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Simultaneous Impact of Multiple Boiling Droplets on a Molten Phase Change Material as a Direct-Contact Solidification Method

Poureslami, Parham | 2023

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  1. Type of Document: M.Sc. Thesis
  2. Language: Farsi
  3. Document No: 55817 (08)
  4. University: Sharif University of Technology
  5. Department: Mechanical Engineering
  6. Advisor(s): Shafii, Mohammad Behshad
  7. Abstract:
  8. Encompassing an interaction between the phase change material (PCM) and the droplets of a heat transfer fluid, the direct contact (DC) method provides a state-of-the-art solution for the meager melting and solidification rates of PCMs. In the DC procedure, when impinging on the molten PCM pool, droplets evaporate, solidifying the portion of the PCM. For the first time, the impact of single and simultaneous double ethanol droplets, having an average diameter of 2.68 mm, on the molten paraffin wax has been scrutinized exhaustively. Experiments have been carried out through high-speed imaging for various Weber numbers ranging from 179 to 464, pool temperatures from 70 to 95°C, and horizontal impact spacing from 4.02 to 12.06 mm. By altering impact parameters, four and five distinct regimes have been observed in the case of single and double droplets, respectively, whose regime maps have been proposed as well. Furthermore, the influences of the impact parameters on the central uprising sheet, formed between two impinging droplets, crater width, crater depth, jet height, and solidified PCM area, created after the impact, have been investigated. It was ascertained that boosting either the Weber number or the impact spacing intensifies the droplets' spreading areas, leading to a larger solidified PCM area. For instance, solidified PCM area at Wed = 373 is, on average, 56% greater than that at Wed = 179. Moreover, increasing the impact spacing diminishes the central uprising sheet height and retards its formation. For instance, the maximum central uprising sheet height dwindles by 57% when the horizontal impact spacing is augmented from 4.02 to 9.38 mm. In contrast, raising the Weber number monotonously strengthens the central uprising sheet
  9. Keywords:
  10. Weber Number ; High Speed Visualization ; Phase Change Material (PCMs) ; Multiple Droplet Impact ; Ethanol Droplet

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