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