Refractance Window Dryer (RWD)

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Refractance Window Dryer (RWD) system operates at low temperatures and at atmospheric pressure and keeps flavor locked within the product being dried. It’s an energy-efficient heat transfer technology as hot water is circulated back in the system for reheating, combined with the simplicity of operation and maintenance which makes it ideal for removing moisture from small batches. Hot forced circulating water at 95℃ to 120℃ beneath the liquid product is the driving force for gentle, yet extremely rapid and efficient infrared heat transfer, assisted by conducted heat. Mechanically boosted airflow carries away evaporated product moisture. all three modes of heat transfer that is, conduction, convection, and radiation occur in the heating of water. The loss of heat energy from heated water to the surroundings occurs by either evaporation or conduction with radiation and convection being internal processes. If a transparent layer of material is placed on the surface of the water then the energy loss can only take place by means of conduction. However, when a moist raw material is placed on the plastic membrane's surface, the water in the material creates a "window" that allows for the passage of infrared energy through the material. Heat behaves as if there were no membrane present, and is directly transferred to the moisture remaining in the material. At this point, all three methods of heat transfer are able to occur and this induces a very rapid heat transfer into the product and rapid evaporation of moisture. This “window” is slowly closed as the product loses moisture, the heat transfer decreases, and the "window" of infrared energy closes and "refracts" back into the heated water source, no longer exposing the material to heat. Thus, the process has an inbuilt regulator, which assists in the entrapment of flavor and the high-quality standards being maintained.