There are many structural types of evaporators. No matter what, the refrigerant vapor must be designed and manufactured so that the refrigerant vapor can quickly leave the heat transfer surface and maintain a reasonable liquid level, so as to make full use of the heat transfer surface. The small amount of gas produced when the refrigerant liquid is throttled can be separated from the liquid by the gas-liquid separation equipment, and only the liquid with the separated gas is sent to the evaporator to absorb heat, so as to improve the heat transfer effect of the evaporator.
If the liquid can vaporize and boil on the wetted heating surface, the root of the bubble will be small, and the volume of the bubble formed will be small, and the bubble will easily leave the heating surface and rise. If the liquid cannot be vaporized and boiled on the wetted heating surface, the volume of the bubble formed will be larger, the roots will be larger, and the number of vaporized cores will be reduced. The vapor bubbles generated at this time will accumulate on the heating surface and develop a vapor film along the heating surface, resulting in an increase in thermal resistance and a decrease in the heat release coefficient. Some commonly used refrigerant liquids have good wetting properties, so they have good heat release properties. Ammonia has better wetting properties than Freon.
The evaporator is one of the most commonly used wastewater evaporators in the process industry. The evaporator passes the secondary steam vaporized by the previous effect evaporator into the heating chamber of the latter effect evaporator as the heating steam of the latter effect evaporator. Evaporation makes full use of the latent heat of vaporization of the secondary steam of each effect, and is a relatively energy-saving evaporation operation.
The evaporator is used in the liquid syrup concentration process of the corn chemical plant. It is to pass the raw steam into the chemical wastewater evaporator to heat the liquid syrup, and the water in the liquid syrup is heated and evaporated to achieve the purpose of concentration. Many reports on the research and application of multi-effect evaporation have been published at home and abroad. However, there are many researches on conventional simulation and optimization design based on the solution of multi-effect evaporation design problems. There are few researches on process simulation and operation optimization problems.
The structure and characteristics of the evaporator, and the working principle of the chemical wastewater evaporator and its application in chemical enterprises are introduced. The tube falling film evaporator is used in the wastewater concentration process. The wastewater flows in the tube and the steam condenses and releases heat in the shell side. . In the evaporator, when the refrigerant liquid on the refrigerant side is mixed with lubricating oil, the oil is very dry at low temperatures, and it is easy to adhere to the heat transfer surface to form an oil film and is not easy to discharge, thereby increasing the heat transfer resistance; At the same time, the formation of an oil film will prevent the refrigerant liquid from wetting the heat transfer surface and reduce the heat transfer efficiency. In severe cases, the refrigerant will not absorb external heat at all and lose its cooling effect.
Water, brine, and air are common cooling media in refrigeration devices. In addition to their physical properties, their heat release intensity is also related to external factors such as the flow velocity, the shape of the flow velocity, and the flow path. If the flow rate is large, the geometry of the flow rate and the flow path are reasonable, the heat release coefficient will increase, but the corresponding power consumption and basic facility costs will also increase. The most suitable flow velocity and fluid channel layout should be determined through technical and economic analysis and comparison.