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Enhanced Solar Still Condensation Using a Radiative Cooling System with Phase Change Materials

Amarlou, Ali | 2018

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  1. Type of Document: M.Sc. Thesis
  2. Language: Farsi
  3. Document No: 50450 (08)
  4. University: Sharif University of Technology
  5. Department: Mechanical Engineering
  6. Advisor(s): Shafii, Mohammad Behshad
  7. Abstract:
  8. Desalination of seawater is one of the best solutions for freshwater supply. Solar desalination is an appropriate way to desalinate seawater. The main disadvantage of solar desalination systems is low daily production. Considering the free radiative cooling potential, the purpose of this project is the increment of the daily yield of solar still by enhancement of condensation process. For transferring cooling potential of radiative cooling from nighttime to the daytime, phase change materials (PCMs) are used. Two types of condensers are fabricated in this project. One of them uses ambient air as a thermal sink and the other one uses radiative cooling which is saved in PCM. Describing procedure of fabricated system, an integrated collector radiates heat to the sky during the night and absorbs solar radiation during the daytime. At first, the thermal heat of PCM transfers to the integrated collector by water and then, this heat is radiated to the sky. By decreasing the temperature of PCM, PCM starts to solidify and cooling is saved by latent heat. During daytime, solar energy which is absorbed by integrated collector increases the temperature of water and water vapor is produced. This vapor is condensed by cooling which is saved in PCM. In the first part of the tests with 4 different experiments, the effect of radiative cooling is evaluated on the daily yield of solar desalination system. Type of condenser is the main difference in these 4 tests. Air condenser, PCM condenser, PCM-Air condenser and Air-PCM condenser are 4 different types of the condensers. In the second part of tests, the area of the collector is reduced to 3/4, 1/2 and 1/4 of initial area and effect of reducing the collector area is investigated. In the first part of tests, the daily yield of the conventional system with Air condenser was about 2.14 kg/m2. In the novel system with 2 condensers which a PCM condenser was added, amount of daily yield was increased 31.2%. In the second part of tests, amount of daily yield was decreased by decreasing the area of the integrated collector. The maximum temperature of water vapor was decreased 10 centigrade degrees but the minimum temperature of PCM was increased just 2 centigrade degrees. This result shows that PCM condenser had better performance than Air condenser in the lower area of the collector
  9. Keywords:
  10. Solar Desalination ; Phase Change Material (PCMs) ; Collectors ; Radiative Cooling ; Collector Area Reduction ; Integrated Collector

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