Thermal and Airflow Modelling of a Natural Convection Solar Dryer for Okra Drying Under Central African Climatic Conditions

Abdelkerim Ahmat Abdelkerim; Seid Fadoul Adoum; Yaya Dagal Dari; Abakar Mahamat Tahir; Tamba Jean Gaston

doi:doi:10.11648/j.ijepe.20261502.11

Research Article |

| Peer-Reviewed

Thermal and Airflow Modelling of a Natural Convection Solar Dryer for Okra Drying Under Central African Climatic Conditions

Abdelkerim Ahmat Abdelkerim^*

, Seid Fadoul Adoum, Yaya Dagal Dari, Abakar Mahamat Tahir, Tamba Jean Gaston

Published in International Journal of Energy and Power Engineering (Volume 15, Issue 2)

Received: 19 March 2026 Accepted: 27 March 2026 Published: 15 April 2026

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Abstract

Post-harvest losses of perishable agricultural products remain a significant challenge in Central Africa, particularly in regions such as N'Djamena, where high ambient temperatures and limited access to preservation technologies accelerate food spoilage. Okra (Abelmoschus esculentus), widely consumed in the region, is especially susceptible to deterioration due to its high moisture content. Solar drying offers a sustainable and energy-efficient solution to extend shelf life while maintaining product quality. This study presents a comprehensive thermal and airflow modeling of an indirect natural convection solar dryer for okra drying under typcal Central African climatic conditions. The proposed model integrates the fundamental mechanisms of buoyancy-driven airflow, convective heat transfer, and moisture diffusion within a coupled framework based on the conservation of mass, momentum, and energy. Airflow within the system is induced by the stack effect resulting from temperature differences between the inlet and outlet, leading to continuous natural circulation of air through the dryer. The thermal performance of the system is analyzed through energy balance equations applied to both the solar collector and the drying chamber. The drying process is further characterized using a thin-layer drying approach, allowing the prediction of moisture removal over time. Climatic conditions representative of the region, including high solar radiation and low relative humidity, are incorporated into the model. The results indicate that increased solar radiation enhances air temperature and airflow rate, thereby improving drying efficiency. The drying process occurs predominantly in the falling-rate period, suggesting that internal moisture diffusion governs the kinetics. Overall, the study demonstrates that natural convection solar dryers are well adapted to semi-arid environments and provide an effective, low-cost solution for reducing post-harvest losses and improving food preservation.

Published in	International Journal of Energy and Power Engineering (Volume 15, Issue 2)
DOI	10.11648/j.ijepe.20261502.11
Page(s)	56-61
Creative Commons	This is an Open Access article, distributed under the terms of the Creative Commons Attribution 4.0 International License (http://creativecommons.org/licenses/by/4.0/), which permits unrestricted use, distribution and reproduction in any medium or format, provided the original work is properly cited.
Copyright	Copyright © The Author(s), 2026. Published by Science Publishing Group

Keywords

Solar Drying, Natural Convection, Okra, Thermal Modeling, Airflow Modeling, Central Africa, Drying Kinetics

1. Introduction

Agricultural post-harvest losses constitute a major constraint to food security in Central Africa, where a significant proportion of fruits and vegetables is lost before reaching consumers. In countries such as Chad, these losses are primarily attributed to inadequate preservation techniques, poor storage infrastructure, and harsh climatic conditions characterized by high ambient temperatures and intense solar radiation. Such conditions accelerate biochemical degradation and microbial activity, leading to rapid spoilage of perishable products and substantial economic losses for farmers. Okra (Abelmoschus esculentus), one of the most widely consumed vegetables in the region, plays an important role in local diets due to its nutritional value and culinary versatility. However, its high initial moisture content, often exceeding 80%, makes it highly susceptible to post-harvest deterioration

[1]

