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Response Details:
I don't know what solution you are referring but I am telling you the answer
Q = hAΔT
or, q = Q/A = hΔT
qwater = hwater*(Thand - Twater)
=(900 W/m2-K )*(30-10)K
= 18000 W/m2
qair = hair*(Thand - Tair)
= (40 W/m2-k)*(30-(-5))K
= 1400 W/m2
as qwater > qair, Hand will feal coller in water
Now, to things to visualize:
1. air is at lower temperature (Tair = -50C) comapred to water at 100C, still qwater is more.
2. vair >vwater still qwater is more.
Now, your confusion why at all the speed is given and convective heat transfer depends on speed of the medium?
Answer is Yes, convective heat transfer depends on the flow of the medium. but convection heat transfer coefficient (h) takes care of this.Now, h is dependent on the type of media, gas or liquid, the flow properties
such as velocity, viscosity and other flow and temperature dependent
properties. and h is given so speed plays no role in calculation.
then why speed is given.. this is for visualization purpose.
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