Exergy Analysis of a Direct Contact Membrane Distillation (DCMD) System Based on Computational Fluid Dynamics (CFD).

Jihyeok Choi,Yusik Kim,Sangho Lee,Juyoung Lee,Yongjun Choi

doi:10.3390/membranes11070525

Jihyeok Choi, Yusik Kim + Show 3 more

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https://doi.org/10.3390/membranes11070525

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Journal: Membranes	Publication Date: Jul 13, 2021
Citations: 5	License type: CC BY 4.0

Affiliation: Kookmin University

Abstract

Understanding the energy efficiency of direct contact membrane distillation (DCMD) is important for the widespread application and practical implementation of the process. This study analyzed the available energy, known as exergy, in a DCMD system using computational fluid dynamics (CFD). A CFD model was developed to investigate the hydrodynamic and thermal conditions in a DCMD module. After the CFD model was verified, it was used to calculate the temperature polarization coefficient (TPC) and exergy destruction magnitudes under various operating conditions. The results revealed that slight decreases and increases in the TPC occurred with distance from the inlet in the module. The TPC was found to increase as the feed temperature was reduced and the feed and permeate flow rates were increased. The exergy destruction phenomenon was more significant under higher feed temperatures and higher flux conditions. Although the most significant exergy destruction in the permeate occurred near the feed inlet, the effect became less influential closer to the feed outlet. An analysis of exergy flows revealed that the efficiency loss in the permeate side corresponded to 32.9–45.3% of total exergy destruction.

Highlights

Membrane distillation (MD) is an emerging technique that is proposed as a promising alternative to multistage flash (MSF), multi-effect distillation (MED), and reverse osmosis (RO) processes [1,2,3]
One of the biggest problems with direct contact membrane distillation (DCMD) is its low energy efficiency associated with the temperature polarization (TP) phenomenon
In the DCMD process, recovering the latent heat in the product water is more difficult than in the other MD configurations, which leads to a further reduction in the energy efficiency of DCMD systems

Summary

Introduction

Membrane distillation (MD) is an emerging technique that is proposed as a promising alternative to multistage flash (MSF), multi-effect distillation (MED), and reverse osmosis (RO) processes [1,2,3]. As the operation of MD systems is not constrained by the osmotic pressure of the feed water, the treatment of RO brine is possible [1,2,5]. Owing to the simplicity and low cost of the DCMD technique, it has been investigated extensively [11,12]. One of the biggest problems with DCMD is its low energy efficiency associated with the temperature polarization (TP) phenomenon. In the DCMD process, recovering the latent heat in the product water is more difficult than in the other MD configurations, which leads to a further reduction in the energy efficiency of DCMD systems

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Results

Conclusion