Baffles, effect

Stau-wand, /. baffle plate, -wirkung, /. damming effect, baffle effect. 

The number of thermocouples positioned within the container will be dependent on the container volume. A sufficient number of thermocouples should be positioned in areas representing the upper, middle, and lower portions of the container. Error in cold spot determinations may be introduced by employing an excessive number of thermocouples within the container. The error may be attributed to thermocouple mass and the resulting baffling effects may influence the normal convection currents of the liquid. 

Jiang, Peijun, Bi, Hsiaotao, Jean, Rong Her, and Fan, Liang Shih. Baffle effects on performance of catalytic circulating fluidized bed reactor, AIChE J., vol. 37, No. 9, pp. 1392-1400(1991). 

Liu et al. (2005) found that the reactant transport and cell performance can be enhanced by the presence of the baffles in the flow channel of the bipolar plate, especially at the operating conditions of low voltage. The beneficial baffle effects become increasingly remarkable with increasing width and/or number of baffles in the tandem array. 

Fypass Flow Effects. There are several bypass flows, particularly on the sheUside of a heat exchanger, and these include a bypass flow between the tube bundle and the shell, bypass flow between the baffle plate and the shell, and bypass flow between the shell and the bundle outer shroud. Some high temperature nuclear heat exchangers have shrouds inside the shell to protect the shell from thermal transient effects. The effect of bypass flow is the degradation of the exchanger thermal performance. Therefore additional heat-transfer surface area must be provided to compensate for this performance degradation. 

This implies that the LMTD or M I D as computed in equations 20 through 26 may not be a representative temperature difference between the two heat-transferring fluids for aU tubes. The effective LMTD or M ID would be smaller than the value calculated, and consequentiy would require additional heat-transfer area. The tme value of the effective M I D may be determined by two- or three-dimensional thermal—hydrauUc analysis of the tube bundle. Baffle—Tube Support PlateXirea. The portion of a heat-transfer tube that passes through the flow baffle—tube support plates is usuaUy considered inactive from a heat-transfer standpoint. However, this inactive area must be included in the determination of the total length of the heat-transfer tube. 

AM(from equation 46) + AM(bypass flow) + AM(entrance/exit effects) + AM (baffle plates)... 

A numerical study of the effect of area ratio on the flow distribution in parallel flow manifolds used in a Hquid cooling module for electronic packaging demonstrate the useflilness of such a computational fluid dynamic code. The manifolds have rectangular headers and channels divided with thin baffles, as shown in Figure 12. Because the flow is laminar in small heat exchangers designed for electronic packaging or biochemical process, the inlet Reynolds numbers of 5, 50, and 250 were used for three different area ratio cases, ie, AR = 4, 8, and 16. 

The numbei of wall baffles and tfiek widtfi B also have a significant effect on As increases, increases (Fig. 6a) up to the of the... 

Fig. 6. (a) Effect of baffling and D/T on power number relative to for standard configuration and (b) effect of dual impeller spacing on power... 

Commonly used heat-transfer surfaces are internal coils and external jackets. Coils are particularly suitable for low viscosity Hquids in combination with turbine impellers, but are unsuitable with process Hquids that foul. Jackets are more effective when using close-clearance impellers for high viscosity fluids. For jacketed vessels, wall baffles should be used with turbines if the fluid viscosity is less than 5 Pa-s (50 P). For vessels equipped with cods, wall baffles should be used if the clear space between turns is at least twice the outside diameter of the cod tubing and the fluid viscosity is less than 1 Pa-s (10... 

Fig. 11. Computer-simulated recirculating patterns in a mixing tank with full baffles (a) elevation view shows circulation patterns generated by turbine blades (b) plane view shows the effect of the baffle on the radial velocity vectors above the turbine blades.

The feed gas is iatioduced neai the lotoi axis. Enriched and depleted gases are extracted by stationary pitot-like scoops. The location and shape of these tubes, and the baffles within the rotor, gready effect the gas dow which recirculates within the rotor, reaching enrichment equiUbtium at a given feed rate. A vacuum is maintained around most of the rotor. The UF leakage around the stationary axial post is confined to the top of the case by the use of a molecular pump. 

Turbulence. Turbulence is important to achieve efficient mixing of the waste, oxygen, and heat. Effective turbulence is achieved by Hquid atomization (in Hquid injection incinerators), soHds agitation, gas velocity, physical configuration of the reactor interior (baffles, mixing chambers), and cyclonic flow (by design and location of waste and fuel burners). 

It is assumed that process conditions and physical properties are known and the following are known or specified tube outside diameter D, tube geometrical arrangement (unit cell), shell inside diameter D shell outer tube limit baffle cut 4, baffle spacing and number of sealing strips N,. The effective tube length between tube sheets L may be either specified or calculated after the heat-transfer coefficient has been determined. If additional specific information (e.g., tube-baffle clearance) is available, the exact values (instead of estimates) of certain parameters may be used in the calculation with some improvement in accuracy. To complete the rating, it is necessary to know also the tube material and wall thickness or inside diameter. 

Find the correction facdor for baffle-confignration effects from Fig. 11-10. 

Find the correction factor for baffle-leakage effects J[ from Fig. 11-11. 

Find the correction factor for the effect of baffle leakage on pressure drop Ri from Fig. 11-16. Cni ves shown are not to be extrapolated beyond the points shown. 

FIG. 11-16 Cor rection factor for baffle-leakage effect on pressure drop. 

A solid longitudinal baffle is provided to form a two-pass shell (Fig. 11-35F). It may be insulated to improve thermal efficiency. (See further discussion on baffles). A two-pass shell can improve thermal effectiveness at a cost lower than for two shells in series. 

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