Session: K20-03: APPLICATIONS OF COMPUTATIONAL HEAT TRANSFER I

Paper Number: 131256

131256 - Influence of Stirring in Seawater Freeze Desalination Inside a Cooled Jacketed Crystallizer 

Abstract: 

Seawater freeze desalination has garnered increasing attention due to its potential to produce fresh water from abundant seawater sources with lower energy and maintenance requirements. The salinity of the water produced in the form of ice, is dependent to the heat and mass transfer during the freezing process. Stirring the unfrozen brine during freezing plays a pivotal role in reducing ice salinity. This study is dedicated to investigating the impact of various stirring rates on produced ice quality in NaCl brine (70 g/L) freezing desalination experiments.  These experiments employ a chilled jacketed glass crystallizer designed to cool the brine from the cylinder's lateral wall. A motor-driven stirrer is used to agitate the brine during the experiments, and three stirring rates: 0 rpm, 30 rpm, and 60 rpm are set in the experiments. The results unequivocally demonstrate that stirring significantly reduces ice salinity. When freezing 50% of the brine, the ice's salinity under stirring rates of 30 rpm and 60 rpm is 14.22±0.09 g/L and 19.11±0.64 g/L, respectively, while the ice produced without stirring (0 rpm) exhibits a salinity of 21.50±0.29 g/L. Moreover, higher rates do not consistently promote salt diffusion and achieve lower ice salinity. When freezing 10% of the brine, a rotation rate of 60 rpm attains a higher desalination efficiency at 96.04% ±0.02% compared to 30 rpm, which yields an efficiency of 95.43%±1.66%. For larger quantities of freezing, a stirring rate of 30 rpm demonstrates superior desalination efficiency compared to 60 rpm. Specifically, at a freezing ratio of 50%, the desalination efficiency is 80.95% ±0.09% for 30 rpm and 75%±1.52% for 60 rpm, respectively. A computational fluid dynamics (CFD) model employed in this study facilitated the simulation and analysis of heat and mass transfer phenomena within the crystallizer system, enabling investigation of these intricate processes across different operating conditions. The utilization of CFD proves to be highly effective in the examination and depiction of flow patterns, temperature distribution, and gradients in salt concentration within the crystallizer. The results emphasize the critical role of stirring in achieving uniformity within the concentrated brine, effectively preventing the formation of highly concentrated layers at the freezing interface. A higher stirring rate during the early freezing stage and a reduced stirring rate in the later freezing stage can contribute to achieving a reasonable desalination efficiency. This research contributes to enhancing water quality and highlights the potential of seawater freeze desalination as a sustainable and efficient solution to address the global freshwater scarcity challenge. It has the potential to revolutionize the desalination landscape by improving freeze desalination techniques towards achieving zero liquid discharge leading that maximizes resource utilization and reduces environmental impact.

Presenting Author: Isam Janajreh Khalifa University of Science and Technology

Presenting Author Biography: Prof. Isam Janajreh is Professor and the associate chair in the Mechanical Engineering department. He received his Ph.D. from Virginia Tech in Eng. Science and Mech. Specialized in fluid-dynamics, thermochemical-conversion, and solid/fluid interactions. He joined VT as visiting professor at ESM & Math Dept. (1998), and then Michelin US R&D and Michelin France heading European Project ’99-04. He joined Parametric Solutions Inc. in Florida (‘05-‘07) heading numerous US governments projects with GE/Pratt/Rolls. He joined Masdar in 2007 as visiting assistant MIT professor, associate (2010), and currently is full professor. His research focus on reactive flow, conjugate heat and solid fluid interaction applied in various engineering application. Including gasification and reforming, desalination, and energy and sustainability. He established the Waste to Energy Laboratory at Masdar/KU that drew funds from Tadweer, Beeah, ADNOC, Ducab, NIST, Sonkeyenergy, Masdar Corp. and several internal MI grants and numerous others. He authored over 140 refereed publications and graduated 27 MS and Ph.D students. Isam is a regular reviewer of EC&M, Appl. Pyrolysis, Ren. Energy, Fuel, Appl. energy, member of ASME, TS&T, Rubber Division, ASCE, and several scientific committees. Isam is also Editor in chief, associate editor, and editor for Int. J. of Enhanced Research in Science, Tech. & Eng., IJTEE, J. of Energy and Power Eng. Solid, J. of Solid Waste Tech. and Management.

Authors:

Hongtao Zhang Khalifa University of Science and Technology
Symeon Savvopoulos Khalifa University of Science and Technology
Md Didarul Islam Khalifa University of Science and Technology
Isam Janajreh Khalifa University of Science and Technology