Conclusions
From the study, the following conclusions may be drawn:
  1. In SMMHP, the terminal temperature difference is very high comparing with that of in TMMHP. As a result, the h of the working fluid produced by the SMMHP is much smaller than that of TMMHP.
  2. Out of four working fluids, methanol has been found to be of the highest h because of its lowest boiling point that enables quick completion of thermodynamic cycle.
  3. Out of three orientations, TMMHP at 45o produces the highest value of h for all four fluids; however, the sequence of h remains the same in all the orientations.
  4. It is proven that MHP made with the metals of variable thermal conductivity (i.e.TMMHP) of ascending order orientation, which initiates the super heater effect in the evaporator, indicates many folds better prospect of h value than that of made with constant conductivity (SMMHP).
  5. While an assumption of single phase flow in SMMHP works well at lower heat inputs, but at moderately high heat inputs it becomes a two-phase flow. However, the super heater effect at the evaporator in TMMHP eliminates that complexity of the two-phase and instantly turns into a single phase flow of vapor which was not possible in SMMHP [6, 7].
  6. In case of water, the upper trend of temperature at the condenser port is uniquely different from that of other liquids. Such a condition demands the coolant flow at lower than the ambient temperature or a coolant of higher Cp. Eventually, the slightly increased temperature of the vapor condensate speeds up the capillary action of the wick.
  7. Even though the values of h in TMMHP are many times higher than those of in SMMHP, the limitation of its value is obvious in both the heat pipes at a relatively higher heat input.
  8. The change of any specific physical property (i.e. density, specific gravity, viscosity) of a fluid singly cannot change the h of that fluid in an MHP, rather it is a compound value developed functionally from both of its physical properties and state variables.