Hi so I have this senior design project involving cooling human skin as it is irradiated by an infrared LED. Human skin not only is super absorbent to IR, but that IR goes THROUGH the thickness of it really well. There are some very long path lengths of IR photons within the human body.
In my heat transfer class, we only saw radiation as dumping all its energy right at the very surface of some block of mystery meat or whatever. In that class we only cared about absorption in terms of how much radiation isn't reflected. We then treated all the radiation that got absorbed as being "stopped" by that surface essentially. After that the heat from this interaction would be distributed by conduction within the receiving block thing.
Million dollar question: What is happening to that topmost surface temperature if absorbed radiation is going THROUGH the surface? So now my deeper layers are being heated by both conduction and direct radiation?
The end goal is to figure out the surface temperature of this irradiated spot of skin, then cool it by cold air convection until a goal surface temperature is reached. Any diagrams in answers would be super helpful. I am a visual creature. Part of my trouble is photons are hard to visualize and I keep picturing bullets stopped by walls when I know photons don't have mass and it's a poor analogy. It's really tripping me up.