Enhancing the Performance of a Double-Slope Solar Still Using Thin and Twisted Fins: A Numerical Study

Document Type : Research Article

Authors
Duraid Thamer Mahmood 1
Ziyad Tariq Sfaieeh 2
1 Middle Technical university, Polytechnic College of Engineering Specializations-Baghdad, Power mechanics Techniques, Baghdad, Iraq
2 Middle Technical University, Engineering Technical College – Baghdad, Fuel and Energy Techniques Engineering Department, Baghdad, Iraq
10.22059/jser.2026.415805.1759
Abstract
Water scarcity is a global issue. Solar desalination systems, particularly double-slope solar stills (DSSS), offer an efficient, affordable approach to produce fresh water. This study systematically investigates the influence of fin geometry (thin vs. twisted) and fin number on the thermo-fluid behavior and productivity of DSSS under hot climatic conditions. Using ANSYS Fluent 2019 R1, the mass, momentum, and energy equations were discretised via the finite volume method to examine simultaneous heat, mass, and fluid flow inside the basin. Results show that using fins significantly enhances system performance. At peak time (12:00 PM), productivity improved from 0.8206 L/h (conventional) to 1.4928 L/h for thin fins (81.91% enhancement) and 1.9535 L/h for twisted fins (138.13% enhancement). Efficiency likewise improved from 28.543% to 59.810% and 80.500%, respectively. On a daily basis, productivity and efficiency increased from 3.514 to 8.761 L/m²·day and from 25.87% to 74.97% using 49 twisted fins, representing improvements of 149.32% and 189.68%. Twisted fins exhibit superior performance by enhancing internal mixing, reducing thermal boundary layer thickness, and improving vapor distribution. Ultimately, the best results were obtained with 49 twisted fins, demonstrating that sophisticated geometric modifications are essential to maximize DSSS productivity and efficiency.
Keywords
Double-slope solar still
Fin geometry
Twisted fins
CFD analysis
Evaporation enhancement
Solar desalination
 [1] Dhivagar, R., Suraparaju, S. K., Jidhesh, P., & Kim, S. C. (2025). Integration of solar photovoltaic panel and A46 phase change material in double-slope solar still: A progressive approach for performance enhancement. Separation and Purification Technology, 374, 133754. https://doi.org/10.1016/j.seppur.2025.133754
[2] Saha, S., Sarker, M. R. I., Kader, M. A., Ahmed, M. M., Tuly, S. S., & Mustafi, N. N. (2024). Development of a vacuum double-slope solar still for enhanced freshwater productivity. Solar Energy, 270, 112385. https://doi.org/10.1016/j.solener.2024.112385
[3] Ghriss, O., Makki, N., Dhaoui, S., Abdel-Aziz, M. M., Bouabidi, A., & Attia, M. E. H. (2025). Experimental assessment of square fin number variation on energy and exergy performance in double-slope solar stills under Tunisia weather conditions. International Communications in Heat and Mass Transfer, 162, 108660. https://doi.org/10.1016/j.icheatmasstransfer.2025.108660
[4] Ghazy, A. (2023). Theoretical study of a double-slope solar still with solar air heater condenser. International Journal of Renewable Energy Development, 12(6), 977–986. https://doi.org/10.14710/ijred.2023.53928
[5] Rajaseenivasan, T., & Srithar, K. (2016). Performance investigation on solar still with circular and square fins in basin with CO₂ mitigation and economic analysis. Desalination, 380, 66–74. https://doi.org/10.1016/j.desal.2015.11.025
[6] Khare, V. R., Singh, A. P., Kumar, H., & Khatri, R. (2017). Modelling and performance enhancement of single slope solar still using CFD. Energy Procedia, 109, 447–455. https://doi.org/10.1016/j.egypro.2017.03.064
[7] Moreno, S., Álvarez, C., Hinojosa, J. F., & Maytorena, V. M. (2022). Numerical analysis of a solar still with phase change material under the basin. Journal of Energy Storage, 55, 105427. https://doi.org/10.1016/j.est.2022.105427
[8] Chung, Y., & Kim, M. S. (2019). Thermal analysis and pack level design of battery thermal management system with liquid cooling for electric vehicles. Energy Conversion and Management, 196, 105–116. https://doi.org/10.1016/j.enconman.2019.05.083
