International Scientific Journal


The present work attempts to demonstrate the competence and reliability of the proposed computational solver for real-scale modelling and analysis of a commercially available evacuated tube collector type solar water heater. A 3-D, transient numerical solver with user-defined functions is modelled using CFD program ANSYS-Fluent 15.0®. The objective is to analyse the evacuated tube collector type solar water heater in two states of operation, namely, static (stagnant charging) and dynamic (retrieval) modes. This work emphasizes the determination of the impact of thermal stratification, and fluid mixing in the storage tank on the outlet temperature profile during discharging. Volume flow rates vary from 3-15 Lpm. The reported findings suggest that with an increase of fluid-flow during discharge, the stratified layers disorient and lead to rapid mixing, which eventually results in an earlier drop in the outlet water temperature. Furthermore, at low fluid-flow rates, the stratified layers remain intact with only a gradual decay in the outlet temperature profile. The analysis reveals that based on the user’s choice, it is possible to vary discharge flow rate until 7 Lpm without a significant drop in the outlet water temperature. Furthermore, computational results have been successfully validated with experimental findings.
PAPER REVISED: 2019-10-01
PAPER ACCEPTED: 2019-10-05
CITATION EXPORT: view in browser or download as text file
  1. Tian Y, Zhao CY. A review of solar collectors and thermal energy storage in solar thermal applications. Applied Energy 2013;104:538-553.
  2. Raj AK, Srinivas M, Jayaraj S. A cost-effective method to improve the performance of solar air heaters using discrete macro-encapsulated PCM capsules for drying applications. Applied Thermal Engineering 2019;146:910-920.
  3. Zalba B, Marın JM, Cabeza LF, Mehling H. Review on thermal energy storage with phase change: materials, heat transfer analysis and applications. Applied Thermal Engineering 2003;23(3):251-283.
  4. Islam MR, Sumathy K, Khan SU. Solar water heating systems and their market trends. Renewable and Sustainable Energy Reviews 2013;17:1-25.
  5. Sabiha MA, Saidur R, Mekhilef S, Mahian O. Progress and latest developments of evacuated tube solar collectors. Renewable and Sustainable Energy Reviews 2015;51:1038-1054.
  6. Rout A, Sahoo SS, Thomas S. Risk modeling of domestic solar water heater using Monte Carlo simulation for east-coastal region of India. Energy 2018;145:548-556.
  7. Perers B. Comparison of thermal performance for flat plate and evacuated tubular collectors. In Advances In Solar Energy Technology 1988;615-619.
  8. Zambolin E, Del Col D. Experimental analysis of thermal performance of flat plate and evacuated tube solar collectors in stationary standard and daily conditions. Solar Energy 2010;84(8):1382-1396.
  9. Sokhansefat T, Kasaeian A, Rahmani K, Heidari AH, Aghakhani F, Mahian O. Thermoeconomic and environmental analysis of solar flat plate and evacuated tube collectors in cold climatic conditions. Renewable Energy 2018;115:501-508.
  10. Budihardjo I, Morrison GL. Performance of water-in-glass evacuated tube solar water heaters. Solar Energy 2009;83(1):49-56.
  11. Morrison GL, Budihardjo I, Behnia M. Water-in-glass evacuated tube solar water heaters. Solar Energy 2004;76(1-3):135-140.
  12. Yildizhan H, Sivrioglu M. Exergy analysis of a vacuum tube solar collector system having indirect working principle. Thermal Science. 2017;21(6B):2813-2825.
  13. Riahi A, Taherian H. Experimental investigation on the performance of thermosiphon solar water heater in the south Caspian sea. Thermal Science. 2011;15(2). pp. 447-456
  14. Zeghib I, Chaker A. Simulation of a solar domestic water heating system. Energy Procedia 2011;6:292-301.
  15. Nitsas MT, Koronaki IP. Experimental and theoretical performance evaluation of evacuated tube collectors under Mediterranean climate conditions. Thermal Science and Engineering Progress 2018;8:457-469.
  16. Abdelhak O, Mhiri H, Bournot P. CFD analysis of thermal stratification in domestic hot water storage tank during dynamic mode. In Building Simulation 2015;8(4):421-429
  17. Levers S, Lin W. Numerical simulation of three-dimensional flow dynamics in a hot water storage tank. Applied Energy 2009;86(12):2604-2614.
  18. Lavan Z, Thompson J. Experimental study of thermally stratified hot water storage tanks. Solar Energy 1977;19(5):519-524.
  19. Assari MR, Tabrizi HB, Savadkohy M. Numerical and experimental study of inlet-outlet locations effect in horizontal storage tank of solar water heater. Sustainable Energy Technologies and Assessments 2018;25:181-190.
  20. Fernandez-Seara J, Uhı FJ, Sieres J. Experimental analysis of a domestic electric hot water storage tank. Part II: dynamic mode of operation. Applied Thermal Engineering 2007;27(1):137-144.
  21. Shah LJ, Furbo S. Entrance effects in solar storage tanks. Solar Energy 2003;75(4):337-348.
  22. Raj AK, Srinivas M, Jayaraj S. CFD modeling of macro-encapsulated latent heat storage system used for solar heating applications. International Journal of Thermal Sciences 2019;139:88-104.
  23. Demain C, Journée M, Bertrand C. Evaluation of different models to estimate the global solar radiation on inclined surfaces. Renewable Energy. 2013;50:710-721.
  24. Zelzouli K, Guizani A, Kerkeni C. Numerical and experimental investigation of thermosyphon solar water heater. Energy Conversion and Management 2014;78:913-922.

© 2020 Society of Thermal Engineers of Serbia. Published by the Vinča Institute of Nuclear Sciences, Belgrade, Serbia. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution-NonCommercial-NoDerivs 4.0 International licence