Thermal characteristics of air-water two-phase flow in a vertical annularly corrugated tube

This investigation studies the thermal characteristics of a vertical annularly corrugated tube with air/water two-phase flow. The recirculating flow formed in the cavities of the corrugated sections of the tube plays a significant role in improving the heat transfer. Additionally, corrugation should affect the flow and thermal characteristics of the upward non-boiling air/water two-phase flow, which necessitates an investigation of the characteristics of this type of flow. A constant heat flux of 800 W was applied to the tube by means of a heated wire. The inlet, outlet and wall temperatures of the corrugated tube were measured to calculate the heat transfer coefficient of the corrugated tube. Also, a Canon SX530 camera was used for recording the pictures of the two-phase flow. The air and water flow rates were varied in the range of 1 to 5 and 2 to 8 (lit/min), respectively. The results showed that the transition between flow patterns occurs sooner in the corrugated tube. Besides, the size of the bubbles in the corrugated tube is smaller than the in smooth tube. It was revealed that the two-phase flow in the corrugated tube have enhanced thermal characteristics compared to that of the smooth tube.