Efficiency, volumetric

The slip of a pump is fraction or percent loss of capacity relative to theoretical. Slip is (1 — Cvoi), w here e oi is the volumetric efficiency. Volumetric efficiency is the actual liquid pumped (usually considered water) relative to that which should theoretically be pumped based on piston displacement. 

Finely dispersed carbon substances introduced into the active mass of pseudocapacitive electrodes of hybrid (asymmetric) capacitors play the most important role in operation of an efficient volumetric collector. 

Coagulation a Collision efficiency volumetric concentration of suspended particles G Velocity gradient t time i... 

In other words, the polymer molecules in the blend solution slug would adsorb and coat the water-wet portions of the pore walls, so that the alkaline agent would have only limited sites for the rock dissolution and ion exchange reactions. Hence, the saved useful alkalinity could be used for the reactions with the organic acids in the crude oil in order to mobilize the residual oil. Moreover, as in the first version of PAAF, chasing fresh polymer slug would provide the mobility control and the efficient volumetric sweep. 

Receivers—high-efficiency volumetric reactors, secondary concentrators... 

NOTE In order to make this as painless as possible, please observe the following recommendations 1) Keep the mixing bowl temperature as close to OC or less as possible 2) Keep the Hypochlorite solution as it is being added as close to OC or less as possible 3) After half the Hypochlorite solution has been added, place a plastic bag with 50-1 OOg ice/salt/water mix into the bowl to help keep temperatures low (use this instead of directly adding ice to the reactants, which adds a considerable volume of water making the process less volumetric ally efficient) 4) Purchase an 81b bag of ice ahead of time ... 

There are two principal mechanisms of enhanced oil recovery increasing volumetric sweep efficiency of the injected fluid and increasing oil displacement efficiency by the injected fluid. In both, chemicals are used to modify the properties of an injected fluid whether water, steam, a miscible gas such as CO2 or natural gas, or an immiscible gas, usually nitrogen. Poor reservoir volumetric sweep efficiency is the greatest obstacle to increasing oil recovery (9). 

Polymer Flooding. Even in the absence of fractures and thief 2ones, the volumetric sweep efficiency of injected fluids can be quite low. The poor volumetric sweep efficiency exhibited in waterfloods is related to the mobiUty ratio, Af, the mobiUty of the injected water in the highly flooded (low oil saturation) rock, divided by the mobiUty of the oil in oil-bearing portions of the reservoir, (72,73). The mobiUty ratio is related to the rock permeabihty to oil, and injected water, and to the viscosity of these fluids by the following equation ... 

The WAG process has been used extensively in the field, particularly in supercritical CO2 injection, with considerable success (22,157,158). However, a method to further reduce the viscosity of injected gas or supercritical fluid is desired. One means of increasing the viscosity of CO2 is through the use of supercritical C02-soluble polymers and other additives (159). The use of surfactants to form low mobihty foams or supercritical CO2 dispersions within the formation has received more attention (160—162). Foam has also been used to reduce mobihty of hydrocarbon gases and nitrogen. The behavior of foam in porous media has been the subject of extensive study (4). X-ray computerized tomographic analysis of core floods indicate that addition of 500 ppm of an alcohol ethoxyglycerylsulfonate increased volumetric sweep efficiency substantially over that obtained in a WAG process (156). 

Gravity override of low density steam leads to poor volumetric sweep efficiency and low oil recovery in steam floods. Nonchemical methods of improving steam volumetric sweep efficiency include completing the injection well so steam is only injected in the lower part of the oil-bearing zone (181), alternating the injection of water and steam (182), and horizontal steam injection wells (183,184). Surfactants frequently are used as steam mobihty control agents to reduce gravity override (185). Field-proven surfactants include alpha-olefin sulfonates (AOS), alkyltoluene sulfonates, and neutralized... 

Surfactants evaluated in surfactant-enhanced alkaline flooding include internal olefin sulfonates (259,261), linear alkyl xylene sulfonates (262), petroleum sulfonates (262), alcohol ethoxysulfates (258,261,263), and alcohol ethoxylates/anionic surfactants (257). Water-thickening polymers, either xanthan or polyacrylamide, can reduce injected fluid mobiHty in alkaline flooding (264) and surfactant-enhanced alkaline flooding (259,263). The combined use of alkah, surfactant, and water-thickening polymer has been termed the alkaH—surfactant—polymer (ASP) process. Cross-linked polymers have been used to increase volumetric sweep efficiency of surfactant—polymer—alkaline agent formulations (265). 

