Spherical tank

In addition, dimensional analysis can be used in the design of scale experiments. For example, if a spherical storage tank of diameter dis to be constmcted, the problem is to determine windload at a velocity p. Equations 34 and 36 indicate that, once the drag coefficient Cg is known, the drag can be calculated from Cg immediately. But Cg is uniquely determined by the value of the Reynolds number Ke. Thus, a scale model can be set up to simulate the Reynolds number of the spherical tank. To this end, let a sphere of diameter tC be immersed in a fluid of density p and viscosity ]1 and towed at the speed of p o. Requiting that this model experiment have the same Reynolds number as the spherical storage tank gives... 

Liquefied ammonia is delivered in rail tankcars to Fisons Limited for storage in a 1,900 tonnes spherical tank at -6° C. Several hundred tonnes of liquefied ammonia could be released on land if either of the two storage tanks, at Shell UK Oil and at Fisons Limited failed. The consequences of f lilure of the Shell tank would be minimal, because a high concrete wall to contain the contents and limit the heat transfer and consequently the rate of evaporation of the liquid. Such protection has not been provided. Because of the storage under pressure there are numerous ways the tank could fail from material defect to missile. The spillage of 50 to 100 tonnes, could kill people if noi [imrnp( , evacuation. 

Spherical tanks fragmented into ten to twenty pieces, whereas cylindrical vessels fragmented into two pieces. Because cylinders at the storage site had been stored parallel to each other, their fragments were launched in specific directions (Figure 2.26). 

Pittman (1972) performed five experiments with titanium-alloy pressure vessels which were pressurized with nitrogen until they burst. Two cylindrical tanks burst at approximately 4 MPa, and three spherical tanks burst at approximately 55 MPa. The volume of the tanks ranged from 0.0067 m to 0.170 m. A few years later, Pittman (1976) reported on seven experiments with 0.028-m steel spheres that were pressurized to extremely high pressures with argon until they burst. Nominal burst pressures ranged from 100 MPa to 345 MPa. Experiments were performed just above ground surface. 

Fixed-Roof Tanks. The effect of internal pressure on plate structures, including tanks and pressure vessels, is important to tank design. If a flat plate is subjected to pressure on one side, it must be made quite thick to resist bending or deformation. A shallow cone-roof deck on a tank approximates a flat surface and is typically built of 3/ 16-in. (4.76-mm) thick steel (Fig. 4a). This is unable to withstand more than a few inches of water column pressure. The larger the tank, the more severe the effect of pressure on the structure. As pressure increases, the practicality of fabrication practice and costs force the tank builder to use shapes more suitable for internal pressure. The cylinder is an economic and easily fabricated shape for pressure containment. Indeed, almost all large tanks are cylindrical. The problem, however, is that the ends must be closed. The relatively flat roofs and bottoms or closures of tanks do not lend themselves to much internal pressure. As internal pressure increases, tank builders use roof domes or spheres. The spherical tank is the most economic shape for internal pressure storage in terms of required thickness, but it is generally more difficult to fabricate than a dome- or umbrella-roof tank because of its compound curvature. 

Natural gas is stored in large spherical tanks because this shape holds the greatest volume for a given amount of containment material. 

LNG carriers for sea transportation are either with spherical tanks or with membrane type tanks. 

Figure 8.16 displays spherical tank cost for liquid storage ranging from 300 to 20,000 bbl. This cost curve may be extrapolated to over 30,000 bbl. Fabrication economics show cost minimized by installing multiple spherical tanks rather than going over 35,000 bbl per tank. Figure 8.16 gives the curve based on the maximum liquid volume con-... 

These spherical tanks are not insulated, since the stored liquids approach the ambient temperature in most countries. Also, insulation problems result from water moisture condensing on the metal walls under the insulation. 

Figure 8.16 is the complete modular LPG storage spherical tank cost, including piping, stairwells, platforms, instruments, controls, steel, foundation, and dike containment. Both material and labor are included in the Fig. 8.16 cost curve, installed and ready to commission. 

Air finfan overhead condensers. Table 8.34 gives the modular cost of the overhead condensers and product coolers. Since this plant is to be installed in Saudi Arabia, cooling tower water is not available. Also, cooling water is not necessary since the products will be stored in spherical tanks requiring 150 to 180°F cooling. This is easy to obtain, even in Saudi Arabia, with air finfan coolers. The square feet of surface area shown in Table 8.34 is the bare tube surface area of each cooler. Please note this is not the extended surface of the outside tube area, but rather the outside bare tube surface area in square feet. Figure 8.4 was used to find the base cost of these air coolers. 

