Energy Engineering and Management

Energy Engineering and Management

The Effect of Air Recirculation on the Efficiency of an Indirect Solar Dryer with a Vacuum Collector Equipped with Phase Change Material and Heat Exchanger

Document Type : Original Article

Authors
1 Department of Mechanical Engineering, University of Jiroft, Jiroft, Iran.
2 Department of BioSystems Engineering, Faculty of Agriculture, University of Kurdistan, Sanandaj, Iran
Abstract
In the process of drying agricultural products, a high initial moisture content leads to increased energy consumption. To reduce this consumption, the use of solar systems, either independently or in combination with other heat sources, is a common method. However, one of the factors reducing efficiency in dryers is the loss of thermal energy in systems with open airflow. Employing a return airflow at the dryer inlet can improve thermal efficiency and reduce product drying time. In this research, an indirect cabinet-type solar dryer equipped with a vacuum tube solar collector and a heat exchanger fitted with Phase Change Material (PCM) was investigated. The effect of different percentages of return airflow (0, 25, 50, and 70 percent) on Specific Energy Consumption (SEC), overall drying process efficiency, and solar collector efficiency in an indirect cabinet-type solar dryer was examined. Furthermore, to analyze the flow behavior and temperature changes within the dryer, a three-dimensional simulation using Computational Fluid Dynamics (CFD) was performed. The numerical results indicated that the 50% return airflow condition was the optimal state, reducing the drying time from 910 seconds (in the zero case) to 545 seconds, achieving the lowest Specific Energy Consumption of 10.62 MJ/kg by utilizing the latent heat capacity of the PCM. The use of the return airflow system up to 50% improved the overall dryer efficiency by up to 29.01% compared to the no-air-recirculation case. However, increasing the return airflow to 70% resulted in a decrease in efficiency due to the air becoming saturated with moisture and an increase in drying time.
Keywords
Subjects

