Instigating buoyancy driven convection to improve membrane distillation performance

Membrane distillation is a thermally driven desalination process that is capable of treating complicated wastewaters with high concentrations of dissolved solids. However, temperature polarization and concentration polarization reduce its distillate production and impede its industrial adoption. Surprisingly, no prior work has considered that temperature and concentration polarization both increase the feed density near the membrane. In this exploratory study, we explore whether these differences in local feed density can instigate buoyancy driven convection in the feed flow and mitigate polarization. We also explore whether we can strengthen this convection by actively heating the feed channel in a direct contact membrane distillation (DCMD) system. For that purpose, we develop several actively heated prototypes and perform a series of experiments to explore how active heating affects distillate production. The prototypes are tested in multiple orientations to determine if buoyancy driven convection is truly taking place. The tests are also performed at multiple feed flowrates and feed concentrations to explore how temperature and concentration polarization affect the development of buoyancy driven convection. Overall, our experiments suggest that, with the cell oriented properly, buoyancy driven convection can be harnessed to significantly improve distillate production. For all flowrates tested, we observed a linear increase in distillate flux with increasing wall heating. The impact of wall heating also increases as the flowrate decreases.

Name thesis:degree_name

Master of Science (M.S.)

Level thesis:degree_level

Masters

Discipline thesis:degree_discipline

Mechanical Engineering

Grantor dc:publisher

Colorado School of Mines. Arthur Lakes Library

Year dc:date.issued

2023

Author dc:creator

• Mabry, Miles

Advisor dc:contributor.advisor

• Tilton, Nils

Committee members dc:contributor.committeemember

• Cath, Tzahi Y.
• DeCaluwe, Steven C.

Statement dc:rights

• Copyright of the original work is retained by the author.

Language dc:language.iso

eng, English

Identifier

T 9654

OAI identifier oai:identifier

oai:repository.mines.edu:11124/178654