Boundary layer effect

Third, design constraints are imposed by the requirement for controlled cooling rates for NO reduction. The 1.5—2 s residence time required increases furnace volume and surface area. The physical processes involved in NO control, including the kinetics of NO chemistry, radiative heat transfer and gas cooling rates, fluid dynamics and boundary layer effects in the boiler, and final combustion of fuel-rich MHD generator exhaust gases, must be considered. 

Fig. 1. General dialysis is a process by which dissolved solutes move through a membrane in response to a difference in concentration and in the absence of differences in pressure, temperature, and electrical potential. The rate of mass transport or solute flux, ( ), is directly proportional to the difference in concentration at the membrane surfaces (eq. 1). Boundary layer effects, the difference between local and wall concentrations, are important in most...

A (3 is caused by boundary-layer effects A 3 is caused by the blade thickness... 

Boundary layer effects Membranes (selective permeability for ions, gases etc.), ion exchangers, controlled release of pharmaceuticals. 

A word should be said about the weak boundary layer effect and silicone release [40,41]. Studies have shown that having loose silicone oil that can transfer to the PSA will lower release, however subsequent adhesion will likely suffer as well. In most commercial instances using silicone liners, a weak boundary layer is not intentionally employed. Additionally, many low transfer silicone liners are commercially available which provide premium release and show low to no PDMS transfer to PSAs, indicating that PDMS transfer is not a necessary condition for easy release. 

Liquid Core Convection and Boundary-Layer Effects 318... 

Equation (4) states that the linear deposition rate vj is a diffusion controlled boundary layer effect. The quantity Ac is the difference in foulant concentration between the film and that in the bulk flow and c is an appropriate average concentration across the diffusion layer. The last term approximately characterizes the "concentration polarization" effect for a developing concentration boundary layer in either a laminar or turbulent pipe or channel flow. Here, Vq is the permeate flux through the unfouled membrane, 6 the foulant concentration boundary layer thickness and D the diffusion coefficient. 

Wang, S.S. and Choi, 1. (1982). Boundary layer effects in composite laminates. Part I free-edge stress singularities J. Appl. Mech. 49, 541-548. 

After this preliminary discussion, we shall now consider the adsorption isotherms in the case of chemisorption involving boundary-layer effects. At equilibrium, the number of oxygen atoms being chemisorbed per unit time and area equals the number of oxygen atoms desorbed per unit time and area. According to (4a) we obtain... 

This book provides a general introduction to membrane science and technology. Chapters 2 to 4 cover membrane science, that is, topics that are basic to all membrane processes, such as transport mechanisms, membrane preparation, and boundary layer effects. The next six chapters cover the industrial membrane separation processes, which represent the heart of current membrane technology. Carrier facilitated transport is covered next, followed by a chapter reviewing the medical applications of membranes. The book closes with a chapter that describes various minor or yet-to-be-developed membrane processes, including membrane reactors, membrane contactors and piezodialysis. 

Guo, X. and S. Mitra. 1999. Enhancement of extraction efficiency and reduction of boundary layer effects in pulse introduction membrane extraction. Anal. Chem. 71 4407 -412. 

Gas injection membrane extraction (GIME) of aqueous samples has been developed to address the issues of boundary layer effects and sample dispersion [66]. This is shown in Figure 4.20. An aqueous sample from the loop... 

Schneider R. W. S., Lanzen J. and Moore P. A. (1998a) Boundary-layer effect on chemical signal movement near the antennae of the sphinx moth, Manduca sexta temporal filters for olfaction. J. Comp. Physiol. A 182, 287-298. 

Advances in fabrication technology have made possible the production of very precisely aligned and spaced hollow fibers. Flow across such fiber arrays can thus be regulated to minimize boundary layer effects or blind spots very high mass transfer efficiencies have been achieved in this manner. 

Accuracy is improved if the flowing gas stream is directed at the probe by a venturi nozzle, or by placing the sensor in the throat of the venturi (Figure 3.74). The venturi ensures a smooth velocity profile and eliminates boundary layer effects while concentrating the flow onto the sensor. These units are available for both liquid and gas services. Other designs are of the insertion probe type. Their flow ranges are a function only of the size of the pipe into which they are inserted, and their performance is a function of the correctness of the insertion depth (as are all Pitot tubes). 

Figure 8-24. Relation between stomatal C02 conductance ( co2 anc net COz uptake for various categories of C3 and C4 plants under optimal conditions and a jV of 360 [xmol C02 mol-1. Ignoring boundary layer effects as a first approximation, note that each line can be represented by Jco2= co2 co2 so tlie slope equals the drop in 0O2 mole fraction across the stomata, which differs for the two photosynthetic types.

Equations (55)—(58) have been used by Brabbs et al. [92] to assist in the selection of four mixtures suitable for examination in order to determine the four primary rate coefficients. For the mixtures selected, Table 23 shows the sensitivities of the growth constants to each of the five reaction rates, calculated from the modified eqn. (53). Table 24 gives a selection of the final results. The rate coefficients themselves were obtained by means of an iterative procedure based on eqn. (53), and using initial independent estimates of 1, 3, 4 and 2 3 in order to derive the first value of 2. Boundary layer effects in the shock tube were allowed for in the initial determination of the growth constants. The apparent 2 determined without these corrections were some 20—60 % larger than the values given in Table 24, with an apparent activation energy of only 11.9 instead of 16.3 kcal. mole . ... 

Values of k2 from a variety of sources have already been presented in Sect. 3.6 and 5.2, and in Tables 15, 24, 28 and 29. Some additional data from low pressure flame studies is given in Table 37. There is also a considerable body of data from shock tube investigations, reported by Baulch et al. [55], for which it is not clear that corrections were applied for boundary layer effects in the shock tube (see Sect. 5.1). This data has been omitted from consideration here — although much of it is in reasonable accord with the expression recommended below for... 

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