Seek said:
Surf Monkey said:
I'm simply questioning how much IR effects the operation of the box and how exactly the IR is brought into play. Given a more detailed explanation of the IR characteristics of the MFLB my curiosity would no doubt be satisfied.
FAQ said:
Has Magic-Flight ever tried increasing the area of contact between the screen and the herb?
Yes, they have. Extensively. It turns out that the shape, size, and angles of orientation all matter. A lot. Surprisingly, these additional aspects make the surface area of contact factor one somewhat less important in the overall design. Certain dimensions have more to do with time rate of change in the degree of criticality due to the specific angles of enclosure as seen from different points in the chamber. It is more of an IR effect than a surface of contact effect. This sort of esoterica can quickly get rather complicated to explain.
Hi,
We stand by our claim that IR effects play a significant part of the overall effectiveness of the design. How significant? At least 25% in regards to the heating and more than 75% in terms of the temperature stabilization. While it is not the majority effect for the heating, it is very important for the overall function and makes more than a noticeable difference in the overall utility of the device. If the Box depended only on conduction characteristics, it would be unusable.
In regards to explanation, as mentioned previously, it has a lot to do with the shape and structure of the emission surface and the enclosing chamber as well as the specific materials chosen for its construction. The main concern is to utilize IR effects to create a zone of criticality in the middle of the load without *also* inducing thermal runaway (combustion). This is NOT a trivial problem! Your intuition is correct in observing that conduction by itself has no way of solving this problem and that the local resistance to airflow is slightly too high for convection to be of much help in this regard. Unfortunately, to really understand the way in which this problem is solved using IR effects in the Box involves more than a little calculus. Several important variables change simultaneously (energy delivered, thermal resistance, time rate of change of accumulated temperature, etc) making direct analysis more than a little difficult -- well beyond what I am going to attempt to explain here. It is in the balancing of these changing variables that success is achieved.
If you are really interested, and presuming that you know enough about the electrical and battery theory aspects, the main ideas for understanding the important IR effects are to 1) understand the means by which the inverse square law is derived (so that you know how to overcome those effects in the near field) and 2) the Stefan Boltzmann law (critical to overall temperature stabilization). In short, for those who understand these sorts of things, the overall pattern is fairly obvious, and it makes more than a little sense to consider the Box an IR performance enhanced device. Without having used these tools, the Box would simply not work very well -- it really does depend on its IR characteristics.
-- Magic-Flight
http://en.wikipedia.org/wiki/Stefan–Boltzmann_law
http://www.britannica.com/EBchecked/topic/564843/Stefan-Boltzmann-law