Thermal Performance Analysis of a Flat Plate Solar Air Heater Using the Finite Element Method

Abstract

Solar air heaters are widely employed for low- and medium-temperature heating applications because of their simple construction, low maintenance requirements, and environmentally friendly operation. However, the thermal efficiency of conventional flat plate solar air heaters is often limited by non-uniform heat transfer and thermal losses through the collector structure. This study presents a numerical investigation of the thermal performance of a flat plate solar air heater using the Finite Element Method (FEM). A three-dimensional model of the collector was developed in CATIA and analyzed under steady-state conditions using ANSYS Workbench. The simulation model consists of a transparent glazing cover, absorber plate, airflow channel, insulation layer, and outer casing. Appropriate engineering material properties and thermal boundary conditions were applied to evaluate temperature distribution, heat flux characteristics, and thermal behavior of the collector. The numerical results indicate that the absorber plate effectively converts the applied solar heat flux into useful thermal energy and transfers it to the flowing air through conduction and convection. The maximum absorber plate temperature obtained during the simulation was approximately 365 K, while the outlet air temperature reached nearly 330 K, corresponding to a temperature rise of about 30 K. Temperature contour and heat flux analyses confirmed uniform heat transfer within the collector and reduced thermal losses due to the insulation layer. The findings demonstrate that finite element analysis provides an efficient and economical approach for predicting the thermal performance of flat plate solar air heaters before prototype fabrication. The developed numerical model can be used as a design tool for optimizing solar thermal collectors and improving their overall efficiency for renewable energy applications.

Introduction

This study investigates the thermal performance of a conventional Flat Plate Solar Air Heater (FPSAH) using the Finite Element Method (FEM) to improve the understanding and optimization of solar thermal systems. As global energy demand rises and fossil fuel reserves decline, solar energy has become an important renewable energy source due to its abundance, sustainability, and zero greenhouse gas emissions during operation.

A flat plate solar air heater converts solar radiation into thermal energy by heating air flowing through a channel beneath an absorber plate. These systems are widely used in crop drying, greenhouse heating, timber seasoning, industrial processes, and residential space heating. However, their efficiency is limited by poor heat transfer between the absorber plate and airflow and by heat losses through the glazing, insulation, and side walls.

Related Work

Previous research has focused on improving solar air heater performance using:

• Artificial roughness (ribs, fins, dimples)
• Baffles and vortex generators
• Corrugated absorber plates
• Porous media
• Optimized airflow configurations

Both Computational Fluid Dynamics (CFD) and Finite Element Method (FEM) have been used to analyze thermal behavior. While many studies examine modified collector designs, relatively few provide detailed 3D FEM analysis of conventional flat plate solar air heaters, including temperature distribution and heat flux visualization.

Research Gap

The literature identifies several gaps:

• Limited use of 3D FEM for analyzing conventional solar air heaters.
• Insufficient visualization of temperature contours, heat flux, and thermal gradients.
• Heavy reliance on costly and time-consuming experimental testing.

This study addresses these limitations by developing a comprehensive numerical model using CATIA V5 and ANSYS Workbench.

Objectives

The main objectives are:

• Develop a 3D CAD model of a flat plate solar air heater.
• Perform steady-state thermal analysis using FEM.
• Evaluate temperature distribution, heat flux, and outlet air temperature.
• Demonstrate FEM as a cost-effective alternative to extensive experimental investigations.
• Support future optimization of solar air heater designs.

Methodology

The study follows these steps:

1. 3D Modeling: A solar air heater model is created in CATIA V5, including the glass cover, aluminum absorber plate, airflow channel, insulation, and outer casing.
2. Finite Element Analysis: The model is imported into ANSYS Workbench for steady-state thermal simulation.
3. Mesh Generation: Tetrahedral finite elements are used, with finer meshes around regions of high thermal gradients.
4. Material Properties: Realistic thermal properties are assigned to aluminum, glass, mild steel, glass wool insulation, and air.
5. Boundary Conditions: Uniform solar heat flux is applied to the absorber plate, ambient air enters at 300 K, pressure outlet conditions are specified, and convective heat transfer is applied to external surfaces.

Expected Contributions

The research provides:

• A complete 3D finite element model of a conventional flat plate solar air heater.
• Detailed analysis of temperature distribution, heat flux, and outlet air temperature.
• A cost-effective simulation approach that reduces the need for prototype fabrication and extensive experiments.

Conclusion

This study presented a finite element analysis of a conventional flat plate solar air heater to evaluate its thermal performance under steady-state operating conditions. A three-dimensional collector model was developed using CATIA and analyzed in ANSYS Workbench to investigate temperature distribution, heat flux characteristics, and outlet air temperature. The numerical model successfully predicted the thermal behavior of the collector and provided detailed visualization of heat transfer within the absorber plate and airflow channel. The simulation results demonstrated that the absorber plate effectively absorbed the applied solar heat flux and transferred the generated thermal energy to the airflow through combined conduction and convection. The maximum absorber plate temperature was found to be approximately 365 K, while the outlet air temperature reached nearly 330 K, corresponding to a temperature rise of about 30 K above ambient conditions. The temperature contour and heat flux analyses confirmed uniform thermal distribution within the collector and indicated that the insulation layer effectively reduced heat losses. The developed finite element model proved to be an efficient tool for evaluating collector performance without extensive experimental testing. The numerical approach reduced design complexity while providing valuable information regarding temperature gradients, heat transfer characteristics, and overall thermal behavior. The obtained results indicate that the proposed flat plate solar air heater is suitable for low- and medium-temperature applications such as agricultural drying, greenhouse heating, and space heating. Future work may focus on experimental validation of the numerical model, transient thermal analysis under varying climatic conditions, and performance enhancement through artificial roughness, modified absorber geometries, or thermal energy storage materials. The developed simulation framework can also be extended for the optimization of advanced solar thermal collectors intended for high-efficiency renewable energy applications.

