Container Transpiration

Additional Transpiration Studies

The next study was conducted for LDPE bottles of 30, 125, 250, and 500 mL capacity. The purpose was to determine if the correlation of the transpiration rate to the bottle opening held up for a variety of bottle sizes. In addition, other variables were added as illustrated in Figures 6.2 and 6.3.

Figure 6.2: Transpiration - 125 ml Bottles

Figure 6.3: Transpiration - 30 ml Bottles

The results for the 250 ml and 500 ml bottles are congruent with the data shown above, with the exception that the transpiration rates are proportionately lower. So the question then becomes, What factor is proportionately effecting the rate of transpiration?

Figure 6.4 shows a comparison of the transpiration rates for all of the bottles capacities as compared to each bottle size surface area. No correlation could be found, indicating that the mechanism for transpiration is not through the bottle walls.

Figure 6.4: Transpiration Rates vs Bottle Surface Area

Figure 6.5 shows a comparison of the transpiration rates for all of the bottles as compared to the ratio of the bottle opening circumference to the solution surface area -- i.e. Transpiration Rate vs. [π * d_c] ÷ [π * (R_b)²] where:

π = 3.14
d_c = cap diameter in centimeters
R_b = radius of bottle (main body)

Figure 6.5: Transpiration Rates vs Bottle Opening Geometry

This study revealed a correlation that fits to within 6 % relative, indicating that transpiration around the cap is the correct mechanism and not through the bottle as previously assumed.

As additional support for this argument, Figure 6.6 shows a dramatic illustration of the fact that there is a near perfect correlation of transpiration rate to bottle opening geometry and no correlation to the bottle surface area.

Figure 6.6: Bottle Opening vs Area Geometries

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