Studying Unsteady Heat and Mass Transfer Condition in a Tubular Solar Still Used for Water Harvesting Implication

Document Type : Research Paper

Author

Associate Professor, Faculty of Agriculture, University of Birjand, Birjand, Iran.

10.22077/jwhr.2026.11055.1202

Abstract

 This study presents a comprehensive unsteady-state mathematical model for analyzing heat and mass transfer processes in a tubular solar still (TSS), aimed at enhancing the accuracy of temperature predictions and freshwater productivity assessments. The model incorporates time-dependent energy balance equations for key components—including the saline water, trough, humid air, and transparent cover—while accounting for convective, evaporative, radiative, and condensative heat transfer mechanisms. Assumptions such as uniform water temperature, negligible vapor leakage, saturated vapor near the water surface, and minimal solar absorption by humid air are employed to simplify the analysis. Mass transfer coefficients are derived from established correlations, and natural convection is modeled using Rayleigh and Grashof numbers for curved surfaces. Simulations under constant solar radiation (750 W/m²) and ambient temperature (28°C) reveal that the trough exhibits the highest temperature (up to 60°C), followed by saline water, humid air, and the cover (lowest at ~40°C), with all components stabilizing after approximately 2 hours. Cumulative distillate yield reaches approximately 0.5 kg after 8 hours of operation. Parametric analyses demonstrate that a 2.5-fold increase in solar radiation intensity results in a 3.4-fold rise in productivity, while enlarging the diameter from 0.1 m to 0.4 m yields a 4.5-fold enhancement, though at increased cost. The model provides valuable insights for optimizing TSS designs in water-scarce regions, highlighting the potential for sustainable, low-cost desalination. 

Keywords

Main Subjects

References

 Ahsan, A., & Fukuhara, T. (2010). Mass and heat transfer model of tubular solar still. Solar energy, 84(7), 1147-1156. https://doi.org/10.1016/j.solener.2010.03.019
Arunkumar, T., Jayaprakash, R., Denkenberger, D., Ahsan, A., Okundamiya, M. S., & Kumar, S. (2012). An experimental study on a hemispherical solar still. Desalination, 286, 342–348. https://doi.org/10.1016/j.desal.2011.11.047
Dunkle, R. V. (1961). Solar water distillation: The roof type still and a multiple effect diffusion still. In Proceedings of the International Developments in Heat Transfer Conference (pp. 895–902).
Elashmawy, M. (2017). Performance study of a modified solar still integrated with evacuated tubes. Solar Energy, 141, 164–171. https://doi.org/10.1016/j.solener.2016.11.031
El-Dessouky, H. T., & Ettouney, H. M. (2002). Fundamentals of salt water desalination. Elsevier. https://doi.org/10.1016/B978-044450810- 2/50000-2
 Eltawil, M. A., & Omara Z. M. (2014). Enhancing the solar still performance using solar photovoltaic, flat plate collector and hot air.
Fudholi, A., Sopian, K., Yazdi, M. H., Ruslan, M. H., Ibrahim, A., & Kazem, H. A. (2014). Performance analysis of solar distillation system: A review. Renewable and Sustainable Energy Reviews, 29, 655–684. https://doi.org/10.1016/j.rser.2013.08.088
Gleick, P. H. (1998). Water in crisis: Paths to sustainable water use. Ecological Applications, 8(3), 571–579. https://doi.org/10.1890/1051- 0761(1998)008[0571:WICPTS]2.0.CO;2
ISLAM, K. S., & Fukuhara, T. (2005). Heat and mass transfer in tubular solar still under steady condition. PROCEEDINGS OF HYDRAULIC ENGINEERING, 49, 727-732. (No DOI available). Kabeel, A. E., & Abdelgaied, M. (2016). Improving the performance of solar still by using phase change material as a thermal storage
Kumar, S., & Tiwari, G. N. (1996). Estimation of convective mass transfer in solar distillation systems. Solar Energy, 57(6), 459–464. https://doi.org/10.1016/S0038-092X(96)00131-0
Malik, M. A. S., Tiwari, G. N., Kumar, A., & Sodha, M. S. (1982). Solar distillation. Pergamon Press.
Mehta, P., Bhatt, N., Bassan, G., & Sathyamurthy (2025). Experimental insights of a novel stepped solar distiller by augmenting condensing cover cooling and heat recovery mechanisims. Solar energy, 249, 113506. 
 Muftah, A. F., Alghoul, M. A., Fudholi, A., Abdul-Majeed, M. M., & Sopian, K. (2014). Factors affecting basin type solar still productivity: A detailed review. Renewable and Sustainable Energy Reviews, 32, 430–447. https://doi.org/10.1016/j.rser.2013.12.052
Nafey, A. S., Abdelkader, M., Abdelmotalip, A., & Mabrouk, A. A. (2000). Parameters affecting solar still productivity. Energy Conversion and Management, 41(17), 1797–1809. https://doi.org/10.1016/S0196-8904(00)00019-0
Naim, M. M., & Abd El Kawi, M. A. (2002). Non-conventional solar stills: Part 1. Desalination, 153(1–3), 55–64. https://doi.org/10.1016/S0011- 9164(02)01057-2
Omara, Z. M., Kabeel, A. E., & Essa, F. A. (2013). Enhancement of solar still performance using finned corrugated absorber. Desalination, 311, 153–160. https://doi.org/10.1016/j.desal.2012.11.005
Panchal, H., & Mohan, I. (2017). Various methods applied to solar still for enhancement of distillate output. Desalination, 415, 76–89. https://doi.org/10.1016/j.desal.2017.04.015
Rohsenow, W. M., Hartnett, J. P., & Cho, Y. I. (1998). Handbook of heat transfer (Vol. 3). New York.
Shukla, S. K., & Sorayan, V. P. (2005). Thermal modeling of solar stills: An experimental validation. Renewable Energy, 30(5), 683–699. https://doi.org/10.1016/j.renene.2004.09.007
Tareemi, A. A., & Sharshi, S.W. (2025). Performance improvement of double-slope solar still using locally sourced sand, coupled with glass cooling integration. Results in Engineering, 26, 105166. https://doi.org/10.1016/j.rineng.2025.105166
Tripathi, R., & Tiwari, G. N. (2004). Thermal modeling of passive and active solar stills for different depths of water. Applied Energy, 78(1),
UNESCO. (2020). The United Nations world water development report 2020: Water and climate change. UNESCO Publishing. 
Water Harvesting Research
Volume 9, Issue 1
March 2026
Pages 18-27

Files

Share

How to cite

Statistics