Heat & Biking: Forced Convection and Heat Transfer

In the morning when I bike to work, it’s normally in mid to upper 70’s.  That’s pretty decent cool weather.  However, when I return, it’s low 90’s to high 80’s even after 6 pm!  😮  But when I do bike home, it doesn’t feel as hot as you’d think!

What the hell is “forced convection”?!  😀  Convection is heat transfer from one medium to the other through the fluid that surrounds the medium.  Basically, you release heat from solids or liquids to surrounding environment.  So in the case of biker, your heat dissipates to the air that surrounds you.  There are two kinds of convections:  free and forced.  Free convection is where the fluid that surrounds the boy in question is not moving, like swimming pool.  Forced convection is where the fluid is now moving, like the river.  What’s this got to do with feeling cooler when biking?!

Well, body temperature is 98 F to begin with.  So when ambient temperature is already in high 80’s to 90’s, there’s going to be not much heat transfer from your body to the air.  Heat transfer is directly related to the difference in temperature after all.  Yet in sitting still, free convection doesn’t help in dissipating your body as it gets hotter.  But once you get moving, air starts to move around you and you now have forced convection.  Forced convection basically, in layman’s terms, strips the heat away from you and thus increases the heat transfer rate despite the low difference in temperature.

So until I get home and stop, my body thinks that it’s rather cool outside still!  Science and engineering can be so nice, huh?!  😀

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