<![CDATA[This study presents an experimental investigation into the effect of graphene metal foam on the heat-transfer performance of a closed-loop geothermal system. The system uses a sealed pipe configuration to circulate a low-temperature working fluid that extracts heat from the subsurface reservoir via conductive heat transfer and transports it to the surface. In this work, the system is modelled using a coaxial heat exchanger heated by an oven to simulate the geothermal reservoir. Two structural specifications of graphene-coated Ni-Fe alloy foam, 85% (90 PPI) and 90% (110 PPI), were employed and tested at a constant flow rate of 0.3 LPM under varying heat source temperatures of 170, 200, and 230 °C. The results show that both foam configurations achieved their highest performance at 230 °C. The overall heat transfer coefficient () reached 749.48 W/m².K for 85% (90 PPI) porosity and 462.78 W/m².K for 90% (110 PPI) porosity, significantly higher than that of a plain tube (103.88 W/m².K). These findings demonstrate that incorporating graphene metal foam, particularly at 85% porosity, effectively enhances heat-transfer performance in closed-loop geothermal systems.]]>
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