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We have learnt that hot air is less dense therefore it rises up. But we also learnt woolen clothes trap air that get warm by body heat, and act as a insulation layer dont allow heat to escape from body.

Why does not that hot air in sweater (woolen clothes) rise away and cool air from outside take its place (like in land breeze sea breeze) so that no insulating layer form, ?

Same why does not hot air above tea rises and make way for cool air from surrounding to come help tea to cool so that no need to blow over tea?

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    $\begingroup$ It's a matter of degree. Just because something happens doesn't mean it happens to the extreme. $\endgroup$
    – DKNguyen
    Oct 2 '21 at 17:28
  • $\begingroup$ True, thanks, does it is slow in sea breeze and land breeze also? $\endgroup$
    – user315475
    Oct 2 '21 at 18:15
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    $\begingroup$ Are you asking why the convection in a sweater and tea does not make a breeze like a land or sea breeze? It does. It's just too weak for you to notice. A land or sea breeze is also over a MASSIVE area moving MASSIVE amounts of air. $\endgroup$
    – DKNguyen
    Oct 2 '21 at 18:28
  • $\begingroup$ Ookkk thank uuuu $\endgroup$
    – user315475
    Oct 3 '21 at 13:18
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Why does not that hot air in sweater (woolen clothes) rise away and cool air from outside take its place (like in land breeze sea breeze) so that no insulating layer form, ?

It does, but it does so more slowly than if there were no sweater because the sweater fibers block the air flow. The sweater basically lowers the convective heat transfer coefficient between the skin and the ambient air outside the sweater.

Same why does not hot air above tea rises and make way for cool air from surrounding to come help tea to cool so that no need to blow over tea?

It does, but it does so more slowly because it is natural (unforced) convection, as opposed to the forced convection when blowing over the tea.

Hope this helps.

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  • $\begingroup$ Thank u but does it is slow in sea breeze and land breeze also? $\endgroup$
    – user315475
    Oct 2 '21 at 18:14
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    $\begingroup$ It is faster in any breeze than no breeze at all. Are you familiar with the term "wind chill factor"? For the same air temperature, you feel colder if it's windy than when it's not. That's because the rate of convective heat transfer from you skin is greater when the air is moving than when it is not. $\endgroup$
    – Bob D
    Oct 2 '21 at 18:35
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    $\begingroup$ @AnshikaSingh So did I answer you question satisfactorily? If not, why not? $\endgroup$
    – Bob D
    Oct 3 '21 at 22:24
  • $\begingroup$ Yes..... Thanks a lot, good answer $\endgroup$
    – user315475
    Oct 4 '21 at 2:32
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    $\begingroup$ Yes, that is correct $\endgroup$
    – Bob D
    Oct 4 '21 at 6:50

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