Evaporators

Evaporators convert materials from a liquid to a gaseous state. They consist of a heat exchanger or bath, valves, manifolds and temperature controls. Many types of evaporators are available. Atmospheric evaporators spray heated wastewater onto a contact medium with a high-surface area. A high-volume air stream then passes through the medium and removes moisture. In falling film evaporators, liquid enters at the top, flows downward inside steam-heated tubes, and exists from the bottom. Steam-heated tubes are also used in rising film, fluidized bed, and forced circulation or crystallizer evaporators. Plate evaporators are similar to plate heat exchangers, but are equipped with large passages for vapor flow. Rotary evaporators or rotavaps are designed to remove solvents from reaction mixtures. They often include a heatable water bath to keep the solvent from freezing during the evaporation process. Both scraped surface and wiped film evaporators are designed to handle highly viscous and sticky products. Thermal evaporators boil fluids at atmospheric pressure. Vacuum distillation devices lower the boiling temperature in order to eliminate chemical degradation that typically occurs at 212° F.  Short path evaporators include an internal condenser eliminate pressure losses caused by piping. Drum evaporators encapsulate 55 gallon drums and apply heat to the outside to evaporate the contents.

Evaporators vary in terms evaporation rate, system capacity, and feed tank capacity. Laboratory-scale devices are designed to handle small batches of material. By contrast, production-scale devices are recommended for commercial operations. Often, pilot scale devices are suitable for intermediate-range operations. Power sources for evaporators include electricity, fuel oil, hot oil, hot water, natural gas, liquid propane, and steam. Some devices are equipped with an integral display and interface for programming and control. Others feature a horizontal design or a 55-gallon drum with an external heating source. In evaporators with mechanical vapor recompression (MVR), the heating medium is vapor compressed to a higher temperature by means of a high-pressure fan. In multiple-effect evaporators with thermal vapor recompression (TVR), the heating medium in the first calandria is the product vapor from one of the associated effects, compressed to a higher temperature by means of a steam ejector. The condensate can be used as boiler feedwater or to preheat air from an associated spray dryer.

Evaporators are used in a variety of applications and industries. For example, some devices are used in alcohol processing, chemical processing, or distillation and food processing facilities. Others are rated for cryogenic use or designed for desalinization or seawater treatment. In the petroleum industry, evaporators are used for gas recovery, liquid recycling, and offshore production. In the plastics industry, evaporators process elastomers, epoxy resins, isocyanates, polyesters, polyethers, polymers, and stabilizers. Pharmaceutical companies use evaporators to handle acid chlorides, amino-acid esters, antibiotics, glucose derivatives, hormones, extracts, and vitamins. Other applications for evaporators include coating and etching, pulp and paper processing, research and development, semiconductor manufacturing, solvent recovery, volatile organic compound (VOC) recovery, and wastewater treatment.

• Rotary Evaporators
  Rotary evaporators (also called "rotavaps") are used to remove solvents from reaction mixtures and can accommodate volumes as large as three liters. They are found in almost every organic laboratory....
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• Flow Induced Noise Emanating from Evaporator Tube Plates (.pdf)
  This work examines, objectively and subjectively, refrigerant noise induced by the flow of R134a through seven different plate-type automotive evaporator tubes with two tube heights and airflow depths...
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• ABCs of Refrigeration Pressure Sensing
  Sealing techniques figure heavily into what technology makes sense in different portions of the refrigeration cycle. Supermarket refrigeration systems, rooftop chillers, walk-in fast-food-restaurant...
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Part Numbers for Evaporators