Geothermal Energy Extraction Using a Novel Combined Coaxial and U-Shaped Closed-Loop System

Abstract

In the present study, a novel combined coaxial and U-shaped closed-loop system was proposed to enhance the thermal performance of the U-shaped geothermal system. The proposed geothermal system consists of two separate energy extraction units, called primary and secondary systems. The primary system consists of an insulated U-shaped tube heat exchanger. In order to extract more thermal energy, a coaxial double-pipe heat exchanger was coupled to the primary system as the secondary system. A conjugate heat transfer (CHT) module incorporating a k-ε turbulent model was employed to simulate the heat extraction and fluid flow within the proposed system. Further, the study extended to analyse the effect of various individual parameters on the thermal performance of the proposed closed-loop system. The results depicted that the proposed system can extract up to 42% higher thermal power than that of an insulated U-shaped tube heat exchanger. Further, the coefficient of performance (COP) of the combined system ranges between 1.03 to 1.22 depending upon the operational parameters. Overall, the proposed geothermal system effectively utilized both the heat loss from the hot primary fluid as well as the thermal energy available in the rock surrounding the insulation of U-shaped geothermal heat exchangers. The outcomes of the present study may be productive for researchers and industries interested in the extraction of clean and renewable energy.