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Modeling and Simulation of Water Desalination by Membrane Distillation

Taghavi, Amir Reza | 2020

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  1. Type of Document: M.Sc. Thesis
  2. Language: Farsi
  3. Document No: 53594 (06)
  4. University: Sharif University of Technology
  5. Department: Chemical and Petroleum Engineering
  6. Advisor(s): Molaei Dehkordi, Asghar
  7. Abstract:
  8. Water desalination is one of the most important issues for human being. Water desalination is the whole process of removing salts from water. This process is widely used in urban, industrial, and commercial applications and its efficiency has been improved with the development of desalination industry. One of the new methods of water desalination is membrane distillation, in which water desalination is performed using an appropriate membrane. In this research work, the membrane distillation process of saline water has been modeled and simulated using Comsol Multisphysics software through simultaneously solving the governing equations of momentum, thermal energy and mass transfer. The model predictions were validated against experimental data reported in the literature and, then, the effects of various design parameters and the operating conditions on the performance of this process were carefully investigated. The obtained simulation results indicate that the flux of direct-contact membrane distillation (DCMD) process increases exponentially with an increase in the feed temperature. It was also found that with increasing salt concentration of the feed, the flux decreases. The simulation results also indicate that the flux of DCMD process was directly related to the velocity of the streams and the size of the membrane pores and inversely related to the salt concentration and permeate flow temperature. While discussing the optimization of energy consumption considering its economy, for this purpose, first a new configuration was proposed to use the hot output from the membrane distillation module to preheat the feed. Then, this configuration was simulated using Aspen Hysys software. Design Expert software was used for the optimization and the feed temperature range was varied from 30 to 80 ℃ and the feed velocity was varied from 0.1 to 3.0 m s– 1. The obtained results indicate that when the feed temperature is 80 ℃ and the feed velocity is about 1.8 m s– 1, the highest efficiency of the system can be obtained. This is because the lowest process cost is paid for a certain flux
  9. Keywords:
  10. Membrane Distillation ; Water Desalination ; Optimization ; Computational Fluid Dynamics (CFD) ; Modeling ; Simulation ; Desalination

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