| Title | Experiment and Modeling of Heat Extraction from a Cylindrical Saturated Porous Tank Using a Coaxial Open Loop Design |
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| Authors | Chuanshan DAI, Jiashu LI, Fei LI, Jinhua LU, Haiyan LEI |
| Year | 2020 |
| Conference | World Geothermal Congress |
| Keywords | downhole heat exchanger, open loop, lattice Boltzmann method, heat extraction rate |
| Abstract | Finding a clean and efficient way of mining heat from a deep geothermal reservoir is still one of most difficult challenges in geothermal exploration. Up to date, borehole heat exchangers (BHE), downhole coaxial heat exchangers (DCHE), downhole heat exchangers (DHE) can be found in some geothermal direct uses with an advantage of “no water withdrawn but heat onlyâ€. In order to overcome the low heat extraction efficiency for the deep downhole coaxial heat exchanger (DCHE), a downhole coaxial open loop (DCOL) configuration was proposed. In this paper, the heat extraction mechanism for the DCOL was experimentally investigated in a lab scale by accounting the effects of geometrical parameters of the wellbore and inner tube, the hydraulic and thermal properties of the surrounding porous media, and inlet water temperature and flowrate, etc.. In addition, a two dimensional axisymmetric fluid flow and heat transfer model was also established and solved numerically by using lattice Boltzmann method (LBM). An extended Brinkman-Forchheimer-Darcy Whitaker model was adopted for simulating the mixed convection in porous media. The effect of thermal insulating property of the inner tube on heat extraction was also studied. Results show that the configuration of DCOL has a larger heat extraction rate comparing with the closed loop of DCHE. The diameter of the wellbore and circulation flowrate of the loop have also a great influence on its final heat extraction rate. |