Title : Heat transfer enhancement in gas pipes using helmholtz resonators: A numerical study
Abstract:
While Helmholtz resonators have long been employed for controlling acoustic phenomena, their potential to enhance mixing and heat transfer has remained largely unexplored. This study investigates the impact of Helmholtz resonators on mixing and heat transfer within a two-dimensional channel containing multiple sets of deep cavities. To achieve this, Fluent 2022 R2 software was employed to solve the unsteady Reynolds-Averaged Navier-Stokes (URANS) equations with the k-ε turbulence model. In the first part of the study, two gases with different temperatures and identical velocities were considered at the channel's inlet, focusing on mixing behavior induced by the Helmholtz resonators. The uniformity of temperature distribution at the outlet served as the parameter for evaluating mixing efficiency. In the second part, a gas with a uniform temperature and velocity distribution was introduced at the channel's inlet, and a constant heat flux was applied to the channel walls. In this case, the time-averaged Nusselt number was calculated to evaluate heat transfer along the channel walls. The first part systematically studied the impact of cavity depth, width, number, and spacing on mixing. The second part focused on varying the number of paired cavities to assess its effect on heat transfer. The numerical findings illustrated the crucial role of Helmholtz resonators in increasing both mixing and heat transfer in the channel. The maximum mixing efficiency occurred for the configuration featuring three paired cavities, in which the temperature difference between the two gases at the outlet decreased by a substantial 87% compared to the inlet. However, the highest level of heat transfer was for the single paired cavity, exhibiting a 200% heat transfer enhancement.
Audience Takeaway Notes:
- We will address the challenges associated with the numerical simulation of unsteady flow in Helmholtz resonators, as well as the necessary boundary conditions to accurately model the physics of the resulting compressible oscillatory flow in channels and deep cavities.
- This study introduces a novel approach to enhance heat transfer in pipes and channels, ubiquitous across industries including power generation, aerospace, electronics cooling, HVAC, and refrigeration, as well as chemical and process industries.
- The proposed method for enhancing heat transfer is fully functional and offers a straightforward, cost-effective implementation.
- We also present instantaneous flow structures, providing insights into the flow dynamics within the channel. This understanding aids in elucidating the mechanisms behind increased mixing, offering potential for innovative approaches to combustion chamber design.
