Energy and exergy analysis of a ground source heat pump system with a slinky ground heat exchanger supported by nanofluid

This work contains the experimental analysis results in real environment conditions of the use of Al2O3-based nanofluid (NF) at different concentration ratios (0.1% and 0.2%) in a ground source heat pump (GSHP) system with a slinky ground heat exchanger (GHE). The energetic and exergic efficiencies of the system were investigated with the data obtained from the experimental results of base fluid (ethylene glycol (EG)-water) (EG volumetric ratio 25%) and NF with Al2O3 concentration ratios of 0.1% and 0.2%. The exergetic model is obtained by applying energy and exergy equations for each system component. Exergetic efficiencies of the system components are evaluated separately and their potential for improvement is presented. According to the results of the energetic analysis, the overall system's coefficient of performance (COP) values for the base fluid and NF with concentration ratios of 0.1% and 0.2% were 4.30, 4.38 and 4.34, respectively. These results show that NF contributes to system performance. However, an increase in system performance was not achieved due to the increase in NF concentration; on the contrary, a decrease in performance was observed. Exergetic efficiencies of the system for base fluid and NF with concentration ratios of 0.1% and 0.2% were 88.3%, 89.7% and 89.0%, respectively, for the heat pump unit, while these values were 78.7%, 79.3% and 79.0% for the entire system, respectively. The results show that the usage of NF with low concentration ratios increases the energetic and exergic efficiency of the system.