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In this study, hollow fiber membrane contactors have been applied for gas dehumidification using tri-ethylene glycol as absorbent. The effects of gas and liquid flow rates, inlet concentration of tri-ethylene glycol and flow direction on dehumidification efficiency have been investigated. The results reveal that membrane contactors can remove water...
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... The first HFM module for air dehumidification was designed and fabricated by Bergero [12]. Fakharnezhad et al. [13] used TEG as the liquid desiccant in an HFM system. They showed that added to elimination of droplet carry-over problem, the system could dehumidify the air to dew points temperature below -10 • C. A flat plate membrane type with internally-cooled exchanger system was developed by Huang et al. [14]. ...
Desiccant systems, as a promising air conditioning technology have opened new aspects as a replacement for vapor compression systems. The liquid desiccant energy exchanger system with natural convection flow is proposed here; the system is a loop with two hollow fiber membrane air-desiccant exchanger of shell-and-tube type that works as the humidifier and regenerator. The LiCl aqueous solution as desiccant directed over the fibers and the air is inside the fibers; the water stream flows outside the modules to provide the required heat exchange. The heat sink and source as merged subparts of the exchangers have a major influence on system performance. The system is examined from the energetic and exergetic viewpoints at different heat sink and heat source temperatures. Keeping the fixed air flow rate and using the standard air properties, the cold and hot water temperatures of 15–25 °C and 50–70 were employed and the effectiveness coefficients including the latent, sensible and total and 2nd law efficiency evaluated. It was shown that the values of NTU and Cr* depend on each other and attenuating effect of NTU reduction is higher than enhancing effect of Cr* increase on effectiveness values. The prominent factor on exergy performance which hinders the effect of the other parameters is the solution flow rate. Also, the highest and lowest values of 2 nd law efficiency are 81% and 5% which are for temperature pairs of (52, 20) and (65,25), respectively.
... They concluded that vapour absorption efficiency increased by 10.8% compared with water. Fakharnezhad et al. [19] experimented on hollow fiber membrane contactors (HFMC) for gas dehumidification using Triethylene glycol as an absorbent and achieved a dew point temperature of −50°C. Bettahalli et al. [20] experimentally analyzed the triple bore HFLDD using CaCl 2 and found that the dehumidification rate increased by 10% compared to single bore HFLDD. ...
In the present study, a novel integral technique based two-point boundary value problem is developed using the simplified polynomial equations to assess the hollow fiber membrane-based liquid desiccant dehumidifier performance for drying application. The developed numerical technique is validated with the experimental data available in the literature and observed a maximum deviation of ± 9.7%. The liquid desiccant chosen is lithium chloride. By considering thermal and moisture effectiveness as performance parameters and choosing the air inlet temperature, air specific humidity, desiccant temperature, and liquid to gas ratio as input parameters, the influence of Lewis number and Stanton number on dehumidifier performance is analyzed. The performance analysis concluded that a high liquid to gas ratio, desiccant temperature, and specific humidity enhance the dehumidifier performance. Further, the variation of performance parameters along the length and thermal mass of the membrane column is also assessed. Moreover, a case study on conventional and desiccant dryers performance in humid climates is assessed and observed that the desiccant dryer is the best alternative compared to the conventional dryer. In addition, for the given operating range and inlet condition, the maximum possible vapour absorption rate (δVAR) and energy exchange for the conventional dryer is found to be 93 g/hr and 0.8 kW, whereas, for the desiccant dryer, it is 164 g/hr, and 1.4kW respectively.
... Apart from that, recent engineering approaches to structural steric effect [606] and blending [594,607] of amine absorbents have been reported. Other applications of membrane contactors include oxygenation/deoxygenation [608,609], ozonation [610][611][612], gas dehumidification [613][614][615][616][617], and olefin/paraffin separation [618,619]. ...
The aggravation of environmental problems such as water scarcity and air pollution has called upon the need for a sustainable solution globally. Membrane technology, owing to its simplicity, sustainability, and cost-effectiveness, has emerged as one of the favorable technologies for water and air purification. Among all of the membrane configurations, hollow fiber membranes hold promise due to their outstanding packing density and ease of module assembly. Herein, this review systematically outlines the fundamentals of hollow fiber membranes, which comprise the structural analyses and phase inversion mechanism. Furthermore, illustrations of the latest advances in the fabrication of organic, inorganic, and composite hollow fiber membranes are presented. Key findings on the utilization of hollow fiber membranes in microfiltration (MF), nanofiltration (NF), reverse osmosis (RO), forward osmosis (FO), pervaporation, gas and vapor separation, membrane distillation, and membrane contactor are also reported. Moreover, the applications in nuclear waste treatment and biomedical fields such as hemodialysis and drug delivery are emphasized. Subsequently, the emerging R&D areas, precisely on green fabrication and modification techniques as well as sustainable materials for hollow fiber membranes, are highlighted. Last but not least, this review offers invigorating perspectives on the future directions for the design of next-generation hollow fiber membranes for various applications. As such, the comprehensive and critical insights gained in this review are anticipated to provide a new research doorway to stimulate the future development and optimization of hollow fiber membranes.
