Exit profile

Figure 19.6 Influence of control by oscillation of fuel in inner duct on NOx emissions annular flow arrangement Um = Up = 7.5 m/s Re = 40,000 p = 1.1 4>j = 2.5 (a) effect of phase on amplitude of oscillation (6) exit profiles of NOx for three conditions of control 1 — RMS pressure 4.0 kPa, 2 — 1.0 kPa, dashed line corresponds to the case without control...

The die exit profile shown in Fig. 7 creates an extrudate that is a U-shaped profile with three sides... 

Fig. 7 U-Profile stack die exploded view (top) section view (lower left) and end view (lower right) (1) extruder mounting plate (2) die adapter plate (3) transition plate (4) preland plate (5) die land plate (6) die bolt hole (7) alignment dowel pin hole (8) thermocouple well (9) pressure transducer port (10) heater band (11) breaker plate recess. Detail (lower right) (A) die exit profile and (B) product profile.

Smulevich G, Angeloni L, Marzocchi MP (1980) Raman exitation profiles of actinomycin... 

Figure 13.1a shows two possible thermal profiles for exothermic plug-fiow reactors. If the rate of heat removal is low and/or the heat of reaction is high, then the temperature of the reacting stream will increase along the length of the reactor. If the rate of heat removal is high and/or the heat of reaction is low, then the temperature will fall. Under conditions between the two profiles shown in Fig. 13.1a, a maximum can occur in the temperature at an intermediate point between the reactor inlet and exit. 

Entrance and Exit Effects In the entrance region of a pipe, some distance is required for the flow to adjust from upstream conditions to the fuUy developed flow pattern. This distance depends on the Reynolds number and on the flow conditions upstream. For a uniform velocity profile at the pipe entrance, the computed length in laminar flow required for the centerline velocity to reach 99 percent of its fully developed value is (Dombrowski, Foumeny, Ookawara and Riza, Can. J. Chem. Engr, 71, 472 76 [1993])... 

FIG. 22-81 Permeant -concentration profile in a pervaporation membrane. 1— Upstream side (swollen). 2—Convex curvature due to concentration-dependent permeant diffiisivity. 3—Downstream concentration gradient. 4—Exit surface of membrane, depleted of permeant, thus unswollen. (Couttesy Elseoier )... 

Ethylene oxidation was studied on 8 mm diameter catalyst pellets. The adiabatic temperature rise was limited to 667 K by the oxygen concentration of the feed. With the inlet temperature at 521 K in SS and the feed at po2, o=T238 atm, the discharge temperature was 559 K, and exit Po =1.187 atm. The observed temperature profiles are shown on Figure 7.4.4 at various time intervals. The 61 cm long section was filled with catalyst. 

Profile factor. The ratio between the maximum exit temperature and the average exit temperature. 

Lapple s method is useful when the upstream pressure of a header is known and the downstream pressure has to be calculated. However, it is often required to develop the pressure profile of the flare headers as a function of the distance from the stack. For this reason, it is more convenient to calculate the pressure drop backward, starting from the flare stack exit where the pressure is atmospheric. Figure 20 provides another plot which enables the pressure loss calculation when the downstream pressure is known. 

The calibration air flows through a thin tube. The probe is placed at the exit of the tube. When the tube is long enough and the tube flow is laminar, the reference velocity for calibration can be calculated from the theoretical, fully developed laminar velocity profile. 

Distortion Another problem with extrusions is caused by distortion of the section by the effect of heat and other environmental conditions such as exposure to water or chemical agents that tend to soften the plastic. These distortions are generally reversals of the profile back to the shape that it had exiting in the die. This action indicates that the post die forming operations were done at a lower than desirable temperature which results in a molded-in stress. When the stress is relieved the product distorts. In some instances these stresses cannot be eliminated by process changes so that the product is inherently deficient in performance. 

In a water cooling tower, the temperature profiles depend on whether the air is cooler or hotter than the surface of the water. Near the top, hot water makes contact with the exit air which is at a tower temperature, and sensible heat is therefore transferred both from the water to the interface and from the interface to the air. The air in contact with the water is saturated at the interface temperature and humidity therefore falls from the interface to the air. Evaporation followed by mass transfer of water vapour therefore takes place and latent heat is carried away from the interface in the vapour. The sensible heal removed from the water is then equal to the sum of the latent and sensible heats transferred to the air. Temperature and humidity gradients are then as shown in Figure 13.18 . 

A substantial investment in algebra is needed to evaluate the six constants, but the result is remarkable. The exit concentration from an open system is identical to that from a closed system. Equation (9.20), and is thus independent of Dt and Dou The physical basis for this result depends on the concentration profile, a(z), for z<0. When Z) = 0, the concentration is constant at a value if until z = 0+, when it suddenly plunges to u(0+). When D >0, the concentration begins at when z = —oo and gradually declines until it reaches exactly the same concentration, u(0+), at exactly the same location, z = 0+. For z>0, the open and closed systems have the same concentration profile and the same reactor performance. 

The main design criteria of most TPE dies are to ensure that changes in flow channel diameter from the extruder barrel bore to the die exit are equal. Most of the viscoelastic materials exhibit a die swell on exit from a die. TPEs tend to show die swell significantly lower than that of typical thermoplastics. This swell must be taken into consideration in designing dies and adjusting extrusion condition to achieve a perfect profile. The die swell normally increases with increasing hardness and shear rate and decreasing temperature. 

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