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Experimental Investigation Into the Performance of Pulsating Heat Pipe Using Nano-Encapsulated Phase Change Material Along with Rgo Nanosheets

Mohammadi, Omid | 2019

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  1. Type of Document: M.Sc. Thesis
  2. Language: Farsi
  3. Document No: 51928 (08)
  4. University: Sharif University of Technology
  5. Department: Mechanical Engineering
  6. Advisor(s): Shafii, Mohammad Behshad; Rezaee Shirin-Abadi, Abbas
  7. Abstract:
  8. Heat pipes are useful devices in heat transfer, renewable energies and cooling systems in particular. According to various application of this systems in different industries, performance improvement of this devices has gained much importance. Working fluid is one of the effective factors on pulsating heat pipes. Since heat transfer in PHPs is natural convection and two-phase, specific heat and thermal conductivity of working fluid have an important role in the performance of pulsating heat pipes. In the present study, the effect of using nano-encapsulated PCM along with reduced graphene oxid (RGO) dispersed in water and their mixture as working fluid has on the performance of PHPs has been investigated, experimentally. Nano-encapsulated PCM at three concentrations of 5, 10 and 20 g/lit and RGO nanosheets at three concentrations of 0.3, 0.6 and 1.2 g/lit were investigated. In order to evaluate the relative effect of specific heat and thermal conductivity, 5 various concentration of the mixture of nanoencapsulated pcm and RGO nanosheets including 0.3-5, 0.3-10, 0.3-20, 0.6-10 and 1.2-10 were prepared and examined. In order to choose the mixture concentrations, one of the additives was chosen at its optimum concentration. All the experiments were conducted in the filling ratio of 50% and vertical orientation. Using nanoencapsulated PCM due to the phase change in constant temperature prevents temperature increment. Therefore it increases effective specific heat. On the other hand, RGO nanosheets due to their high thermal conductivity, lead to increase thermal conductivity of working fluid. Results showed that using the mixture of materials leads to 38% decrease in thermal resistance and improvement in the performance of PHPs. The effect of using nanoencapsulated PCM was more than RGO nanosheets which is attributed to noticeable increment of thermal conductivity in comparison with negligible increment of effective specific heat. In fact, the improvement reason in case of nanocapsules is incresement of mixing. The optimum concentrations for nanocapsules, nanosheets and their mixture are 10, 0.3 and 0.3-5 g/lit, respectively
  9. Keywords:
  10. Pulsating Heat Pipe ; Phase Change Material (PCMs) ; Nano-Encapsulated Phase Change Paraffin ; Carbon Nanosheets ; Nanofluid ; Reduced Graphene Oxide

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