THERMAL PERFORMANCE EVALUATION OF GROUND HEAT EXCHANGERS WITH NANO FLUIDS AND DIFFERENT PIPING SYSTEMS: EXPERIMENTAL STUDY IN IRAQ
Keywords:
Water Ground heat exchanger, Nano fluid, piping systems, Under Ground Thermal energy, Heating performance, IraqAbstract
This study presents an advanced experimental evaluation of the thermal and hydraulic performance of a vertical Ground Heat Exchanger (GHE) system designed for heating and cooling applications. The field experiments were conducted in Al-Shirqat district, Saladin Governorate, Iraq, a region characterized by specific soil properties and climatic conditions that represent a significant challenge for renewable energy systems. The system was implemented using two separate metal networks; the first consists of copper pipes and the second of aluminum pipes, with each network installed at a total length of 30 meters at a depth of 3.5 meters. This configuration aims to conduct a precise physical comparison of the thermal conductivity efficiency of each metal with the surrounding medium and evaluate their environmental durability. The research results indicated that copper pipes slightly outperformed aluminum by approximately 2–3%, suggesting concluding that soil thermal resistance is the dominant factor. To enhance efficiency, a Nano fluid was employed, leading to an increase in heat transfer rate by 19% for copper and 12% for aluminum, due to improved thermo physical properties and nanoparticle dispersion, despite the flow regime remaining within the Laminar phase according to analytical calculations (Re = 1231). In-depth analysis demonstrated that the structural innovation of the "Combined System" (hybrid connection) with the Nano fluid was the most effective method. At an optimal flow rate of 1 L/min, the system reached its peak performance with a heat transfer rate (Q) of 821.24 W, effectively covering a significant portion of the 900 W design load, while achieving the highest Coefficient of Performance (COP) of 6.84. Conversely, increasing the flow rate to 2 L/min led to a marked decline in thermal feasibility; the high velocity reduced the residence time, causing the temperature difference ( ∆T) to drop to only 2.7 °C, while friction losses surged beyond 3600 Pa. The study concludes that operating the system at 1 L/min represents the "Optimal Operating Condition," ensuring a precise balance between maximum thermal absorption and minimized pumping costs, providing a pioneering engineering model for sustainable energy applications in harsh environments.
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