The inlet nozzle

Process engineering and design using Visual Basic 

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Impingement Baffle The tube bundle is customarily protected against impingement by the incoming fluid at the shell inlet nozzle wmen the shell-side fluid is at a high velocity, is condensing, or is a two-phase fluid. Minimum entrance area about the nozzle is generally equal to the inlet nozzle area. Exit nozzles also require adequate area between the tubes and the nozzles. A full bundle without any provision for shell inlet nozzle area can increase the velocity of the inlet fluid by as much as 300 percent with a consequent loss in pressure. 

Deterioration of tubes near the inlet nozzle of condenser shells due to impingement of water and steam mixtures can be alleviated through the use of appropriately placed and sized baffles or impact plates or by applying clip-on impingement shields to the tubes (see Case History 11.3). 

An example will help illustrate one use of velocity head. A compressor is being considered for reuse in another application, and the question was raised as to the size of the inlet nozzle. The original conditions are stated as follows ... 

This is a low value, therefore, the possibility exists of an up-rate relative to any nozzle flow limits. At this point, a comment or two is in order. There is a rule of thumb that sets inlet nozzle velocity limit at approximately 100 fps. But because the gases used in the examples have relatively high acoustic velocities, they will help illustrate how this limit may be extended. Regardless of the method being used to extend the velocity, a value of 150 fps should be considered maximum. When the sonic velocity of a gas is relatively low, the method used in this example may dictate a velocity for the inlet nozzle of less than 100 fps. The pressure drop due to velocity head loss of the original design is calculated as follows ... 

The up-rate looks feasible considering that none of the inlet nozzle guidelines have been exceeded, the Mach number is still a low value, and the pressure drop is not significant. If the pressure drop had been significant, the effect of the drop could have been evaluated with respect to the compressor head and possibly a usable compromise worked out. 

Figure 11-1. This steam turbine-driven centrifugal compressor, shown just prior to shipping, has all nozzles in the upper half of the casing. Note the non-vertical orientation of the inlet nozzle. Courtesy of A-C Compressor Corporatior ...

Other types of pressure-relief valves do not depend upon the back pressure for their performances. However, to ensure that the safety valves work at their maximum capacity, back pressure is limited to 50 percent of the relief valve set pressure. In the balanced bellows type valve, the spring does not act directly on the disk. Instead, it serves on a bellows first, which in turn acts on the disk. In case of the piston type, it works on the same principle as the bellows type, except that the bellows is replaced by a piston (see Figure 17B). The cross-sectional area of both the piston and the bellows is the same as the inlet nozzle of the valve and the effect of the back pressure on the top and the bottom of the disk creates equal balancing forces. That is, P,A is always equal to F, as shown in Figure 17B. 

Nozzles should be sized according to pipe sizing criteria, such as those provided in API RP 14E. The outlet nozzle is generally the same size as the inlet nozzle. To prevent baffle destruction due to impingement, the entering fluid velocity is to be limited as ... 

If an interior centrifugal (cyclone) separator is used, the inlet nozzle size should be the same size as the pipe. If the internal design requires... 

The hub disc forms the back portion of the impeller. The hub disc has the proper design to form one-half of the inlet nozzle of the impeller and carries the blade and cover disc on the shaft. 

With no other available escape route, the fluid is passed to the outside of the impeller by centrifugal force and into the volute where its kinetic energy is converted into pressure. At the point of discharge (i.e., discharge nozzle), the fluid is highly pressurized compared to its pressure at the inlet nozzle of the pump. This pressure drives the... 

The instrument in my laboratory uses laser desorption ionization with a Nd YAG laser and a TOF-MS. The particles are drawn into the instrument on a continuous basis and undergo a supersonic expansion when they pass through the inlet nozzle. During the expansion, the particles pick up different speeds that are a function of their size. They then pass through two scattering lasers. The time it takes the particle to travel between the two lasers can be correlated with particle size, allowing the particle size to be determined precisely. Knowing the particle speed and position, it is possible to time its arrival at the center of the spectrometer with a Nd YAG laser pulse (266 nm). The pulse is able to desorb ionized species from the particle, which can then be analyzed by the spectrometer. 