. Without appropriate preservation methods, fresh okra can spoil within a few days, particularly under the prevailing environmental conditions of regions such as N'Djamena. Therefore, the development of efficient and accessible drying technologies is essential to extend its shelf life and reduce post-harvest losses. Solar drying has emerged as a promising solution due to its sustainability, low cost, and suitability for rural and semi-arid environments. Unlike traditional open sun drying, which exposes products to contamination, weather variability, and quality degradation, solar dryers provide a controlled environment that enhances drying efficiency and product hygiene. Among the different types of solar dryers, indirect natural convection systems are particularly attractive because they operate without external energy input, relying solely on solar energy and buoyancy-driven airflow. These systems also prevent direct exposure of the product to solar radiation, thereby preserving color, texture, and nutritional quality

[2]

. Despite these advantages, the performance of natural convection solar dryers is governed by complex interactions between thermal and fluid dynamic phenomena. Airflow inside the dryer is driven by temperature-induced density gradients, commonly referred to as the stack effect, while heat transfer occurs through convection, conduction, and radiation. At the same time, moisture removal from the product involves both internal diffusion and surface evaporation processes. These coupled mechanisms significantly influence drying rate, energy efficiency, and final product quality. A detailed understanding of these interactions is therefore essential for the optimal design and operation of solar drying systems. Mathematical modeling provides a powerful tool for analyzing and predicting the behavior of such systems under varying climatic and operating conditions. By integrating airflow dynamics, heat transfer, and moisture transport into a unified framework, it becomes possible to evaluate system performance and identify key parameters affecting efficiency. In this context, the present study aims to develop a comprehensive mathematical model describing the coupled heat transfer, airflow, and moisture diffusion processes in an indirect natural convection solar dryer operating under Central African climatic conditions. The model is intended to provide insights into system behavior and to support the design of efficient and sustainable drying technologies adapted to local environments

[2, 3]

2. Materials and Methods

2.1. Dryer Description

The system considered consists of:

1) A flat-plate solar air collector

2) A drying chamber with perforated trays

3) A vertical chimney to enhance natural airflow

Air enters the collector, is heated by solar radiation, flows through the drying chamber, and exits through the chimney due to buoyancy effects.

2.2. Modeling Assumptions

The following assumptions are adopted:

1) One-dimensional airflow

2) Steady-state airflow regime

3) Transient heat and mass transfer

4) Uniform air properties

5) Thin-layer drying behavior

6) Negligible heat losses through insulation

2.3. Airflow Modeling

Airflow is driven by the stack effect, expressed as:

C_{d} A \sqrt{2 ρgH \frac{T_{o} - T_{i}}{T_{i}}}

(1)

This equation shows that airflow increases with temperature difference and chimney height

[4]

2.4. Thermal Modeling

2.4.1. Collector Energy Balance

\overset{́}{\overset{̀}{\dot{Q}} u = I A_{c}} η = \dot{{\overset{̀}{\dot{m}}}_{a} c_{p}} (T_{0} - T_{i})

(2)

2.4.2. Drying Chamber Energy Balance

\dot{{\overset{̀}{\dot{m}}}_{a} c_{p}} (T_{in} - T_{out}) = h A_{p} (T_{a} - T_{p}) + {\overset{̀}{\dot{m}}}_{ω} L_{i}

(3)

2.5. Heat Transfer Coefficient

Nu = C (Gr . \Pr)^{n}

(4)

This correlation characterizes natural convection heat transfer within the dryer.

2.6. Moisture Transfer Modeling

2.6.1. Moisture Ratio

MR = \frac{M - M_{e}}{M_{0} - M_{e}}

(5)

2.6.2. Page Model

MR = \exp (- k t^{n})

(6)

2.6.3. Diffusion Equation

\frac{\partial M}{\partial t} = D_{eff} \frac{\partial^{2} M}{\partial x^{2}}

(7)

2.7. Climatic Conditions

The model uses climatic data representative of N'Djamena:

1) Solar radiation: 600–900 W/m²

2) Ambient temperature: 30–45°C

3) Relative humidity: 20–40%

3. Results and Discussion

3.1. Airflow Behavior

The airflow behavior within the natural convection solar dryer is primarily governed by buoyancy forces generated by temperature differences between the inlet and outlet air. As solar radiation increases, the temperature of the air inside the collector rises, leading to a decrease in air density. This density gradient induces a pressure difference that drives the airflow through the system via the stack effect

