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16 pages, 2401 KiB

Open AccessArticle

Determination of Heat and Mass Transport Correlations for Hollow Membrane Distillation Modules

by Peter M. Hylle, Jeppe T. Falden, Jeppe L. Rauff, Philip Rasmussen, Mads Moltzen-Juul, Maja L. Trudslev, Cejna Anna Quist-Jensen and Aamer Ali

Energies 2023, 16(8), 3447; https://doi.org/10.3390/en16083447 - 14 Apr 2023

Cited by 3 | Viewed by 1385

Abstract

Development and optimization of the membrane distillation (MD) process are strongly associated with better understanding of heat and mass transport across the membrane. The current state-of-the-art on heat and mass transport in MD greatly relies upon the use of various empirical correlations for [...] Read more.

Development and optimization of the membrane distillation (MD) process are strongly associated with better understanding of heat and mass transport across the membrane. The current state-of-the-art on heat and mass transport in MD greatly relies upon the use of various empirical correlations for the Nusselt number (Nu), tortuosity factor (τ), and thermal conductivity (

κ_{m}

) of the membrane. However, the current literature lacks investigations about finding the most representative combination of these three parameters for modeling transport phenomena in MD. In this study, we investigated 189 combinations of Nu,

κ_{m}

, and τ to assess their capability to predict the experimental flux and outlet temperatures of feed and permeate streams for hollow fiber MD modules. It was concluded that 31 out of 189 tested combinations could predict the experimental flux with reasonable accuracy (R² > 0.95). Most of the combinations capable of predicting the flux reasonably well could predict the feed outlet temperature well; however, the capability of the tested combinations to predict the permeate outlet temperatures was poor, and only 13 combinations reasonably predicted the experimental temperature. As a generally observed tendency, it was noted that in the best-performing models, most of the correlations used for the determination of

κ_{m}

were parallel models. The study also identified the best-performing combinations to simultaneously predict flux, feed, and permeate outlet temperatures. Thus, it was noted that the best model to simultaneously predict flux, feed, and permeate outlet temperatures consisted of the following correlations for τ, Nu, and

κ_{m}

:

= \frac{ε}{1 - {(1 - ε)}^{1 / 3}}

,

N u = 0.13 {(R e)}^{0.64} {(P r)}^{0.38}

,

κ_{m} = (1 - ε) κ_{p o l} + ε κ_{a i r}

where ε, Re, Pr,

κ_{p o l}

, and

κ_{a i r}

represent membrane porosity, Reynolds number, Prandtl number, thermal conductivities of polymer and air, respectively. Full article

(This article belongs to the Special Issue Thermal Performance of Membrane Distillation)

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12 pages, 4717 KiB

Open AccessArticle

Wet Flue Gas Desulphurization (FGD) Wastewater Treatment Using Membrane Distillation

by Noah Yakah, Imtisal-e- Noor, Andrew Martin, Anthony Simons and Mahrokh Samavati

Energies 2022, 15(24), 9439; https://doi.org/10.3390/en15249439 - 13 Dec 2022

Cited by 4 | Viewed by 2901

Abstract

The use of waste incineration with energy recovery is a matured waste-to-energy (WtE) technology. Waste incineration can reduce the volume and mass of municipal solid waste significantly. However, the generation of high volumes of polluting flue gases is one of the major drawbacks [...] Read more.

The use of waste incineration with energy recovery is a matured waste-to-energy (WtE) technology. Waste incineration can reduce the volume and mass of municipal solid waste significantly. However, the generation of high volumes of polluting flue gases is one of the major drawbacks of this technology. Acidic gases are constituents in the flue gas stream which are deemed detrimental to the environment. The wet flue gas desulphurization (FGD) method is widely employed to clean acidic gases from flue gas streams, due to its high efficiency. A major setback of the wet FGD technology is the production of wastewater, which must be treated before reuse or release into the environment. Treating the wastewater from the wet FGD presents challenges owing to the high level of contamination of heavy metals and other constituents. Membrane distillation (MD) offers several advantages in this regard, owing to the capture of low-grade heat to drive the process. In this study the wet FGD method is adopted for use in a proposed waste incineration plant located in Ghana. Through a mass and energy flow analysis it was found that MD was well matched to treat the 20 m³/h of wastewater generated during operation. Thermal performance of the MD system was assessed together with two parametric studies. The thermal efficiency, gained output ratio, and specific energy consumption for the optimized MD system simulated was found to be 64.9%, 2.34 and 966 kWh/m³, respectively, with a total thermal energy demand of 978.6 kW. Full article

