Title: Development of a 2D numerical transient model to study geothermal coaxial borehole field heat exchangers

Authors: Mohamed Salah Saadi; Rabah Gomri

Addresses: Department of Génie Climatique, Laboratoire de Génie Climatique, Université Mentouri Constantine 1, 25000, Constantine, Algeria ' Department of Génie Climatique, Laboratoire de Génie Climatique, Université Mentouri Constantine 1, 25000, Constantine, Algeria

Abstract: A numerical 2D transient model to study geothermal coaxial borehole field heat exchangers under thermal interferences has been built and implanted in MATLAB; it has been compared against two analytical solutions and the numerical code COMSOL where the results has been found identical. A coaxial borehole heat exchanger has been selected regarding to its better performances. The results show that porous grounds are more suitable for these systems, when porosity is 0% the thermal load decreases by 15.725% than the case where porosity is 45%; also, it has been found that after occurrence of phase change in the saturated sub-ground, effective thermal properties changes in a way to make the withdrawn thermal load decreases in a more intense manner, it reduces by 5.36% than the case where the process is not accounted for and this is during the last 843 h since the process start; the last part of the thermal investigations yields that the underground-water flow is favoured for the system performance.

Keywords: geothermal energy; axial effects; thermal interferences; phase change; porosity; under ground-water flow; finite volume method.

DOI: 10.1504/IJRET.2019.102859

International Journal of Renewable Energy Technology, 2019 Vol.10 No.4, pp.348 - 373

Received: 25 Sep 2018
Accepted: 06 Mar 2019
Published online: 08 Oct 2019 *

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