Heat Transfer, Pressure Drop, Flow Structure, and Exergy Destruction Through Inclined Corrugated Tube With Air Injection

ABSTRACT

Gas–liquid two‐phase flow is one of the most complex types of flow in fluid dynamics. This kind of flow is highly sensitive, and changes in the flow pattern can result even from minor geometrical variations, making it important to conduct experimental investigations in which the effects of geometric changes are studied. Circumferentially corrugated tubes are of widespread interest in the thermal industry, where the occurrence of gas/liquid two‐phase flow is inevitable. This research presents experimental results on how air injection affects an enhanced tube installed at an incline. The tube had uniform circumferential corrugations. Three inclination angles were studied: 15°, 30°, and 45°. A constant heat flux was applied to the tube, and the flow direction was upward. Four different water superficial Re numbers (5580, 11160, 16740, and 22320) were tested for each inclination angle. In addition, four air superficial Re numbers of (138, 420, 690, and 975) were examined for each water flow rate. The results showed that, within the scope of the study, the flow regime in the corrugated tube was predominantly wavy‐slug flow. Increasing the tube inclination from 15° to 45° led to approximately a 32% rise in the Nusselt number and a 62% rise in pressure drop. These increases were observed at a 45° inclination with air and water superficial Re of 975 and 22320, respectively. Also, the maximum Nu number ratio (Nu _tp /Nu _sp ) was found to be 26% (heat transfer augmentation) and was seen at the tube with 45° and at the Re _sg of 975 Re _sl 22320. The maximum dimensionless exergy destruction value occurred at the 45° inclination, specifically at a water Re _sl of 55820 and an air Re _sg of 975, where it reached 0.00063.