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The purpose of this paper is to recommend a validated numerical model for simulation the flue gases heat recovery recuperators. Due to fulfill of this demand, the influences of ash fouling characteristics during the transient/steady-state simulation and optimization of a 3D complex heat exchanger equipped with inner plain fins and side plate fins are studied.

For the particle dispersion modeling, the discrete phase model is applied and the flow field has been solved using SIMPLE algorithm.

According to obtained results, for the recuperator equipped with combine inner plain and side plate fins, determination of ash fouling characteristics is really important, effective and determinative. It is clear that by underestimating the ash fouling characteristics, the achieved results are wrong and different with reality.

Finally, the configuration with inner plain fins with characteristics of: d_i =5 mm, d_o = 6 mm, d_g = 2 mm, d_k = 3 mm and NIPFT = 9 and side plate fins with characteristics of: T_F = 3 mm, P_F = 19 mm, NSPF = 17·2 = 34, W_F = 10 mm, H_F = 25 mm, L_F = 24 mm and ß = 0° is introduced as the optimum model with the best performance among all studied configurations.

Overall costs of £20,000 a day for operating the very largest tankers make it important to extend the period between drydockings as much as possible, to keep the time spent in port to a minimum, and to avoid even small losses of speed in service.

Trials to develop environmentally friendly marine paints based on natural materials as replacement for copper and tin compounds for fouling and marine corrosion control.

Green algae, tubeworms in dead powder form and garlic were used as natural anti‐fouling components in the paints developed. Electrochemical technique was employed for testing the potential of both tubeworms and garlic in terms of inhibition of steel corrosion in seawater. Marine paint formulations containing each of the three selected natural materials were applied onto PVC and un‐primed steel surface, which were immersed in natural seawater for the assessment of their anti‐fouling and anti‐corrosion properties. The results of visual assessment and seawater analysis were also used for such an evaluation.

Tubeworms act as mixed type inhibitor while garlic affects the potential cathodic process of steel in seawater. Tubeworms‐based paint, with 25 per cent in the dry paint film, could protect steel surface from marine corrosion up to 7 months. The paints containing algae and garlic, and the corresponding algae/garlic free paints, resisted slime film formation. Steel and PVC coated surfaces with paint containing algae showed the best anti‐fouling potential within the prepared series.

The investigation only involved the application of the dead form of green algae and tubeworms as effective pigments in the developed paints. It is recommended that further research should focus on extracting and identifying the active components in each organism against fouling and marine corrosion.

The paint formulations developed (containing 25 per cent by weight tubeworms in the paint film) could be used to protect un‐primed steel surface against fouling and marine corrosion for a reasonably long duration.

The application of one paint formulation on un‐primed steel surface for its protection from both fouling and marine corrosion is novel. The electrochemical studies of steel in natural seawater in presence of tubeworms and garlic are original.

Last month the author considered the effects of fouling on harbour installations and power stations after briefly surveying the history of measures taken to prevent it. This month, emphasis is on ships. Satisfactory anti‐corrosive and anti‐fouling compositions, properly applied, have an important beneficial effect on the frictional resistance, and without sufficient precaution, fouling and corrosion of a ship's hull eventually often add over 20% to the resistance of a new ship.

NEW ANTI‐FOULING SYSTEM. Localised penetration of anti‐corrosive paint systems on hulls can be caused by fouling organisms; they also encourage the growth of sulphate‐reducing bacteria in slimes which tend to decompose many anti‐corrosive paints. These are only two of the effects of fouling. Although less concerned with corrosion than we are in modern times, the Phoenicians in 800 B.C. were aware of some of the other effects of fouling and used copper sheathing as an anti‐fouling measure. Similarity between the principles and materials employed then and those in use today is outstanding, for copper remains the most widely used toxic included in anti‐fouling paints. There was one period in naval history, however, when the use of copper had unfortunate results. This was in the late 19th century with the introduction of iron ships. The practice of fitting copper sheathing was carried over to iron hulls; the iron hull was immediately rendered anodic to the copper and considerable corrosion ensued, while the copper, being the cathode, failed to pass into solution and therefore its toxic qualities were lost and fouling continued unabated. The fouling problem influenced the British Admiralty towards discontinuing the use of iron ships.

It is well established that in both cold and warm sea water there can be rapid growth of large fouling organisms, which can be seen at low tides growing on jetties, platforms and rig legs etc.

The cathodic protection firm of F. A. Hughes & Co. Ltd. are patenting a new system, Toxion, which prevents both fouling and corrosion of ships' hulls below the water‐line. The first ship fully equipped with this system, the P. & O. S.S. Ballarat, drydocked in October this year on the Tyne, after trading for 14 months, making three round trips to Australia and spending on average 5½ weeks in Australian ports. Below are given details of the system and the findings at this last drydocking.

This suspension bridge, with its main span of 3,300 ft., is expected to be opened in 1963. It will be the largest in Europe and the fourth largest in the world. A number of interesting improved techniques will be used in protecting it from corrosion and, in particular, the post‐tensioning cables which anchor the side towers to the base rock are expected to last over a century.

Shipping is one of the major British industries and a valuable source of ‘invisible exports’ by virtue of its earnings of foreign currencies. One of the major costs incurred by shipping companies is that of preventing the corrosion of their vessels and at a rough estimate it is probable that something like £30 million is expended annually in countering the corrosion of ships and harbour installations. Ships are constructed mainly of steel and their protection is essentially a particular aspect of the problem of protecting steel against corrosion. Aluminium alloys and newer materials such as plastic sheets are being increasingly used on board ships, but these materials do not offer quite the same difficulty as regards protection nor is the problem yet of the same magnitude. Painting is the most widely used means of protection and the present article deals with some of the problems associated with the painting of ships from the point of view of a paint manufacturer.

The bio‐fouling and corrosion characteristics of 60/40 brass were investigated in the Palk Bay waters of the Mandapam Coast, India, over a period of a year. The experimental methods included corrosion rate by weight loss measurement and analysis of the corrosion product by X‐ray diffraction. The bio‐fouling characteristics of 60/40 brass were studied in terms of seasonality of recruitment of organisms and quantification of the fouling community development pattern. The XRD analysis of the products on brass threw more light on the protective nature of the compounds formed and their impact on the overall corrosion rate of the material. The organisms found in fouling deposits on brass included algae, bryozoans and hydroids. The results of the study are discussed in the light of the sea‐water characteristics and monsoonal effects.