Vaporizers design features

All electrical devices are inherent ignition sources. Special design features are required to prevent the ignition of flammable vapors and dusts. The fire and explosion hazard is directly proportional to the number and type of electrically powered devices in a process area. 

A hydrogen peroxide still is used to concentrate peroxide by removing water. The still is of high-purity aluminum, a material that is noncatalytic to the decomposition of peroxide vapor. The still is designed to produce 78% hydrogen peroxide. It will explode spontaneously at about 90%. Illustrate some recommended design features for this still. 

Factors influencing jet breakup may include (a) flow rates, velocities and turbulence of liquid jet and co-flowing gas, (b) nozzle design features, (c) physical properties and thermodynamic states of both liquid and gas, (d) transverse gas flow,[239] (e) dynamic change of surface tension, 1151[2401 (f) swirlj241 242 (g) vaporization and gas compressibility,[243] (h) shock waves,[244] etc. 

Water activity (aw) is the ratio of the partial vapor pressure of water above a solution to that of pure water at the same specific temperature. It plays an important role in evaluating the microbial, chemical, and physical stability of foods during storage and processing. The vapor pressure in the headspace of a food sample can be measured directly by a manometer. A manometer has one or two transparent tubes and two liquid surfaces where pressure applied to the surface of one tube causes an elevation of the liquid surface in the other tube. The amount of elevation is read from a scale that is usually calibrated to read directly in pressure units. Makower and Myers (1943) were the first to use this method to measure vapor pressure exerted by food. Later, the method was improved, in terms of design features of the apparatus, by various scientists (Taylor, 1961 Labuza et al., 1972 Lewicki, 1987). Trailer (1983), Lewicki (1989), and Zanoni et al. (1999) used a capacitance manometer instead of a U-tube manometer for the measurement of vapor pressure. Lewicki et al. (1978) showed that the precision and reproducibility of the method can be improved by the simultaneous measurement of the water vapor pressure and temperature of the food sample. The method is reviewed in detail by Rizvi (1995) and Rahman (1995). 

The vapor pressure manometer (VPM) provides a means for rapid determination of water activity. The method was suggested by Mak-ower and Myers (1943) to measure water vapor pressure exerted by food. This method was improved by Taylor (1961), Labuza et al. (1972), and Trailer (1983). Sood and Heldman (1974), Labuza et al. (1976), and Lewicki et al. (1978) studied design features, accuracy, and precision of the VPM. Trailer (1983) and Zan-oni et al. (1999) discussed the design and setup of a water vapor pressure capacitance manometer. 

That the evaporator could be made as efficient as economically justifiable. Thermal efficiency of an evaporator is increased by multiple-effect operation, by recompression of the vapor, by a combination of these, and by a number of other design features. While sea water evaporators had rarely been made with more than three effects, commercial evaporators of six and seven effects are common and ten-effect evaporators have been used. 

Several manufacturers make explosimeters or combustible gas indicators. Although they differ somewhat in design and operating features, their operation is based on the fact that a measurable amount of heat is released when a combustible gas or vapor is burned. Most meters contain a battery-operated electrical circuit known as a Wheatstone bridge, which is balanced by means of controls on the outside of the instrument. 

Fuel - Fuel supplies to boilers, furnaces, gas turbine and engine drivers, etc., are designed with features such as multiple fuels, propane vaporizer backup, and a liquid fuel surge tank, to promote reliabihty. The failure of any one fuel to a process unit or utihty generation facihty is used as the basis for evaluating a potential overpressure. 

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