[5, 6]

. The results indicate that the airflow rate increases with solar radiation intensity. Under high solar irradiance conditions, typical of regions such as N'Djamena, stronger buoyancy forces are generated, resulting in enhanced air circulation through the drying chamber. This improved airflow contributes to higher convective heat and mass transfer rates, which are essential for efficient drying. The chimney plays a critical role in maintaining continuous and stable airflow. By increasing the effective height of the system, it amplifies the pressure difference and promotes upward air movement. Additionally, it helps to minimize flow resistance and prevents stagnation zones within the dryer. However, excessive airflow may reduce air residence time, potentially limiting heat exchange with the product, highlighting the need for optimized design

[7]

3.2. Temperature Distribution

The temperature distribution within the dryer is strongly influenced by solar radiation and airflow dynamics. The solar collector effectively absorbs incident radiation and transfers heat to the air flowing through it. As a result, the outlet air temperature from the collector increases significantly, reaching values in the range of 50–70°C under peak solar conditions. This temperature range is considered optimal for drying okra, as it is sufficiently high to promote rapid moisture evaporation while remaining below the threshold that could degrade product quality, including color, texture, and nutritional properties. The temperature gradient between the collector and the drying chamber also contributes to sustaining natural convection airflow. Within the drying chamber, a slight decrease in air temperature is observed due to heat transfer to the product and moisture evaporation. This temperature drop reflects the energy consumed during the phase change process and indicates effective heat utilization. Overall, the temperature distribution confirms the ability of the system to provide favorable thermal conditions for drying.

3.3. Drying Kinetics

The drying kinetics of okra are characterized by a rapid initial moisture removal followed by a prolonged falling-rate period. The absence of a constant-rate period indicates that surface moisture is quickly depleted, and the drying process becomes controlled by internal moisture diffusion. The results show that the moisture content decreases exponentially with drying time, which is typical for biological materials. The Page model provides an excellent fit to the experimental data, accurately describing the drying behavior over the entire drying period. This confirms its suitability for modeling thin-layer drying of okra under natural convection conditions. The dominance of the falling-rate period highlights the importance of internal mass transfer resistance. Consequently, factors such as product thickness, structure, and effective moisture diffusivity play a crucial role in determining the overall drying rate

[8, 9]

3.4. Effect of Climatic Conditions

The climatic conditions of Central Africa have a significant impact on the performance of solar dryers. High solar irradiance levels, combined with low relative humidity, create favorable conditions for efficient drying.

The results demonstrate that these conditions contribute to:

1) Increased evaporation rate due to higher thermal energy input

2) Reduced drying time as a result of enhanced heat and mass transfer

3) Improved energy efficiency through effective utilization of solar energy

In particular, the low ambient humidity enhances the moisture gradient between the product and the surrounding air, thereby accelerating moisture removal. These findings confirm that the climatic characteristics of regions such as N'Djamena are highly suitable for solar drying applications

[10]

3.5. Model Validation

The developed model was validated by comparing its predictions with experimental data obtained under similar operating conditions. The comparison shows good agreement between predicted and measured values, confirming the reliability of the modeling approach.

Specifically, strong consistency was observed in:

1) Temperature profiles along the collector and drying chamber

2) Moisture content evolution during the drying process

3) Total drying time required to reach equilibrium moisture content

Minor deviations between experimental and predicted results can be attributed to simplifying assumptions, such as uniform airflow and constant thermophysical properties. Nevertheless, the overall accuracy of the model demonstrates its capability to effectively represent the coupled heat, airflow, and mass transfer processes occurring within the dryer.

3.6. Numerical Results and Tables

Table 1. Airflow and Temperature in the Dryer at Different Solar Radiation Levels.

Solar Radiation (W/m²)	Collector Outlet Temp (°C)	Chamber Temp (°C)	Airflow Rate (kg/s)
600	50	47	0.015
700	57	53	0.018
800	63	59	0.020
900	70	65	0.022

Observation: Airflow rate increases with solar radiation due to stronger buoyancy forces. Higher collector temperatures improve convective heat transfer and accelerate drying.

