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How does the structural type of chemical wastewater evaporator affect heat transfer in the evaporator?


发布时间:

2019-05-06

There are many structural types of chemical wastewater evaporators. Regardless of which type, it is important to ensure that the refrigerant vapor can quickly leave the heat transfer surface and maintain a reasonable liquid level height during design and production, effectively making full use of the heat transfer surface. The small amount of vapor generated during refrigerant liquid throttling can be separated from the liquid through vapor-liquid separation equipment. Only the separated liquid is sent into the evaporator to absorb heat and improve the heat transfer efficiency of the evaporator. If a liquid can vaporize and boil on a wet heating surface, the root of the bubble is small, and the volume of the formed bubble is not large. The bubble is easy to leave the heating surface and rise. If the liquid cannot vaporize on a wetted heating surface

How does the structural type of chemical wastewater evaporator affect heat transfer in the evaporator?

There are many structural types of chemical wastewater evaporators. Regardless of which type, it is important to ensure that the refrigerant vapor can quickly leave the heat transfer surface and maintain a reasonable liquid level height during design and production, effectively making full use of the heat transfer surface. The small amount of vapor generated during refrigerant liquid throttling can be separated from the liquid through vapor-liquid separation equipment. Only the separated liquid is sent into the evaporator to absorb heat and improve the heat transfer efficiency of the evaporator.
If a liquid can vaporize and boil on a wet heating surface, the root of the bubble is small, and the volume of the formed bubble is not large. The bubble is easy to leave the heating surface and rise. If the liquid cannot vaporize and boil on a wet heating surface, the volume of the formed bubbles will be larger, and the root will also be larger, resulting in a decrease in the number of vaporized cores. At this point, the generated bubbles will gather on the heating surface and develop a vapor film along the heating surface, causing an increase in thermal resistance and a decrease in heat release coefficient. Some commonly used refrigerant liquids have good wetting properties, therefore they have good heat release performance. Ammonia has better wetting performance than Freon.
In the evaporator, when lubricating oil is mixed with the refrigerant liquid on the refrigerant side, the oil will dry up at low temperatures and easily adhere to the heat transfer surface, forming an oil film that is difficult to discharge, thereby increasing the heat transfer resistance; At the same time, the formation of an oil film can also hinder the wetting of the heat transfer surface by the refrigerant liquid, reduce the heat transfer efficiency, and in severe cases, make the refrigerant completely unable to absorb external heat and lose its cooling effect.
Water, salt water, and air are common cooling media in refrigeration devices, and their heat release intensity is not only related to their physical properties, but also to external factors such as flow velocity, shape of flow velocity, and flow path. When the flow velocity is high, the geometric shape of the flow velocity and the flow path are reasonable, the heat release coefficient increases, but the corresponding power consumption and basic facility costs also increase. The most suitable flow rate and layout of fluid channels should be determined through technical and economic analysis and comparison.

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