<P> Vacuum dryer is the equipment with the help of which vacuum drying is carried out . In the pharmaceutical industry vacuum dryer is known by a common name called vacuum oven . Vacuum dryers are made up of cast iron so that they can bear the high vacuum pressure without any kind of deformation . The oven is divided into hollow trays which increases the surface area for heat conduction . The oven door is locked air tight and is connected to vacuum pump to reduce the pressure . </P> <P> The materials to be dried are kept on the trays inside the vacuum dryer and pressure is reduced by means of vacuum pump . The dryer door is tightly shut and steam is passed through the space between trays and jacket so that the heat transfer occurs by conduction . Water vapors from the feed is sent into the condenser and after drying vacuum pump is disconnected and the dried product is collected from the trays . </P> <P> Vacuum dryer can be used to dry heat sensitive hygroscopic and toxic materials . If the feed for drying is a solution, it can be dried using vacuum dryer as the solvent can be recovered by condensation . To improve quality of products, such as for fruit preservation, hybrid drying combining osmotic dehydration followed by heat pump drying and microwave - vacuum drying proved effective . </P>

Difference between tray dryer and vacuum tray dryer