This paper presents an experimental investigation of three triply periodic minimal surface based gyroid sheet samples with varying cell size and porosity. The thermal and hydraulic performances of the samples were analyzed and compared under different design parameters (cell size and porosity). The experimental results revealed that the gyroid structures achieved uniform temperature distribution, allowing for the disruption of the thermal boundary layer and enhancing heat transfer. The gyroid structure characterised by small cell size and low porosity (Gyroid-A: 15 mm/0.75) dissipates more heat from its surface compared to the structure with large cell size and high porosity (Gyroid-C: 32 mm/0.9). Gyroid-A also exhibits higher Nusselt number and convection heat transfer coefficient with 51.5 % increase as compared to Gyroid-C. In addition, Gyroid-A has the lowest thermal resistance (with maximum of 45.4 % reduction) and the highest specific pressure drop as compared to the other gyroid structures. Moreover, Gyroid-A exhibits lower total entropy generation (75.9 % reduction) and higher overall performance evaluation criteria, PEC (more efficient heat transfer in relation to flow resistance) as compared to Gyroid-C. The experimental results of this work is important for the design and optimization of heat transfer applications utilizing gyroid sheet structures for effective heat dissipation.