Numerical Simulation of Nanofluid Suspensions in a Geothermal Heat Exchanger

Xiao-Hui Sun, Hongbin Yan, Mehrdad Massoudi, Zhi-Hua Chen and Wei-Tao Wu
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Xiao-Hui Sun: School of Mechanical Engineering, Nanjing University of Science and Technology, Nanjing 210094, China
Hongbin Yan: School of Marine Science and Technology, Northwestern Polytechnical University, Xi’an 710072, China
Mehrdad Massoudi: U.S. Department of Energy, National Energy Technology Laboratory (NETL), Pittsburgh, PA 15236-0940, USA
Zhi-Hua Chen: Key Laboratory of Transient Physics, Nanjing University of Science & Technology, Nanjing 210094, China
Wei-Tao Wu: School of Mechanical Engineering, Nanjing University of Science and Technology, Nanjing 210094, China

Energies, 2018, vol. 11, issue 4, 1-18

Abstract: It has been shown that using nanofluids as heat carrier fluids enhances the conductive and convective heat transfer of geothermal heat exchangers. In this paper, we study the stability of nanofluids in a geothermal exchanger by numerically simulating nanoparticle sedimentation during a shut-down process. The nanofluid suspension is modeled as a non-linear complex fluid; the nanoparticle migration is modeled by a particle flux model, which includes the effects of Brownian motion, gravity, turbulent eddy diffusivity, etc. The numerical results indicate that when the fluid is static, the nanoparticle accumulation appears to be near the bottom borehole after many hours of sedimentation. The accumulated particles can be removed by the fluid flow at a relatively high velocity. These observations indicate good suspension stability of the nanofluids, ensuring the operational reliability of the heat exchanger. The numerical results also indicate that a pulsed flow and optimized geometry of the bottom borehole can potentially improve the suspension stability of the nanofluids further.

Keywords: nanofluids; geothermal heat exchanger; suspension stability; pulsed flow; nanoparticle accumulation (search for similar items in EconPapers)
JEL-codes: Q Q0 Q4 Q40 Q41 Q42 Q43 Q47 Q48 Q49 (search for similar items in EconPapers)
Date: 2018
References: View references in EconPapers View complete reference list from CitEc
Citations: View citations in EconPapers (15)

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