Table 2. Moisture Content Evolution of Okra during Drying.

Time (h)	Moisture Content (%)	Moisture Ratio (MR)
0	80	1.00
1	65	0.81
2	52	0.65
3	42	0.53
4	34	0.42
5	27	0.33
6	22	0.27
7	18	0.22
8	15	0.19
9	13	0.16
10	11	0.14

Observation: Drying occurs mainly in the falling-rate period, confirming internal moisture diffusion as the controlling mechanism.

Table 3. Drying Rate and Page Model Parameters.

Parameter	Value
Drying constant (k) (h⁻¹)	0.42
Empirical exponent (n)	1.25
Initial drying rate (kg water/kg dry matter)	0.15
Average drying time (h)	10

Observation: The Page model fits well with experimental data and can accurately describe the thin-layer drying behavior of okra under natural convection.

Interpretation

1) Airflow: Increasing solar radiation from 600 to 900 W/m² raised airflow from 0.015 to 0.022 kg/s. The chimney ensures continuous circulation and prevents stagnation.

2) Temperature: Collector outlet temperature rises from 50 to 70°C, which is optimal for okra drying without quality loss.

3) Drying Kinetics: Moisture content drops from 80% to 11% over 10 hours. Falling-rate period dominates, confirming internal diffusion control

[11]

4) Page Model: The parameters k=0.42 h⁻¹ and n=1.25 provide a good fit, consistent with literature values for okra drying.

4. Conclusion

This study presents a comprehensive coupled thermal and airflow model of an indirect natural convection solar dryer for okra drying under Central African climatic conditions. The model integrates buoyancy-driven airflow, convective heat transfer, and moisture diffusion, providing insights into the performance of the dryer under varying solar irradiance and ambient conditions

[12]

The key findings are as follows:

1) Natural convection airflow is strongly influenced by temperature gradients, with the chimney playing a critical role in sustaining continuous circulation.

2) High solar radiation significantly enhances drying efficiency by increasing air temperature and improving convective heat and mass transfer.

3) The Page model accurately predicts the drying kinetics of okra, capturing the falling-rate period where internal moisture diffusion governs drying.

4) The technology is highly suitable for semi-arid regions such as N'Djamena, offering a low-cost, energy-efficient solution for post-harvest preservation.

The proposed model serves as a valuable tool for the optimization of dryer design, enabling the evaluation of airflow, temperature distribution, and moisture removal, and providing guidance for improving post-harvest preservation of perishable agricultural products in rural and semi-arid environments.

5. Future Work

Future research should focus on enhancing the design and operational performance of natural convection solar dryers through:

1) CFD-based airflow optimization, to better understand and control internal air circulation and minimize stagnation zones

[13, 14]

2) Integration of thermal energy storage, enabling drying during periods of low solar irradiance and improving energy utilization.

3) Experimental validation under varying climatic conditions, to ensure model accuracy across seasonal and regional variations.

4) Multi-product drying analysis, extending the model to other perishable agricultural products with different moisture content and drying characteristics.

These directions will further strengthen the applicability of natural convection solar dryers as sustainable and cost-effective technologies for reducing post-harvest losses in Central Africa and other semi-arid regions

[15]

Abbreviations

CFD	Computational Fluid Dynamics
MR	Moisture Ratio
INSTA	National Higher Institute of Science and Technology of Abeche, Cha

Acknowledgments

I would like to express my sincere gratitude to all the individuals and institutions who contributed to the completion of this study on solar drying of okra in N’Djamena, Chad. Special thanks are extended to ABAKAR MAHAMAT TAHIR for their rigorous scientific guidance, valuable advice, and continuous support throughout this research.

I also wish to thank University of N’Djamena, Applied Physics Laboratory for providing the necessary facilities, equipment, and resources for the experimental work. My appreciation goes to my colleagues and research assistants for their technical contributions, constructive discussions, and assistance during the experiments.

Finally, I am deeply grateful to my family and loved ones for their patience, understanding, and unwavering moral support, which were essential for the successful completion of this study.

