Effect Of Nanofluids On The Heat Performance Of Heat Pipe

With the increasing attention to the energy conservation and environmental protection all over the globe, coupled with the rapid development of science and technology, many devices and electronic components tend to be miniaturized, while their energy demand are much higher than their predecessors. As a result, the thermal density of devices and electronic components increased dramatically. For many devices, a prerequisite for the optimal and reliable operation is the heat rejection, Therefore the heat dissipation of electronic equipment is particularly prominent. While for some special cases, the heat pipe using traditional working fluids can hardly meet the challenge of increasing demand of heat removal. As we know, a heat pipe depends on the phase change of its internal working fluid to conduct heat, therefore the performance of working fluid is very important for a heat pipe to transfer heat of. As an innovative technology, nanofluid can be used to improve the heat transfer of a heat pipe. In recent years, researchers have begun to put this new fluid into a heat pipe, in order to improve the heat transfer performance of the heat pipe.This work employed nanofluid as the working fluid in the gravity heat pipe without wick. The experiments were carried out to explore the heat transfer enhancement of the gravity heat pipe with nanofluid in it. Some glass heat pipes were made to observe the flow pattern of the working fluid at the earlier stage of experiment. In this work, effects of the type of working fluid, filling ratio and heating temperature on the efficiency of heat pipe were researched. The thermal performance of different heat pipes was also compared. The working fluids used in the experiments included Al2O3, CuO and TiO2 nanofluids and DI water.The experimental results showed that the start-up performance and the surface temperature of the heat pipe condenser section for a gravity heat pipe were greatly improved after nanofluid was used under the same working conditions. Accordingly, the average temperature difference between the evaporating and condensing parts in the heat pipe was decreased by adding nanoparticles in the based fluid.The thermal performance of the gravity heat pipe increased with increase in the filling ratio firstly and then decreased apparently, which indicated that an optimal filling ratio existed. The optimal filling ratio of working fluid in the heat pipe was about 30% and 40% for different nanofluids and deionized water, respectively, under the defined experimental conditions.Comparing with the heat pipe filled with deionized water, it can be found that the heat transfer coefficient of the heat pipe filled with nanofluid was higher than that of the heat pipe filled with deionized water, while the thermal resistance of the former was lower than that of the later.According to the experimental data, we can know that the nanofluid could increase the heat transfer coefficient and improve the thermal performance of the gravity heat pipe significantly.