... Dehumidification using hollow fiber membrane belongs to the category of membrane liquid dehumidification. It combines membrane separation technology with liquid dehumidification technology, which can effectively prevent direct constant between high humidity air and desiccant and eliminate the possibility of mutual pollution between desiccant and air 5,6 . Hollow fiber membrane material is an important part to determine the dehumidification efficiency. ...
Hollow fiber membranes are used in industrial processes widely. Porosity is one of the important parameters affecting the humidification performance of hollow fiber membrane components. The aim of this study was to analyze the effect of porosity of hollow fiber membrane on humidification performance. In order to perform this analysis, a model based on the finite element method was used to simulate numerically the heat and mass transfer under 6 porosity conditions. Five working conditions with different air flow was considered in order to get more data. The results show that when the porosity increases from 0.35 to 0.8, the humidification performance is greatly improved. However, when it increases from 0.8 to 0.9, the humidification performance is almost unchanged. Considering the humidification performance and support strength of hollow fiber membrane, it is suggested to control the porosity of hollow fiber membrane between 0.65 and 0.8.
... Thus, the calcium and magnesium ions in water, which are harmful to human health, will not enter the air stream. The heat and mass transfer characteristics of the hollow fiber membrane bundle for humidification/dehumidification have been investigated by many researchers theoretically [18,[21][22][23][24] and experimentally [25][26][27][28]. ...
Cross-flow hollow fiber membranes are commonly applied in humidification/dehumidification. Hollow fiber membranes vibrate and deform under the impinging force of incoming air and the gravity of liquid in the inner tube. In this study, fiber deformation was caused by the pulsating flow of air. With varied pulsating amplitudes and frequencies, single-fiber deformation was investigated numerically using the fluid–structure interaction technique and verified with experimental data testing with a laser vibrometer. Then, the effect of pulsating amplitude and frequency on heat and mass transfer performance of the hollow fiber membrane was analyzed. The maximum fiber deformation along the airflow direction was far larger than that perpendicular to the flow direction. Compared with the case where the fiber did not vibrate, increasing the pulsation amplitude could strengthen Nu by 14–87%. Flow-induced fiber vibration could raise the heat transfer enhancement index from 13.8% to 80%. The pulsating frequency could also enhance the heat transfer of hollow fiber membranes due to the continuously weakened thermal boundary layer. With the increase in pulsating amplitude or frequency, the Sh number or Em under vibrating conditions can reach about twice its value under non-vibrating conditions.
... Also, due to direct gas-liquid contact, liquid droplets can be carried upwards. One way to prevent such problems is to use hollow fiber membrane contactors (HFMCs) [17]. Membrane contactors unlike most other membrane processes that use a dense selective layer on one side of the fibers, are usually not selective. ...
In this study, tri-ethylene glycol (TEG) based nanofluids of carbon nanotubes (CNT), silica (SiO2) and aluminum oxide (Al2O3) in different weight percents of 0.01 and 0.05 wt% were employed to improve the properties of TEG for water vapor absorption in a hollow fiber membrane contactor (HFMC). To do so, the impact of various operational parameters including nanofluid type, nanoparticles (NPs) concentration, liquid and gas flow rate on water vapor separation were elucidated. According to obtained results, CNT nanofluid was more capable on water vapor absorption toward SiO2 and Al2O3, so that the injection of CNT nanofluid led to water vapor absorption enhancement up to 10.8 % as compared to TEG solution alone. The results also indicated that the gas flow rate has an inverse relationship with the amount of water vapor absorption efficiency, whereas increasing the liquid flow rate has no tangible effect on absorption efficiency, which is because of the very high solubility of water vapor in TEG. Ultimately, dynamic light scattering (DLS) analysis was carried out to evaluate the stability of nanofluids and size distribution of nanostructures in the base fluid.
... This eliminates the possibility of the desiccant contaminating the air with each other. Water vapor is dehumidi ed through the membrane driven by the partial pressure of water vapor on both sides of the membrane [2] . Dehumidifying separation membrane material is an important part of determining dehumidifying e ciency. ...
The effect of porosity on the humidification efficiency of countercurrent hollow fiber membrane humidification system was investigated by using numerical simulation method to study polypropylene (PP) porous fiber membrane material. Firstly, the correctness of the numerical model was verified by experiments, and then the influence of porous fiber membrane material on humidification efficiency was further explored by changing the porosity of the model. The simulation results show that the humidification capacity and efficiency of the humidification component increase with the increase of porosity. When the porosity is between 0.35-0.8, the humidification capacity and efficiency increase significantly. However, when the porosity is between 0.8-0.9, although the humidification amount and humidification efficiency value are high, the increment is not obvious, and the porosity of the fiber film is inversely proportional to the support strength of the film, and the larger the porosity is, the shorter the service life of the film material is. Therefore, it is suggested to design the porosity of polypropylene (PP) film material between 0.65 and 0.8. It can not only ensure the high humidification capacity and efficiency of the fiber membrane, but also prolong the service life of the membrane.
