The other thing (from a safety standpoint) is that the sublimation is "dry" since the solid Carbon dioxide at normal pressures phase changes to the gaseous form instead of a liquid. Additional factors are the heat exchange within the box (how well the air is circulated), the moisture content in the box (water can condense and freeze on the surface of the dry ice, inhibiting the sublimation), etc. It all involves Heat flow, so the biggest ones I see are Temperature (heat flow is about the temperature difference) the thermal conductivity (Insulation ability) of the container and the surface area of the dry ice (block vs pellets vs slices, etc). The rate of sublimation will depend on several factors. The EXP equation essentially is calculated using a curve where the value is compounded continually. [in a financial model with interest, Hans' calculation is like calculating compound interest by interpolating along a straight line within a year assuming compounding is done only once per year. If you compare our equations, Hans equation uses an approximation that: The larger it is (both positive and negative) the more off it is. And it is is very close when the absolute value of k is very small (ie close to zero). Wt at any time = (InitalWt)* exp(-kt) which is the equation I offered. Through some rearrangement (that I won't bore you with) the solution to this is that: The rate of change in dry ice the change in Weight over time It should be first order (dependent and the amount of the ice) so that should equal a constant times the amount of ice. LN(a) is the area underneath the curve of the function 1/x from x =1 to x=a. The LN pops up in science a lot when integrating (taking the area under a curve). It is an irrational number equal to about 2.718. The natural log is the logarithm to base e. It is akin to using 10 to the power with the base 10 LOGarithm. The EXPonential function is the inverse of the natural logarithm (LN function).
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