[1] Jahromi, M. S. B., Iranmanesh, M., Samimi-Akhijahani, H. "Thermo-economic evaluation of a solar dryer with evacuated heat pipe collector and energy storage", Journal of Applied and Computational Sciences in Mechanics, Vol. 32, No. 1, pp. 39-58, 2021, https://doi.org/10.22067/jacsm.2021.56640.0
[2] Iranmanesh, M., Samimi-Akhijahani, H., Jahromi, M. S. B. "CFD modeling and evaluation of the performance of a solar cabinet dryer equipped with evacuated tube solar collector and thermal storage system", Renewable Energy, Vol. 145, pp. 1192-1213, 2020, https://doi.org/10.1016/j.renene.2019.06.038
[3] Salami, P., Safvati, M., Jahromi, M. S. B., Kalantar, V., Samimi-Akhijahani, H. "classification of fruit solar dryers and the role of phase change materials in enhancing performance: a review", Solar Energy, Vol. 297, p. 113570, 2025, https://doi.org/10.1016/j.solener.2025.113570
[4] Jahromi, M. S. B., Sayedolasgari, A., Madhankumar, S., Samimi-Akhijahani, H., Salami, P. "Thermal energy storage-centric solar drying with phase change materials: intelligent optimization via neural and evolutionary regression models", Journal of Energy Storage, Vol. 141, p. 119192, 2026, https://doi.org/10.1016/j.est.2025.119192
[5] Azaizia, Z., Kooli, S., Hamdi, I., Elkhal, W., Guizani, A. A. "Experimental study of a new mixed mode solar greenhouse drying system with and without thermal energy storage for pepper", Renewable Energy, Vol. 145, pp. 1972-1984, 2020, https://doi.org/10.1016/j.renene.2019.07.055
[6] Rabha, D. K., Muthukumar, P. "Performance studies on a forced convection solar dryer integrated with a paraffin wax-based latent heat storage system", Solar Energy, Vol. 149, pp. 214-226, 2017, https://doi.org/10.1016/j.solener.2017.04.012
[7] Murugesan, G. K., Murugesan, C., Sakthivel, M., Tamilkolundu, S. "Experimental investigation on a solar dryer assisted with minimum phase change material (PCM) placed on the inner walls of drying chamber", Journal of Energy Storage, Vol. 98, p. 113069, 2024, https://doi.org/10.1016/j.est.2024.113069
[8] Grecia, K. J., Luce, A. A., Buenaventura, M. A., Ubando, A., Gue, I. H. "Design and evaluation of a mango solar dryer with thermal energy storage and recirculated air", Proc. IEEE 11th Int. Conf. Humanoid, Nanotechnology, Information Technology, Communication and Control, Environment, and Management (HNICEM), pp. 1-5, 2019, https://doi.org/10.1109/HNICEM48295.2019.9072900
[9] Motahayyer, M., Arabhosseini, A., Samimi-Akhijahani, H. "Numerical analysis of thermal performance of a solar dryer and validated with experimental and thermo-graphical data", Solar Energy, Vol. 193, pp. 692-705, 2019, https://doi.org/10.1016/j.solener.2019.10.001
[10] Ajithkumar, A., GaneshKumar, P. "Impact of organic PCM on drying kinetics and nutritional quality of sweet potato in indirect solar dryer", Journal of Energy Storage, Vol. 132, p. 117716, 2025, https://doi.org/10.1016/j.est.2025.117716
[11] Alktranee, M., Al-Yasiri, Q., Mohammed, K. S., Arici, M., Szabo, M., Bencs, P. "Energy, exergy, and economic analysis of indirect solar dryer integrated with phase change material cans", Energy Conversion and Management: X, Vol. 26, p. 100986, 2025, https://doi.org/10.1016/j.ecmx.2025.100986
[12] Aghkhani, M. H., Abasspour-Fard, M. H., Bayati, M. R., Mortezapour, H., Saedi, S. I., Moghimi, A. "Performance analysis of a solar dryer equipped with a recycling air system and desiccant chamber", Journal of Agricultural Machinery, Vol. 3, pp. 92-103, 2014, https://doi.org/10.22067/jam.v3i2.25164
[13] Ahmadi, M., Samimi-Akhijahani, H., Salami, P. "Thermo-economic and drying kinetic analysis of oleaster using a solar dryer integrated with phase change materials and recirculation system", Journal of Energy Storage, Vol. 68, p. 107351, 2023, https://doi.org/10.1016/j.est.2023.107351
[14] Iranmanesh, M., Jahromi, M. S. B. "Effect of forced convection and pcm materials on an indirect solar dryer equipped with evacuated heat pipe collector", Modares Mechanical Engineering, Vol. 19, No. 11, pp. 2607-2614, 2019, https://doi.org/10.1001.1.10275940.1398.19.11.17.1
[15] Jahromi, M. S. B., Kalantar, V., Samimi-Akhijahani, H. "Evaluation of performance, energy, and exergy analysis of a solar parabolic dish collector connected to a dryer with nanofluid and PCM", Journal of Energy Storage, Vol. 98, p. 112969, 2024, https://doi.org/10.1016/j.est.2024.112969
[16] Shalaby, S. M., Bek, M. A., El-Sebaii, A. A. "Solar dryers with PCM as energy storage medium: a review", Renewable and Sustainable Energy Reviews, Vol. 33, pp. 110-116, 2014, https://doi.org/10.1016/j.rser.2014.01.073
[17] Matapour, A., Samimi-Akhijahani, H., Zareei, S. "Experimental and numerical study of thermal performance of a solar rotary dryer with thermal storage mechanism", Journal of Energy Storage, Vol. 82, p. 109843, 2024, https://doi.org/10.1016/j.est.2023.109843
