Study on the Effect of Porosity on Countercurrent Hollow Fiber Membrane Humidification System

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.

Simulation of coupled transient heat and water vapor transfer in porous fiber membrane with different fiber orientations and porosity

The transfer process of heat and water vapor in a porous fiber membrane was investigated through the simulation of a 3D model for optimizing the configuration design. 3D models with different fiber orientations and porosity were constructed by the parameter input method, and the accuracy of the model was validated by the coefficient of determination (R2) between the apparent velocity of the model and the air permeability of the membrane. The permeability of 3D model was used to reflect the discrepancy in fiber orientation of the model. The influences of fiber orientation and porosity on heat and water vapor transfer were surveyed by the coupled physics of heat transfer and dilute substance transfer. Since there was no temperature difference in the entire domain, heat conduction (10−9 W/m2) and moisture convection (10−14 mol·m−2·s−1) were faint in the model. With the diffusion of water vapor in the moisture, the heat convection flux and water vapor diffusion flux gradually decreased and reached equilibrium. When the permeability was increased by adjusting the fiber orientation (from 1.002 to 1.200 m2), the heat convection flux and water vapor diffusion flux followed a similar growth pattern due to the coupling effect of heat transfer and water vapor transfer. The R2 for the heat convection flux and water vapor transmission rate of the simulations and experiments with different porosity (44.87, 47.64 and 50.15%) were 0.999 and 0.923, respectively, which demonstrated the validation of the simulation in heat and water vapor transfer.

Porous Fiber Processing and Manufacturing for Energy Storage Applications

The objective of this article is to provide an overview on the current development of micro- and nanoporous fiber processing and manufacturing technologies. Various methods for making micro- and nanoporous fibers including co-electrospinning, melt spinning, dry jet-wet quenching spinning, vapor deposition, template assisted deposition, electrochemical oxidization, and hydrothermal oxidization are presented. Comparison is made in terms of advantages and disadvantages of different routes for porous fiber processing. Characterization of the pore size, porosity, and specific area is introduced as well. Applications of porous fibers in various fields are discussed. The emphasis is put on their uses for energy storage components and devices including rechargeable batteries and supercapacitors.