Effect of flow velocity

Figure 7 reports calculations of the effect of flow velocity on the critical capillary pressure for the constant-charge electrostatic model and for different initial film thicknesses. 

Figure 2. Effect of flow velocity on conversion and selectivity for CH4 oxidation over 10 layers of 40 mesh Pt-10% Rh gauze. The feed contained 16% CH4 in air and the front layer of gauze was maintained at 1227 5°C.

Fig. 7.6 Effect of flow velocity on oxygen electrodes of different dimensions. Open circles represent O2 - saturated water and full circles represent areated water. The electrodes are (a) 50pm diameter Pt disks (b) 50pm diameter Pt disks with 25pm Teflon membrane (c) 300pm Pt disks and (d) 10pm Pt disk with 6.25pm Teflon membrane (adapted from Fatt, 1976)...

TABLE 2.1 Effect of Flow Velocity on the Magnitude of the k a of the Ap and B22t Soil Horizons from Nottoway County"... 

The effects of flow velocity leading to band spreading are not discussed here, since a fairly comprehensive treatment has been given by Yost et al. (1980). 

Leu, H.G., C. E Ouyang, and T. Y. Pai (1997). Effects of flow velocity and depth on the rates of reaeration and BOD removal in a shallow open channel. Water Science Technol. Proc. 1995 5th lAWQ Asian Regional Conf. on Water Quality and Pollut. Control, Feb. 7-9 1995, Manila, Philippines, 35, 8, 57-67. Elsevier Science Ltd. Oxford. England. Mandt, M. G. and B. A. Bell (1982). Oxidation Ditches in Wastewater Treatment. Ann Arbor Science Publishers, Ann Arbor, Ml, 48. 

Effect of Flow Velocity. The flow velocity determines the shear rate and the pressure gradient. Therefore, the magnitude of a viscous force acting on a water droplet is directly related to flow velocity. This viscous force determines whether droplets can pass through pore throats smaller than themselves. It is also a factor in breakup of droplets into smaller droplets. 

Recently, Prein and Molander [54], also using a rotating-cylinder electrode, explored the effect of flow velocity (i.e., rotational velocity) on the ECP of Type 304SS in oxygenated water at 288 °C. These workers found that the ECP at low oxygen concentrations is quite sensitive to flow rate, and their data are in semiquantitative agreement with the MPM. 

Fig. 37. Effect of flow velocity on the surface morphology of Alloy-600 after exposure to 0.1 m NaCl at 200°C flow velocity 132cm/s [33]. Reproduced fiom Corrosion J. 41, 197 (1985) by permission of the Editor.

Effect of flow velocity. An increase in flow rate through the column also increases the product throughput with a resulting payoff in decreased separation efficiency. A change in the flow velocity influences all contributions to the variance except the contribution of the feed band because the time scale for flow relative to time scales for dispersion. 

Figure 6 represents the relationship between tomato juice viscosity and flow velocity. The measurement was done with the juice prepared from canned paste, using a disc rotating viscosimeter. The value, viscosity multiplied by velocity was nearly Independent of the velocity. This suggests that the effect of flow velocity on the pressure drop would be small. This allows the variation of juice feed velocity in a wide range without significant change in pressure drop. 

Figure 14. Effect of flow velocity on plutonium distribution on basalt, ANL Neg. 122-75-316...

The solid and dashed lines in Figures 16 and 17 are the model prediction. The model predicted the experimental data fairly well. Figure 18 depicts the effect of flow velocity on the permeability decline. It can... 

Shalhi [1993] constructed a table from literature data that qualitatively demonstrates the effects of flow velocity on fouling in certmn processing operations. Part of this table has been used to produce Table 11.7. It can be seen that there is no consistent trend. 

The effect of flow velocity on biofilm removal is illustrated on Fig. 14.14 [Nesaratnam and Bott 1984]. The curves show that as the velocity is increased the rate of removal of established biofilm increases, and the apparent final biofilm thickness is less. There are two effects related to velocity and include ... 

FIGURE 14.14. The effect of flow velocity on the removal of biofilms ot Pseudomonas fluorescens using sodium hypochlorite. 

Low levels of residual chlorine may be regarded as a biostat, i.e. preventing colonisation or restricting biofilm development. In a particular laboratory experiment [Kaur et al 1988] chlorine levels as low as 0.2 - 0.6 mg/l inhibited biofilm attachment and growth. The effect of flow velocity and chlorine concentration are shown on Fig. 14.14. 

In most cases VOC degradation in iron reactors has been described by a pseudo first order rate law with respect to dissolved VOC concentration normalized to tile BET iron sm-face. Other kinetic expressions are used to consider reactive site saturation and increased iron surface passivation (e.g. Wust et al., 1999 Farrel et al., 2000) or more complex reaction pathways (Arnold and Roberts, 2000). The objective of this study is to evaluate three principal processes related to problems of temporal upscaling, i.e. lag time processes, the effect of flow velocity on degradation rates and the extent and effect of passivation reactions. 

Passivation of iron granulates in permeable barriers used for in situ groundwater remediation may result in a shorter life time and in contaminant breakthrough earlier than expected. Therefore, mineral reactions or generally the effect of other groundwater constituents on the long term reactivity of iron is of major interest for the application of this technology in environmental clean up. For interpretation of column experiments it is also important to estimate the effect of flow velocity on the extent of passivation due to mineral reactions. 

The Bailes and Larkai model incorporates a number of assumptions such as the use of a monodispersion and uniform interdroplet spacing. However, developing a model incorporating a typical droplet distribution with random droplet spacing would be significantly more complicated. No attempt is made, either, to incorporate file effects of flow velocity or regime, and the experimental results do not indicate whether tests were carried out in laminar or turbulent flow (though laminar flow can be deduced). These parameters would also have had an effect on droplet collision frequency, and therefore the rate of coalescence. 

Casey, E., Glennon, B. and Hamer, G. 2000. Biofllm development in a membrane-aerated biofllm reactor effect of flow velocity on performance. Biotechnology and Bioengineering, 67,476-486. 

Figure 10.29 Effect of flow velocity on corrosion rate of copper in 3% NaCl (a) test of 10-minute duration and (b) test of 100-hour duration [21],...

NACE TM0274 appears to be an outgrowth of the previously mentioned TM0171 test method. It is similar in many aspects. The major difference is the use of a dynamic recirculation loop which accommodates both a high temperature test station and a low temperature test station in which corrosion coupons can be placed. This method can be used for (1) the quantitative measurement of the general corrosion rates of metallic materials for consideration for use in high-purity water, (2) the determination of the effects of flow velocity, and (3) the estimation of the release rate of metallic elements to the aqueous medium. No provisions... 

For evaluation of the effect of flow velocity on corrosion in pipelines, NACE Standard Test Method of Conducting Controlled Velocity Laboratory Corrosion Tests (TM0270) can be used to evaluate several steel samples at one time, at velocities up to 8 ft/s (244 cads). 

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