[18] Sabiha, M. A., Saidur, R., Mekhilef, S., Mahian, O. "Progress and latest developments of evacuated tube solar collectors", Renewable and Sustainable Energy Reviews, Vol. 51, pp. 1038-1054, 2015, https://doi.org/10.1016/j.rser.2015.07.016
[19] Jahromi, M. S. B., Kalantar, V., Samimi-Akhijahani, H., Kargarsharifabad, H. "Recent progress on solar cabinet dryers for agricultural products equipped with energy storage using phase change materials", Journal of Energy Storage, Vol. 51, p. 104434, 2022, https://doi.org/10.1016/j.est.2022.104434
[20] Namjoo, M., Golbakhshi, H., Kamandar, M. R., Jahromi, M. S. B. "Performance evaluation using artificial neural network technique and exergetic impact of cold plasma pretreatment on hybrid ultrasound/convective drying of ginger slices", Thermal Science and Engineering Progress, Vol. 73, p. 104679, 2026, https://doi.org/10.1016/j.tsep.2026.104679
[21] Norton, T., Sun, D. W. "Computational fluid dynamics (CFD)- an effective and efficient design and analysis tool for the food industry: a review", Trends in Food Science & Technology, Vol. 17, No. 11, pp. 600-620, 2006, https://doi.org/10.1016/j.tifs.2006.05.004
[22] Yongson, O., Badruddin, I. A., Zainal, Z. A., Narayana, P. A. "Airflow analysis in an air conditioning room", Building and Environment, Vol. 42, No. 3, pp. 1531-1537, 2007, https://doi.org/10.1016/j.buildenv.2006.01.002
[23] Khoshhal, A., Rahimi, M., Alsairafi, A. A. "CFD investigation on the effect of air temperature on air blowing cooling system for preventing tube rupture", International Communications in Heat and Mass Transfer, Vol. 36, No. 7, pp. 750-756, 2009, https://doi.org/10.1016/j.icheatmasstransfer.2009.04.001
[24] Jahromi, M. S. B., Kalantar, V., Samimi-Akhijahani, H. "Design and performance analysis of a new flat solar heating porous collector equipped with vertical copper pipe and porous medium for medicinal plant drying", Energy, Vol. 334, p. 137653, 2025, https://doi.org/10.1016/j.energy.2025.137653
[25] Arabhosseini, A., Samimi-Akhijahani, H., Motahayyer, M. "Increasing the energy and exergy efficiencies of a collector using porous and recycling system", Renewable Energy, Vol. 132, pp. 308-325, 2019, https://doi.org/10.1016/j.renene.2018.07.132
[26] Gunjo, D. G., Mahanta, P., Robi, P. S. "Exergy and energy analysis of a novel type solar collector under steady state condition: experimental and CFD analysis", Renewable Energy, Vol. 114, pp. 655-669, 2017, https://doi.org/10.1016/j.renene.2017.07.072
[27] Hung, T. C., Huang, T. J., Lee, D. S., Lin, C. H., Pei, B. S., Li, Z. Y. "Numerical analysis and experimental validation of heat transfer characteristic for flat-plate solar air collector", Applied Thermal Engineering, Vol. 111, pp. 1025-1038, 2017, https://doi.org/10.1016/j.applthermaleng.2016.09.126
[28] Rehman, S., Mohandes, M. "Artificial neural network estimation of global solar radiation using air temperature and relative humidity", Energy Policy, Vol. 36, No. 2, pp. 571-576, 2007, https://doi.org/10.1016/j.enpol.2007.09.033
[29] Aboghrara, A. M., Baharudin, B. T., Alghoul, M. A., Adam, N. M., Hairuddin, A. A., Hasan, H. A. "Performance analysis of solar air heater with jet impingement on corrugated absorber plate", Case Studies in Thermal Engineering, Vol. 10, pp. 111-120, 2017, https://doi.org/10.1016/j.csite.2017.04.002
[30] Khazaei, J., Chegini, G. R., Bakhshiani, M. "A novel alternative method for modeling the effects of air temperature and slice thickness on quality and drying kinetics of tomato slices: superposition technique", Drying Technology, Vol. 26, No. 6, pp. 759-775, 2008, https://doi.org/10.1080/07373930802046427
[31] Rashidi, M., Arabhosseini, A., Samimi-Akhijahani, H. "Evaluation of energetic and exergetic efficiency of a solar collector equipped with porous plate, recycling system and reflectors", Iranian Journal of Biosystems Engineering, Vol. 51, No. 2, pp. 371-384, 2020, https://doi.org/10.22059/ijbse.2020.279686.665183
[32] Mokhtarian, M., Tavakolipour, H., Ashtari, A. K. "Effects of solar drying along with air recycling system on physicochemical and sensory properties of dehydrated pistachio nuts", LWT, Vol. 75, pp. 202-209, 2017, https://doi.org/10.1016/j.lwt.2016.08.056
[33] Madhankumar, S., Kumar, M. L., Jahromi, M. S. B., Kumar, K. D. H., Singh, A. K., Kumar, V. "Thermal and environmental assessment of a solar dryer with phase change material and enhanced absorber plates", Journal of Energy Storage, Vol. 153, p. 121045, 2026, https://doi.org/10.1016/j.est.2026.121045
[34] Pawar, V. R., and Sobhansarbandi, S., "CFD modeling of a thermal energy storage based heat pipe evacuated tube solar collector", Journal of Energy Storage, Vol. 30, p. 101528, 2020, https://doi.org/10.1016/j.est.2020.101528