Since water boils more readily in a vacuum, a key aspect in optimising the efficiency of the dehydration process is to increase the exposure of the water to the vacuum by maximizing diffuser surface area for a reasonable amount of time while maintaining the highest flow rate. The water boils off into vapor and is then pulled out of the vacuum chamber and through a condenser, returning the water vapor to a liquid state. The condenser can be located either inside or outside vacuum chamber. The water is then pulled out of the system by a vacuum pump. Apparently, in order to optimize the efficiency and capacity of vacuum dehydration, it is important to maximize the heat and mass transfer inside the vacuum chamber.
Temperature is the driving force for heat and mass transfer.
Therefore, the following parameters, such as vacuum pressure, operating temperature, surface area of diffuser, and flow rate, need to be considered. The higher the vacuum, the lower the boiling temperature and the more water that can be vaporised. Maximum vacuum is preferred for vacuum dehydration. Water vapor increases pressure in the chamber and further slows the mass transfer of water from a liquid state to a vapor state. The condenser can be located either inside or outside of vacuum chamber.