Stacks weight

The anode plate at the center of the stack used as a methanol reservoir permit a more efficient fuel distribution and reduces the stack weight. In Fig. 9.4 (right) six dual side stacks were connected in series to generate a 600 mW mobile phone charger that developed a power density of 25 mW.cm. ... 

The 10 1 cantilever arm is loaded with a variety of stacked weights shown in Fig. 13.14c. By requiring only one-tenth of the actual stretching force applied at the free end of the tensile specimens at the other end of the lever arm, this mechanical advantage permits easy application of loads by hand. The test temperature was precisely controlled at 50-80°C in an efficient air-heated chamber shown in Fig. 13.14b. 

As discussed above, transport of current through the BPs results in power loss. BPs account for about 80% of the stack weight and up to 45% of the cost (Hermann et ah, 2005) thus an accurate calculation of power loss in the BPs is of vital importance for stack design. 

An additional requirement that has to be satisfied is a high level of surface hydrophilicity. Non-wettable plate surfaces result in unstable reactant flows that have to be countered with higher pressure drops and gas stoichiometries and hence higher parasitic power drains. This requirement has lead to the development of hybrid coatings that can provide the low ICR and high wettability. At this time, the bipolar plates account for 75% of the total stack weight and x% of the stack cost. Table 15.4 summarizes some of the targets for bipolar plates for automotive fuel cells. 

For a fuel ceU stack, mass- and volume-specific power densities are more useful parameters. The mass power density is the ratio of power to stack weight, measured in kilowatts per kilogram. Clearly, light-weight stack materials are required to increase the mass power density of a stack. Volume power density is the ratio of power to stack volume, measured in kilowatts per liter or kilowatts per cubic meter. Thus, for increasing the volume power density, one requires to reduce the stack size and simplify the stack system. 

Laminates. Laminate manufacture involves the impregnation of a web with a Hquid phenoHc resin in a dip-coating operation. Solvent type, resin concentration, and viscosity determine the degree of fiber penetration. The treated web is dried in an oven and the resin cures, sometimes to the B-stage (semicured). Final resin content is between 30 and 70%. The dry sheet is cut and stacked, ready for lamination. In the curing step, multilayers of laminate are stacked or laid up in a press and cured at 150—175°C for several hours. The resins are generally low molecular weight resoles, which have been neutralized with the salt removed. Common carrier solvents for the varnish include acetone, alcohol, and toluene. Alkylated phenols such as cresols improve flexibiUty and moisture resistance in the fused products. 

Production and consumption of wood products and residues are measured ia various units, based on common usage and their metric equivalents (2—4). Pulpwood logs and fuelwood are commonly measured ia cords. A cord refers to a stacked pile of wood, with outside dimensions of 4 by 4 by 8 ft (1.22 by 1.22 by 2.44 m) and a volume of 128 ft (3.62 m ). The weight of a cord depends on density of wood and bark and on moisture content. In the United States, it can range from 1.3 to 1.7 short tons (1.2 to 1.5 metric tons), air dried. 

The soft-mud process is used to make handmade btick. Mote water is added to the clay to make a thinner paste, typicaHy about 20 to 30% by weight of water. The resulting slurry is packed into molds that have a sand or water coating on them that acts as a release agent. The wet brick shapes ate removed from the molds when they have set up enough to handle and ate then stacked for drying and burning. 

Molecular Weight EPA Method 3 is used to determine carbon dioxide and oxygen concentrations and dry molecular weight of the stack-gas stream. Depending on the intended use of the data, these values can be obtained with an integrated sample (see Fig. 25-28) or a grab sample (see Fig. 25-29). In addition, the instrumental analyzer... 

With the grab sampling technique, a samphng probe is placed at the center of the stack, and a sample is drawn direcfly into an Orsat analyzer or a Fyrite-type combustion-gas analyzer. The sample is then analyzed for carbon dioxide and oxygen content. With these data, the diy molecular weight of the gas stream can then be calculated. 

A further deficiency of natural rubber, compared with the synthetics, is its very high molecular weight coupled with a variable microgel content. Whilst this is desirable in that it reduces the tendency of stacked bales of rubber to flatten out... 

Consider coal burning in a boiler house. The assessor may not be able to measure the mass of sulfur dioxide (SOj) leaving the boiler stack, because of access problems and the lack of suitable sampling ports on the stack. The only information available is that the coal is of soft quality, containing 3% sulfur by weight and, on average, 1,000 kg of coal is burned each day. 

Example The maximum flare load of a system is 1,000,000 Ibs/hr of vapor. The pressure at the base of the flare stack is 2 psig, the average molecular weight of the vapor is 50, at a temperature of 200°F at the combined header to the flare stack. The distance from the drum to the stack is 500 ft. The line consists of two 90° welding elbows and an orifice for a flow controller. The total pressure drop at the knock-out drum is 0.5 psi. Determine the pressure at the inlet of the knock-out drum. 

We shall now provide a second example to illustrate step-by-step calculations. In this example a flare stack is estimated to be 80% efficient in combusting HjS off-gas. The total off-gas through the stack is 400,000 kg/hr, of which 7.0 weight percent is H2S. The physieal stack height is 250 m, the stack diameter is 5.5 m, and the stack emission velocity is 18 m/s. The stack emission temperature is 15°C. The meteorological conditions may be described as a bright sunny day with a mean wind speed of 3 m/s. 

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