The requirement for larger exchange areas in conjunction with a compact construction has been met by the development of shell and tube heat exchangers. Whether installed as a single unit or a part of complete installation shell and tube heat exchangers offer significant advantages:-
• Corrosion resistance.
• Outstanding heat transfer.
• Extremely low-pressure drop.
• Space-saving arrangement by installing in the horizontal or vertical position.
• Simple replacement of the inner tubes for repair and cleaning owing to a construction designed to permit easy servicing.
The standard range includes shell and tube exchangers in various sizes with exchange areas ranging from 2.5 to 25 m2. The shell diameters are DN150, 200 and 300. The standard design has a glass shell, glass tubes, PTFE end plates and baffles and either glass or stainless steel end covers. The tube bank is made up of single tubes sealed individually into two tube plates.
These are exchangers of fused glass construction are used for cooling and condensation. These heat exchangers are made entirely of glass i.e. the exchange tubes are fused to the jacket. This result in the following main advantage:
• No seal points between the shell and the coil.
• Outstanding corrosion resistance since borosilicate glass is the only wetted part and therefore
• Optimum conditions for the production of extremely pure products.
Silicon Carbide Shell and Tube Heat are used for High Corrosive and or High purity applications. Silicon Carbide is a material of construction with excellent corrosion and temperature resistance properties. In this application, SiC can operate with the temperature difference of 200 deg C between the shell side and tube side. The exchange area normally ranges from 0.2 M2 to 25 M2. The function of such a heat exchanger is heating, cooling condensation. The Silicon Carbide Shell and Tube Heat exchangers are used when Graphite heat exchangers reach their limit. Silicon Carbide tubes provide excellent corrosion resistance for all high demanding applications. These exchanges have superb heat transfer efficiency thanks to Silicon Carbide are about 70% compact vis-à-vis glass equipment (lesser heat exchange area required for the same heat transfer). The maintenance cost is low due to the easy removal of headers for direct access required for cleaning or inspection on the tube side.
Glass installations are known for their high operational reliability and extremely low maintenance requirements. ATR uses modular construction with Schott Duran 3.3 borosilicate glass for the chemical plant construction as it has got all the flexibility for providing corrosion resistant installations to withstand temperatures as high as 200 deg C. Other corrosion-resistant materials of construction such as glassed steel, tantalum, titanium, PTFE, graphite etc are routinely combined with Schott components to provide an optimum solution for a particular application or process duty.
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