Design and optimization of a downhole coaxial heat exchanger for an enhanced geothermal system (EGS)

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dc.contributor.author Yekoladio, Peni Junior
dc.contributor.upauthor Bello-Ochende, Tunde
dc.contributor.upauthor Meyer, Josua P.
dc.date.accessioned 2014-05-12T10:59:31Z
dc.date.available 2014-05-12T10:59:31Z
dc.date.issued 2013
dc.description.abstract The present study considers the design, performance analysis and optimization of a downhole coaxial heat exchanger for an enhanced geothermal system (EGS). The optimum mass flow rate of the geothermal fluid for minimum pumping power and maximum extracted heat energy was determined. In addition, the coaxial pipes of the downhole heat exchanger were sized based on the optimum geothermal mass flow rate and steady-state operation. Transient effect or time-dependent cooling of the Earth underground, and the optimum amount and size of perforations at the inner pipe entrance region to regulate the flow of the geothermal fluid were disregarded to simplify the analysis. The paper consists of an analytical and numerical thermodynamic optimization of a downhole coaxial heat exchanger used to extract the maximum possible energy from the Earth’s deep underground (2 km and deeper below the surface) for direct usage, and subject to a nearly linear increase in geothermal gradient with depth. The thermodynamic optimization process and entropy generation minimization (EGM) analysis were performed to minimize heat transfer and fluid friction irreversibilities. An optimum diameter ratio of the coaxial pipes for minimum pressure drop in both limits of the fully turbulent and laminar fullydeveloped flow regime was determined and observed to be nearly the same irrespective of the flow regime. Furthermore, an optimum geothermal mass flow rate and an optimum geometry of the downhole coaxial heat exchanger were determined for maximum net power output. Conducting an energetic and exergetic analysis to evaluate the performance of binary power cycle, higher Earth’s temperature gradient and lower geofluid rejection temperatures were observed to yield maximum firstand second-law efficiencies. en_US
dc.description.librarian hb2014 en_US
dc.description.uri http://www.elsevier.com/locate/renene en_US
dc.identifier.citation Yekoladio, PJ, Bello-Ochende, T & Meyer, JP 2013, 'Design and optimization of a downhole coaxial heat exchanger for an enhanced geothermal system (EGS)', Renewable Energy, vol. 55, no. 7, pp. 128-137. en_US
dc.identifier.issn 0960-1481 (print)
dc.identifier.issn 1879-0682 (online)
dc.identifier.other /10.1016/j.renene.2012.11.03
dc.identifier.uri http://hdl.handle.net/2263/39771
dc.language.iso en en_US
dc.publisher Elsevier en_US
dc.rights © 2012 Elsevier Ltd. All rights reserved.Notice : this is the author’s version of a work that was accepted for publication in Renewable Energy. Changes resulting from the publishing process, such as peer review, editing, corrections, structural formatting, and other quality control mechanisms may not be reflected in this document. Changes may have been made to this work since it was submitted for publication. A definitive version was subsequently published in Renewable Energy, vol. 55, no. 7, pp.128-137, 2013. doi : 10.1016/j.renene.2012.11.03 en_US
dc.subject Exergy analysis en_US
dc.subject Downhole coaxial heat exchanger en_US
dc.subject Binary cycle en_US
dc.subject Enhanced geothermal system (EGS) en_US
dc.subject Entropy generation minimization (EGM) en_US
dc.title Design and optimization of a downhole coaxial heat exchanger for an enhanced geothermal system (EGS) en_US
dc.type Postprint Article en_US


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