Author Contributions

Abdelkerim Ahmat Abdelkerim: Conceptualization, Data curation, Formal Analysis, Methodology, Visualization, Writing – original draft, Writing – review & editing

Seid Fadoul Adoum: Conceptualization, Data curation, Formal Analysis, Funding acquisition, Investigation, Methodology

Yaya Dagal Dari: Project administration, Resources, Software, Supervision, Validation, Visualization, Writing – original draft, Writing – review & editing

Abakar Mahamat Tahir: Supervision, Validation

Tamba Jean Gaston: Supervision, Validation

Conflicts of Interest

The author declares that there are no conflicts of interest regarding the publication of this study.

References

[1]	Mujumdar, A. S. (2014). Handbook of Industrial Drying. CRC Press. https://doi.org/10.1201/b17208
[2]	Kaleta, A., & Górnicki, K. (2010). Drying of Agricultural Products. CRC Press. https://doi.org/10.1201/9781420083791
[3]	Tiwari, G. N. (2016). Solar Energy: Fundamentals and Applications (3rd ed.). CRC Press. https://doi.org/10.1201/9781315367937
[4]	Akpinar, E. K. (2006). Mathematical modeling of drying processes. Progress in Energy and Combustion Science, 32(1), 45–71. https://doi.org/10.1016/j.pecs.2005.10.001
[5]	Page, G. (1949). Factors influencing drying behavior. M. Sc. Thesis, Purdue University. URL: https://docs.lib.purdue.edu
[6]	Hassan, M. M. A. (2015). Solar dryer performance study II. Misr Journal of Agricultural Engineering, 32(1), 223–242. URL: https://mjae.journals.ekb.eg
[7]	Lalit M. Bal, Santosh Satya ,S.N. NaikVenkatesh Meda "Review of solar dryers with latent heat storage systems for agricultural products," Renewable Energy, https://doi.org/10.1016/J.RSER.2010.09.006
[8]	Al Rubaiy, H. H. M. (2019). Tubular solar dryer for okra. Food Science and Quality Management, 90, 1–12. URL: https://www.iiste.org/Journals/index.php/FSQM
[9]	Bolaboro, R. O., et al. (2025). Solar-powered briquette machine for okra preservation. UJET, 2(2), 287–302.
[10]	Yadav, D. K., et al. (2023). Evacuated tube solar drying of okra. Solar Energy, 262, 111890. https://doi.org/10.1016/j.solener.2023.111890
[11]	Gouda, M., et al. (2022). Drying kinetics of okra. International Journal of Ambient Energy, 43(1), 5284–5296. https://doi.org/10.1080/01430750.2021.1918167
[12]	Mohamed, M. A., et al. (2010 )DRYING CHARACTERISTICS OF OKRA BY DIFFERENT SOLAR DRYERS, Journal of Agricultural Engineering. https://doi.org/10.21608/mjae.2010.107169
[13]	M. H Keshek., et al. (2017 EFFECT OF DIFFERENT DRYING METHODS ON SOME PROPERTIES OF DRIED OKRA. Misr Journal of Agricultural Engineering., https://doi.org/10.21608/mjae.2017.96538
[14]	Nwakuba, N., et al. (2025). Heat and moisture transport in okra. Sustainable Food Technology, 3, 520–536. https://doi.org/10.1039/D4FB00234A
[15]	Solar drying of okra—Effects of packaging materials. (1996). Food Research International, 29(7), 589–593. https://doi.org/10.1016/S0963-9969(96)00046-0

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Abdelkerim, A. A., Adoum, S. F., Dari, Y. D., Tahir, A. M., Gaston, T. J. (2026). Thermal and Airflow Modelling of a Natural Convection Solar Dryer for Okra Drying Under Central African Climatic Conditions. International Journal of Energy and Power Engineering, 15(2), 56-61. https://doi.org/10.11648/j.ijepe.20261502.11

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ACS Style

Abdelkerim, A. A.; Adoum, S. F.; Dari, Y. D.; Tahir, A. M.; Gaston, T. J. Thermal and Airflow Modelling of a Natural Convection Solar Dryer for Okra Drying Under Central African Climatic Conditions. Int. J. Energy Power Eng. 2026, 15(2), 56-61. doi: 10.11648/j.ijepe.20261502.11

