Keywords
winglets, heat transfer, solar air heater, pressure drop, attack angles
Abstract
Solar air heaters (SAHs) offer a sustainable energy solution, but their efficiency in using solar radiation to heat air can be further optimized. Delta winglet vortex generators (WVG) have proven effective in enhancing heat transfer from the SAH absorber plate to the air passing through the SAH, yet a comprehensive understanding of how different WVG arrangements impact both heat transfer and pressure drop is lacking. This research investigates pairs of WVGs in a common flow-up arrangement at various attack angles and Reynolds numbers (Re), aiming to bridge this knowledge gap and guide the improvement of SAH design.
Numerical simulations were conducted using ANSYS FLUENT 2023R2, with the model verified through a mesh independence study followed by comparison to a smooth duct and common flow-down simulations. The simulations employed a 3D, incompressible, steady-state flow model with the RNG k-ε turbulence model for accurate representation of airflow within the SAH.
Key findings demonstrate that the Nusselt Number (Nu) increases with the Re for the common flow-up WVG arrangement. Furthermore, Nu initially increases with an attack angle from 30° to 60° before decreasing from 60° to 90° for Re=3500 and 6500. At higher Re (Re=10000, 13000, 16000), the optimal attack angle for maximizing Nu shifts to 45°. The friction factor (f) demonstrates an initial increase as the attack angle rises from 30° to 60°, followed by a decrease as α continues to increase from 60° to 90°. Notably, a maximum thermal efficiency factor (TEF) of 1.7 was achieved at Re=3500 and an attack angle of 30°, indicating the potential for significant SAH performance improvement using the common flow-up configuration. However, higher TEFs were reported in the literature using pairs of WVGs in common flow-down configurations. These findings highlight the interplay between geometric parameters and flow conditions, providing valuable insights for optimizing SAH design.
Primary Advisor
O. Jianu
Co-Advisor
P. Henshaw
Program Reader
J. Stagner
Degree Name
Master of Science
Department
Mechanical, Automotive and Materials Engineering
Document Type
Major Research Paper
Convocation Year
2024