Baffle impingement

Dimensions of baffle impingement plate Figure 5-22. Dimensions of Baffle Impingement Plate. 

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. 

Impingement baffles are generally made of rectangular plate, although circular plates are more desirable. Rods and other devices are sometimes used to protect the tubes from impingement. In order to maintain a maximum tube count the impingement plate is often placed in a conical nozzle opening or in a dome cap above the shell. 

Impingement baffles or flow-distribution devices are recom-men oed for axial tube-side nozzles when entrance velocity is high. 

Erosion-corrosion problems on the outside of tubes are frequently associated with impingement of wet, high-velocity gases such as steam. This typically involves peripheral tubes at the shell inlet nozzle (Fig. 11.9). Baffle and tube interfaces may also be affected. 

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). 

No baffles or impinge- Radially injected spray or increased flow... 

Impingement baffles are placed opposite the shell-side inlet no//lc. The flow into the shell hits the impingement baffle and is dispersed around the tubes, rather than impinging directly on the top tubes. I his keeps the full force of the momentum of the flow from impinging on and eroding the top tubes. 

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 ... 

Goses with entroined liquid droplets tlow between the zig-zog bottles. The gos con eosily moke the turns while the liquid droplets impinge upon the wolls ot the baffles ond coolesce to o size such thot they drop downword, being too heovy to be corried in the gos. 

There are many baffle type impingement separators. The efficiency of operation for entrainment is entirely a function of the contacting action inside the particular unit. There are no general performance equations which will predict performance for this type of unit therefore manufacturers performance data and recommendations should be used. A few of the many available units are shown in Figures 4-28 to 4-31. Many use the Chevron-style verdcal plates as shown in Figures 4-17A and 4-30. 

The efficiency of this type of unit varies, and is a function of the effectiveness of the impingement baffling arrangement. About 70% of separator applications can use the line-type unit the other 30% require the vessel construction. The preference of the designer and problems of the plant operator are important in the final selection of a unit to fit a separation application. 

Besides preventing a destruction of the tubes, impingement plates serve to spread out and distribute the incoming fluid into the tube bundle. If they are used in proper relation to the bundle cross-flow baffles, the fluid can be effectively spread across the bundle near the inlet end. If this is not accomplished, part of the tube area will be stagnant, and its heat transfer will be less than the other parts of the... 

Figure 10-21C. Impingement baffle located in inlet nozzle neck.

Figure 10-21 A. Impingement baffles and fluid-flow patterns. (Used by permission Brown Root, Inc.)...

When scale drawings are made, the effectiveness of impingement baffles can be evaluated easily. Sometimes it is necessary to relocate or make slight size changes in order to properly protect the tubes and direct the vapor flow. 

The basic purpose of an oil separator is to clean the pressurized air of any oil contamination, which is highly detrimental to pneumatically controlled instrumentation. A separator consists of an inlet, a series of internal baffle plates, a wire mesh screen, a sump, and an outlet. The pressurized air enters the separator and immediately passes through the baffle plates. As the air impinges on the baffle plates it is forced into making sharp directional changes as it passes through each baffle section. As a result, the oil droplets separate from the air and collect on the baffles before dropping into the separator s sump. 

Goses with entroined liquid droplets flow between the zig-zag baffles. The gos can easily make the turns while the liquid droplets impinge upon the walls of the baffles and coalesce to a size such that they drop downward, being too heavy to be carried in the gas. 

Impingement separators employ baffles to achieve the separation. The gas stream flows easily round the baffles, whereas the solid particles, due to their higher momentum, tend to continue in their line of flight, strike the baffles and are collected. A variety of baffle... 

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