Thermal performance analysis of an energy pile with triple helix ground heat exchanger

• Published in: Geothermics 2022-09, Vol.104, p.102459, Article 102459
• Main Authors: Farajollahi, Amir Hamzeh, Asgari, Behrad, Rostami, Mohsen
• Format: Article
• Language: English
• Subjects: Computational fluid dynamics; Computer applications; Design of experiments; Diameters; Energy; Energy pile; Fluid dynamics; Geothermal energy; Geothermal power; Ground source heat pump; Heat; Heat exchangers; Heat pumps; Helix ground heat exchanger; HVAC equipment; Hydrodynamics; Mathematical models; Optimization; Parameter sensitivity; Performance evaluation; Pipes; Renewable energy; Response surface methodology; Soils
• ISSN: 0375-6505; 1879-3576
• DOI: 10.1016/j.geothermics.2022.102459

•A novel triple helix energy pile is presented.•The triple helix ground heat exchanger increases the performance by 24%.•The effect of various design parameters on the performance is investigated.•The pipe thermal interaction plays an important role in the proposed energy pile.•The helix pitch is the most influential parameter. A Ground Source Heat Pump (GSHP) is a renewable energy-based HVAC system that extracts or supplies heat from/to the ground via a Ground Heat Exchanger (GHE). One of the most commonly used types of GHE in GSHP systems is the energy pile. In this realm, the GSHP system with a triple helix energy pile has become the focus of attention. To this aim, a comprehensive three-dimensional transient Computational Fluid Dynamics model of the energy pile with triple helix GHE and the surrounding soil is developed. The effect of several parameters, including helix pitch, helix diameter and pipe diameter, on the thermal performance of the system, is investigated. Simulated cases are chosen using the design of experiments methodology. To evaluate the thermal performance of GSHP, an objective parameter is defined as the ratio of the load provided to the load required by the building. The sensitivity of the objective parameter to the studied parameters and surface response curves are analyzed using the response surface model. Also, the optimization process was implemented to obtain the optimum system. It is demonstrated that, the tiple helix GHE enhance the objective parameter by 24% compared to conventional helix GHE. According to the obtained results, the helix pitch has the greatest impact on GSHP thermal performance. Furthermore, the pipe thermal interaction, in addition to the surface area between GHE pipes and the surrounding soil, plays an important role in thermal performance of GSHP. [Display omitted]