Paper Contents
Abstract
This paper presents the results of a CFD-based investigation into heat transfer and friction characteristics in rectangular solar air heater ducts equipped with broken double arc-shaped ribs combined with staggered rib pieces. The study considers a rib configuration with a relative gap position of 0.65, a relative staggered rib position of 0.6, a relative staggered rib size of 2.0, an arc angle of 30, and a relative roughness height of 0.043. The relative roughness pitch is varied from 8.0 to 11.0. The analysis focuses on the impact of this variation on the Nusselt number, friction factor, and the thermo-hydraulic performance parameter, with comparisons made against a smooth duct under identical conditions. Although conventional rough ribs effectively enhance heat transfer, they tend to be uneconomical and complex in design and manufacturing. In contrast, the broken double arc-shaped ribs combined with staggered rib pieces and varied gap widths offer increased contact area. This extended surface interaction allows more time for heat transfer from the ribs to the flowing air, thereby improving thermal performance. When comparing these configurations to smooth ducts and those with symmetrical roughness, the broken arc-staggered rib setup shows superior efficiency and cost-effectiveness across varying relative roughness pitches and Reynolds numbers. Smooth ducts, lacking surface friction elements, fail to deliver adequate heat transfer and are thus impractical for effective thermal applications. Among passive heat transfer enhancement techniques, surface rib roughness has been particularly effective. Such modifications disrupt the laminar sublayer in turbulent flows, promote localized wall turbulence, and significantly boost heat transfer coefficients. However, this enhancement is accompanied by an increase in pressure drop. In the current study, the optimal relative roughness pitch was observed to be 10.0.
Copyright
Copyright © 2025 Luxmi Kant. This is an open access article distributed under the Creative Commons Attribution License.
