Noninvasive interrogation of local flow phenomena in twisted tape swirled flow via positron emission particle tracking (PEPT)

• Published in: Nuclear engineering and design 2022-02, Vol.387 (C), p.111601, Article 111601
• Main Authors: Wiggins, Cody S., Carasik, Lane B., Ruggles, Arthur E.
• Format: Article
• Language: English
• Subjects: Diameters; Flow measurement; Fluid flow; Heat exchangers; Heat transfer; Heat transfer enhancement; Heat transport; Inserts; Interrogation; Local flow; Measurement techniques; Nuclear heat; Particle tracking; Positron emission; Positron Emission Particle Tracking; Radioactive tracers; Secondary flow; Swirl flow; Turbulent flow; Twisted tape; Velocity; Velocity distribution; Vortices; Vorticity
• ISSN: 0029-5493; 1872-759X
• DOI: 10.1016/j.nucengdes.2021.111601

•Positron emission particle tracking (PEPT) is used to measure flow in twisted tape swirled flow.•The utility of PEPT for measurements in engineering systems lacking optical access is discussed and demonstrated.•Measurements confirm the presence of secondary vortices, indicating the possibility for local flow stagnation and hot spots in heat transfer systems.•PEPT is seen to be a useful tool for code validation and systems design for the nuclear fission and fusion communities. Twisted tape inserts are often used to enhance the performance of heat exchangers. Previous simulations suggest the existence of secondary vortices and modified axial velocity profiles in these swirled flows, with only limited experimental evidence for these predictions. In this work, positron emission particle tracking (PEPT) is used to interrogate turbulent twisted tape swirl flow in a pipe. PEPT is a noninvasive, radiotracer based flow measurement technique that does not require optical access, making it suitable for measurements in a number of engineering flow systems. The existence of the modified velocity profile and secondary flows is confirmed using PEPT, and flow is seen to still be developing 20 diameters downstream of the twisted channel entrance. Secondary vortices are further confirmed by the presence of increased vorticity in these regions, and turbulent fluctuations are seen to increase in magnitude near these flow structures. These results are in line with predictions and point to possible regions of reduced heat transfer and hot spots in twisted tape based heat exchangers. Suggestions are made for future experiments to investigate heated flows, utilizing the ability of PEPT to image flows in opaque systems for validating simulation of flows in engineering equipment, such as nuclear heat transport equipment.