2007, Piran, Slovenia

Environmental Ergonomics XII
Igor B. Mekjavic, Stelios N. Kounalakis & Nigel A.S. Taylor (Eds.), © BIOMED, Ljubljana 2007
Then, if the relationship between Esk/Emax and φ 2 in the model presented here is treated as a
simple mass transfer problem without regarding the heat transfer, it can be as shown in Fig. 5,
with δ/ rc given as a parameter. As can be seen from this figure, the relationship where Esk/Emax
is simply proportional toφ 2 cannot usually be established unless δ/ rc is small and especially
when δ/ rc >1, Esk/Emax, does not decrease much even whenφ 2 decreases. When it comes to the
parameter δ/ rc here, rc is related to the characteristics of skin surface, physiological and other
human body conditions, while δ is related to the air velocity, clothing and other external
conditions. In the case of Fig. 2, the calculated value of δ/ rc is 24.3 as a result of estimating δ
and rc by the practical method mentioned above. Therefore even if there are some differences
between this estimated value and Fig. 5, or if the differences in the details of the model and
real subjects are taken into account, the above-mentioned relationship between skin
wettedness Esk/Emax and true skin wet area ratio Aw/A will not change greatly. In the concept
of skin wettedness proposed by Gagge and Nishi (1977), evaporative heat loss from the skin
surface is taken into account and it takes the position of correcting area A, based on the
assumption that the mass transfer coefficient hD is constant, rather than correcting the mass
transfer coefficient when explaining the difference found between actual evaporative heat loss
498
1
0.8
0.6
0.4
Wet area Dry area
0 Φ r c
35.0
349
35.4
35.3
35.2
35.1
35.5
r
Temp. [ ] R. H. [%]
0.2
20 50
30 50
30 10
0
0.0001 0.001 0.01 0.1 1
Φ 2 [ - ]
Figure 2 Relationship between Esk/Emax
andφ 2
35.6
r c
y=0
y
y=-L
Figure 4 Temperature distribution
near the skin surface
1
0.8
0.6
0.4
0.2
0.039
δ /r c =10
2
0.022
0.024
0.026
0.028
0.5
0
0.020
0.015
0.010
0
0 0.2 0.4 0.6 0.8 1
Φ 2 [ - ]
0.005
0.030 0.0310.0320.0330.0340.035
0.038
0.037
0.036
0 Φ r
c
r
Wet area Dry area
y=δ
y=0
Figure 3 Vapor concentration
distribution in the boundary layer
film
Figure 5 Relationship between Esk/Emax
2
r c
y