3.6 Methods
75
the temperature. The temperature was recorded using the Datataker continuously at
10 sec intervals for the duration of the experiments.
3.6.4 Data Analysis Method
All the experiments were conducted for 60 min and the data recorded by the Datataker
were converted to Microsoft Excel worksheets for graphical representations. These
graphical representations were termed cooling curves. The data from each of the thermocouples (1–11) were averaged to get the mean temperature. Ambient temperature
was recorded by thermocouple number 12, as indicated in Table 3.3. The ambient
was subtracted from the mean (i.e. mean–ambient) and was tabulated for PWAT
and PCM. Identical experiments were performed without any material (PWAT or
PCM) inside the helmet and these experiments were termed the Control. For all the
materials (i.e. PWAT and PCM) at different speeds, the drops in temperature were
calculated by subtracting the values of (mean–ambient) of the control experiments
from the values of (mean–ambient) of the materials (PWAT or PCM). This new value
was termed the DIT (drop in temperature). The maximum value in every series of
DIT was referred to as the MDIT (maximum drop in temperature).
3.7 Differential Scanning Calorimetry
Differential Scanning Calorimetry (DSC) comprises an insulated chamber containing
two individual calorimeters, namely, sample and reference calorimeters. Each
calorimeter accommodates a platinum resistance sensor (thermometer) and a resistance heater. When an exothermic or endothermic change occurs in a sample, power
is continuously and automatically removed or applied to one or both of the calorimeters to compensate for the change to either the sample or reference. Hence, the
temperature of both calorimeters is identical and the system is in equilibrium.
A Perkin-Elmer Pyris 1 DSC instrument was incorporated in the current study,
utilising an ice-water slurry (2–5 °C) as a source of coolant. The instrument’s heat
flow sensitivity was 0.2 μW, with a temperature precision of ±0.01 °C. The lower
stable temperature for this system was 20 °C. The enclosed chamber was purged with
pure nitrogen (99.99%) at a flow rate of 20 mL min
−1 . During thermal scanning, a
continuous nitrogen flow in the DSC sample chamber was maintained to ensure
minimal sample degradation. High purity standard indium (T m = 156.60 °C) and
zinc (T m = 419.47 °C) were used to calibrate the instruments for temperature and
enthalpy 28.45 °C and 108.37 Jg
−1 respectively. The calibration was periodically
checked and maintained. Pyris
™ software (Version 3.81) for Windows was used in
conjunction with the Perkin-Elmer instrument for analysis of the results. The DSC
experiments for the PCM samples used in the research, the endothermic approach
was taken with a heating rate of 2 °C per minute.
75
the temperature. The temperature was recorded using the Datataker continuously at
10 sec intervals for the duration of the experiments.
3.6.4 Data Analysis Method
All the experiments were conducted for 60 min and the data recorded by the Datataker
were converted to Microsoft Excel worksheets for graphical representations. These
graphical representations were termed cooling curves. The data from each of the thermocouples (1–11) were averaged to get the mean temperature. Ambient temperature
was recorded by thermocouple number 12, as indicated in Table 3.3. The ambient
was subtracted from the mean (i.e. mean–ambient) and was tabulated for PWAT
and PCM. Identical experiments were performed without any material (PWAT or
PCM) inside the helmet and these experiments were termed the Control. For all the
materials (i.e. PWAT and PCM) at different speeds, the drops in temperature were
calculated by subtracting the values of (mean–ambient) of the control experiments
from the values of (mean–ambient) of the materials (PWAT or PCM). This new value
was termed the DIT (drop in temperature). The maximum value in every series of
DIT was referred to as the MDIT (maximum drop in temperature).
3.7 Differential Scanning Calorimetry
Differential Scanning Calorimetry (DSC) comprises an insulated chamber containing
two individual calorimeters, namely, sample and reference calorimeters. Each
calorimeter accommodates a platinum resistance sensor (thermometer) and a resistance heater. When an exothermic or endothermic change occurs in a sample, power
is continuously and automatically removed or applied to one or both of the calorimeters to compensate for the change to either the sample or reference. Hence, the
temperature of both calorimeters is identical and the system is in equilibrium.
A Perkin-Elmer Pyris 1 DSC instrument was incorporated in the current study,
utilising an ice-water slurry (2–5 °C) as a source of coolant. The instrument’s heat
flow sensitivity was 0.2 μW, with a temperature precision of ±0.01 °C. The lower
stable temperature for this system was 20 °C. The enclosed chamber was purged with
pure nitrogen (99.99%) at a flow rate of 20 mL min
−1 . During thermal scanning, a
continuous nitrogen flow in the DSC sample chamber was maintained to ensure
minimal sample degradation. High purity standard indium (T m = 156.60 °C) and
zinc (T m = 419.47 °C) were used to calibrate the instruments for temperature and
enthalpy 28.45 °C and 108.37 Jg
−1 respectively. The calibration was periodically
checked and maintained. Pyris
™ software (Version 3.81) for Windows was used in
conjunction with the Perkin-Elmer instrument for analysis of the results. The DSC
experiments for the PCM samples used in the research, the endothermic approach
was taken with a heating rate of 2 °C per minute.