Tubular configurations

Fig. 4. Schematic representation of the cross section of tubular configuration for SOFC.

The existence of interlaminar stresses means that laminated composite materials can delaminate near free edges whether they be at the edge of a plate, around a hole, or at the ends of a tubular configuration used to obtain material properties. In all cases, delamination could cause premature failure so must be considered in specimen design because othen/vise the specimen does not represent the true physical situation. 

A configuration for electrically connecting tubular cells to form a stack is described in Section 8.1.2 under sealless tubular configuration (Figure 8-6). The cells are connected in a series-parallel array by nickel felt strips that are exposed to the reducing fuel gas. In this arrangement, the nickel felt strips and cell interconnections extend the length of the cell. 

Sealless Tubular Configuration The most developed solid oxide fuel cell is the Siemens Westinghouse tubular cell. This approach results in eliminating seal problems between adjacent cells. A schematic representation of the cross section of the present Siemens Westinghouse... 

Figure 8-3 Cross Section (in the Axial Direction of the +) of an Early Tubular Configuration for SOFCs [(8), Figure 2, p. 256]...

Figure 8-5 Cross Section of Present Tubular Configuration for SOFCs (2)...

The fuel gas composition also has a major effect on the cell voltage of SOFCs. The performance data (33) obtained from a 15 cell stack (1.7 cm active electrode area per cell) of the tubular configuration (see Figure 8-1) at 1000°C illustrate the effect of fuel gas composition. With air as the oxidant and fuels of composition 97% H2/3% H2O, 97% CO/3% H2O, and 1.5% H2/3% CO/75.5% CO2I2OV0 H2O, the current densities achieved at 80% voltage efficiency were -220, -170, and -100 mA/cm, respectively. The reasonably close agreement in the current densities obtained with fuels of composition 97% H2/3% H2O and 97% CO/3% H2O indicates that CO is a useful fuel for SOFCs. However, with fuel gases that have only a low concentration of H2 and... 

This case is of particular importance because it represents the configuration of the Integrated Planar SOFC (IP-SOFC) developed by Rolls-Royce Fuel Cell Systems, the tubular configuration developed by Siemens Power Corporation, and the segmented configuration. 

When the current is collected through an internal and an external mesh (case 3), the current path is fairly straight, as visible from Figure 4.25. In this case, the tubular configuration operates in a condition that is very close to that of the planar configuration. The in-plane resistance is minimized, but, the manufacturability is more complex. 

Figure 7.8 shows the diagram of voltage versus current. As can be seen, the new designs, HPD5 and Delta9, both present an increase in current density with respect to the traditional tubular configuration. This allows lower production costs. 

The interconnect normally links the anode of one cell to the cathode of the next. It must, of course, be an electronic conductor and also a gas barrier preventing the direct meeting of fuel and oxidant gases. Fig. 4.27 illustrates how the interconnection is achieved in the case of the so-called planar fuel cell stack. In the later discussion of the ceramics-based cells a tubular configuration is described, but the principles are the same. 

The live, hydrated fiber exists in a tubular configuration that conforms to available space within the boll locule. When the boll opens, removal of water causes the internal layers of the fiber to twist and collapse, and the primary wall, which is less able to shrink because of its network structure, wrinkles and molds to the underlying fiber layers, producing folds and convolutions (twists), and compression marks (Figure 5.41). Fibers often collapse in a nonuniform elliptical pattern, whose cross section has a convex and a concave side (see Figure 5.27 and Figure 5.38). 

Figure 8.42 shows the basic configuration of electrofiltration, where an electric field is applied across micro or ultrafiltration membranes in flat sheet, tubular, and SWMs. The electrode is installed on either side of the membrane with the cathode on the permeate side and the anode on the feed side. Usually, the membrane support is made of stainless steel or the membrane itself is made of conductive materials to form the cathode. Titanium coated with a thin layer of a noble metal such as platinum could, according to Bowen [93], be one of the best anode materials. Wakeman and Tarleton [94] analyzed the particle trajectory in a combined fluid flow and electric field and suggested that a tubular configuration should be more effective in use of electric power than flat and multitubular module. 

Crossflow filtration membranes can be produced in flat sheet, hollow fiber, tubular formats when using polymeric materials, and in monolith and tubular configurations when using inorganic membrane materials. Table 14.2 summarizes the various module configurations. 

Hulburt and Katz (HI7) developed a framework for the analysis of particulate systems with the population balance equation for a multivariate particle number density. This number density is defined over phase space which is characterized by a vector of the least number of independent coordinates attached to a particle distribution that allow complete description of the properties of the distribution. Phase space is composed of three external particle coordinates x and m internal particle coordinates Xj. The former (Xei, x 2, A es) refer to the spatial distribution of particles. The latter coordinate properties Ocu,Xa,. . , Xt ) give a quantitative description of the state of an individual particle, such as its mass, concentration, temperature, age, etc. In the case of a homogeneous dispersion such as in a well-mixed vessel the external coordinates are unnecessary whereas for a nonideal stirred vessel or tubular configuration they may be needed. Thus (x t)d represents the number of particles per unit volume of dispersion at time t in the incremental range x, x -I- d, where x represents both coordinate sets. The number density continuity equation in particle phase space is shown to be (HI 8, R6)... 

Extrusion can be defined as paste flow and extrudate formation from ceramic paste [1]. A membrane support must provide a high mechanical resistance and permeability. Tubular configurations correspond to this criterion and are adapted to the tangential filtration. 

In conclusion, it can be stated that the extrusion technique is the most important method of preparing ceramic supports, because the tubular configuration is the most common configuration. In the literature, there are an increasing... 

These membranes were developed during the last ten years in mainly flat and tubular configuration and by using alumina as the base material. They are... 

Fig. 6 Branson sonochemical reactor employing indirect sonication in a tubular configuration.

Results from two studies involving high volume recovery of multicomponent process effluents are presented here as illustrations of recent applications of hyperfiltration membranes in a tubular configuration supported by porous stainless steel. The first is a laboratory separation of dyes frcm a saline dye manufactiaring process effluent and the second a pilot renovation of wash water from a dye range for reuse. 

In Eig. 2.12, the principle of compression sealing of membranes with a tubular configuration is depicted. The membrane tube is mounted in a metal end-cap and the space in between end-cap and membrane filled by the sealing material. Compressive forces are obtained upon increasing the temperature and the magnitude of these forces can be tuned by proper selection of the metal type and sealing material, based... 

Based on the tubular configuration, and presuming a total module diameter of about 2 meter including the space required for insulation, the module of Fig. 2.15 can be designed with a height of about 4.5 meter which contains 160 m of membrane surface area. In order to meet an oxygen production of 30.000 Nm /hr, 32 of these module units will be needed. 

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