Different liquids have different saturated vapor pressures. At a temperature of 70°C, water starts to boil at a pressure of about 30kPa, while oil can only boil at a low pressure of 5Pa. At the same temperature, the saturated vapor pressure of oil is much lower than that of water. Therefore, when the pressure of the oil liquid surface is reduced below the saturated vapor pressure of water by vacuuming, the water in the oil liquid will violently vaporize and overflow from the oil in the form of steam. Through the suction of the vacuum, the oil enters the vacuum tank from the top and sprays down through the nozzle.