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An experimental facility to examine the effect of carbon nanotubes (CNT) on the performance of a horizontal V-grooved heat pipe was build. The circular heat pipe was made of copper with an inner diameter of 10 mm and equipped with 10 axial V-grooves with 1 mm depth and 1 mm mouth. The experiment was performed using water as working fluid with mass percentage of CNT of 0%, 1%, 3% and 5%. The optimum fill ratio of the heat pipe was first determined by examining the fill ratio effect on the total resistance. This optimum fill ratio was then used throughout the whole experiment. The evaporator of the heat pipe was heated using a copper heater block equipped with 6 cartridge heaters. The power input to the evaporator was varied from 60 W to 240 W in steps of 60 W with maintaining steady-state operation at each power level. The condenser was cooled by a water jacket fed by a chiller. The surface temperature of the heat pipe was measured by 7 K-type self-adhesive thermocouples connected to data acquisition system. The experimental results showed that the performance of the heat pipe improved with the use of CNT-water mixture in terms of a reduction in the thermal resistance. The results also showed that this enhancement is a function of the amount of CNT additive.

In this work, both dimensional analyses using Buckingham Pi-theorem and scaling of the energy equation have been applied successfully in fluid to fluid modeling for post dry out to model the Freon (R-134a) data available in the literature and convert it to water equivalent data. Also the results are compared with the available data in the literature for water. Experimental data sets in two fluids are assumed to be equivalent if the values of the dimensionless groups are equal for both fluids. Both methods are used and the results are compared with the experimental data at different operating conditions. The Katto and the Ahmad modeling dimensionless parameters coming from the analysis using Pi-theorem predicted successfully the equivalent data of water at moderate mass fluxes. However, at too high or low mass fluxes, this method deviated from the experimental data. However, the fluid to fluid modeling using the scaling of energy equation is applicable at any operating conditions and the results are too close to the experimental data.