What is the evaporation efficiency of a falling film evaporator
Information summary：Let's analyze the evaporation efficiency of the falling film evaporator in detail. The conclusion is that the falling film evaporator has a high evaporation efficiency and is an efficient and energy-saving evaporator. We will explain its efficiency performance and core reasons in detail.
Let's analyze the evaporation efficiency of the falling film evaporator in detail. The conclusion is that the falling film evaporator has a high evaporation efficiency and is an efficient and energy-saving evaporator. We will explain its efficiency performance and core reasons in detail.
1. The core performance of evaporation efficiency
The heat transfer coefficient of a falling film evaporator is very high, generally reaching 2000~6000 W/(m 2 ·℃), much higher than that of a kettle evaporator. Its single effect evaporation intensity is high, and it can achieve rapid evaporation. It can also easily achieve multi effect combination, further improving energy efficiency and output. Under the same heat exchange area, its evaporation capacity is much greater than that of traditional evaporators such as immersion evaporators.
2. The fundamental reason for high efficiency
Unique film-forming flow method
The material liquid is evenly distributed through the top film distributor and flows in a uniform liquid film shape from top to bottom along the inner wall of the heat exchange tube. The liquid film is extremely thin, greatly reducing thermal resistance, and heat can be quickly transferred to the material liquid, resulting in a fast evaporation rate; At the same time, the liquid film flows and updates quickly, making it less likely to form a scale layer and avoiding the obstruction of heat transfer by the scale layer.
Comparison: Immersive evaporator liquid immersion tube bundle has high thermal resistance and is prone to local overheating and scaling, resulting in low efficiency.
Simultaneous enhancement of heat transfer and evaporation
The liquid film is in a turbulent state driven by gravity and secondary steam, which enhances heat transfer inside the tube; The material liquid evaporates while flowing inside the tube, and the secondary steam and liquid film flow downward together, reducing the boiling point of the material liquid and forming a temperature difference driving force, further accelerating evaporation.
Short residence time of the liquid material
The residence time of the liquid in the evaporator is only a few seconds to tens of seconds, which belongs to short-term evaporation. It not only reduces the decomposition of heat sensitive materials, but also ensures efficient circulation and improves the processing capacity per unit time.
3. Key factors affecting its evaporation efficiency
Uniformity of film distribution: The film distributor is the core. If the film distribution is uneven, some pipe walls without liquid film will dry and scale, greatly reducing efficiency.
Material properties: The lower the viscosity and the lower the boiling point rise, the higher the efficiency; Materials with high viscosity need to be preheated to reduce viscosity, otherwise the liquid film is prone to thickening or even breaking.
Operating parameters: The higher the heating steam pressure (temperature), the better the vacuum degree (low boiling point of the feed liquid), the greater the heat transfer temperature difference, and the higher the efficiency; The feeding amount needs to match the heat exchange area, too much is prone to liquid accumulation, and too little is prone to wall drying.
Cleanliness of heat exchange tubes: Scaling on the tube wall can significantly increase thermal resistance, and regular cleaning is necessary to maintain efficiency.
4. Applicable scenarios and limitations of efficiency advantages
Advantage adaptation: Suitable for handling liquids with large processing capacity, moderate viscosity, heat sensitivity (such as food and pharmaceutical liquids), and less prone to scaling. Multi effect or MVR combination results in more prominent energy saving and further improved evaporation efficiency.
Limitations: For high viscosity, crystallization prone, and scaling prone liquid materials, if pre-treatment is not in place, efficiency will decrease; High requirements for feed stability, not suitable for intermittent small batch production.
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