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131A Aluminium Alloy Sand or Die Castings (suitable for Pistons, etc.).

One of the most pressing problems of our times is the supply of adequate quantities of drinking water in areas not bestowed with abundant natural resources. Studies have shown the desalting of seawater to be economically sound for certain localities. Of all the available methods, the multi‐stage flash distillation is a proven method. The MSF type desalination plants may be operated independently (single purpose) or linked to power stations (dual purpose). In the MSF type desalination plants, the largest single item of cost is heat exchanger tubes. Design studies have shown that about one‐tenth of a square foot of condensing surface is required to produce one gallon of fresh water per day. For a combined capacity of one billion gallons per day at ¼ sq. ft. of tube, a tube length of 80,000 miles would be required. In MSF type desalination plants, the initial capital cost swallows up to 33% of the money, operating costs about 21% and the remaining 26% goes on power. The colossal amount of heat exchanger surface required in MSF type plants makes it mandatory to investigate new condenser tube materials which may provide ease of fabrication, maximise economy and be abundantly available.

Developed in the U.S.A., the collapsible aluminium tube now represents over 60% of the collapsible tubes made in the U.K. The metal is resistant to a wide range of products and where necessary it readily takes protective and decorative coatings. This article considers the tube in relation to content and environment and also covers test procedures.

The purpose of this paper is to present investigations on the significant influence of the tube material and fin density on fluid elastic instability and vortex shedding in a parallel triangular finned tube array subjected to water cross flow.

The experiment was conducted on finned tube arrays with a fin height of 6 mm and fin density of 3 fins per inch (fpi) and 9 fpi. A dedicated setup has been developed to examine fluid elastic instability and vortex shedding. Nine parallel triangular tube arrays with a pitch to tube diameter ratio of 1.78 were considered. The plain tube arrays, coarse finned tube arrays and fine finned tube arrays each of steel, copper and aluminium materials were tested. Plain tube arrays were tested to compare the results of the finned tube arrays having an effective tube diameter same as that of the plain tube.

A significant effect of fin density and tube material with a variable mass damping parameter was observed on the instability threshold. In the parallel triangular finned tube array subjected to water cross flow, a delay in the instability threshold was observed with an increase in fin density. For steel and aluminium tube arrays, the natural frequency is 9.77 Hz and 10.38 Hz, which is close to each other, whereas natural frequency of the copper tubes is 7.40 Hz. The Connors’ stability constant K for steel and aluminium tube arrays is 4.78 and 4.87, respectively, whereas it is 5.76 for copper tube arrays, which increases considerably compared to aluminum and steel tube arrays. The existence of vortex shedding is confirmed by comparing experimental results with Owen’s hypothesis and the Strouhal number and Reynolds number relationship.

This paper’s results contribute to understand the effect of tube materials and fin density on fluid elastic instability threshold of finned tube arrays subjected to water cross flow.

Aluminium is being increasingly used in refinery construction. Applications range from storage tanks to moisture‐proofing pipe insulation; from heat exchangers to structural elements. The main reasons for this are its good resistance to many types of corrosion, low weight, low cost per unit volume, high thermal conductivity, non‐magnetic and non‐sparking characteristics, good reflectivity and good appearance. From the design engineer's point of view, the metal has the further advantages of good workability and high strength in its alloys. The author describes some of the current practices and experiences in the U.S.A.

The effects of a number of metals and alloys on the thermal stability of Avtur 50 have been evaluated from ASTM‐CRC and high temperature coker tests. The materials tested are used in current aircraft fuel systems or are possible alternatives for fuel systems of supersonic aircraft where they will be in contact with hot fuel. The alloys currently used in aircraft fuel systems have been classified and their probable effects on the stability of hot fuel listed. A number of the materials affected stability adversely, particularly alloys containing significant amounts of copper, and the use of these should be avoided. The pick‐up of copper by Avtur 50 at ambient temperature from alloys such as brass and gun‐metal has also been investigated. The results indicated that sufficient copper to affect thermal stability adversely is readily picked up from these alloys.

In thermal and nuclear power plants, numerous corrosion phenomena observed in copper alloy condenser tube nests have been identified by means of metallography. Particular importance has been given in the paper to verification of secondary dezincification, initiated at the boundaries of the α‐grains in copper tubes. Typical phenomena of corrosion under stress and of erosion‐corrosion have been observed in other copper alloy tube nests, with circulation of sea and river water. In some instances a semi‐quantitative check of the phenomenon on the whole tube nest, by means of eddy currents, has been made possible through the simultaneous application of metallographic analysis.

ZIRCONIUM Corrosion in hot water and steam. Metallic zirconium and its alloys have assumed much importance as construction and protection material in nuclear reactors cooled with water or heavy water. Among the properties favouring this application are low neutron absorption, favourable mechanical characteristics, and a high corrosion resistance to water and steam. This corrosion resistance can be further improved by using suitable zirconium alloys. Even so, there are still certain undesirable corrosion phenomena which cause trouble. These have been made the subject of further research, e.g. in the metal laboratory of the Metallgesellschaft A.G., Frankfurt‐am‐Main. In this connection, a distinction must be made between two phenomena which occur simultaneously but are, as far as it's known at present, basically independent of each other, viz. oxidation and hydrogen absorption. But the extent to which the hydrogen freed in the course of the oxidation process can be absorbed by the zirconium and thereby cause brittleness depends not only on the external conditions but also on the type and quantity of the alloying components. During oxidation, the slow formation of a thin, bluish oxide film is liable to be followed by a more rapid ‘breakaway’ corrosion process in which a white oxide is formed that will soon peel off. There is, as yet, no satisfactory theory which would appear to provide a full explanation of all the phenomena encountered. The author discusses the research methods, the corrosion phenomena as such, the influence of certain alloying constituents on these phenomena and the various attempts at interpreting them.—(H. W. Schleicher, Metalloberfläche, 1961, 15 (8), 234–240.)

Chester Street, Aston, Birmingham, 6. The ‘Donald’ Patent Barrel Lifter Truck and Stand, the three‐in‐one appliance. Barrels up to 7 cwts. lifted and transported by one man. ‘Donald’ Patent Barrel Lifter Stands for Oil Stores.