A hydrostatic tank gauge applied to a pressurized, spherical tank. (Courtesy of The Foxboro Co.)... 

A catastrophic explosion and major fire occurred within a major refinery as operations prepared a system for valve maintenance. This refinery stored a flashing flammable fluid (isobutane with a boiling point of 11° F or —12° C) in two spherical tanks. The spheres connected to an alkylation unit via a 10-inch (25 cm) line. Operating line pressure was about 50 psig (345 kPa gauge) and one of the valves in this underground system was in an open pit. [9]... 

A spherical tank, 1 m in diameter, is maintained at a temperature of 120°C and exposed to a convection environment. With h = 25 W/m2 °C and T. = 15°C, what thickness of urethane foam should be added to ensure that the outer temperature of the insulation does not exceed 40PC What percentage reduction in heat loss results from installing this insulation ... 

Considei a 4 m-diameter spherical tank initially filled with liquid nitrogen at 1 atm and - 196°C. I he tank is exposed to 20 C ambient air with a heat transfer coefficient of 25 W/m °C. The temperature of the thin-shellcd spherical tank is observed to be almost the same as itie temperature of the nitrogen inside. Disregarding any radiation heat exchange, deierrnine the rate of evaporation of the liquid nitrogen in the tank as a result of the heat transfer from the ambient air. 

Consider a thick-walled spherical tank of inner radius z, =... 

A 3-m internal diameter spherical tank made of 2-cm-thlck stainless steel (k = 15 W/m O is used to store iced water at r i == 0°C. Ttie tank is located in a room whose temperature is 7 j - 22°C. The walis of the room are also at 22°C. The outer surface of the tank is black and heat transfer between the outer surface of the tank and the surroundings is by natural convection and radiation. The convection heat transfer coefficients at the inner and the outer surfaces of the tank are h, = 80 W/m °C and I12 = 10 W/m °C, respectively. Determine (a) the rate of heat transfer to the iced water in the lank and (b) the amount of ice at 0 C that melts during a 2d-h period. 

A 3-m-diameter spherical tank containing some radioactive material is buried in the ground (k = 1.4 W/ni C). The distance between the top surface of the tank and the ground surface is 4 m. If the surface temperatures of the tank and the ground are 140°C and I5°C, respectively, determine the rate of heat transfer from the tank. 

A 6-m-diaraeier spherical tank is filled with liquid oxygen at — 1 S4 C, The tank is Ihin-shellcd and its temperature can be taken to be the same as the oxygen temperature. The tank is insulated with 5-cm-thick super insulation that has an effective thermal conductivity of 0.00015 W/m °C. The tank -is exposed to ambient air at 15 C with a heat transfer coefricieiit of 14 W/m °C, The rate of heat transfer to the tank is... 

A 6-m-diameter spherical tank is filled with liquid o.xygen (p = 1141 kg/ra , - 1,71 kJ/kg °C)at - l84 C.Itis observed tlial tlie temperature of oxygen increase.s to - 183°C in a 144-hoiir period. The average rate of heat transfer to the tank is... 

A 50-cm-diameter spherical tank is filled with iced water at O C. The tank is thin-shelled and its temperature can... 

A 1.8-m-diameter spherical tank of negligible thickness contains iced water at 0°C. Air at 25°C flows over the lank with a velocity of 7 tn/.s. Determine the rate of heal transfer to the tank and the rate at which icc melts. The heat of fusion of water at O C is 333.7 kJ/kg. 

A 3-in-inteinal-diameler spherical tank made of 1-cm-Ihick stainless steel (k = 15 W/m °C) is used to store iced water at 0°C, The tank is located outdoors at 30 C and is subjected to winds at 25 km/h. Assuming Ihe entire steel lank to be at 0°C and thus its tliermai resistance to be negligible, determine (o) the rate of heat transfer to the iced water in the tank and (P) be amount of ice at O C that melts during a 24 h period. The heat of fusion of water at atmospheric pressure is li. j = 333,7 kJ/kg, Disteg,ird any heat transfer hy radiation,... 

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