Experimental and Theoretical Investigation on Thermal Conductivity of Combined Nanofluids

Iranidokht, Vahid | 2012

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  1. Type of Document: M.Sc. Thesis
  2. Language: Farsi
  3. Document No: 43830 (08)
  4. University: Sharif University of Technology
  5. Department: Mechanical Engineering
  6. Advisor(s): Shafii, Mohammad Behshad
  7. Abstract:
  8. Application of nanotechnology in the field of heat transfer has increased recently. The need to increase heat transfer rate yet decrease the size of cooling equipment, brought about lots of attention to thermal properties of Nanofluids. Nanofluid is the suspension of nanometer-sized solid particles in base liquid. Research on convective heat transfer of nanofluids which is only two decades old, shows great potential in increasing heat transfer rate. Although there is a remarkable research on thermal conductivity of Nanofluids, negligible research was conducted on combined Nanofluids . Developed Theory for thermal conductivity of combined nanofluid can be used to modeling the thermal conductivity of human blood. One of the most important applications of these studies could be in modeling and evaluating thermal conductivity of human blood.
    In this dissertation, we firstly studied the effective thermal conductivity of some nanofluid with one particle both theoretically and experimentally. In the next step, to predict increase of effective thermal conductivity of combined nanofluids theoretically a model was proposed based on Brownian motion of nanoparticles. Then an experimental setup was developed to measure effective thermal conductivity of such nanofluid. Contrary to expectations the results showed that thermal conductivity of combined nanofluid is even lower than the thermal conductivity of primary nanofluids. Investigations revealed that Agglomeration of different particles in combined nanofluid was the reason for this unexpected observation. To solve the problem, the idea of creating homonymous electric ion on particles’ surface was proposed. the idea was realized by changing the PH of nanofluid and using the proper surfactant. After the modification experimental results match the theoretical results perfectly. Results showed no significant increase in thermal conductivity of combined nanofluids compared to that of primary nanofluids
  9. Keywords:
  10. Nanofluid ; Brownian motion ; Surfactants ; Combined Nanofluid ; Effective Thermal Conductivity

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