[9] Hashemian, N., & Noorpoor, A. (2023). Thermo-eco-environmental investigation of a newly developed solar/wind powered multi-generation plant with hydrogen and ammonia production options. Journal of Solar Energy Research, 8(4), 1728–1737. https://doi.org/10.22059/JSER.2024.374028.1388
[10] Hafs, H., Ansari, O., & Bah, A. (2023). Performance evaluation of a production system of solar desalination by using rectangular channels with PCM at different seasons. Acta Ecologica Sinica, 43(4), 690–700. https://doi.org/10.1016/j.chnaes.2022.09.001
[11] Hameed, H. G., Diabil, H. A. N., & Al-Moussawi, M. A. (2023). A numerical investigation of the enhancement of single-slope single-basin solar still productivity. Energy Reports, 9, 484–500. https://doi.org/10.1016/j.egyr.2022.11.199
[12] Aftiss, R., Najim, M., & Hissouf, M. (2024). Numerical study of PCM-integrated solar still efficiency enhancement. International Journal of Low-Carbon Technologies, 19, 443–454. https://doi.org/10.1093/ijlct/ctae004
[13] AbdelMeguid, H., & El Awady, W. M. (2024). Optimising solar still performance through glass cover optical properties: A mathematical modeling and theoretical investigation. Ain Shams Engineering Journal, 15(3), 102589. https://doi.org/10.1016/j.asej.2023.102589
[14] Abed, A. F., Alshukri, M. J., & Hachim, D. M. (2024). Improving solar still performance via the integration of nanoparticle-enhanced phase change materials: A novel pyramid-shaped design with a numerical simulation approach. Journal of Energy Storage, 97, 112980. https://doi.org/10.1016/j.est.2024.112980
[15] Aftiss, R., Najim, M., Tbatou, T., & Hissouf, M. (2025). Numerical study of conventional solar still integrated dynamic PCM layer. Desalination, 600, 118493. https://doi.org/10.1016/j.desal.2024.118493
[16] Kavasoğulları, B., Aktemur, C., & Karagöz, M. E. (2026). Numerical investigation of the effect of fin inclination on melting dynamics and energy storage in a PCM-filled square enclosure. Journal of Engineering Research, 14(2), 2097–2117. https://doi.org/10.1016/j.jer.2025.12.021
[17] Yazdanparast, S. A., Setareh, M., & Basirat Tabrizi, H. (2026). Numerical investigation of melting characteristics of fin-assisted single and dual PCM latent heat storage system under time-dependent solar heat flux. Discover Mechanical Engineering, 5(1), Article 14. https://doi.org/10.1007/s44245-026-00185-z
[18] Togun, H., Homod, R. Z., Sadeghinezhad, E., & Kazi, S. N. (2023). Navier–Stokes equations and high-resolutions: Advancements in accurate incompressible flow simulations. Knowledge-Based Engineering and Sciences, 4(2), 51–59. https://doi.org/10.51526/kbes.2023.4.2.51-59
[19] da Silva Junior, L. G., de Oliveira, J. P. J., Ribeiro, G. B., & Pinto, L. F. (2023). Experimental and numerical analysis of a low-cost solar still. Eng, 4(1), 380–403. https://doi.org/10.3390/eng4010023
[20] Gaur, M. K., & Tiwari, G. N. (2010). Optimisation of number of collectors for integrated PV/T hybrid active solar still. Applied Energy, 87(5), 1763–1772. https://doi.org/10.1016/j.apenergy.2009.10.019
[21] Kumar, S., & Tiwari, G. N. (1997). Estimation of convective mass transfer in solar distillation systems. Solar Energy, 57(6), 459–464. https://doi.org/10.1016/S0038-092X(96)00122-3
[22] Tiwari, G. N., Shukla, S. K., & Singh, I. P. (2003). Computer modeling of passive/active solar stills by using inner glass temperature. Desalination, 154(2), 171–185. https://doi.org/10.1016/S0011-9164(03)80018-8
[23] Ghazy, A., & Alrowais, R. (2022). Experimental performance of single-slope basin solar still coupled with a humidification–dehumidification cycle. Sustainability, 14(23), 15755. https://doi.org/10.3390/su142315755
[24] Agrawal, R., & Singh, K. D. P. (2022). Experimental investigation and computational modelling of double slope solar still integrated with eutectic phase change material. Journal of Energy Storage, 52, 104802. https://doi.org/10.1016/j.est.2022.104802
Journal of Solar Energy Research
Volume 11, Issue 3
Summer 2026
Pages 4021-4035