Entrance configurations

Several general implications of CE/MS hyphenation have to be taken into consideration. As discussed, both electrical circuits of CE and ESI have to be maintained. This goal is best accomplished if the CE capillary exit is kept at ground potential, as normally done in CE. This is nontrivial and places severe demands on the MS entrance configuration. These aspects are discussed in more detail in Ref. 14. 

TABLE 5-3 Effect of Entrance Configuration on Values of C and n in Eq. (5-53) for Pr = 1 (Gases and Other Fluids with Pr about 1)... 

It is worth noting that the duct entrance configuration affects simultaneously developing flow [98,99]. The local Nusselt number is different for each duct entrance configuration. For practice usage, Bhatti and Shah [45] suggest the following formula for the calculation of the mean Nusselt number. 

TABLE 5.13 Nusselt Number Ratios for a Smooth Circular Duct with Various Entrance Configurations for Pr = 0.7 [2]... 

Transition Flow. The lower limit of the critical Reynolds number Recrit for a parallel plate duct is reported to be between 2200 and 3400, depending on the entrance configurations and disturbance sources [143]. The following friction factor formula developed by Hrycak and Andrushkiw [144] is recommended for transition flow in the range of 2200 < Re < 4000 ... 

Entrance configurations Schematics Aspect ratio a Critical Reynolds number Recrit... 

FIGURE 7.84 Influence of hood configuration on hood entrance wake size, 8. 

To optimize the design of the manifold configuration, a number of numerical calculations were conducted for three types of manifolds shown in Fig. 2.66. Figure 2.67 shows the velocity distribution at 2 mm from the inlet to the microchannels, from which one can conclude that configuration 1 and 2 ensure uniform velocity distribution at the entrance. 

The proportionality factor k depends on several parameters, in particular on the optical configuration for observation (i.e. the solid angle through which the instrument collects fluorescence, which is in fact emitted in all directions) and on the bandwidth of the monochromators (i.e. the entrance and exit widths see Chapter 5). 

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