This study introduces a transformative redesign of circular solar air heaters (SAHs) to enhance thermal efficiency and reduce pressure drop through rotational airflow dynamics. The proposed system features two symmetrically arranged inlet ducts coupled with interconnected air vessels, inducing a controlled vortex flow pattern that maximizes turbulence and convective heat transfer. A three-dimensional computational fluid dynamics framework was employed to solve the Navier–Stokes equations for turbulent forced convection and the energy equation for heat transfer within the solar collector. The numerical model integrates the RNG κ-ε turbulence model to resolve turbulent stresses and incorporates surface-to-surface radiation modeling to account for radiative exchange between the absorber plate and glass cover. The numerical findings are confirmed by the experimental results measured on the day of testing. In the studied test case with 0.015 kg s−1 air mass flow rate and 1000 <InlineEquation ID="IEq1"> <InlineMediaObject> <ImageObject Color="BlackWhite" FileRef="10973_2025_14807_Article_IEq1.gif" Format="GIF" Height="16" Rendition="HTML" Resolution="72" Type="Linedraw" Width="52" /> </InlineMediaObject> <EquationSource Format="TEX">${\text{W}}\;{\text{m}}^{ - 2}$</EquationSource> <EquationSource Format="MATHML"><math> <mrow> <mtext>W</mtext> <mspace width="0.277778em" /> <msup> <mrow> <mtext>m</mtext> </mrow> <mrow> <mo>-</mo> <mn>2</mn> </mrow> </msup> </mrow> </math></EquationSource> </InlineEquation> solar heat flux, the computed thermal efficiency is 88%, while the value of pressure loss is reduced to 180 Pa, which is much less than 700 Pa for the collector with a single-inlet duct as the base model, whose thermal efficiency is 86%. This considerable reduction in air pressure drop resulted in a high thermohydraulic efficiency of 82% for the proposed solar collector, which is much greater than 60% for the base model. The study infers that the designed circular solar air heater with rotating airflow, two inlet ducts, and connected air chambers can be a very efficient heat exchanger for air heating.

Design and performance evaluation of a novel circular solar air heater

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发表日期：

2025年9月29日

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S. A. Gandjalikhan Nassab

摘要

This study introduces a transformative redesign of circular solar air heaters (SAHs) to enhance thermal efficiency and reduce pressure drop through rotational airflow dynamics. The proposed system features two symmetrically arranged inlet ducts coupled with interconnected air vessels, inducing a controlled vortex flow pattern that maximizes turbulence and convective heat transfer. A three-dimensional computational fluid dynamics framework was employed to solve the Navier–Stokes equations for turbulent forced convection and the energy equation for heat transfer within the solar collector. The numerical model integrates the RNG κ-ε turbulence model to resolve turbulent stresses and incorporates surface-to-surface radiation modeling to account for radiative exchange between the absorber plate and glass cover. The numerical findings are confirmed by the experimental results measured on the day of testing. In the studied test case with 0.015 kg s⁻¹ air mass flow rate and 1000 ${\text{W}}\;{\text{m}}^{ - 2}$ $W m^{- 2}$ solar heat flux, the computed thermal efficiency is 88%, while the value of pressure loss is reduced to 180 Pa, which is much less than 700 Pa for the collector with a single-inlet duct as the base model, whose thermal efficiency is 86%. This considerable reduction in air pressure drop resulted in a high thermohydraulic efficiency of 82% for the proposed solar collector, which is much greater than 60% for the base model. The study infers that the designed circular solar air heater with rotating airflow, two inlet ducts, and connected air chambers can be a very efficient heat exchanger for air heating.