(This article belongs to the Special Issue Thermal Performance of Membrane Distillation)

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19 pages, 1862 KiB

Open AccessArticle

Performance Study of Eductor with Finite Secondary Source for Membrane Distillation

by Ravi Koirala, Xing Zhang, Eliza Rupakheti, Kiao Inthavong and Abhijit Date

Energies 2022, 15(22), 8620; https://doi.org/10.3390/en15228620 - 17 Nov 2022

Cited by 1 | Viewed by 1393

Abstract

This is an experimental work performed to identify the influence of direct contact condensation inside an eductor. The fluid used in the experiments is water in two different phases: liquid and vapor, for primary and secondary flows, respectively. This study was conducted in [...] Read more.

This is an experimental work performed to identify the influence of direct contact condensation inside an eductor. The fluid used in the experiments is water in two different phases: liquid and vapor, for primary and secondary flows, respectively. This study was conducted in an attempt to establish the suitability of an eductor as a combined vacuum generator and condenser for membrane desalination applications. The pressure and temperature measurements at critical points in the flow paths have been summarized to identify the influence of primary flow on secondary fluid saturation and condensation. In addition, the mechanism of phase change has been explained through the photography of fluid flow in a two-dimensional eductor. A consistent oscillation of the gas-liquid interface was observed during steady-state operations of the eductor. This work also contributes to the validation of future computational research. It will provide a baseline for computational thermal fluid analysis related to the mixing of condensing and non-condensing flow. In general, the research encompasses the practical operational scenario and provides information on the heat and mass transfer of direct contact condensation with a finite secondary source. Full article

(This article belongs to the Special Issue Thermal Performance of Membrane Distillation)

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18 pages, 4538 KiB

Open AccessArticle

Solar Energy Driven Membrane Desalination: Experimental Heat Transfer Analysis

by Hosam Faqeha, Mohammed Bawahab, Quoc Linh Ve, Oranit Traisak, Ravi Koirala, Aliakbar Akbarzadeh and Abhijit Date

Energies 2022, 15(21), 8051; https://doi.org/10.3390/en15218051 - 29 Oct 2022

Viewed by 1497

Abstract

In the direct contact membrane distillation (DCMD) system, the temperature polarization due to boundary layer formation limits the system performance. This study presents the experimental results and heat transfer analysis of a DCMD module coupled with a salinity gradient solar pond (SGSP) under [...] Read more.

In the direct contact membrane distillation (DCMD) system, the temperature polarization due to boundary layer formation limits the system performance. This study presents the experimental results and heat transfer analysis of a DCMD module coupled with a salinity gradient solar pond (SGSP) under three different flow channel configurations. In the first case, the feed and permeate channels were both empty, while in the next two cases, the feed and permeate channels were filled with a porous spacer material. Two different spacer geometries are examined: 1.5 mm thick with a filament angle of 65°, and 2 mm thick with a filament angle of 90°. The study considers only the heat transfer due to conduction by replacing the hydrophobic membrane normally used in a DCMD module with a thin polypropylene sheet so that no mass transfer can occur between the feed and permeate channels. The Reynolds number for all three configurations was found to be between 1000 and 2000, indicating the flow regime was laminar. The flow rate through both the feed and permeate sides was the same, and experiments were conducted for flow rates of 5 L/min and 3 L/min. It has been found that the highest overall heat transfer coefficient was obtained with the spacer of 2 mm thickness and filament angle of 90°. Full article

(This article belongs to the Special Issue Thermal Performance of Membrane Distillation)

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13 pages, 3603 KiB

Open AccessArticle

Osmotic Membrane Distillation Crystallization of NaHCO₃

by Mar Garcia Alvarez, Vida Sang Sefidi, Marine Beguin, Alexandre Collet, Raul Bahamonde Soria and Patricia Luis

Energies 2022, 15(7), 2682; https://doi.org/10.3390/en15072682 - 6 Apr 2022

Cited by 8 | Viewed by 3047

Abstract

A new crystallization process for sodium bicarbonate (NaHCO₃) was studied, proposing the use of osmotic membrane distillation crystallization. Crystallization takes place due to the saturation of the feed solution after water evaporation on the feed side, permeating through the membrane pores [...] Read more.

