The primary element of solar thermal energy employment systems for useful heating is the solar air heaters. The present work focuses on the energetic analysis of a mixed-mode corrugated aluminium plate solar air heater (MMCAASH). The absorbing plate is made of a corrugated aluminium alloy plate. The MMCAASH can absorb the energy from the sun and then transfer this energy to the flow over the absorber plate effectively. To determine thermal performance, the experiments were considered for airflow rates of 0.0073 kg/s (free) and 0.015, 0.02 and 0.025 kg/s (forced). The effects of mass flow rates were studied on the temperatures of the aluminium absorber plate, outlet air temperatures, temperature differences, and first law efficiencies of MMCAASH. The maximum temperature differences were 47.8 ℃, 44.7 ℃, 39.1 ℃ and 34.2 ℃ for the flow rates of 0.0073, 0.015, 0.02 and 0.025 kg/s, respectively. The first law efficiencies varied from 18.46 % to 64.74 % for the corresponding flow rates. The results concluded that the thermal efficiency of MMCAASH depended significantly on the radiation from the sun and the rate of mass flow.