Abstract
Improving the thermal efficiency of Trombe walls is crucial for optimizing passive solar heating systems. Despite extensive research, the effect of ribbed surfaces on the thermo-hydrodynamic behavior has not been fully explored. This study aims to address this gap by performing a three-dimensional CFD analysis to investigate the combined effects of rib density (Nr = 3, 5, 7, 9) and rib geometry (rectangular, pentagonal, hexagonal, octagonal, triangular, and semi-circular) on heat transfer and fluid dynamics within Trombe walls. The simulations were conducted using ANSYS Fluent (2020 R1) under laminar flow conditions (Re = 600–1600), with boundary conditions including a constant solar flux of 748 W/m2, an ambient temperature of 293.75 K, and an external wind speed of 1 m/s. The model was validated against experimental data correlations for the Nusselt number (Nu) and friction factor (f), with deviations of less than 6%. The results show that ribbing significantly enhances heat transfer by disturbing the boundary layer and promoting vortex formation. The optimal configuration (Nr = 5) increases the Nusselt number by 68.3% at Re = 1600 (from 12.41 to 20.88). Triangular ribs provide the highest thermal enhancement, nearly doubling Nu (a 99.4% increase, from 12.41 to 24.75), but incur significant friction penalties, with f rising by 169.4% (from 0.0489 to 0.1317). In contrast, semi-circular ribs strike a balance, yielding a thermal enhancement factor (TEF) of 1.51 (+ 50.6%) and increasing heat flux by 12.7%. These findings demonstrate that Nr = 5 with the appropriate rib geometry can optimize Trombe wall efficiency, making it suitable for nearly zero-energy buildings (nZEBs).
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The datasets used and analyzed during the current study available from the corresponding author on reasonable request.
Abbreviations
- L:
-
Length of the Trombe wall (mm)
- H:
-
Height of the Trombe wall (mm)
- W:
-
Width of the Trombe wall (mm)
- L1, L2, L3, L4 :
-
Characteristic lengths of the studied configurations (mm)
- h1, h2:
-
Heights of the inlet and outlet openings (mm)
- e1, e2, e3 :
-
Thicknesses of different layers (mm)
- Nr:
-
Number of internal ribs
- Re:
-
Reynolds number (-)
- f:
-
Friction factor (-)
- Po:
-
Poiseuille number (-)
- j:
-
Colburn factor (-)
- ν:
-
Kinematic viscosity (m2/s)
- ρ:
-
Density of air (kg/m 3 )
- u, v, w:
-
Velocitys component
- P:
-
Pressure (Pa)
- µ:
-
Dynamic viscosity (Pa.s)
- Nu:
-
Nusselt number (-)
- η:
-
Thermal enhancement factor (-)
- Q:
-
Heat flux (W)
- T:
-
Temperature (K)
- k:
-
Thermal conductivity (W/m.K)
- Cp:
-
Specific heat capacity (J/kg.K)
- Pr:
-
Prandtl number (-)
- α:
-
Thermal diffusivity
- ΔP:
-
Pressure drop (Pa)
- h:
-
Convective heat transfer coefficient (W/m2.K)
- Re:
-
Reynolds number
- Nu:
-
Nusselt number
- Pr:
-
Prandtl number
- Po:
-
Poiseuille number
- j:
-
Colburn factor
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**Jamal-Eddine Salhi** : Formal analysis, Writing - original draft, Writing - review & editing, Conceptualization, Methodology**Tarik Zarrouk: ** Writing - review & editing, supervision, Resources, Fund Acquisition**Supriya Jain** : Writing - review & editing, Supervision**Mohamed Barboucha** : Investigation, Methodology, Writing - review & editing.**Md Irfanul Haque Siddiqui** : Formal analysis, Methodology, Writing - review & editing, supervision.**Shahid Parvez** : Visualization, Writing - review & editing**Geleta Afessa Moreda** : Formal analysis, Methodology, Writing – review, Visualisation & editing.
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Salhi, JE., Zarrouk, T., Jain, S. et al. Optimizing the heating performance of Trombe walls with ribbed surfaces using three-dimensional CFD analysis. Sci Rep (2026). https://doi.org/10.1038/s41598-026-47339-3
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DOI: https://doi.org/10.1038/s41598-026-47339-3


