- Joined
- Jul 14, 2010
- Messages
- 330
Well, you asked for science so science you shall recieve!
First off, there are three types of heat transfer. Conduction, convection, and radiation. When thermal energy (heat) is transferred through a fluid (eithere a liquid or a gas) convection and radiation are the most important modes.
Even a slight breeze will carry the air warmed by the fire away from you very quickly (convection). Anything that blocks the wind will make the local area stay warmer (convection is reduced), so you are right. They work because they are a wind block, but they do more than that.
Wooden reflectors actually do help with radiation. Here is a quick experiment. Build a wooden wall that you can quickly set up or lay flat. Now build a fire. set up the wall, take it down, set it up again, (see you're getting warmer
). What you will probably notice is that it gets lighter around the fire when the wall is set up. this is because it is reflecting light back. It fact, if it didn't reflect the light you could not see it.
There is a second benefit linked to radiation. Without the reflector, radiative energy would travel unimpeded away from the fire. With even a wooden reflector the energy is either reflected immediately or absorbed. The less effective the barrier is as a reflector, the more effective it is as an enegry collector. This will still bennefit you because as the wood heats up it will increase it's blackbody radiation. Everything radiates energy at some wavelength, and the hotter it is, the more energetic that emmitted radiation is. Although the blackbody radiation does not transfer a significant amount of radiation to you, it does prevent you from radiating nearly as much energy into the forrest. Trust me, as someone who makes a living being locked in a room with 40 teenagers, the human body radiates a lot of thermal energy.
First off, there are three types of heat transfer. Conduction, convection, and radiation. When thermal energy (heat) is transferred through a fluid (eithere a liquid or a gas) convection and radiation are the most important modes.
Even a slight breeze will carry the air warmed by the fire away from you very quickly (convection). Anything that blocks the wind will make the local area stay warmer (convection is reduced), so you are right. They work because they are a wind block, but they do more than that.
Wooden reflectors actually do help with radiation. Here is a quick experiment. Build a wooden wall that you can quickly set up or lay flat. Now build a fire. set up the wall, take it down, set it up again, (see you're getting warmer
). What you will probably notice is that it gets lighter around the fire when the wall is set up. this is because it is reflecting light back. It fact, if it didn't reflect the light you could not see it. There is a second benefit linked to radiation. Without the reflector, radiative energy would travel unimpeded away from the fire. With even a wooden reflector the energy is either reflected immediately or absorbed. The less effective the barrier is as a reflector, the more effective it is as an enegry collector. This will still bennefit you because as the wood heats up it will increase it's blackbody radiation. Everything radiates energy at some wavelength, and the hotter it is, the more energetic that emmitted radiation is. Although the blackbody radiation does not transfer a significant amount of radiation to you, it does prevent you from radiating nearly as much energy into the forrest. Trust me, as someone who makes a living being locked in a room with 40 teenagers, the human body radiates a lot of thermal energy.
