Internal baffles, design

Some exchanger designs require that inlet nozzles he placed close to the tubesheet to obtain the best use of the surface in that immediate area. Fabrication problems limit this dimension. Therefore, internal baffling must be used to force the incoming fluid across the potentially stagnant areas. 

In Effects of Motion on Design of Process Facilities for Floating Systems" Rice provides a theoretical analysis coupled with motion-simulation work in an effort to understand fluid motion inside process equipment on floating vessels. This work has led to the establishment of process-equipment sizing criteria for all types of vessel motion transmitted from the marine vessel. Design of internal baffling and other internals to dampen and control the fluid motion is reviewed. 

Section 3 and the effects on other equipment 1s listed below. design of the Internal baffling... 

Cross-flow devices can be constructed in either horizontal or vertical pressure vessels. Horizontal vessels require less internal baffling since the ends of almost all plates conduct oil directly to the oil/watcr interface and sediments to the sediment area below the water flow area. Vertical units, although requiring collection channels on one end to enable oil to rise to die oil/water interface and on the other end to allow sand to settle to the bottom, can be designed for more efficient sand removal. 

It can he shown mathematically that an efficient dis-persed-gas unit must have a high gas induction rate, a small-diameter-induced gas bubble, and a relatively large mixing zone Design of the induction nozzle or rotor and of internal baffles is critical to unit efficiency. 

Preheater vibration. Air preheaters or any type of waste-heat recovery device designed for horizontal flow across vertical tubes, may be subject to vibration produced by the velocity of gas across the tube banks. The velocity produces a vortex-shedding wave pattern that could correspond to the natural harmonic frequency of the tube bank. If the natural harmonic frequency is reached, excessive vibration of the tubes will occur. Redesign of the internal baffle system by inserting dummy baffles can stop the vibration. 

Ammonia Vaporizer A shell and tube-type heat exchanger with two passes per shell on the tube side. This unit should contain internal baffles. Operating pressure is 1240 kPa, with a design pressure of approximately 1400 kPa. This exchanger is made from mild steel. 

Some mixing chambers have curved bottoms that enhance movement of materials. Others have internal baffles or some similar design to increase turbulence and eliminate dead spots in the chamber. Shafts can enter the chamber from the top (allowing easier cleanup) or from the bottom (allowing easier vacuum degassing). 

The gasification reactor is a vertical, steel pressure vessel with a refractory lining. There are no internal baffles or catalyst beds. Preheated hydrocarbon feedstock and oxidant are fed under precise flow control to the specially designed combustor in the top of the reactor. Steam is pre-mixed with the oxygen to serve as a flame moderator. For liquid feedstocks, the oxidant enters the reactor as a rotating vortex around the hydrocarbon vortex spray in the combustion zone. 

The reactors and regenerators of the first few TCC units were designed for operation with activated-clay catalyst of 30 to 60 mesh. They were provided with internal baffle systems in order to achieve efficient contact between vapors and catalyst (133). However, the granular catalyst was not used commercially because pelleted catalyst of about 4-mm. average... 

Internal baffles are used to improve mixing in fluids that tend to rotate along with the impeller rather than being mixed. Baffles reduce the flow of fluids to speeds much lesser than that of the impeller. This increase in shear provides additional turbulence leading to improved mixing of the fluids. Baffles are typically designed to have a width of 1/12 to 1/10 of the vessel diameter and are located slightly off of the internal vessel wall to prevent accumulation of the material. 

Internal mixing of electrolytes is driven by gas lift. Feed headers run the full width of the electrodes, giving even distribution of electrolyte flows. Internal baffles complete the process by preventing channeling of the gas flow. One intent of these design features is to permit controlled acid injection into the brine in order to limit the oxygen content of the chlorine gas, without the need for extensive recirculation devices. Internal circulation is promoted by the use of a split baffle. 

A conceptual industrial-scale unit, a 20-pass, 500 litre OBR, is shown below. This would be capable of a continuous production rate of 2 te/h if a 15 min mean residence time is assumed. The design is based upon a 100 mm tube diameter fitted with standard orifice baffles (with a hole diameter of 50mm) spaced at 150mm. Each tube is approximately 3.5m long. The reactor is heated by a fluid-filled outer shell, fitted with internal baffling to promote efficient fluid flow. 

Grace JR, Jarrison D. Design of fluidised beds with internal baffles. Chem Proc Eng 6 127-130, 1970. 

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