Permeability Of Hollow Fiber Membranes Research Articles

Experimental study on the mass transfer permeability of hollow fiber membranes for a humidifier in a proton exchange membrane fuel cell

A membrane humidifier is a device used to increase proton conductivity in a fuel cell system, enhancing the performance and longevity of the fuel cell. In this study, a hollow fiber membrane is tested under various operating conditions to determine the membrane humidifier performance by estimating the amount of water vapor through the membrane. The results show that the mass transfer rate increases with increasing temperature, flow rate, and relative humidity while it decreases with pressure and membrane thickness. Particularly, temperature affects the mass transfer rate the most. When the temperature is increased from 50°C to 80°C, the performance improves by approximately 4.5 times. In contrast, the flow rate affects it the least; an approximately 2.5 times increase in the flow rate results in a 16% improvement in performance. Furthermore, the counterflow consistently exhibits greater efficiency than the co-flow. Moreover, the water vapor permeability through the membrane is assessed. The membrane permeability increases with decreasing membrane thickness and pressure and increasing temperature and inlet relative humidity. The findings indicate that 1°C rise in temperature leads to an increase of approximately 5% in permeability and approximately 19% increase in pressure, resulting in an approximately 15% decrease in permeability.

Oxygen permeability of hollow fiber membranes of composition Ba0.5Sr0.5Co0.78W0.02Fe0.2O3–δ

Hollow fiber membranes of composition Ba0.5Sr0.5Co0.78W0.02Fe0.2O3–δ (BSCFW2) have been synthesized by the phase inversion method. The structure of hollow fiber membranes has been studied by scanning electron microscopy, and the phase composition of the material before and after the tests has been determined.

Novel method for treatment of hollow fiber membranes using hypochlorite

A novel hypochlorite treatment method that enhances hydraulic permeability of hollow fiber membranes used in ultra-filtration was successfully devised and tested. Dope containing polysulfone/poly vinyl pyrrolidon (PVP-K90)/N-methyl-2-pyrrolidone (NMP) in mass ratio of 15:5:80, respectively, were used to produce hollow fibers via dry-jet wet spinning process. NMP in 1:1 ratio and distilled water were used as bore fluid. Hollow fiber membrane samples were post-treated using the novel, 95°C water and traditional hypochlorite treatments. State of membranes before and after post-treatment were morphologically compared using SEM microphotographs of fiber cross-section in conjuncton with image proceesing techniques. It was observed that in general both the novel and the traditional methods results in elimination of PVP swelling alone with alteration of pore size and pore distribution. This was confirmed by an increase in water flux of the hollow fibers that were subjected to these two post-treatment methods. Atomic force microscopy analysis vividly pointed to an intense increase in the roughness of the inner and outer surfaces of the membranes. This was attributed to the effect of post-treatment methods. It was found that in general post-treatments involving hypochlorite, increases the surface roughness of the membranes. However, increase in rate of the roughness of inner surface of traditionally hypochlorite treated hollow fiber membrane was found to be much higher than those subjected to the novel treatment method. It was established that the developed novel hypochlorite treatment method can be successfully used for production of high permeable hollow fiber membranes which have vast potential in therapeutic applications.

Gas permeability of hollow fiber membranes in a gas-liquid system

Designing an effective intravenous membrane oxygenator requires selecting hollow fiber membranes (HFMs) which present minimal resistance to gas exchange over extended periods of time. To evaluate HFMs, we developed a simple apparatus and methodology for measuring HFM permeability in a gas-liquid environment which has the capability of studying a variety of fiber types in any liquid of interest, such as blood. Using this system, we measured the O 2 and CO 2 exchange permeabilities of Mitsubishi MHF 200L composite HFMs and KPF 280E microporous HFMs in water at 37°C. The membrane permeability measured for the MHF 200L composite fiber was 7.9 × 10 −6 ml/s/cm 2/cmHg for O 2 and 8.4 × 10 −5 ml/s/cm 2/cmHg for CO 2, and for the KPF 280E microporous fiber, 1.4 × 10 −5 ml/s/cm 2/cmHg for O 2 and 3.2 × 10 −4 ml/s/cm 2/cmHg for CO 2. The permeabilities of the microporous HFMs were over two orders of magnitude less than what would be measured in a gas-gas system due to liquid infiltration of the pores, emphasizing the importance of measuring permeability in a gas-liquid system for relevant applications such as intravenous oxygenation. Furthermore, both O 2 and CO 2 permeabilities of the microporous fiber were consistent with a liquid infiltration depth of only 1%. The O 2 permeability of the MHF fiber was found to be less than the overall exchange permeability ultimately required of our intravenous oxygenation device ( K ≈ 1 × 10 −5 ml(STP)/s/cm 2/cmHg). Consequently, the MHF 200L composite fiber appears unsuitable for intravenous oxygenation devices such as ours.

A transient experiment to measure the diffusive permeability of hollow fiber membranes

A precise and rapid transient diffusion experiment has been developed to measure the diffusive permeability of hollow fibers. In this experiment a sealed hollow fiber containing a radioactive solute is exposed sequentially to several well-stirred solute-free reservoirs. This method was used to measure the diffusive permeability of collagen and Cuprophan hollow fibers in an isotonic saline solution for a spectrum of 14C labelled solutes: urea, sucrose and polyethylene glycol (PEG). To study the effect of environment on membrane permeability, collagen membranes were investigated with urea, sucrose and tritiated water in the following solutions with varying ionic strength and hydrogen ion concentration: pH2 HCl, distilled water and pH2 HCl with 0.8 M NaCl. In each environment, the membranes showed the expected decreases in diffusive permeaability with increasing molecular weight. Collagen membranes ranged from 4 (urea) to 40 (PEG) times the permeability of Cuprophan membranes. The Cuprophan data are consistent with results obtained elsewhere using scaled-down dialyzers. In response to environmental changes, the diffusive permeability of collagen membranes changed overall by a factor of 3 with the following rank: pH 2 HCl > distilled water > pH2 HCl and 0.8 M NaCl. The hydraulic permeability of these membranes changed by a factor of 2 but in a different order pH2 HCl > pH2 HCl and 0.8 M NaCl > distilled water. These permeability changes can be explained in terms of the known environmental dependence for the structure of collagen membranes and have been shown to be consistent with trends predicted by simple transport models.