2007, Piran, Slovenia

9,0
8,0
7,0
6,0
5,0
4,0
3,0
2,0
1,0
0,0
CAF [°C] = 395 R e,T,r - 5.0
r 2 = 0.99
-1,0
0,010 0,015 0,020 0,025 0,030 0,035
Clothing
To examine the derived clothing characteristics for evaporative cooling, a mixed
linear model was used where the main treatment effect was the ensemble, and
participants were treated as a random factor. In all cases, there was a significant
difference among ensembles. To determine where the differences occurred, a Tukey's
HSD multiple comparison procedure was used. For Re,T,r, Re,T,stat, im,r and im,stat, there
were no differences among Cotton Coveralls, Work Clothes and Tyvek in that order,
followed by NexGen and Tychem, both of which were different from all others. The
exception was im,r for Cotton Coveralls, which had the highest permeability index and
was different from the others.
DISCUSSION
The first step in the current study was to estimate the total resultant insulation from
the static values of a manikin test. Kenney et al. (1993) used two critical conditions at
warm, humid and hot, dry environments to solve for the two unknowns in Equation 1.
In reporting values for work clothes (military BDU), they found a total resultant
insulation of 0.050 m 2 °C W -1 as compared to 0.133 for the current study. Similarly
for vapour barrier, they reported a much lower value (0.035) than the current value of
0.136, and the current study did not use a hood. Part of the difference might be due to
the reduction due to wetting of the clothing. If an 80% reduction is taken for
illustration (CFI = 0.2) there would be a 17% decrease in total evaporative resistance.
While it is very difficult to infer directly what the reduction in clothing insulation due
to wetting was, the error in determining evaporative resistance is systematic in the
vicinity of 10%.
In the current study, the total resultant evaporative resistance for Work Clothes,
Tyvek and the vapour barrier were supported by values reported by others. Caution
must be used for vapour permeable water barriers. NexGen had a total evaporative
resistance than reported elsewhere. It is likely that different films have different
evaporative resistances. Looking at the permeability index in Table 1, the resultant
values were higher than the static values and this was expected. The values for static
permeability index where similar to those reported in the ISO 9920 appendices.
As the WBGT
WBGT Clothing Adjustment Factor [°C]
Total Resultant Evaporative Resistance [m 2 kPa W -1 ]
clothing adjustment
factor increases, it is
reasonable to believe
there would be a
reduction in the total
resultant evaporative
resistance. There
appeared to be a linear
relationship for the
50% relative humidity
conditions in the
current study, but the
absence of data
between the vapourbarrier
at the high end
the other ensembles near the low end does not preclude a non-linear relationship.
Further, the clothing adjustment factor for vapour-barrier clothing changes with the
relative humidity, but not for the other ensembles. This actually means there may be a
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