A new crystallization process for sodium bicarbonate (NaHCO₃) was studied, proposing the use of osmotic membrane distillation crystallization. Crystallization takes place due to the saturation of the feed solution after water evaporation on the feed side, permeating through the membrane pores to the osmotic side. The process operational parameters, i.e., feed and osmotic velocities, feed concentration, and temperature were studied to determine the optimal operating conditions. Regarding the feed and osmotic velocities, values of 0.038 and 0.0101 m/s, respectively, showed the highest transmembrane flux, i.e., 4.4 × 10⁻⁸ m³/m²·s. Moreover, study of the temperature variation illustrated that higher temperatures have a positive effect on the size and purity of the obtained crystals. The purity of the crystals obtained varied from 96.4 to 100% In addition, the flux changed from 2 × 10⁻⁸ to 7 × 10⁻⁸ m³/m²·s with an increase in temperature from 15 to 40 °C. However, due to heat exchange between the feed and the osmotic solutions, the energy loss in osmotic membrane distillation crystallization is higher at higher temperatures. Full article

(This article belongs to the Special Issue Thermal Performance of Membrane Distillation)

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17 pages, 4030 KiB

Open AccessArticle

The Application of Open Capillary Modules for Sweeping Gas Membrane Distillation

by Marek Gryta

Energies 2022, 15(4), 1454; https://doi.org/10.3390/en15041454 - 16 Feb 2022

Cited by 1 | Viewed by 1751

Abstract

The paper presents the sweeping gas membrane distillation realised by using the capillary module (length 1.1 m and area 0.1 m²) without housing (module shell). During the tests, the feed was flowing inside the hydrophobic polypropylene membranes. The studies were performed [...] Read more.

The paper presents the sweeping gas membrane distillation realised by using the capillary module (length 1.1 m and area 0.1 m²) without housing (module shell). During the tests, the feed was flowing inside the hydrophobic polypropylene membranes. The studies were performed for two variants of process: with pre-heating (313–330 K) and without heating of the feed (brines). Under low gas flow (0.005 m/s) the evaporation performance varied in the range of 0.15–0.25 L/m²h, depending on the relative humidity (42–63%) and the air temperature (293–300 K). The application of feed pre-heating to 330 K led to an increase in the evaporation performance to 2.4 L/m²h. The permeate flux increased by 60% when the air flow velocities between the capillaries increased to 1.8–2.5 m/s. Increasing the feed flow rate from 0.1 to 0.59 m/s led to increase the permeate flux about 20% for feed temperature 293–310 K, and over 55% for feed temperature higher than 323 K. Full article

(This article belongs to the Special Issue Thermal Performance of Membrane Distillation)

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13 pages, 2072 KiB

Open AccessArticle

Carbon Black/Polyvinylidene Fluoride Nanocomposite Membranes for Direct Solar Distillation

by Marcello Pagliero, Marina Alloisio, Camilla Costa, Raffaella Firpo, Ermias Ararsa Mideksa and Antonio Comite

Energies 2022, 15(3), 740; https://doi.org/10.3390/en15030740 - 20 Jan 2022

Cited by 13 | Viewed by 2738

Abstract

Water reclamation is becoming a growing need, in particular in developing countries where harvesting the required energy can be a challenging problem. In this context, exploiting solar energy in a specifically tailored membrane distillation (MD) process can be a viable solution. Traditional MD [...] Read more.

