Flow and Thermal Modeling for Enhanced Direct Contact Membrane Distillation Performance
| dc.contributor.advisor | Schaefer, Laura | |
| dc.creator | Perdue, Dani | |
| dc.date.accessioned | 2021-05-03T21:04:41Z | |
| dc.date.available | 2021-05-03T21:04:41Z | |
| dc.date.created | 2021-05 | |
| dc.date.issued | 2021-04-28 | |
| dc.date.submitted | May 2021 | |
| dc.date.updated | 2021-05-03T21:04:41Z | |
| dc.description.abstract | Desalination of brackish seawater is considered to be the primary solution to the freshwater shortage in several regions around the world. Direct contact membrane distillation (DCMD) is a thermally-driven desalination technology where hot, brackish water flows over a hydrophobic membrane that is in direct contact with cold, clean water. The temperature difference on either side of the membrane causes a vapor pressure differential that drives water vapor from the hot solution through membrane pores to condense on the other side. Although DCMD has some benefits such as operating at atmospheric pressure and at a low temperature range, there are also challenges that prevent this technology from being commercialized. These disadvantages include system designs that lower water output as it relates to energy efficiency and that increase resistance to heat and mass transfer. Therefore, there has been an uptick in research focused on what mechanisms play the most significant role in either causing or overcoming these obstacles. The work presented here takes a detailed look at two thermal parameters, the temperature polarization coefficient (TPC) and the thermal efficiency (TE), that impact heat and mass transfer. A Monte Carlo simulation was performed to calculate the exergy, or available energy on a microscopic level, within the membrane. As porosity and mass flow rate increased, the exergy of the system increased. On a macroscopic level, as the feed temperature increased, the exergy also increased. It was found that through the exergetic relationship between physical microscopic properties and macroscopic thermal properties, the TPC and the TE were improved, which could inform future DCMD system designs. Additionally, this study explores the benefits of spacers, or turbulence promotors, in terms of the effect on the flow as well as those that generate heat to help lower the effects of temperature polarization and improve thermal efficiency along the length of the membrane. Through ANSYS Fluent, a 3D DCMD system is simulated to account for turbulent flow, phase change, material properties, and other boundary conditions to fully understand computationally if heat-generating spacers enhance thermal parameters. When compared to an empty channel or a non-heat generating spacer-filled channel, it was found that the heat generating spacer-filled channel produces more permeate flux and has a higher TPC and TE. Although this analysis does not explore how producing this additional heat will impact the energy efficiency of the whole system, initial results suggest that this research area could lead to novel approaches for the field of DCMD. | |
| dc.format.mimetype | application/pdf | |
| dc.identifier.citation | Perdue, Dani. "Flow and Thermal Modeling for Enhanced Direct Contact Membrane Distillation Performance." (2021) Diss., Rice University. <a href="https://hdl.handle.net/1911/110406">https://hdl.handle.net/1911/110406</a>. | |
| dc.identifier.uri | https://hdl.handle.net/1911/110406 | |
| dc.language.iso | eng | |
| dc.rights | Copyright is held by the author, unless otherwise indicated. Permission to reuse, publish, or reproduce the work beyond the bounds of fair use or other exemptions to copyright law must be obtained from the copyright holder. | |
| dc.subject | membrane distillation | |
| dc.subject | temperature polarization coefficient | |
| dc.subject | thermal efficiency | |
| dc.subject | modeling | |
| dc.subject | performance | |
| dc.title | Flow and Thermal Modeling for Enhanced Direct Contact Membrane Distillation Performance | |
| dc.type | Thesis | |
| dc.type.material | Text | |
| thesis.degree.department | Mechanical Engineering | |
| thesis.degree.discipline | Engineering | |
| thesis.degree.grantor | Rice University | |
| thesis.degree.level | Doctoral | |
| thesis.degree.name | Doctor of Philosophy |
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