Results and Discussions
Using gathered data in this investigation various curves are plotted as
shown from Fig. 3 to Fig. 22. Figure 3 shows time required for reaching
steady state temperature for different working fluids. It is found that
water takes the least time out of four liquids while the other three
delayed approximately the same period of time. Ethanol and iso-propanol
are almost entwined in terms of temperature rise as well as attaining
steady-state condition—this may occur because of their proximity of
boiling points (BP). On the other hand, methanol took the longest time
to reach but at a higher temperature range than the other three. It is
observable that not only the methanol’s boiling point is low but also is
its flash point. Methanol’s flash point is only 11 o C
which is 5.6 degrees less than that of ethanol. This indicates the
earlier boiling and condensation of methanol than other fluids, which
becomes chaotic within the narrow space of the micro heat pipe.
Consequently, methanol takes longer period of time to reach thermal
equilibrium thus to attend steady state than that of others. Therefore,
the heat capacity of a fluid not only depends on its thermophysical
properties (i.e. density, SG etc.) but also on its chemical bonding
(i.e. hydrogen bonding for water).
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Figure 3. Time required for reaching steady-state of different fluids
The trends of temperature rises at the evaporator section for using
different fluids in TMMHP are shown in Figure 4. However, water’s
character is specifically non-linear and on the order of three. This may
happen because of the three are organic compounds and have similar
chemical bonding, and the water as an inorganic compound is made up from
hydrogen and oxygen’s covalent bond.
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Figure 4. Rise of fluid temp. vs. heat input at the evaporator