... The water and waste heat loss caused by low-temperature flue gas emission has attracted the attention of a large number of researchers, and a variety of technical solutions [7] have also been proposed for the water and waste heat recovery from flue gas. Common technical methods are condensation [8][9][10], absorption [11][12][13] or membrane separation [14,15]. Condensation method using a recuperative heat exchanger or a spray tower [16,17], the flue gas temperature is reduced to a temperature below the dew point of water vapor. ...
Ceramic membrane condensers that are used for water and waste heat recovery from flue gas have the dual effects of saving water resources and improving energy efficiency. However, most ceramic membrane condensers use water as the cooling medium, which can obtain a higher water recovery flux, but the waste heat temperature is lower, which is difficult to use. This paper proposes to use the secondary boiler air as the cooling medium, build a ceramic membrane condenser with negative pressure air to recover water and waste heat from the flue gas, and analyze the transfer characteristics of flue gas water and waste heat in the membrane condenser. Based on the experimental results, it is technically feasible for the ceramic membrane condenser to use negative pressure air as the cooling medium. The flue gas temperature has the most obvious influence on the water and heat transfer characteristics. The waste heat recovery is dominated by latent heat of water vapor, accounting for 80% or above. The negative pressure air outlet temperature of the ceramic membrane condenser can reach 50.5 °C, and it is in a supersaturated state. The research content of this article provides a new idea for the water and waste heat recovery from flue gas.
... This makes combined technologies of membrane based liquid desiccant gas dehumidification of great interest for future dehumidification [8,25,26]. This process has recently been reviewed in detail in [27]. ...
Here we propose combined process for gas streams dehumidification using porous polypropylene membrane contactor heat-exchanger with liquid coolant absorbent and report the results on its operation performance. The technique enables effective removal of condensable components of gas mixtures to ultimate residual pressures by a synergetic contribution of two effects – suppression of the equilibrium water vapor pressure at low temperatures and water vapor removal by hygroscopic absorbent. The method is examined in the process of air stream dehumidification with ethylene glycol-water absorbents. Experimental data on the process performance at different gas fluxes (0.3–12 m³(STP)·m⁻²·h⁻¹), pressures (2.5 – 9 bar), chilled absorbent temperatures (−30 ÷ 3 °C) and absorbent compositions (0–100 wt% of ethylene glycol) is reported. It is revealed the performance of contactor is mostly limited by viscosity of the cooling absorbent, allowing to achieve dew point temperature of the processed gas down to −30 °C with a water vapors stage cut over 90% at gas flux over 10 m³(STP)·m⁻²·h⁻¹ and packing density of hollow fiber membrane up to 3000 m²/m³ with 35%:65% (wt.) water-ethylene-glycol absorbent. A technical scheme for industrial dehumidification setup is proposed and the results of the model setup performance are evaluated in comparison with traditional desiccant, wheel adsorbent and refrigeration processes. It is shown the proposed technique provides much wider range of acceptable gas dew point temperatures as compared to conventional refrigerant process and more preferred energetically compared to desiccant and wheel dehumidification.
... However, the feasibility of membrane contactors in terms of liquid desiccant dehumidification has not been proven. In 2016, Fakharnezhad et al. [44] tested the dehumidification performance of hollow fiber membrane contactors with TEG as the desiccant. The results reveal that the contactor can remove water vapor effectively, even at low water dew point as low as −te °C. ...
This paper provides a comprehensive literature review of the latest research on liquid desiccant air dehumidification, with an emphasis on manipulation methods from components, systems to materials. Energy comsuption for indoor humidity control is significant, especially in tropical and subtropical areas. Liquid desiccant dehumidification can independently remove moisture from the supply air. It has many advantages, including effective humidity control, utilization of low-grade thermal energy, higher supply air quality and energy storage potential. With the development in recent decades, this technology and its economic value are close to being viable in practice. However, the system still faces some limitations due to the use of corrosive desiccants with low heat capacity and insufficient wettability on packing columns. This paper firstly summarized the bottlenecks of liquid desiccant dehumidification in practical applications, including droplet carrying problems, low liquid/air contact area due to poor wettability, large temperature change during heat/mass transfer, and large heat requirement, etc.Then the optimization methods for improving the system feasibility and performance were reviewed, from these three aspects: 1) Component optimization: New type of dehumidifers/regenerators, including the hollow-fiber membrane dehumidifiers, electrodialysis and vacuum regenerators; 2) System optimization: Combined with solar collector, vapour compression, heat pump or waste heat recovery; 3) Material optimization: Modification of desiccants and membrane materials, and modifications of packing/plate surfaces. This review will help to identify research gaps and explore new pathways to further improve the practical feasibility of liquid desiccant air dehumidification.
