Source:ThinkGeoEnergy – Geothermal Energy News
Original URL:https://www.thinkgeoenergy.com/novel-borehole-heat-exchanger-design-developed-by-itaca-researchers/
A research team from the ITACA institute of the Universitat Politècnica de València in Valencia, Spain, has developed a novel borehole heat exchanger (BHE) design that can improve the efficiency of geothermal heat pump systems.
The findings from the study have been published as a paper, “New trilobular geometry using advanced materials for experimentally validated enhanced heat transfer in shallow geothermal applications,” by Urchueguia et al in the Renewable Energy journal (https://doi.org/10.1016/j.renene.2023.119816).
“This technology constitutes today an efficient and sustainable alternative to conventional air conditioning systems,” said Javier F. Urchueguía, from the Information Technology Research Group against Climate Change (ICTvsCC) of the ITACA Institute of the UPV and author of the paper, together with Borja Badenes, Miguel A. Mateo Pla, Bruno Armengot and Hossein Javadi.
The trilobular configuration
A central element of the novel BHE design is the trilobular geometry of the heat exchanger. This involved the use of three high conductivity satellite pipes which surrounds a low conductivity internal return pipe. According to the researchers’ assessment, this configuration was most promising compared to other BHE designs, including coaxial, single and double U-tubes, spiral, and helical designs.
The schematic of the trilobular design is shown below. he development, design and formulation of this new BHE configuration is currently subject to Intellectual Property Protection (IP) patent
The main advantage of the design is its superior thermal efficiency compared to more traditional systems. This helps reduce installation and operational costs, thereby creating new opportunities for the deployment of geothermal heat pump systems, both for heating and cooling. The proposal also stands out for the use of innovative materials.
“Our work offers a more sustainable and efficient alternative in the design of heating and cooling systems,” added Borja Badenes.
Results of thermal tests
Thermal response tests (TRT) were executed at the Geothermal Laboratory of the Universitat Politècnica de Valencia to validate the performance of the novel BHE design.
Two different trilobular BHEs were tested – one that had expanded graphite as conductive filler, and one that had graphene to improve its thermal conductivity. The performance of the trilobular BHEs were compared to two single-U heat exchanges, one of which was made with standard PE-100 material while the other was made up of advanced plastic and installed with improved grouting.
The experimental findings demonstrated that the trilobular geometry has reduced borehole resistance from value of 0.149 to 0.07 mK/W. This allows for higher injection rate without creating an unsustainable change in ground temperature.
A promising improvement for heating and cooling systems
The study provides some excellent insight on how the performance of geothermal heat pump systems can be improved with heat exchanger design changes and the use of innovative materials. This is particularly crucial at a time when geothermal heat pump systems are considered crucial in decarbonization efforts in cities, and have been showcased to have highly diverse applications.
“These results have important implications for the geothermal energy industry, and offer a promising energy alternative for the future of heating and cooling buildings, contributing to the fight against climate change and the promotion of renewable energies,” concluded Javadi.
Source: ITACA institute of the Universitat Politècnica de València
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