow condition. The results show that tube aide heat transfer coefficients decreased with the increose in pitch and reached a maximum at the ratio 0.05 of indentation depth to inside tube diameter and that the tube side coefficients of two start corrugated tubes were slightly smaller than those of single start tubes. Friction factors were expressed by the equation including pitch and indentation depth. From these results, the relation between tube side heat transfer coefficients and pressure drop per unit length was presented.