Heat transfer intensification and scaling mitigation in bubbling-enhanced membrane distillation for brine concentration
Membrane distillation (MD) technology is being extensively studied to address operational challenges such as undesired thermal efficiency and scaling phenomenon in recovering valuable solutes and minimizing brine disposal. This study has explored the working mechanisms of utilizing gas–liquid two-ph...
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sg-ntu-dr.10356-796112020-09-26T22:00:21Z Heat transfer intensification and scaling mitigation in bubbling-enhanced membrane distillation for brine concentration Fane, Anthony Gordon Chen, Guizi Yang, Xing Lu, Yinghong Wang, Rong School of Civil and Environmental Engineering Nanyang Environment and Water Research Institute Singapore Membrane Technology Centre DRNTU::Engineering::Environmental engineering::Water treatment Membrane distillation (MD) technology is being extensively studied to address operational challenges such as undesired thermal efficiency and scaling phenomenon in recovering valuable solutes and minimizing brine disposal. This study has explored the working mechanisms of utilizing gas–liquid two-phase flow to enhance heat transfer and mitigate scaling formation in MD concentration process, based on the quantification of heat-transfer coefficients and local scaling-resistance associated with bubble size properties. With the aid of direct observation and statistical analysis on the bubble characteristics in a specially-designed direct contact MD (DCMD) module, it was found that the bubbles with small mean bubble size and narrow size distribution were preferred for creating even flow distribution, intensifying mixing and enhancing surface shear rate. Compared to non-bubbling DCMD, the heat-transfer coefficient and temperature polarization coefficient (TPC) reached up to 2.30- and 2.13-fold, respectively, at an optimal gas flowrate of 0.2 L min−1. With the theoretical expressions for local scaling resistance derived based on the resistance-in-series model, the relative permeation flux (Jw/o|t=t1/Jw/o|t=0) in non-bubbling MD was quantified and found to rapidly decline by 65% as the concentration process progressed, consistent with the increasing trend of the ratio of local scaling resistance to the overall resistance (rfl/rov). Fortunately, the introduction of gas bubbles has shown benefits for supersaturation brine concentrating MD process – remarkably decreased the local-scaling resistance due to bubble-intensified shear stress and enhanced hydrodynamics. Also, the total water removal for the brine concentration process was significantly improved by 131% and the discharged brine volume was reduced accordingly at appropriately selected gas flow rates. Nevertheless, at inappropriately high gas flowrates, high energy consumption and potential fiber breakage should be avoided. NRF (Natl Research Foundation, S’pore) EDB (Economic Devt. Board, S’pore) Accepted version 2014-09-22T07:06:51Z 2019-12-06T13:29:17Z 2014-09-22T07:06:51Z 2019-12-06T13:29:17Z 2014 2014 Journal Article Chen, G., Yang, X., Lu, Y., Wang, R., & Fane, A. G. (2014). Heat transfer intensification and scaling mitigation in bubbling-enhanced membrane distillation for brine concentration. Journal of Membrane Science, 470, 60-69. 0376-7388 https://hdl.handle.net/10356/79611 http://hdl.handle.net/10220/20937 10.1016/j.memsci.2014.07.017 en Journal of membrane science © 2014 Elsevier B. V. This is the author created version of a work that has been peer reviewed and accepted for publication by Journal of Membrane Science. It incorporates referee’s comments but changes resulting from the publishing process, such as copyediting, structural formatting, may not be reflected in this document. The published version is available at: [http://dx.doi.org/10.1016/j.memsci.2014.07.017]. 39 p. + 13 p. figures application/pdf application/pdf |
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DRNTU::Engineering::Environmental engineering::Water treatment Fane, Anthony Gordon Chen, Guizi Yang, Xing Lu, Yinghong Wang, Rong Heat transfer intensification and scaling mitigation in bubbling-enhanced membrane distillation for brine concentration |
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Membrane distillation (MD) technology is being extensively studied to address operational challenges such as undesired thermal efficiency and scaling phenomenon in recovering valuable solutes and minimizing brine disposal. This study has explored the working mechanisms of utilizing gas–liquid two-phase flow to enhance heat transfer and mitigate scaling formation in MD concentration process, based on the quantification of heat-transfer coefficients and local scaling-resistance associated with bubble size properties.
With the aid of direct observation and statistical analysis on the bubble characteristics in a specially-designed direct contact MD (DCMD) module, it was found that the bubbles with small mean bubble size and narrow size distribution were preferred for creating even flow distribution, intensifying mixing and enhancing surface shear rate. Compared to non-bubbling DCMD, the heat-transfer coefficient and temperature polarization coefficient (TPC) reached up to 2.30- and 2.13-fold, respectively, at an optimal gas flowrate of 0.2 L min−1. With the theoretical expressions for local scaling resistance derived based on the resistance-in-series model, the relative permeation flux (Jw/o|t=t1/Jw/o|t=0) in non-bubbling MD was quantified and found to rapidly decline by 65% as the concentration process progressed, consistent with the increasing trend of the ratio of local scaling resistance to the overall resistance (rfl/rov). Fortunately, the introduction of gas bubbles has shown benefits for supersaturation brine concentrating MD process – remarkably decreased the local-scaling resistance due to bubble-intensified shear stress and enhanced hydrodynamics. Also, the total water removal for the brine concentration process was significantly improved by 131% and the discharged brine volume was reduced accordingly at appropriately selected gas flow rates. Nevertheless, at inappropriately high gas flowrates, high energy consumption and potential fiber breakage should be avoided. |
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School of Civil and Environmental Engineering |
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School of Civil and Environmental Engineering Fane, Anthony Gordon Chen, Guizi Yang, Xing Lu, Yinghong Wang, Rong |
format |
Article |
author |
Fane, Anthony Gordon Chen, Guizi Yang, Xing Lu, Yinghong Wang, Rong |
author_sort |
Fane, Anthony Gordon |
title |
Heat transfer intensification and scaling mitigation in bubbling-enhanced membrane distillation for brine concentration |
title_short |
Heat transfer intensification and scaling mitigation in bubbling-enhanced membrane distillation for brine concentration |
title_full |
Heat transfer intensification and scaling mitigation in bubbling-enhanced membrane distillation for brine concentration |
title_fullStr |
Heat transfer intensification and scaling mitigation in bubbling-enhanced membrane distillation for brine concentration |
title_full_unstemmed |
Heat transfer intensification and scaling mitigation in bubbling-enhanced membrane distillation for brine concentration |
title_sort |
heat transfer intensification and scaling mitigation in bubbling-enhanced membrane distillation for brine concentration |
publishDate |
2014 |
url |
https://hdl.handle.net/10356/79611 http://hdl.handle.net/10220/20937 |
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1681057916566634496 |