Physical Based Model of Air-Cooled Thermosyphon

This study developed a numerical model applicable to air-cooled thermosyphon. The thermosyphon consisted of flat tubes with multiport microchannels in a parallel configuration. The flat tubes were embedded in a heated block at the evaporator, and only one side of the heating block was attached to the heat source. The air-cooled condenser was covered with louver fins with airflow passing through. The model incorporated various heat transfer mechanisms, including falling film condensation and evaporation, nucleate boiling, conduction, and thermal spreading. The analysis was conducted with frontal velocity across the condenser ranging from 0.5 m/s to 4 m/s, filling ratios of 20% to 60%, the heating power of 110 W to 330 W, and geometric influences of thermosyphon such as heater and fin. The result reveals that the total thermal resistance decreases with the rise of power and air flow rate, which spans from 0.03 to 0.05 K/W. For further elaboration of the prediction, it is found that the thermal resistance decreases with a decreasing filling ratio. The pressure drop increases with a rising air flow rate ranging from 10 Pa to 120 Pa. Besides, the power variation imposes a negligible effect on the airside pressure drop. Finally, the current model gives uniform underprediction on the experimental data, and an optimal filling ratio is presented. The pressure drop prediction reveals a low prediction error of 7%.