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5 Conclusions
In the case of PCM materials, at higher temperatures, heat absorbed is maximised
when it reaches the melting point. When it is beyond the melting point, all the
heat had been absorbed by the latent heat of fusion. No further cooling takes place
after all the PCM microcapsules have melted, but forced convection might provide a
small amount of cooling. If the temperature drops in the surrounding environment,
the already melted PCM microcapsules would solidify and release heat, providing
comfort to the motorcyclist. Thus, by the application of PCM materials, there would
be benefits if the temperature rises or falls in the surroundings.
The amount of heat absorbed by the application of PWAT or PCM materials
is close enough to the metabolic heat produced by the average sized human head.
This research indicates that a sufficient amount of heat is being absorbed by textile
substrates containing PWAT or PCM materials to reduce the heat stress of the
motorcyclist.
The forced convection of the air at different speeds in the wind tunnel also
contributes to a further drop in temperature within the helmet, depending on the
speeds. At higher speeds, the temperature drop is much higher than at lower speeds.
At the beginning of this study, it was expected that a drop in temperature of 2–
3 °C within the helmet would be obtained to achieve the cooling needed. However,
by using these innovative approaches, the cooling achieved has been much greater,
especially at higher speeds. Hence, the heat stress in the helmet has been reduced for
the motorcyclist. In addition, no external power supply (from batteries or electrical
source) is needed for cooling the helmet by this approach.
The addition of materials (PWAT or PCM) can be included in the textile liner for
achieving further cooling. In the case of the exhausted PWAT material, additional
water can be added (dry after the experiments due to water being evaporated), or
for the exhausted PCM (due to all the PCM microcapsules completing phase change
after absorption of heat), additional PCM material can be included to achieve further
cooling. The regression analysis curves for PWAT materials can directly be used up
to 75 kph or extrapolated for higher speeds to predict the drop in temperature and
the amount of heat absorbed, respectively, based on the speed of the motorcyclist.
Two equations were derived from this research for PWAT materials. The first equation y = 2.4024e
0.0181x deals with the calculation of maximum drop in temperature at
various speeds. This equation can be used directly or extrapolated for various speeds
to predict the maximum drop in temperature. The second equation y = 12.986e
0.0072x
deals with the amount of heat absorbed at various speeds. Similar to the first equation,
this equation can also be used directly or extrapolated for various speeds to predict
the amount of heat absorbed.
In case of PCM materials, an approach was taken to calculate the total amount of
heat absorbed considering the start and end temperatures at different speeds. This was
based on the experimental results obtained from the DSC graphs using the equation
W = (m × H)/t. This approach was specific to the experiments conducted in this
research using various PCM materials.
The extensive experimental data from this research established that, for enclosed
motorcycle helmets, the behaviour of PWAT materials was better predicted by the
equations derived in this study, rather than that previously published research. The
5 Conclusions
In the case of PCM materials, at higher temperatures, heat absorbed is maximised
when it reaches the melting point. When it is beyond the melting point, all the
heat had been absorbed by the latent heat of fusion. No further cooling takes place
after all the PCM microcapsules have melted, but forced convection might provide a
small amount of cooling. If the temperature drops in the surrounding environment,
the already melted PCM microcapsules would solidify and release heat, providing
comfort to the motorcyclist. Thus, by the application of PCM materials, there would
be benefits if the temperature rises or falls in the surroundings.
The amount of heat absorbed by the application of PWAT or PCM materials
is close enough to the metabolic heat produced by the average sized human head.
This research indicates that a sufficient amount of heat is being absorbed by textile
substrates containing PWAT or PCM materials to reduce the heat stress of the
motorcyclist.
The forced convection of the air at different speeds in the wind tunnel also
contributes to a further drop in temperature within the helmet, depending on the
speeds. At higher speeds, the temperature drop is much higher than at lower speeds.
At the beginning of this study, it was expected that a drop in temperature of 2–
3 °C within the helmet would be obtained to achieve the cooling needed. However,
by using these innovative approaches, the cooling achieved has been much greater,
especially at higher speeds. Hence, the heat stress in the helmet has been reduced for
the motorcyclist. In addition, no external power supply (from batteries or electrical
source) is needed for cooling the helmet by this approach.
The addition of materials (PWAT or PCM) can be included in the textile liner for
achieving further cooling. In the case of the exhausted PWAT material, additional
water can be added (dry after the experiments due to water being evaporated), or
for the exhausted PCM (due to all the PCM microcapsules completing phase change
after absorption of heat), additional PCM material can be included to achieve further
cooling. The regression analysis curves for PWAT materials can directly be used up
to 75 kph or extrapolated for higher speeds to predict the drop in temperature and
the amount of heat absorbed, respectively, based on the speed of the motorcyclist.
Two equations were derived from this research for PWAT materials. The first equation y = 2.4024e
0.0181x deals with the calculation of maximum drop in temperature at
various speeds. This equation can be used directly or extrapolated for various speeds
to predict the maximum drop in temperature. The second equation y = 12.986e
0.0072x
deals with the amount of heat absorbed at various speeds. Similar to the first equation,
this equation can also be used directly or extrapolated for various speeds to predict
the amount of heat absorbed.
In case of PCM materials, an approach was taken to calculate the total amount of
heat absorbed considering the start and end temperatures at different speeds. This was
based on the experimental results obtained from the DSC graphs using the equation
W = (m × H)/t. This approach was specific to the experiments conducted in this
research using various PCM materials.
The extensive experimental data from this research established that, for enclosed
motorcycle helmets, the behaviour of PWAT materials was better predicted by the
equations derived in this study, rather than that previously published research. The