Abstract
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.
| Original language | English |
|---|---|
| Article number | 111601 |
| Journal | Nuclear Engineering and Design |
| Volume | 387 |
| DOIs | |
| State | Published - Feb 2022 |
| Externally published | Yes |
Funding
The authors are grateful to Nitant Patel, Roque Santos, and Matthew Herald for their assistance in collecting data. We thank Alan Stuckey and Jon Wall of the University of Tennessee Graduate School of Medicine for their time and the use of their facilities for radiotracer activation. Emily Clark and Arnold Lumsdaine performed simulations of twisted tape swirl flow that revealed secondary flow phenomena and suggested this work as the start of a validation exercise. Financial support for this work was provided by the National Nuclear Security Administration Stewardship Sciences Academic Alliances award DE-NA0001983. This material is based on work supported under a Nuclear Energy University Program Integrated University Program graduate fellowship.
| Funders | Funder number |
|---|---|
| University of Tennessee Graduate School of Medicine | |
| National Nuclear Security Administration | DE-NA0001983 |
Keywords
- Flow measurement
- Heat transfer enhancement
- Positron Emission Particle Tracking
- Swirl flow
- Twisted tape