Session: 06-04: Heat Transfer in CSP Applications 2

Paper Number: 128357

128357 - Enhancement of Heat Transfer in Solar Air Heater With Semi-Circular Shaped Transverse Rib. 

Abstract: 

Heat transfer devices are widely used in various industrial and home applications for heat conversion and recovery. Artificial roughness in the form of repetitive ribs on a surface is employed to enhance heat transfer rates. Solar technologies have made significant advancements, and while efficiency varies among different technologies, some solar panels today can convert sunlight into electricity with relatively high efficiency. The efficiency of solar panels is commonly measured as a percentage of sunlight that gets converted into usable electricity. The use of a solar air heater contributes to energy conservation by utilizing renewable solar energy to heat air for various purposes, reducing the need for conventional energy sources. These systems are often employed in residential, commercial, or industrial settings where space heating is required. The current work aims to develop a numerical model to predict the fluid flow and heat transfer characteristics of a solar air heater using semi-circular-sectioned transverse rib roughness.  Computational fluid dynamics (CFD) simulations in solar air heaters with semi-circular transverse ribs were used to study the fluid flow and heat transmission characteristics of the system. The heat transfer and fluid flow characteristics of fully developed turbulent flow were examined in a rectangular duct with repeated transverse semi-circular sectioned rib roughness on the absorber plate. Once a numerical solution was completed using the commercial program Fluent ANSYS 16, the Dittus-Boelter correlation was used to validate the results. The numerical study was conducted at constant relative roughness height (e/D = 0.042), heat flux (1000 W/m2), Reynolds number (3800–18,000), and relative roughness pitch (between 7.14 and 17.86). The semi-circular transverse rib roughened duct with specific geometrical parameters, P/e = 10.71 and e/D = 0.042, provided the best thermo-hydraulic performance within the examined range of parameters. Within this optimum configuration, the maximum thermo-hydraulic performance parameter was found to be 1.7328 at Reynolds number 15,000. hese trends are associated with the interactions between the fluid flow and the roughened surfaces within the solar air heater. As the flow Reynolds number decreases, the flow becomes more laminar, and the impact of the roughened surface on heat transfer becomes more significant. Additionally, reducing the relative roughness pitch may result in increased interactions between the fluid and the roughness elements, affecting both heat transfer and friction.The outcomes of this research can be applied to the development of more efficient and cost-effective solar air heaters, which can contribute to sustainable and renewable energy solutions for space heating and other thermal applications.

Keywords: solar air heater; Nusselt number; friction factor; semi-circular rib; CFD

Presenting Author: Mebratu Assaye Mengistu Academia sinica

Presenting Author Biography: Mebratu Assaye Mengistu
email: mebriye44@gmail.com, Phone +886 978 904 321
PhD Student in sustainable chemical science and technology program, institute of Academia sinica, Taipei Taiwan

Authors:

Muluken Biadgelegn Wollele Academia Sinica
Mebratu Assaye Mengistu Academia sinica