Water vaporization from

Water vapor from moist product Sensible and latent heat gains People... 

Fusion Process. In the fusion process, also frequendy referred to as fusion cook, inert gas is continuously sparged from the bottom of the reactor to carry away water vapor from the reaction mixture. The exhaust is then either vented away or sent to a fume scmbber, which is frequendy a small vessel with water atomi2ing no22les. After the reaction is completed, the finished resin may be discharged, filtered, and packaged without solvent. More frequendy, it is cooled to a safe temperature, then dissolved in the desired type and amount of solvent in a thinning tank, filtered, and packaged, or pumped... 

Adsorbent Applications. One of the earliest uses for activated alumina was removal of water vapor from gases and this remains an... 

Studies of the interactions between water and the Hpid constituents of the stratum corneum suggest that the supply of water per se is not responsible for skin quaHty and condition. Water vapor from lower layers provides a constant supply of moisture to the epidermis. Instead, the abiHty of the skin to retain the moisture is critical, and this abiHty depends on the HpidlameUar bilayers that occupy the spaces between the ceUs of the stratum corneum (44—46). 

An interesting and novel use of a soHd desiccant, the reduction of cold condensate corrosion in automotive exhaust systems, illustrates a hybrid closed—open system. Internal corrosion occurs in mufflers when the water vapor in the exhaust condenses after the engine is turned off and the muffler cools. Carbon dioxide dissolves in the condensate to form an acidic soup. In an essentially closed static drying step, an acid- and heat-resistant desiccant located in the muffler adsorbs water vapor from the exhaust gas as it cools to prevent formation of corrosive acidic condensate. When the engine is restarted, the system becomes open, and the desiccant is regenerated by the hot exhaust gas to be ready for the next cooldown step (19). 

Condensation Scrubbing The collection efficiency of scrubbing can be increased by the simultaneous condensation of water vapor from the gas stream. Water-vapor condensation assists in particle removal by two entirely different mechanisms. One is the deposition of particles on cold-water droplets or other surfaces as the result of... 

Water vapor is a serious interfering substance in this technique. A moisture trap such as a drying agent or a water vapor condenser is required to remove water vapor from the air to be analyzed. 

Monthly evaporation estimates can be made using the Kohler-Nordenson-Fox equation with a pan coefficient of 0.7. The Kohler-Nordenson-Fox equation describes evaporation as the combination of water loss due to radiation heat energy and the aerodynamic removal of water vapor from a saturated surface. The general form for the combination equation is ... 

By solving the partial ptessute of water vapor from the equation above, we receive... 

When the airflow meets a surface whose temperature is lower than the dewpoint, water vapor from the air condenses on the surface of the cooling coil. If all air comes into contact with the cold surface, the state of the air after the process will be at point 3. Some air always escapes the cold surface, and therefore the state of air after contact with the coil is a mixture of saturated air (3) and escaped air (1). The mixing point (2) lies on the line connecting points 1 and 3, as shown in Example 8. The nearer point 2 is to point 3, the more effective is the cooling coil. 

The influence of the absorption oi water vapor from the atmosphere into the fluid... 

Gas dehydration is the process of removing water vapor from a gas stream to lower the temperature at which water will condense from the stream. This temperature is called the dew point of the gas. Most gas sales contracts specify a maximum value for the amount of water vapor allowable in the gas. Typical values are 7 Ib/MMscf in the Southern U.S., 4 Ib/MMscf in the Northern U.S. and 2 to 4 Ib/MMscf in Canada. These values correspond to dew points of approximately 32°F for 7 lb/ MMscf, 20°F for 4 lb MMscf, and 0°F for 2 Ib/MMscf in a 1,000 psi gas line. 

For water vapor From Figure 6-17, ratio = 0.859 actual water vapor capacity = 300 (0.859) = 257 Ibs/hr Total mixture actual capacity = 202 -t 257 = 459 Ibs/hr... 

For 3 inch Hg abs and 95°F saturation, the fraction of water vapor from Figure 6-20 is 0.77 lbs water vapor/lb air. 

Design a partial condenser to cool a mixture of hydrogen chloride-water vapor from 178°F to 90°F using 60 gal per min of chilled water at 70°F The unit is to have the acid mixture in the tubes, because this will allow for a cheaper construction than if this material were in the shell. The tube-side material is to be impervious graphite, and the shell and shell-side baffles are to be steel. The acid vapor is essentially at its dew point. 

Moisture in a gas stream might be water vapor from the air or a water scrubber unit, or it could be some other condensable vapor being carried in the gas stream. It is important in compressor volume calculations to know the moisture (or condensable vapor) condition of the gas. 

Calcium sulfate, the substance used to absorb water in desiccators, provides an example of this temperature sensitivity. Anhydrous calcium sulfate absorbs water vapor from the atmosphere to give the hydrated salt. The reaction has a negative AS° because water molecules become more constrained when gaseous water molecules move into the solid state. The reaction also has a negative AH ° because of the electrical forces of attraction... 

Desiccators are used to store chemicals that react slowly with water. Calcium sulfate chips in the bottom of the desiccator absorb water vapor from the atmosphere. The blue chips contain an indicator that turns pink when the calcium sulfate is saturated with water. 

Mass transfer in freeze-drying refers to the transfer of water vapor from the sublimation front through open channels in the partially dried layer, created by prior sublimation of ice, through the headspace of the vial, past the lyostopper, through the chamber, to the condenser. 

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