Control method and device for dropwise condensation heat-transferring property of super-hydrophobic surface

Abstract

The invention discloses a control method and device for a condensation heat-transferring property of a super-hydrophobic surface. The control method is characterized by comprising the following steps: modifying the surface of a condensation heat exchanger into a super-hydrophobic surface with a micro structure; utilizing a device which comprises a computer, a control module and a realizing moduleto firstly realize dropwise condensation; and applying mechanical bandwidth micro-vibration to the main body of the condensation heat exchanger so as to compel a condensate water drop in a certain size or within a certain size scope to quickly drop from the surface of the condensation heat exchanger, thereby achieving the purpose of controlling the dropwise condensation heat-transferring property. The control method has the beneficial effects that the condensation heat transfer can be strengthened while the strength of heat exchange property is controlled. By applying micro-vibration to a heat exchange surface, the wetting state of the condensate water drop is changed and the condensate water drop can easily drop from the heat exchange surface; and simultaneously, the applied mechanical vibration is wide-frequency vibration which acts on condensate water drops in different sizes. The control on the dropwise condensation heat-transferring strength is realized by controlling a dropping diameter in a dropwise condensation process.

Description

technical field [0001] The invention relates to a method and device for controlling the heat transfer performance of droplet condensation on a super-hydrophobic surface, and belongs to the technical field of heat transfer enhancement and control. Background technique [0002] Since the discovery of droplet condensation by Schmidt et al. in the 1930s, droplet condensation heat transfer has attracted the attention of the industry for its high-efficiency heat transfer performance. In order to obtain a good drop-like condensation heat exchange surface, many methods have been adopted, such as plating gold, silver, rhodium, palladium, molybdenum and other precious metals on the heat exchange surface. Due to the high price of these metals, this method is difficult to use in the industry. promote. Adding organic accelerators to steam, such as fluorinated carbon disulfide, can also achieve bead condensation. This method can only be used in special cases because it pollutes the steam...

AI Technical Summary

Problems solved by technology

In order to obtain a good drop-like condensation heat exchange surface, many methods have been adopted, such as plating gold, silver, rhodium, palladium, molybdenum and other precious metals on the heat exchange surface. Due to the high price of these metals, this method is difficult to use in the industry. to promote

Adding organic accelerators to steam, such as fluorinated carbon disulfide, can also achieve bead condensation. This method can only be used in special cases because it pollutes the steam and condensate and will cause fouling and corrosion to the condensation surface. application

After the 1990s, the industry began to try to coat the heat exchange surface with low surface energy materials such as PTFE, PFA and ETFE films to achieve bead condensation, but because these coatings are bound to the surface by physical or chemical adsorption, the binding force is weak. Weak, short service life, generally only hundreds of hours, in the case of harsh operating environment, the application life will be shortened, therefore, it has not been applied in engineering

However, the current research shows that in the case of condensation, because the steam can enter the microstructure of the superhydrophobic surface and form Wenzel (Wenzel) water droplets with strong "stickiness", the droplets on the superhydrophobic surface cannot fall off quickly, In other words, the superhydrophobic surface does not form strong superhydrophobic Cassie state water droplets under condensation conditions, and the superhydrophobic surface fails

Therefore, in the current droplet condensation process realized by superhydrophobic surfaces, the condensed droplets will naturally fall off under the action of gravity after growing to a certain threshold, and the larger the size of the dropped droplets, the greater the thermal resistance, making the condensation transfer The thermal coefficient, especially at low condensing loads, cannot be greatly improved

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