International Scientific Journal

Thermal Science - Online First

online first only

Theoretical and experimental investigation of the evacuated tube solar water heater system

In this study, the evacuated tube solar water heater (ETSWH) system using thermosyphon has been investigated experimentally as well as theoretically. Solar radiation and ambient temperature data from Chiang Mai province were used for the modeling system by Explicit Finite Difference Method (EFDM). The effects of thermosyphon diameters and number of evacuated tubes on the net saving of solar water heater system were analyzed. The mathematical results showed that the optimal number of evacuated tubes and thermosyphon diameter occurs at 8 evacuated tubes, which are 15.88 mm of evaporator diameter and 22.22 mm of condenser diameter under personal hygiene conditions. The solar water heater system at optimal parameters was constructed and tested for the system prototype. The theoretical results were validated by the experimental results. It was found that the theoretical results can be used to predict temperature, heat transfer rate, and thermal efficiency to show good agreement with the experimental results as well as previous research. The experimental and theoretical results showed that the maximum temperature for hot water was 65.25oC and 71.66oC, respectively. Moreover, the thermal efficiency of the system based on the theoretical result was 60.11%, with relative error being about 3.04% of the experimental result.
PAPER REVISED: 2018-09-01
PAPER ACCEPTED: 2018-12-23
  1. Han, J, et al., Solar water heaters in China: a new day dawning, Energy Policy, 38 (2010), pp. 383-391.
  2. Liang, R.,, Performance analysis of a new-design filled-type solar collector with double U-tubes, Energy and Buildings, 57 (2013), pp. 220-226.
  3. Morrison, G.L., et al., Water-in-glass evacuated tube solar water heaters, Solar Energy, 76 (2004), pp. 135-140.
  4. Budihardjo, I., Morrison, G.L, Performance of water-in-glass evacuated tube solar water heaters, Solar Energy, 83 (2008), pp. 49-56.
  5. Chow, T.T.,, Performance evaluation of evacuated tube solar domestic hot water systems in Hong Kong. Energy and Buildings, 43 (2011), pp. 3467-3474.
  6. Riahi, A., Taherian, H., Experimental Investigation on the Performance of Thermosyphon Solar Water Hater In the South Caspian Sea, Thermal Science, 15 (2011), pp. 447-456.
  7. Jafarkazemi, F., et al., Energy and exergy efficiency of heat pipe evacuated tube solar collectors, Thermal Science, 20(2016), pp.327-335.
  8. Nada, S.A., et al., Performance of a two-phase closed thermosyphonsolar collector with a shell and tube heat exchanger, Applied Thermal Engineering, 24 (2004), pp. 1959-1968.
  9. Samuel, L.A., Colle, S., An experimental study of two-phase closed thermosyphons for compact solar domestic hot-water systems, Solar Energy, 76 (2004), pp. 141-145.
  10. Esen, M., Esen, H., Experimental investigation of a two-phase closed thermosyphon solar water heater, Solar Energy, 79 (2006), pp. 459-468.
  11. Kim, Y., Seo, T., Thermal performances comparisons of the glass evacuated tube solar collectors with shapes of absorber tube, Renewable Energy, 32 (2007), pp. 772-795.
  12. Azad, E., Theoretical and experimental investigation of heat pipe solar collector, Experimental Thermal and Fluid Science, 32 (2008), pp. 1666-1672.
  13. Ayompe, L.M.,, Validated TRNSYS model for forced circulation solar water heating systems with flat plate and heat pipe evacuated tube collectors, Applied Thermal Engineering, 31 (2011), pp. 1536-1542.
  14. John, D., Anderson, J.R., Computational fluid dynamics, McGraw-Hill, New York,1995.
  15. Cengel, Y.A., Heat transfer a practical approach, McGraw-Hill, New York, 2004.
  16. ESDU, Performance of two-phase closed thermosyphon, Engineering Sciences Data Unit, London, 1981.
  17. Soylemez, M.S., On the thermoeconomical optimization of heat pipe heat exchanger HPHE for waste heat recovery, Energy Conversion and Management, 44 (2003), pp. 2509-2517.
  18. Government Savings Bank,, 2016 (accessed 10 December 2016).
  19. Wannagosit, C.,, Computational Study of Water Heater System with Evacuated Glass Tube Solar Collector, Proceedings, 8th STISWB, Yangon, Myanmar, June, 2016, pp. 450-460.
  20. AS1056.1, 1991. Standards Australia, Storage Water Heaters - General Requirements.
  21. Caglar, A., Yamal, C., Performance analysis of a solar-assisted heat pump with an evacuated tubular collector for domestic heating, Energy and Buildings, 54 (2012), pp. 22-28.
  22. Wang, J.,, Medium-temperature solar collectors with all-glass solar evacuated tubes, Energy Procedia, 70 (2015), pp. 126 - 129.