4.3 Temperature Drop Using PWAT Material
95
Table 4.1 Maximum drop in temperature achieved by PWAT material at various speeds
Speeds (kph) Corresponding
time of MDIT a
(h:mm:ss)
Control ‘A’
(Mean–Ambient)
(°C)
Material ‘B’
(Mean–Ambient)
(°C)
MDIT a (B–A)
(°C)
0
0:00:40
23.1
21.0
– 2.1
15
0:57:40
9.9
6.2
– 3.8
35
0:56:10
5.3
1.0
– 4.3
55
0:23:50
12.0
5.0
– 7.0
75
0:27:00
11.0
2.3
– 8.8
a Maximum drop in temperature
Figure 4.18 indicates the drop in temperature with a wind speed of 0 kph. It was
observed from the figure that both the control curve (blue) and the PWAT material
curve (pink) start declining in temperature in a gradual and slow manner that is due
to the radiant heat dissipation and conduction. The highest drop in temperature is
only 2.1 °C over the total experimental time of 60 min. The PWAT material curve is
always below the control curve because more heat is being absorbed by the PWAT
material compared to the helmet alone.
Also it was observed from the figure that as the time increases, there is only a
slight drop in temperature. The drop in temperature achieved with 0 kph speed is
the minimal amount as compared to the other speeds, which was observed from the
cooling curve that is almost horizontal as shown in Fig. 4.18. This is because the
wind inside the tunnel is stationary, and the heat loss is mainly due to radiation and
a small amount due to conduction.
The comparison graph for PWAT material at 15 kph speed is shown in Fig. 4.19.
It was observed that the resultant cooling achieved at 15 kph speed is also very low.
This is because at a low speed of 15 kph, sufficient water had not evaporated from
the PWAT material to give adequate cooling inside the helmet. A maximum drop
in temperature (MDIT) of 3.8 °C was achieved over the total experimental time of
60 min (Table 4.1).
Figure 4.20 shows the comparison graph for PWAT material at 35 kph speed. It
was observed that the resultant cooling achieved at 35 kph speed is also low which
is because at a low speed of 35 kph speed sufficient water had not evaporated from
the PWAT material. A maximum drop in temperature of 4.3 °C was achieved over
the total experimental time of 60 min.
Figure 4.21 shows the comparison graph for PWAT material at 55 kph speed. It
was observed that the resultant cooling achieved at 55 kph speed is much higher as
compared to the low-velocity tests. This was due to the increased speed and the fact
that the amount of water evaporated from the PWAT material was high. The highest
drop in temperature is 7.0 °C, over the total experimental time of 60 min.
The comparison graph for PWAT material at 75 kph speed is shown in Fig. 4.22.
It was observed that the resultant cooling achieved at the speed of 75 kph is very
high as compared to the low-velocity tests, and also, it is higher than the value for
95
Table 4.1 Maximum drop in temperature achieved by PWAT material at various speeds
Speeds (kph) Corresponding
time of MDIT a
(h:mm:ss)
Control ‘A’
(Mean–Ambient)
(°C)
Material ‘B’
(Mean–Ambient)
(°C)
MDIT a (B–A)
(°C)
0
0:00:40
23.1
21.0
– 2.1
15
0:57:40
9.9
6.2
– 3.8
35
0:56:10
5.3
1.0
– 4.3
55
0:23:50
12.0
5.0
– 7.0
75
0:27:00
11.0
2.3
– 8.8
a Maximum drop in temperature
Figure 4.18 indicates the drop in temperature with a wind speed of 0 kph. It was
observed from the figure that both the control curve (blue) and the PWAT material
curve (pink) start declining in temperature in a gradual and slow manner that is due
to the radiant heat dissipation and conduction. The highest drop in temperature is
only 2.1 °C over the total experimental time of 60 min. The PWAT material curve is
always below the control curve because more heat is being absorbed by the PWAT
material compared to the helmet alone.
Also it was observed from the figure that as the time increases, there is only a
slight drop in temperature. The drop in temperature achieved with 0 kph speed is
the minimal amount as compared to the other speeds, which was observed from the
cooling curve that is almost horizontal as shown in Fig. 4.18. This is because the
wind inside the tunnel is stationary, and the heat loss is mainly due to radiation and
a small amount due to conduction.
The comparison graph for PWAT material at 15 kph speed is shown in Fig. 4.19.
It was observed that the resultant cooling achieved at 15 kph speed is also very low.
This is because at a low speed of 15 kph, sufficient water had not evaporated from
the PWAT material to give adequate cooling inside the helmet. A maximum drop
in temperature (MDIT) of 3.8 °C was achieved over the total experimental time of
60 min (Table 4.1).
Figure 4.20 shows the comparison graph for PWAT material at 35 kph speed. It
was observed that the resultant cooling achieved at 35 kph speed is also low which
is because at a low speed of 35 kph speed sufficient water had not evaporated from
the PWAT material. A maximum drop in temperature of 4.3 °C was achieved over
the total experimental time of 60 min.
Figure 4.21 shows the comparison graph for PWAT material at 55 kph speed. It
was observed that the resultant cooling achieved at 55 kph speed is much higher as
compared to the low-velocity tests. This was due to the increased speed and the fact
that the amount of water evaporated from the PWAT material was high. The highest
drop in temperature is 7.0 °C, over the total experimental time of 60 min.
The comparison graph for PWAT material at 75 kph speed is shown in Fig. 4.22.
It was observed that the resultant cooling achieved at the speed of 75 kph is very
high as compared to the low-velocity tests, and also, it is higher than the value for