Borehole heat exchanger with nanofluids as heat carrier

Results show that copper is characterized by highest borehole thermal resistance reduction, that reaches the value of about 3.8%, in comparison to that of base fluid, when nanoparticles volumetric concentration is 1%, but also the second one highest pressure drop. In this case, the cost of copper-based nanofluid is about 10 € m−1, i.e. about 12% of total cost of BoreHole Heat Exchange - Ground Source Heat Pump system.