Heat transfer of aqueous suspensions of carbon nanotubes (CNT nanofluids) |
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| Affiliation: | 1. School of Aeronautic Science and Engineering, Beihang University, Beijing, PR China;2. Mechanical Engineering Department, Prince Mohammad Endowment for Nanoscience and Technology, Prince Mohammad Bin Fahd University, Al-Khobar 31952, Saudi Arabia;3. RAK Research and Innovation Center, American University of Ras Al Khaimah, P.O. Box 10021, Ras Al Khaimah, United Arab Emirates;4. School of Chemical and Process Engineering, University of Leeds, Leeds, UK;1. Korea Institute of Geoscience and Mineral Resources, 124 Gwahak-ro, Yuseong-gu, Daejeon 34132, Republic of Korea;2. College of Civil Engineering, Nanjing Tech University, 30 Puzhu Road(S), Nanjing, Jiangsu Province 211800, China;3. School of Civil Engineering, Chungbuk National University, 1 Chungdae-ro, Seowon-gu, Cheongju, Chungbuk 28644, Republic of Korea;4. Department of Civil and Environmental Engineering, Korea Advanced Institute of Science and Technology (KAIST), 291 Daehak-ro, Yuseong-gu, Daejeon 34141, Republic of Korea;5. Applied Science Research Institute, Korea Advanced Institute of Science and Technology (KAIST), 291 Daehak-ro, Yuseong-gu, Daejeon 34141, Republic of Korea;1. Department of Engineering Systems and Management (ESM), Masdar Institute of Science and Technology, Abu Dhabi, United Arab Emirates;2. Department of Mechanical Engineering, Faculty of Engineering, University of Malaya, 50603 Kuala Lumpur, Malaysia;3. UM Power Energy Dedicated Advanced Centre (UMPEDAC), Level 4, Wisma R&D, University of Malaya, 50603 Kuala Lumpur, Malaysia;4. Centre of Research Excellence in Renewable Energy (CoRE-RE), King Fahd University of Petroleum and Minerals (KFUPM), Dhahran, 31261, Saudi Arabia;5. Department of Mechanical & Aerospace Engineering, Monash University, Clayton, Victoria, 3168, Australia;1. Institute of Thermal Science and Power Systems, School of Energy Engineering, Zhejiang University, Hangzhou 310027, People’s Republic of China;2. State Key Laboratory of Clean Energy Utilization, Zhejiang University, Hangzhou 310027, People’s Republic of China;3. Key Laboratory of Refrigeration and Cryogenic Technology of Zhejiang Province, Zhejiang University, Hangzhou 310027, People’s Republic of China |
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| Abstract: | This paper is mainly concerned about the heat transfer behaviour of aqueous suspensions of multi-walled carbon nanotubes (CNT nanofluids) flowing through a horizontal tube. Significant enhancement of the convective heat transfer is observed and the enhancement depends on the flow conditions (Reynolds number, Re), CNT concentration and the pH, with the effect of pH smallest. Given other conditions, the enhancement is a function of axial distance from the inlet, increasing first, reaching a maximum, and then decreasing with increasing axial distance. The axial position of the maximum enhancement increases with CNT concentration and Re. Given CNT concentration and the pH level, there appears to be a Re above which a big increase in the convective heat transfer coefficient occurs. Such a big increase seems to correspond to the shear thinning behaviour. For nanofluids containing 0.5 wt.% CNTs, the maximum enhancement reaches over 350% at Re = 800, which could not be attributed purely to the enhanced thermal conduction. Particle re-arrangement, shear induced thermal conduction enhancement, reduction of thermal boundary due to the presence of nanoparticles, as well as the very high aspect ratio of CNTs are proposed to be possible mechanisms. |
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