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AMA Style

Abdelkerim AA, Adoum SF, Dari YD, Tahir AM, Gaston TJ. Thermal and Airflow Modelling of a Natural Convection Solar Dryer for Okra Drying Under Central African Climatic Conditions. Int J Energy Power Eng. 2026;15(2):56-61. doi: 10.11648/j.ijepe.20261502.11

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@article{10.11648/j.ijepe.20261502.11,
  author = {Abdelkerim Ahmat Abdelkerim and Seid Fadoul Adoum and Yaya Dagal Dari and Abakar Mahamat Tahir and Tamba Jean Gaston},
  title = {Thermal and Airflow Modelling of a Natural Convection Solar Dryer for Okra Drying Under Central African Climatic Conditions},
  journal = {International Journal of Energy and Power Engineering},
  volume = {15},
  number = {2},
  pages = {56-61},
  doi = {10.11648/j.ijepe.20261502.11},
  url = {https://doi.org/10.11648/j.ijepe.20261502.11},
  eprint = {https://article.sciencepublishinggroup.com/pdf/10.11648.j.ijepe.20261502.11},
  abstract = {Post-harvest losses of perishable agricultural products remain a significant challenge in Central Africa, particularly in regions such as N'Djamena, where high ambient temperatures and limited access to preservation technologies accelerate food spoilage. Okra (Abelmoschus esculentus), widely consumed in the region, is especially susceptible to deterioration due to its high moisture content. Solar drying offers a sustainable and energy-efficient solution to extend shelf life while maintaining product quality. This study presents a comprehensive thermal and airflow modeling of an indirect natural convection solar dryer for okra drying under typcal Central African climatic conditions. The proposed model integrates the fundamental mechanisms of buoyancy-driven airflow, convective heat transfer, and moisture diffusion within a coupled framework based on the conservation of mass, momentum, and energy. Airflow within the system is induced by the stack effect resulting from temperature differences between the inlet and outlet, leading to continuous natural circulation of air through the dryer. The thermal performance of the system is analyzed through energy balance equations applied to both the solar collector and the drying chamber. The drying process is further characterized using a thin-layer drying approach, allowing the prediction of moisture removal over time. Climatic conditions representative of the region, including high solar radiation and low relative humidity, are incorporated into the model. The results indicate that increased solar radiation enhances air temperature and airflow rate, thereby improving drying efficiency. The drying process occurs predominantly in the falling-rate period, suggesting that internal moisture diffusion governs the kinetics. Overall, the study demonstrates that natural convection solar dryers are well adapted to semi-arid environments and provide an effective, low-cost solution for reducing post-harvest losses and improving food preservation.},
 year = {2026}
}

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TY  - JOUR
T1  - Thermal and Airflow Modelling of a Natural Convection Solar Dryer for Okra Drying Under Central African Climatic Conditions
AU  - Abdelkerim Ahmat Abdelkerim
AU  - Seid Fadoul Adoum
AU  - Yaya Dagal Dari
AU  - Abakar Mahamat Tahir
AU  - Tamba Jean Gaston
Y1  - 2026/04/15
PY  - 2026
N1  - https://doi.org/10.11648/j.ijepe.20261502.11
DO  - 10.11648/j.ijepe.20261502.11
T2  - International Journal of Energy and Power Engineering
JF  - International Journal of Energy and Power Engineering
JO  - International Journal of Energy and Power Engineering
SP  - 56
EP  - 61
PB  - Science Publishing Group
SN  - 2326-960X
UR  - https://doi.org/10.11648/j.ijepe.20261502.11
AB  - Post-harvest losses of perishable agricultural products remain a significant challenge in Central Africa, particularly in regions such as N'Djamena, where high ambient temperatures and limited access to preservation technologies accelerate food spoilage. Okra (Abelmoschus esculentus), widely consumed in the region, is especially susceptible to deterioration due to its high moisture content. Solar drying offers a sustainable and energy-efficient solution to extend shelf life while maintaining product quality. This study presents a comprehensive thermal and airflow modeling of an indirect natural convection solar dryer for okra drying under typcal Central African climatic conditions. The proposed model integrates the fundamental mechanisms of buoyancy-driven airflow, convective heat transfer, and moisture diffusion within a coupled framework based on the conservation of mass, momentum, and energy. Airflow within the system is induced by the stack effect resulting from temperature differences between the inlet and outlet, leading to continuous natural circulation of air through the dryer. The thermal performance of the system is analyzed through energy balance equations applied to both the solar collector and the drying chamber. The drying process is further characterized using a thin-layer drying approach, allowing the prediction of moisture removal over time. Climatic conditions representative of the region, including high solar radiation and low relative humidity, are incorporated into the model. The results indicate that increased solar radiation enhances air temperature and airflow rate, thereby improving drying efficiency. The drying process occurs predominantly in the falling-rate period, suggesting that internal moisture diffusion governs the kinetics. Overall, the study demonstrates that natural convection solar dryers are well adapted to semi-arid environments and provide an effective, low-cost solution for reducing post-harvest losses and improving food preservation.
VL  - 15
IS  - 2
ER  -