Water reclamation is becoming a growing need, in particular in developing countries where harvesting the required energy can be a challenging problem. In this context, exploiting solar energy in a specifically tailored membrane distillation (MD) process can be a viable solution. Traditional MD guarantees a complete retention of non-volatile compounds and does not require high feed water temperatures. In this work, a suitable amount of carbon black (CB) was incorporated into the whole matrix of a polymeric porous membrane in order to absorb light and directly heat the feed. The mixed matrix membranes were prepared forming a uniform CB dispersion in the PVDF dope solution and then using a non-solvent induced phase separation process, which is a well-established technique for membrane manufacturing. CB addition was found to be beneficial on both the membrane structure, as it increased the pore size and porosity, and on the photothermal properties of the matrix. In fact, temperatures as high as 60 °C were reached on the irradiated membrane surface. These improvements led to satisfactory distillate flux (up to 2.3 L/m²h) during the direct solar membrane distillation tests performed with artificial light sources and make this membrane type a promising candidate for practical applications in the field of water purification. Full article

(This article belongs to the Special Issue Thermal Performance of Membrane Distillation)

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11 pages, 4177 KiB

Open AccessArticle

Thermal Performance of Integrated Direct Contact and Vacuum Membrane Distillation Units

by Alessandra Criscuoli

Energies 2021, 14(21), 7405; https://doi.org/10.3390/en14217405 - 6 Nov 2021

Cited by 9 | Viewed by 2237

Abstract

An integrated membrane distillation (MD) flowsheet, consisting of direct contact membrane distillation (DCMD) and vacuum membrane distillation (VMD) units, was proposed and analysed in terms of thermal performance and water recovery factor, for the first time. The same lab-scale membrane module (40 cm [...] Read more.

An integrated membrane distillation (MD) flowsheet, consisting of direct contact membrane distillation (DCMD) and vacuum membrane distillation (VMD) units, was proposed and analysed in terms of thermal performance and water recovery factor, for the first time. The same lab-scale membrane module (40 cm²) was used for carrying out experiments of DCMD and VMD at fixed feed operating conditions (deionised water at 230 L/h and ~40 °C) while working at the permeate side with deionised water at 18 °C and with a vacuum of 20 mbar for the DCMD and the VMD configuration, respectively. Based on experimental data obtained on the single modules, calculations of the permeate production, the specific thermal energy consumption (STEC) and the gained output ratio (GOR) were carried out for both single and integrated units. Moreover, the calculations were also made for a flow sheet consisting of two DCMD units in series, representing the “traditional” way in which more units of the same MD configuration are combined to enhance the water recovery factor. A significant improvement of the thermal performance (lower STEC and higher GOR) was obtained with the integrated DCMD–VMD flowsheet with respect to the DCMD units operating in series. The integration of DCMD with VMD also led to a higher permeate production and productivity/size (PS) ratio, a metric defined to compare plants in terms of the process intensification strategy. Full article

(This article belongs to the Special Issue Thermal Performance of Membrane Distillation)

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Review

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18 pages, 1230 KiB

Open AccessReview

Localized Heating to Improve the Thermal Efficiency of Membrane Distillation Systems

by Alessandra Criscuoli and Maria Concetta Carnevale

Energies 2022, 15(16), 5990; https://doi.org/10.3390/en15165990 - 18 Aug 2022

Cited by 7 | Viewed by 1752

Abstract

Membrane distillation (MD) is a thermal-based membrane operation with high potential for the treatment of aqueous streams. However, its implementation is limited and only few examples of MD pilots can be found in desalination. One of the reasons behind this is that MD [...] Read more.

Membrane distillation (MD) is a thermal-based membrane operation with high potential for the treatment of aqueous streams. However, its implementation is limited and only few examples of MD pilots can be found in desalination. One of the reasons behind this is that MD requires thermal energy for promoting the evaporation of water, which implies higher energy consumption with respect to pressure-driven membrane operations, like reverse osmosis (RO). Recently, among the different methods investigated to improve the thermal efficiency of MD, attempts for obtaining a localized heating of the feed, close to the membrane surface, were carried out. This work reviews experimental activities on the topic, dealing with both modified membranes, used under solar irradiation or coupled to an electric source, and specifically designed heated modules. The main results are reported and points of action for further optimization are identified. In particular, although at an early stage, this type of approach led to improvements in membrane flux and to a reduction of energy consumption with respect to conventional MD. Nevertheless, long tests to ensure a stable performance time, the optimization of operating conditions, the development of methods to control fouling issues, and the identification of the best module design, together with the scale-up of membranes/modules developed, represent the main research efforts needed for future implementation of localized heating strategy. Full article

(This article belongs to the Special Issue Thermal Performance of Membrane Distillation)

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