Browsing by Author "Ahmed, Atef Fathy"

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    Influence of physical shape and salting on tomato drying performance using mixed mode solar and open-air methods in semi-cloudy weather
    (Springer Nature, 2025-07-20) Elwakeel, Abdallah Elshawadfy; Ali, Guma; Eldin, Abdalla Zain; Alsebiey, Mohamed Mahmoud; Tantawy, Aml Abubakr; AL-Harbi, Mohammad S.; Ahmed, Atef Fathy; Metwally, Khaled A.
    SD Solar drying is increasingly recognized as a sustainable and energy-efficient solution for preserving agricultural products, offering a practical alternative to fossil fuel-dependent methods and traditional open sun drying (OSD). However, its overall performance is highly influenced by environmental variability and system design. This study provides a detailed evaluation of a newly developed direct solar dryer (DDSD) for tomato dehydration, conducted under real and fluctuating climatic conditions in Aswan, Egypt, from February 22 to 27, 2025. During the trial period, solar irradiance ranged widely from 88 to 826 W/m2 due to intermittent cloud cover, while ambient temperatures fluctuated between 22 and 34 °C—conditions representative of actual field environments. Tomato samples were prepared in three physical forms—halves, quarters, and 6 mm slices—and subjected to two pretreatment methods (salted and unsalted) to assess their effects on drying kinetics. The DDSD demonstrated significantly better performance than OSD, reducing drying durations by 25–39.6%. The most efficient results were achieved for salted 6 mm slices, which dried in just 9 h—substantially faster than the 29 h for unsalted halves in DDSD and 48 h in OSD. These samples also exhibited the highest effective moisture diffusivity (Deff) (5.92 × 10⁻⁹ m2/s), reflecting enhanced internal moisture transport. Among 12 drying models evaluated, the Logistic model most accurately described the drying behavior in the DDSD, with an excellent statistical fit (R2 = 0.999524, χ2 = 6.74 × 10⁻5, RMSE = 0.006868). Economically, the DDSD, integrated with a photovoltaic (PV) system, required a modest initial investment of $520 and achieved a payback period of just 1.82 years for salted slices due to faster processing and increased throughput. From an environmental perspective, the system is projected to offset approximately 105.68 metric tons of CO₂ emissions over a 20-year lifespan, with an energy payback time of only 1.10 years and potential revenue of $1321.04 from carbon credits. These findings underscore the DDSD’s potential as a cost-effective, environmentally sustainable, and technically efficient solution for agricultural drying in solar-rich regions.
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    Performance evaluation of a triple-sided solar dryer in terms of energy-exergy analysis, sustainable indicators and CFD simulation during drying tilapia fish strips
    (Springer Nature, 2025-11-17) Ghanem, Tarek Hussien M.; Oraiath, Awad Ali Tayoush; Nsasrat, Loai S.; Ali, Guma; Younis, Omar Shahat; Eldin, Abdalla Zain; Elmolakab, Khaled Mohamad; Alhumedi, M.; Ahmed, Atef Fathy; Tantawy, Aml Abubakr; Elwakeel, Abdallah Elshawadfy
    Fixed flat-plate solar collectors suffer from low energy efficiency during mornings and evenings due to suboptimal solar incidence angles, reducing thermal output. While tracking systems improve efficiency by following the sun’s path, their high initial costs, mechanical complexity, and need for advanced control systems limit widespread adoption. These drawbacks demonstrate the importance of cost-effective, efficient alternatives that balance performance and simplicity in solar thermal applications. Thus, a triple-sided solar dryer (TSSD) integrated with intelligent airflow gating was developed to overcome these issues. This study evaluates the performance of a TSSD for drying tilapia strips at three thicknesses (4, 8, and 12 mm) using computational fluid dynamics (CFD), energy-exergy analysis, and sustainability indicators. According to the CFD simulations, they were employed to analyze airflow patterns, temperature distribution, and velocity profiles inside the TSSC and drying room (DR) during a day from 8 a.m. to 5 p.m. Additionally, the CFD was used to estimate the highest air temperature inside the drying to choose the appropriate speed of the air exhaust fan. The simulation analysis indicated that the highest air temperatures were 188.67, 124.4, and 96.51 °C, at three corresponding air velocities of the exhaust fan (1.0, 1.5, and 2.0 m/s), respectively, under a solar intensity of 872 W/m². Where the best velocity of the air exhaust fan was 2 m/s, it provided a uniform drying temperature of 96.51 °C, at solar noon (less than 100 °C). On the other hand, the energy-exergy analysis and sustainable indicators were estimated over two consecutive drying days (8 a.m.–5 p.m.) to assess the thermal behavior of the TSSC and TSSD. The energy analysis showed that the TSSC attained a maximum input energy of 1752.72 W and a useful energy of 810.31 W. Its energy efficiencies ranged from 40.79% to 57.21%. Meanwhile, the maximum drying efficiency was 8.19%, 8.51%, and 8.46% for tilapia strip thicknesses of 4, 8, and 12 mm, respectively. Furthermore, the exergy efficiency ranged from 7.28% to 32.83% (TSSC) and from 66.5% to 87.19% (DR). Additionally, sustainability indicators, such as improvement potential (IP) ranging from 1.19 to 7.22 W, waste exergy ratio (WER) between 0.67 and 0.93, and sustainability index (SI) from 1.08 to 1.49, showed that the system is both environmentally friendly and effective in its operations. The results show that the TSSD is an effective, eco-friendly, and affordable option compared to traditional solar drying systems, providing the best heat performance, better energy-exergy efficiency, and less harm to the environment for drying tilapia.