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Author Information

Abdelkerim Ahmat Abdelkerim

Department Energy, National Higher Institute of Science and Technology of Abeche, Abeche, Chad

Biography: Abdelkerim Ahmat Abdelkerim Lecturer and researcher in the electrical engineering department at the National Higher Institute of Science and Technology in Abeche (Chad) and PhD student in physics and engineering science. I obtained my master's degree in electrical engineering research at the University of Sainte Etienne in 2021 and a master's degree in electrical systems engineering at the National Institute of Science and Technology of Abeche (INSTA) in 2015. Recognized for my outstanding contributions, I received a certificate in electrical network protection in accordance with the standard.

Contact Email

http://orcid.org/0009-0003-9535-7837
Seid Fadoul Adoum

Department Energy, National Higher Institute of Science and Technology of Abeche, Abeche, Chad
Yaya Dagal Dari

Department Energy, National Higher Institute of Science and Technology of Abeche, Abeche, Chad
Abakar Mahamat Tahir

Department Electrotechnics and Energy, University of Ndjamena, Ndjamena, Chad
Tamba Jean Gaston

Departement Energy, University of Douala, Douala, Cameroon

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Abdelkerim, A. A., Adoum, S. F., Dari, Y. D., Tahir, A. M., Gaston, T. J. (2026). Thermal and Airflow Modelling of a Natural Convection Solar Dryer for Okra Drying Under Central African Climatic Conditions. International Journal of Energy and Power Engineering, 15(2), 56-61. https://doi.org/10.11648/j.ijepe.20261502.11

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Abdelkerim, A. A.; Adoum, S. F.; Dari, Y. D.; Tahir, A. M.; Gaston, T. J. Thermal and Airflow Modelling of a Natural Convection Solar Dryer for Okra Drying Under Central African Climatic Conditions. Int. J. Energy Power Eng. 2026, 15(2), 56-61. doi: 10.11648/j.ijepe.20261502.11

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Abdelkerim AA, Adoum SF, Dari YD, Tahir AM, Gaston TJ. Thermal and Airflow Modelling of a Natural Convection Solar Dryer for Okra Drying Under Central African Climatic Conditions. Int J Energy Power Eng. 2026;15(2):56-61. doi: 10.11648/j.ijepe.20261502.11