Fig. 1. Detail of reaction zone of the metal-atom reactor. Suitable reactor dimensions are 15-18 cm diameter, 5 mm wall thickness and 36-46 cm depth. The water-cooled electrodes are 7.5 cm apart. The central substrate inlet tube, a 6 mm od Pyrex slightly constricted at the end, extends 5 cm below the liquid nitrogen level. A 14 mm od Pyrex tube which serves as a substrate deflector is positioned 5 cm below the inlet nozzle and is suspended horizontally between the electrodes. A built-in Pyrex syphon tube extends to the bottom of the reactor for the removal of air sensitive products under an inert atmosphere.

The impaction efficiency (17) for particles depends directly on the particle diameter (D), the flow velocity of the air (V), and the particle density (p) it varies inversely with the gas viscosity (p,) and with a parameter (Db) that is representative of the impactor s physical dimensions (e.g., the inlet nozzle diameter) and that is related to the curvature of the airstream. 

The flow of vapor and entrained droplets in the piping upstream of a drum separator can be treated as homogeneous with no inierfacial slippage. At the inlet nozzle, the droplets have a "momentum of p r with being the velocity of the vapor and entrained droplets. 

This rat is called a 20-lb rat. Not that the rat weighed 20 lb. The 20 lb refers to the pressure drop of 20 psig that the liquid encountered as it flowed across the rat s now-lifeless body. Before the introduction of this pressure restriction, the butane entering the reflux drum was at its bubble point. Our question is, will the introduction of the rat, at the inlet nozzle, cause the butane, as it enters the vessel, to flash ... 

Shell-side flow. The hot shell-side flow enters the exchanger, as shown in Fig. 19.1, through the top inlet nozzle. Not shown on this sketch is the impingement plate, which is simply a square piece of metal, somewhat larger than the inlet nozzle. Its function is to protect the tubes from the erosive velocity of the shell-side feed. The plate lies across the upper row of tubes. 

Vertical height between the inlet nozzle and the vapor outlet... 

The jet effect of an inlet nozzle also may interfere with the phase separation. Ideally the liquid should be introduced uniformly over the cross section, but a baffle at the inlet nozzle may reduce such a disturbance adequately. More elaborate feed diffusers sometimes may be worthwhile. Figure 18.1 shows a perforated baffle. 

Figure 18.2. A design of an oil-water separator for the conditions of Example 18.1, showing particularly the diffuser at the inlet nozzle and baffles at the outlets. (Hooper and Jacobs, 1979).

An analysis of the temperature distribution in a mold (Fig. 4.54) at the final moment of filling for two reactive systems with different values of G shows that the temperature along the central line increases monotonically downstream (at distance x) from the inlet nozzle. At high values of the gelation criterion, the temperature at locations close to the injection nozzle is maximum near the mold wall. Moving down stream, the position of the temperature maximum shifts to the center, except at the frontal zone. Here the temperature is nearly constant, because the major part of the... 

The way the inlet nozzle enters the vessel it is protecting can also have a serious impact on inlet pressure losses. Of course, the ones which give the biggest pressure drops are also the most economic vessel penetrations. 

The pipe run is to terminate with 145 psig pressure at the fractionator inlet nozzle. Here the inlet nozzle is 45 ft above the pump discharge nozzle. 

Schmidt et al. [111] developed an atmospheric pressure laser ionization (APLI) source based on REMPI in pulsed gas expansions close to the inlet nozzle orifice (at high... 

Calculate the pressure drop for the conditions of Example 7.20. Assume that the nozzle velocities are 5 ft/s (1.52 m/s), that the fluid density is 55 lb/ft3 (881 kg/m3), and that there are 24 baffles. Assume that there is also an impingement plate at the inlet nozzle. Calculate the pressure drop for both fouled and clean conditions. 

Also, to prevent flooding the inlet nozzle, Scheiman allows a minimum of 6 in (0.152 m) from the bottom of the nozzle to the liquid surface or a minimum of 12 in (0.305 m) from the center line of the nozzle to the hquid surface. Branan [49] recommends using 12 in (0.305 m) plus 14 of the inlet nozzle outside diameter or 18 in (0.4570 m) minimiun. Gerunda specifies a length equal to 0.5 D or 2 ft (0.610 m) minimum, which is used in Figure 6.4. 

To completely design the vessel, the minimum and maximum velocity in the inlet nozzle is obtained by using the empirical criteria ... 

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