References

[1] H. Kidane, I. Farkas, and J. Buzás, “Role of Computational Fluid Dynamics in Solar Air Heating: A Comprehensive Overview of Applications, Benefits, and Future Directions,” Journal of Thermal Analysis and Calorimetry, vol. 150, pp. 8861–8877, 2025. [2] M. S. El-Sebaey, A. Ellman, S. Shams El-Din, and F. A. Essa, “Thermal Performance Evaluation for Two Designs of Flat-Plate Solar Air Heater: An Experimental and CFD Investigation,” Processes, vol. 11, no. 4, Art. no. 1227, 2023. [3] C. Mund, S. K. Rathore, and R. K. Sahoo, “Analysis of Solar Air Heaters Based on Computational Fluid Dynamics,” Journal of Thermal Analysis and Calorimetry, vol. 149, no. 5, pp. 1831–1857, 2024. [4] G. H. Ngo, R. Kumar, and D. Lee, “Computational Fluid Dynamics Analysis of Heat Transfer and Fluid Flow Characteristics in Solar Air Heater Using Discrete Arc-Shaped Baffles,” Journal of Thermal Analysis and Calorimetry, vol. 150, pp. 16551–16567, 2025. [5] K. Nidhul, A. K. Yadav, S. Anish, and U. C. Arunachala, “Thermo-Hydraulic and Exergetic Performance of a Cost-Effective Solar Air Heater: CFD and Experimental Study,” Renewable Energy, vol. 184, pp. 627–641, 2022. [6] C. E. Bensaci, A. Moummi, F. J. Sánchez de la Flor, E. A. Rodríguez Jara, A. Rincón-Casado, and A. Ruiz-Pardo, “Numerical and Experimental Study of the Heat Transfer and Hydraulic Performance of Solar Air Heaters with Different Baffle Positions,” Renewable Energy, vol. 155, pp. 1231–1244, 2020. [7] T. Chompookham, S. Eiamsa-ard, K. Buanak, P. Promvonge, N. Maruyama, and M. Hirota, “Thermal Performance Augmentation in a Solar Air Heater with Twisted Multiple V-Baffles,” International Journal of Thermal Sciences, vol. 205, Art. no. 109295, 2024. [8] S. Yadav and J. L. Bhagoria, “Heat Transfer and Friction Factor Characteristics of Solar Air Heater Having Artificial Roughness: A Review,” Renewable and Sustainable Energy Reviews, vol. 23, pp. 60–79, 2013. [9] V. B. Gawande, A. S. Dhoble, D. B. Zodpe, and S. Chamoli, “A Review of CFD Methodology Used in Literature for Predicting Thermo-Hydraulic Performance of Roughened Solar Air Heaters,” Renewable and Sustainable Energy Reviews, vol. 54, pp. 550–605, 2016. [10] A. Kumar, R. P. Saini, and J. S. Saini, “Heat and Fluid Flow Characteristics of Roughened Solar Air Heater Ducts: A Review,” Renewable Energy, vol. 47, pp. 77–94, 2012. [11] M. K. Sahu, M. Matheswaran, and P. Bishnoi, “Experimental Study of Thermal Performance and Pressure Drop on a Solar Air Heater with Different Orientations of Arc-Shaped Rib Roughness,” Journal of Thermal Analysis and Calorimetry, vol. 144, no. 4, pp. 1417–1434, 2021. [12] R. Roy and B. Kundu, “Appropriate Transient Thermal Analysis of an Absorber Plate in Flat-Plate Solar Collectors from Beginning to End Operational Conditions,” arXiv preprint arXiv:2110.00837, 2021. [13] J. A. Duffie, W. A. Beckman, and N. Blair, Solar Engineering of Thermal Processes, Photovoltaics and Wind, 5th ed. Hoboken, NJ, USA: John Wiley & Sons, 2020. [14] S. P. Sukhatme and J. K. Nayak, Solar Energy: Principles of Thermal Collection and Storage, 5th ed. New Delhi, India: McGraw-Hill Education, 2021. [15] Y. A. Çengel and A. J. Ghajar, Heat and Mass Transfer: Fundamentals and Applications, 6th ed. New York, NY, USA: McGraw-Hill Education, 2020. [16] T. L. Bergman, A. S. Lavine, F. P. Incropera, and D. P. DeWitt, Fundamentals of Heat and Mass Transfer, 9th ed. Hoboken, NJ, USA: John Wiley & Sons, 2023. [17] F. P. Incropera, D. P. DeWitt, T. L. Bergman, and A. S. Lavine, Introduction to Heat Transfer, 7th ed. Hoboken, NJ, USA: John Wiley & Sons, 2020. [18] J. P. Holman, Heat Transfer, 11th ed. New York, NY, USA: McGraw-Hill Education, 2020. [19] ANSYS, Inc., ANSYS Mechanical User\'s Guide, Release 2024 R2. Canonsburg, PA, USA: ANSYS, Inc., 2024. [20] Dassault Systèmes, CATIA V5 User Guide. Vélizy-Villacoublay, France: Dassault Systèmes, 2023.

Copyright

Copyright © 2026 Ravish Kumar, Vijay Sahu. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.