International Scientific Journal


The flat plate solar water heater, using the closed-loop oscillating heat pipes, was constructed and investigated. The flat plate collector consisted of 10 pipes of closed-loop oscillating heat pipes and the collector area was 1.5×1 m2. Each closed-loop oscillating heat pipes was made of a copper capillary tube with a 1.5 mm inner diameter, a 2.8 mm outer diameter, and had 20 turns. The distilled water was used as the working fluid with a filling ratio of 50% the tube’s total internal volume. The evaporator section of the closed-loop oscillating heat pipes was placed on the absorber plate of the collector, and its condenser section was wrapped around the copper tube, in which hot water flowed through. The solar water heater was tested under the solar simulator with halogen lamps generating the uniform artificial solar energy. The irradiation intensity and the water flow rate of the solar water heater were adjusted. It was found that the thermal performance of the solar water heater clearly improved with an increase in the irradiation intensity from 480-1086 W/m2. However, the water flow rate in the range of 1.5-3.0 Lpm, had a thermal performance that was slightly different. The thermal efficiency of 0.67 was archived at the high irradiation intensity of 947-1086 W/m2. Moreover, the mathematical model to predict the thermal efficiency of the flat plate solar water heater with the closed-loop oscillating heat pipes was obtained.
PAPER REVISED: 2021-04-29
PAPER ACCEPTED: 2021-05-11
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THERMAL SCIENCE YEAR 2021, VOLUME 25, ISSUE Issue 5, PAGES [3607 - 3614]
  1. Nada, S.A., et al., Performance of a Two-Phase Closed Thermosyphon Solar Collector with a Shell and Tube Heat Exchanger, Applied Thermal Engineering, 24 (2004), 13, pp. 1959-1968
  2. Esen, M., Esen, H., Experimental Investigation of a Two-Phase Closed Thermosyphon Solar Water Heater, Solar Energy, 79 (2005), 5, pp. 459-468
  3. Hussein, H.M.S., et al., Performance of Wickless Heat Pipe Flat Plate Solar Collectors Having Different Pipes Cross Sections Geometries and Filling Ratios, Energy Conversion & Management, 47 (2006), 11-12, pp. 1539-1549
  4. Hussein, H.M.S., Theoretical and Experimental Investigation of Wickless Heat Pipes Flat Plate Solar Collector with Cross Flow Heat Exchanger, Energy Cnversion & Management, 48 (2007), 4, pp. 1266-1272
  5. Azad, E., Theoretical and Experimental Investigation of Heat Pipe Solar Collector, Experimental Thermal and Fluid Science, 32 (2008), 8, pp. 1666-1672
  6. Wei, L., et al., A Study on a Flat-Plate Type of Solar Heat Collector with an Integrated Heat Pipe, Solar Energy, 97 (2013), pp. 19-25
  7. Deng, Y., et al., Experimental Investigation of Performance for the Novel Flat Plate Solar Collector with Micro-Channel Heat Pipe Array (MHPA-FPC), Applied Thermal Engineering, 54 (2013), 2, pp. 440-449
  8. Deng, Y., et al., Experimental Study of the Thermal Performance for the Novel Flat Plate Solar Water Heater with Micro Heat Pipe Array Absorber, Energy Procedia, 70 (2015), pp. 41-48
  9. Allouhi, A., et al., Forced-Circulation Solar Water Heating System using Heat Pipe-Flat Plate Collectors: Energy and Exergy Analysis, Energy, 180 (2019), pp. 429-443
  10. ESDU., Heat Pipes-Performance of Two-Phase Closed Thermosyphons, Data Item No. 81038, Engineering Sciences Data Unit, London, 1981
  11. Faghri, A., Heat Pipe Science and Technology, Taylor & Francis, Washington, USA, 1995
  12. Akachi, H., et al., Pulsating Heat Pipes, Proceedings, 5th International Heat Pipe Symposium, Melbourne, Australia, 1996, pp. 208-217
  13. Arab, M., et al., Experimental Investigation of Extra-Long Pulsating Heat Pipe Application in Solar Water Heaters, Experimental Thermal and Fluid Science, 42 (2012), pp. 6-15
  14. Abad, H.K.S., et al., A Novel Integrated Solar Desalination System with a Pulsating Heat Pipe, Desalination, 311 (2013), pp. 206-210
  15. Nguyen, K.B., et al., Effect of Working-Fluid Filling Ratio and Cooling-Water Flow Rate on the Performance of Solar Collector with Closed-Loop Oscillating Heat Pipe, Journal of Mechanical Science and Technology, 26 (2012), 1, pp. 251-258
  16. Jililian, M., et al., Simulation and Optimization of Pulsating Heat Pipe Flat-Plate Solar Collectors Using Neural Networks and Genetic Algorithm: a Semi-Experimental Investigation, Clean Technologies and Environmental Policy, 18 (2016), 7, pp.2251-2264
  17. Gao, Y., et al., Thermal Properties of Solar Collector Comprising Oscillating Heat Pipe in a Flat-Plate Structure and Water Heating System in Low-Temperature Conditions, Energies, 11 (2018), 10, pp. 1-12
  18. Jin, H., et al., Experimental Study of Transparent Oscillating Heat Pipes Filled with Solar Absorptive Nanofluids, International Journal of Heat and Mass Transfer, 139 (2019), pp. 789-801
  19. Charoensawan, P., et al., Closed Loop Pulsating Heat Pipes-Part A: Parametric Experimental Investigations, Applied Thermal Engineering, 23 (2003), 16, pp. 2009-2020
  20. Charoensawan, P., Terdtoon, P., Thermal Performance of Horizontal Closed-Loop Oscillating Heat Pipes, Applied Thermal Engineering, 28 (2008), 5-6, pp. 460-466
  21. ASHRAE Standard 93-77, Methods of testing solar collectors based on thermal performance, New York, 1977, pp. 8

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