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Preparation of Nano Fluid from Carbon Nanostructures to Enhance Heat Transfer in Cooling Towers

Askari, Saeed | 2015

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  1. Type of Document: M.Sc. Thesis
  2. Language: Farsi
  3. Document No: 47620 (06)
  4. University: Sharif University of Technology
  5. Department: Chemical and Petroleum Engineering
  6. Advisor(s): Syfkordi, Ali Akbar; Lotfi, Roghayeh
  7. Abstract:
  8. In this paper, carbon structures such as multi wall carbon nano tubes, graphene and hybrid graphene-iron oxide, for utilisation in wet cooling towers in order to improve heat transfer are being discussed. All synthesized nanoparticles are prepared by chemical vapour deposition and wet chemical methods. Nature and structure of the created particles is also being examined by using X-Ray diffraction, transmission electron microscope and scanning electron microscope. The water used in this research is a kind of brine water, currently being used in industrial cooling towers at oil-rich regions of southern Iran. Performing the ICP test on the available water and by exact determination of its minerals we were able to produce a type of water similar to the one mentioned. To have stable nanofluids Gum Arab, Twenn80, Triton X100, CTAB and Terpolymer has been used as surfactants. Moreover, rheological properties such as viscosity, density and surface tension are being discussed. Results are showing that the density of the nanofluids is small and negligible but viscosity of them increases with increase in particles concentration. However, in lower particles concentration, the increase of viscosity is also negligible. In order to study the impact of nanoparticles on the thermal conductivity, KD2Pro device has been used as well as a well-designed laboratory system with wall by constant heat flux in order to study their impact on the convection heat transfer coefficient. An increase of 19.5% 14% 34% and 30% in thermal conductivity at 40˚C and a improve of 15% , 10 % , 18 % and 14% in convection heat transfer coefficient has been observed for MWNTs, FMWNTs, Graphene and hybrid Graphene-iron oxide, respectively. In order to discuss the impact of the nanofluids on functionality of the cooling towers a laboratory system has been designed, in which, the changes in functionality of the cooling tower are determined by the parameters such as tower characterisation (NTU), inlet and outlet water temperature gradient and tower efficiency at three inlet water temperature (33˚C 40˚C 45˚C) and three ware to air flow rate. Using the nanofluids also led to a reduction of 10%, 9.7%, 19.4% and 25.9% in the water consumption being used for MWNTs, FMWNTs, Graphene and hybrid Graphene-iron oxide, respectively. The highest improvement was related to the functionality of the tower in the lowest water to air flow rate 0.85 and the 45˚C temperature of the incoming hot fluid to the tower. The improvement in the tower characterisation factor was 27.3%, 18.3%, 16.6% and 14% for MWNTs, FMWNTs, Graphene and hybrid Graphene-iron oxide, respectively
  9. Keywords:
  10. Nanofluid ; Thermal Conductivity ; Multi-Walled Carbon Nanotube ; Cooling Tower ; Graphene-Iron Oxide ; Convection Coefficient

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