A novel caudal-fin-inspired hourglass-shaped self-agitator for air-side heat transfer enhancement in plate-fin heat exchanger

• Published in: Energy conversion and management Vol. 187; pp. 297 - 315
• Main Authors: Li, Kuojiang, Wang, Sheng, Ke, Zhaoqing, Chen, Chung-Lung
• Format: Journal Article
• Language: English
• Published: Oxford Elsevier Ltd 01.05.2019; Elsevier Science Ltd
• Subjects: Aerodynamics; Agitation; Agitators; Caudal-fin-inspired hourglass-shaped self-agitator; Flapping; Fluid dynamics; Fluid flow; Fluid-structure interaction; Friction factor; Heat exchangers; Heat transfer; Heat transfer enhancement; High speed cameras; Kinetic energy; Mutual coupling; Nusselt number; Parameters; Particle image velocimetry; PIV measurements; Plate-fin heat exchanger; Plate-fin heat exchangers; Plates (structural members); Pressure drop; Reynolds number; Strain; Tandem configuration; Velocity measurement; Vibration; Working conditions; Heat transfer enhancement; Plate-fin heat exchanger; PIV measurements; Caudal-fin-inspired hourglass-shaped self-agitator; Fluid-structure interaction
• ISSN: 0196-8904; 1879-2227
• DOI: 10.1016/j.enconman.2019.03.048

•Caudal-fin inspired hourglass-shaped self-agitators installed in heated plate-fin channels are experimentally studied.•The vibration motion and vortex dynamics are investigated.•Intensive vortices generated by agitator have a good mixing performance.•The thermal-hydraulic performance is enhanced by caudal-fin inspired hourglass-shaped self-agitators. A novel caudal-fin-inspired hourglass-shaped self-agitator installed inside a plate-fin heat exchanger has been experimentally investigated to characterize its thermo-hydraulic performance. Because of fluid-structure interaction between the air and the caudal-fin-inspired hourglass-shaped self-agitator, there is periodic conversion between fluid kinetic energy and elastic strain energy. Vortices generated by the self-sustained vibration of the self-agitator enhance flow mixing and thus heat transfer performance. Experiments were conducted at a wide range of Reynolds numbers from 400 to 10,000, which covered the laminar-transitional-turbulent regime. Experimental correlations of pressure drop as a function of a dimension parameter, friction factor, and Nusselt number have been proposed. Mutual coupling motions and effects of multiple-row flapping caudal-fin-inspired hourglass-shaped self-agitators in parallel and tandem configurations were studied by using a high-speed camera. A stereo Particle Image Velocimetry system was used to conduct detailed flow field measurements to quantify the flow mixing level. Parameter studies for the stream-wise distance (i.e., the pitch) between the neighboring caudal-fin-inspired hourglass-shaped self-agitators have been investigated to exploit the best performance of the heat exchanger equipped with caudal-fin-inspired hourglass-shaped self-agitators. For the chosen plate-fin heat exchanger and assigned working conditions, the best heat transfer performance was obtained with twelve-row self-agitators with a pitch of 12.5 mm, which caused a 200% increase in the Nusselt number over the clean channel at the same Reynolds number. However, the best overall performance was obtained with six-row self-agitators with a pitch of 25 mm, which caused a 68% enhancement in thermal-hydraulic characteristics compared to the clean channel at the same Reynolds number.