Water Surface Tension: Investigating Condensation Formation

In summary: So it's not just the solid's energy, but the difference in energy between the two interfaces that determines how wetting will occur.In summary, the conversation discusses a project demonstrating the venturi effect and the observation of water droplets forming in the corners of the housing. The question of how surface energy and roughness of the housing material play a role in this is raised, with the possibility that a lower surface energy material may make it harder for droplets to cling to the surface. However, there is confusion about the relationship between surface energy and wetting, as a lower surface energy material may actually allow water to wet the surface more easily. Further discussion is needed to determine the best solution for managing fluid in the housing.
  • #1
vettett15
13
0
Hey guys,

I'm working on a project which demonstrates the venturi effect, by flowing gas through a nozzle (which is housed in a 2 piece housing) and it flows out the exit, the air is picking up water along the way. We have noticed that water droplets are forming in the corners of the housing and not flowing back to the bottom to be picked back up by the venturi nozzle, we believe this is condensation forming there.

A question came up on how the surface energy of the housing material (plastic) plays a role in this along with surface roughness. At first I thought a material with a higher surface energy would allow the water to wet the surface better thus allowing it to drain back down. But after thinking about it for awhile I'm wondering if the opposite is true, a lower surface energy material would make for a more sphere like droplet which would make it harder for the droplet to hang on into the corner. I started to change my thinking after taking a couple of different materials and putting a droplet of water on them, it seemed that the materials with the lower surface energy thus a more sphere like shape "slid" along the surface easier.

Bottom line, I have two questions:

1. Do you think a lower surface energy material will "hang" onto a droplet of water more so than a higher surface energy material?

2. Why do corners seem to "hang" onto droplets in the first place?

Thanks,
Pete
 
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  • #2
If I understand you, making the surface hydrophobic (high interfacial energy) will result in smaller droplets that could pushed out of the housing by the airflow. As the interfacial energy decreases, water more easily wets the surface, which could result in larger volumes of water in the housing.

Droplets probably rest in the interior corners because the airflow is more stagnant, allowing droplets to grow over time.

Or am I not understanding you?
 
  • #3
Andy,

My understand is, and perhaps I'm wrong, a higher energy surface will allow water to wet more easily and vice versa. I suppose the question is, if water is building up in an interior corner would it be better to have a higher or lower surface energy material? My thought is a lower surface energy material will create a more sphere like droplet which I think will allow the droplet to fall back into the base more easily.
 
  • #4
That's exactly backwards- the lower the interfacial energy, the more easily water wets the surface. For example, Rain-X is a hydrophobic (high interfacial energy) coating for windshields.

Fluid management is outside my expertise- for example, I could picture use of hydrophilic surfaces just in the interior corners to trap a limited amount of water, and high energy surfaces elsewhere to move the excess water out. OTOH, use of high interfacial energy surfaces everywhere could *prevent* droplets of water from forming in the first place.
 
  • #5
Hmm, here is where I got my data from: http://web.mit.edu/nnf/education/wettability/wetting.html

Which states: When the solid has a high affinity for water - in which case it is called hydrophilic (high energy e.g. glass)- water spreads. In the opposite case of hydrophobic (low energy e.g. teflon) surfaces, water does not spread but, instead, forms at equilibrium a spherical cap resting on the substrate with a 'contact angle'.

I also "backed" that up by remembering very low surface energy materials (some plastics) are very hard to bond to because they don't let the adhesive wet the surface, which makes sense.

I appreciate the help, hopefully we can figure out the right answers.
 
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  • #6
There could be some confusion because of the need to account for the air-solid interface. If the water-solid interface has a lower energy than the air-solid interface, water will displace air and wet the surface. If the water-solid interface has a higher energy than the air-solid interface, air will displace the water.
 

Related to Water Surface Tension: Investigating Condensation Formation

What is water surface tension?

Water surface tension is the cohesive force that causes the molecules of water to stick together and form a surface that resists external forces.

How does water surface tension affect condensation formation?

Water surface tension plays a crucial role in the formation of condensation. It allows water molecules to cling to each other and form droplets on surfaces, rather than spreading out as a thin film.

What factors can affect water surface tension?

Temperature, pressure, and the presence of solutes can all impact water surface tension. Higher temperatures and lower pressures generally reduce surface tension, while the presence of solutes can either increase or decrease surface tension depending on their chemical properties.

How can we investigate condensation formation?

There are several ways to investigate condensation formation, including using a microscope to observe droplet formation on different surfaces, measuring the amount of condensation formed under different conditions, and conducting experiments to manipulate factors such as temperature and pressure.

Why is understanding water surface tension and condensation formation important?

Understanding these concepts is crucial for various industries such as agriculture, engineering, and materials science. It also helps us understand natural phenomena like the water cycle and the formation of clouds and fog.

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