Microbial-enhanced oil recovery involves injection of carefully chosen microbes. Subsequent injection of a nutrient is sometimes employed to promote bacterial growth. Molasses is the nutrient of choice owing to its low (ca 100/t) cost. The main nutrient source for the microbes is often the cmde oil in the reservoir. A rapidly growing microbe population can reduce the permeabiHty of thief zones improving volumetric sweep efficiency. Microbes, particularly species of Clostridium and Bacillus, have also been used to produce surfactants, alcohols, solvents, and gases in situ (270). These chemicals improve waterflood oil displacement efficiency (see also Bioremediation (Supplement)). 

Ratio of the ac tual flow rate (entering compressor) to the displacement rate is the volumetric efficiency T va- The volumetric efficiency is... 

Similar to volumetric efficiency, isentropic (adiabatic) efficiency T is the ratio of the work required for isentropic compression of the gas to work input to the compressor shaft. The adiabatic efficiency is less than one mainly due to pressure drop through the valve ports and other restricted passages and the heating of the gas during compression. 

When the suc tion pressure is lowered, the influence of the clearance will increase, causing in the extreme cases the entire volume to be used for reexpansion, which drives the volumetric efficiency to zero. 

Employing wood chips, Cowan s drying studies indicated that the volumetric heat-transfer coefficient obtainable in a spouted bed is at least twice that in a direct-heat rotaiy diyer. By using 20- to 30-mesh Ottawa sand, fluidized and spouted beds were compared. The volumetric coefficients in the fluid bed were 4 times those obtained in a spouted bed. Mathur dried wheat continuously in a 12-in-diameter spouted bed, followed by a 9-in-diameter spouted-bed cooler. A diy-ing rate of roughly 100 Ib/h of water was obtained by using 450 K inlet air. Six hundred pounds per hour of wheat was reduced from 16 to 26 percent to 4 percent moisture. Evaporation occurred also in the cooler by using sensible heat present in the wheat. The maximum diy-ing-bed temperature was 118°F, and the overall thermal efficiency of the system was roughly 65 percent. Some aspec ts of the spouted-bed technique are covered by patent (U.S. Patent 2,786,280). 

One manner in which size may be computed, for estimating purposes, is by employing a volumetric heat-transfer concept as used for rotary diyers. It it is assumed that contacting efficiency is in the same order as that provided by efficient lifters in a rotaiy dryer and that the velocity difference between gas and solids controls, Eq. (12-52) may be employed to estimate a volumetric heat-transfer coefficient. By assuming a duct diameter of 0.3 m (D) and a gas velocity of 23 m/s, if the solids velocity is taken as 80 percent of this speed, the velocity difference between the two would be 4.6 m/s. If the exit gas has a density of 1 kg/m, the relative mass flow rate of the gas G becomes 4.8 kg/(s m the volumetric heat-transfer coefficient is 2235 J/(m s K). This is not far different from many coefficients found in commercial installations however, it is usually not possible to predict accurately the acdual difference in velocity between gas and soRds. Furthermore, the coefficient is influenced by the sohds-to-gas loading and particle size, which control the total solids surface exposed to the gas. Therefore, the figure given is only an approximation. 

The disadvantage is that volumetric efficiency is usually much less than conventional trays or packed contactors. Applications are usually limited to cases when only a few transfer units or a single eqiiihbriiim stage is required. Since many of these applications tend to be in heat-transfer sei vice, the following discussion will be in terms of thermal properties and thermal measures of performance. 

See also Treybal [Am. ln.st. Chem. Eng. J., 4, 202 (1958) 6, 5M (I960)] and Olander [Chem. Eng. Sci, 18, 47 (1963) 19, 275 (1964)]. The remaining discussion is confined to measured values of stage efficiency or volumetric overall coefficients. These are largely of value only for the particiilar systems studied. For this reason, one fairly complete study will be described, and the others will only be mentioned. 

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