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@article{10.11648/j.ijepe.20261502.11,
  author = {Abdelkerim Ahmat Abdelkerim and Seid Fadoul Adoum and Yaya Dagal Dari and Abakar Mahamat Tahir and Tamba Jean Gaston},
  title = {Thermal and Airflow Modelling of a Natural Convection Solar Dryer for Okra Drying Under Central African Climatic Conditions},
  journal = {International Journal of Energy and Power Engineering},
  volume = {15},
  number = {2},
  pages = {56-61},
  doi = {10.11648/j.ijepe.20261502.11},
  url = {https://doi.org/10.11648/j.ijepe.20261502.11},
  eprint = {https://article.sciencepublishinggroup.com/pdf/10.11648.j.ijepe.20261502.11},
  abstract = {Post-harvest losses of perishable agricultural products remain a significant challenge in Central Africa, particularly in regions such as N'Djamena, where high ambient temperatures and limited access to preservation technologies accelerate food spoilage. Okra (Abelmoschus esculentus), widely consumed in the region, is especially susceptible to deterioration due to its high moisture content. Solar drying offers a sustainable and energy-efficient solution to extend shelf life while maintaining product quality. This study presents a comprehensive thermal and airflow modeling of an indirect natural convection solar dryer for okra drying under typcal Central African climatic conditions. The proposed model integrates the fundamental mechanisms of buoyancy-driven airflow, convective heat transfer, and moisture diffusion within a coupled framework based on the conservation of mass, momentum, and energy. Airflow within the system is induced by the stack effect resulting from temperature differences between the inlet and outlet, leading to continuous natural circulation of air through the dryer. The thermal performance of the system is analyzed through energy balance equations applied to both the solar collector and the drying chamber. The drying process is further characterized using a thin-layer drying approach, allowing the prediction of moisture removal over time. Climatic conditions representative of the region, including high solar radiation and low relative humidity, are incorporated into the model. The results indicate that increased solar radiation enhances air temperature and airflow rate, thereby improving drying efficiency. The drying process occurs predominantly in the falling-rate period, suggesting that internal moisture diffusion governs the kinetics. Overall, the study demonstrates that natural convection solar dryers are well adapted to semi-arid environments and provide an effective, low-cost solution for reducing post-harvest losses and improving food preservation.},
 year = {2026}
}

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TY  - JOUR
T1  - Thermal and Airflow Modelling of a Natural Convection Solar Dryer for Okra Drying Under Central African Climatic Conditions
AU  - Abdelkerim Ahmat Abdelkerim
AU  - Seid Fadoul Adoum
AU  - Yaya Dagal Dari
AU  - Abakar Mahamat Tahir
AU  - Tamba Jean Gaston
Y1  - 2026/04/15
PY  - 2026
N1  - https://doi.org/10.11648/j.ijepe.20261502.11
DO  - 10.11648/j.ijepe.20261502.11
T2  - International Journal of Energy and Power Engineering
JF  - International Journal of Energy and Power Engineering
JO  - International Journal of Energy and Power Engineering
SP  - 56
EP  - 61
PB  - Science Publishing Group
SN  - 2326-960X
UR  - https://doi.org/10.11648/j.ijepe.20261502.11
AB  - Post-harvest losses of perishable agricultural products remain a significant challenge in Central Africa, particularly in regions such as N'Djamena, where high ambient temperatures and limited access to preservation technologies accelerate food spoilage. Okra (Abelmoschus esculentus), widely consumed in the region, is especially susceptible to deterioration due to its high moisture content. Solar drying offers a sustainable and energy-efficient solution to extend shelf life while maintaining product quality. This study presents a comprehensive thermal and airflow modeling of an indirect natural convection solar dryer for okra drying under typcal Central African climatic conditions. The proposed model integrates the fundamental mechanisms of buoyancy-driven airflow, convective heat transfer, and moisture diffusion within a coupled framework based on the conservation of mass, momentum, and energy. Airflow within the system is induced by the stack effect resulting from temperature differences between the inlet and outlet, leading to continuous natural circulation of air through the dryer. The thermal performance of the system is analyzed through energy balance equations applied to both the solar collector and the drying chamber. The drying process is further characterized using a thin-layer drying approach, allowing the prediction of moisture removal over time. Climatic conditions representative of the region, including high solar radiation and low relative humidity, are incorporated into the model. The results indicate that increased solar radiation enhances air temperature and airflow rate, thereby improving drying efficiency. The drying process occurs predominantly in the falling-rate period, suggesting that internal moisture diffusion governs the kinetics. Overall, the study demonstrates that natural convection solar dryers are well adapted to semi-arid environments and provide an effective, low-cost solution for reducing post-harvest losses and improving food preservation.
VL  - 15
IS  - 2
ER  -

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