To those who have watched Ironman, I am sure you noticed that when Ironman and the bad guy (forgot his name) flew high up into the sky, both of them has ice particles accumulated on their armor suits.
Obviously, that is a phenomenon termed as Icing. Icing happens mainly due to Supercooled Water Droplets (SCWD) being held in suspension in the air. SCWD, as its name suggests, means that water droplets (not water vapour) are cooled down to below 0 degree Celcius and it still maintain its liquid form and not solid form.
Yes, I know you are thinking that it is impossible to have water remain in liquid form even below 0 degree Celcius.
Trust me. This is possible. And, there is reason for it. I will put it in a very simple way for you to understand.
For water vapour to condense to liquid, it needs hygroscopic nuclei. And for liquid to undergo sublimation to change its form into solid ice, it needs ice nuclei. However, when water vapour is cooled to below its freezing point and there is no ice nuclei around, that means only condensation can take place and hence water droplets are formed. These particles are what we called as SCWD and they are very unstable, mind you. They are in the air, awaiting any ice nuclei to come and form ice with them immediately.
Now can you tell me what is the biggest ice nuclei in the air?
Answer: Aeroplanes. The moment these SCWD touches the aircraft's skin, ice forms straightaway on it. Just like what you see in some of the scenes in Ironman (suit testing scene where he pushed the armor suit to the limit by flying high high up into the sky; the fighting scene where he lured his enemy to the same place too).
For icing to happen to an aircraft, there are conditions that need to be present:
1) Aircraft skin temperature is below zero and SCWD are present in the atmosphere; or
2) Outside air temperature is below zero and SCWD are present in the atmosphere.
In temperature band between 0-10degree Celcius, the air contains mainly large SCWD. Between 10-40degree Celcius, mainly mixture of small SCWD and ice crystals present. While temperature below 40degree Celcius contains only of ice crystals. Ice crystals are harmless.
For the next post, when I am free, I will post about types of Icing. And probably some of the icing consequences to an aircraft too.
Obviously, that is a phenomenon termed as Icing. Icing happens mainly due to Supercooled Water Droplets (SCWD) being held in suspension in the air. SCWD, as its name suggests, means that water droplets (not water vapour) are cooled down to below 0 degree Celcius and it still maintain its liquid form and not solid form.
Yes, I know you are thinking that it is impossible to have water remain in liquid form even below 0 degree Celcius.
Trust me. This is possible. And, there is reason for it. I will put it in a very simple way for you to understand.
For water vapour to condense to liquid, it needs hygroscopic nuclei. And for liquid to undergo sublimation to change its form into solid ice, it needs ice nuclei. However, when water vapour is cooled to below its freezing point and there is no ice nuclei around, that means only condensation can take place and hence water droplets are formed. These particles are what we called as SCWD and they are very unstable, mind you. They are in the air, awaiting any ice nuclei to come and form ice with them immediately.
Now can you tell me what is the biggest ice nuclei in the air?
Answer: Aeroplanes. The moment these SCWD touches the aircraft's skin, ice forms straightaway on it. Just like what you see in some of the scenes in Ironman (suit testing scene where he pushed the armor suit to the limit by flying high high up into the sky; the fighting scene where he lured his enemy to the same place too).
For icing to happen to an aircraft, there are conditions that need to be present:
1) Aircraft skin temperature is below zero and SCWD are present in the atmosphere; or
2) Outside air temperature is below zero and SCWD are present in the atmosphere.
In temperature band between 0-10degree Celcius, the air contains mainly large SCWD. Between 10-40degree Celcius, mainly mixture of small SCWD and ice crystals present. While temperature below 40degree Celcius contains only of ice crystals. Ice crystals are harmless.
For the next post, when I am free, I will post about types of Icing. And probably some of the icing consequences to an aircraft too.
This entry was posted
on Friday, May 09, 2008
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