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Submicron polypropylene (PP) fibers of three different sizes (300 nm, 600 nm, and 900 nm) were prepared via electrospinning. The fibers were blended with microglass (MG) fibers to form composite media in varying fiber concentrations to obtain PP to MG fiber surface area ratios ( AR ) of 0.5, 1 and 2. The effects of fiber size and amount of electrospun PP fibers on wettability and filtration performance of the blended PP + MG media were measured. The wettability of the filter media were characterized by a modified Washburn test and expressed as the lipophilic to hydrophilic ( L / H ) ratio. The wettability characterization shows that hydrophobicity of filter media increases with the amount and size of electrospun PP fibers. In liquid–liquid coalescence experiments the amount and fiber diameter of the electrospun PP fibers significantly affected the separation efficiency and the pressure drop as compare to MG fiber only media. The separation efficiency was greatest for the smallest fibers (300 nm) and the intermediate AR of 1.0. The pressure drop tended to increase with the amount of PP fiber and with fiber diameter.

Glass fiber filter media are widely used in separation of droplets from liquid aerosols. In prior works two possible enhancements to the performance of the glass fiber media were studied: (1) the capture efficiencies were increased by augmenting the glass fibers with sub-micron sized electrospun polymer fibers, and (2) the pressure drop was decreased by modifying the filter media with insertion of 45° drainage channels. In this paper we report the simultaneous application of these two enhancements on the performance of the filter media. Filters were fabricated by inserting low surface energy woven polymer fiber drainage channels at various angles within non-woven glass fiber filter media augmented with Nylon sub-micron fibers. The effects of the presence and geometry of the drainage channels on the filter performance were evaluated experimentally. The sub-micron fibers gave the filter high coalescence and separation efficiencies while the drainage channels reduced the filter pressure drop. The micro glass fiber media augmented with 100 nm Nylon fibers and modified with Polypropylene fiber drainage channels at 45° downward angles had the overall best performance.

One of the major causes of diesel engine maintenance problems is water contamination in fuels. This paper discusses fabrication, characterization, and testing of non-woven glass fiber mats augmented with an electrospun layer of poly(vinylidene fluoride-co-hexafluoropropylene) (PVDF-HFP) fibers for the separation of secondary water dispersions from ultralow sulfur diesel. The PVDF-HFP fibers had an average fiber diameter of 334 nm. All PVDF-HFP layers had water contact angles greater than 150° with relatively low hysteresis values, making them superhydrophobic. Water separation experiments showed that glass fiber media augmented with electrospun PVDF-HFP fiber mats significantly improved water separation, with water removal efficiencies reaching 99%, as compared to glass fiber media without the PVDF-HFP layer.

Fibrous filters are used to remove liquid aerosols from gas streams. Filter media capture fine liquid droplets; the captured liquid droplets coalesce to form big drops and saturate the filter media. This captured liquid typically drains from the filter by gravity. The saturation, or liquid holdup in the filter, constricts the gas flow, reduces capture efficiency, increases pressure drop, and increases the operating costs of the filter. Liquid holdup in the filter also decreases the on-stream life of the filter and requires replacing the filter, which requires shutting down the process and/or equipment being used, which adversely affects the economy of the process. Filter performance improves when the liquid saturation is reduced without reduction in capture efficiency. In this article, glass microfiber filter media are modified with nonwoven polypropylene fabric drainage structures to reduce saturation and drag resistance. The experimental results show that the geometry with embedded nonwoven drainage cha...

The surface energy, or wettability, of the fibers in coalescence filter media controls the performance of coalescing filters. High surface energy fibers capture and hold onto droplets, slowing their movement through the filter and hence increase coalescence between drops. Low surface energy fibers allow drops to slip through the filter with little or no hindrance but do not contribute significantly to the coalescence. In this work we present experimental data on the performance of composite filters made of high surface energy fibers with layers of low surface energy woven mats of fibers as drainage channels. Drainage channels provide pathways for coalesced liquid to rapidly flow out of the filter without compromising with the capture efficiency. Hence the saturation or hold-up of liquid, in the filter decreases. This reduces the pressure drop, and increases the filtration index and filter life. In this paper, filters were fabricated by layering woven and nonwoven polymer fiber drainage channels into non-woven glass fiber filter media. The effect of the presence and geometry of the drainage channels on the filter performance was evaluated. The high surface energy glass fibers provide the desired coalescence while the low surface energy polymer fibers of the drainage channels reduced the filter saturation. The experimental results show that filter media embedded with Teflon® fiber drainage channels at 45° downward angles had the overall best performance.

Fibrous coalescing filters are commonly used to separate water-in-oil emulsions. Wettability of the fibers significantly influences the filter performance. The wettability of the filter media depends on surface properties of fiber materials and porosity of the filter medium. The wettability of the filter media is characterized using modified Washburn’s equation and expressed in terms of the lipophilic to hydrophilic (L/H) ratio. In this work, layered media were prepared with varying compositions of hydrophilic micro glass fibers and hydrophobic polypropylene or polyester fibers to achieve a range of L/H values. By varying the fiber composition and thickness of hydrophilic and hydrophobic layers in the media, filter media with different wetting properties can be prepared. Water and Viscor-1487 oil (a diesel fuel calibration fluid) were used as test liquids for the wettability characterization. The filter media were tested in liquid–liquid coalescence experiments in which fine emulsions of water droplets were dispersed in the Viscor-1487 liquid. The experimental results show that the layered hydrophilic/hydrophobic structures significantly reduce the pressure drop and improve the filter performance as compared to media constructed with only micro glass fibers.

This paper discusses the fabrication and characterization of electrospun nanofiber mats made up of poly(4-methyl-1-pentene) polymer. The polymer was electrospun in different weight concentrations. The mats were characterized by their basis weight, fiber diameter distribution, contact angles, contact angle hysteresis, and air permeability. All of the electrospun nonwoven fiber mats had water contact angles greater than 150 degrees making them superhydrophobic. The permeabilities of the mats were empirically fitted to the mat basis weight by a linear relation. The experimentally measured air permeabilities were significantly larger than the permeabilities predicted by the Kuwabara model for fibrous media.

Coalescing filters are used to remove liquid aerosols from gas streams. The captured liquid typically drains from the filter by action of gravity. The saturation or hold-up of liquid in the filter constricts the gas flow, increases pressure drop, and increases the operating costs of the filter. Filter performance can be improved if the liquid saturation is reduced without reduction in capture efficiency. In this paper filter media are modified with drainage structures to reduce saturation and to reduce drag resistance. The media are tested in horizontal and vertical orientations to determine whether their orientation with gravity influences the performance. The experimental results show that with no-drainage-channels the media oriented with flow vertically downward operates the best whereas with drainage channels the horizontally oriented media had the best performance. The results also show embedded woven drainage channels at 45° downward angles have the overall best performance. These results are limited to glass microfiber media and woven polymer meshes as drainage channels. The results show significant improvements in filter performance and warrant a more extensive study.

The gross calorific value (GCV) is an important property defining the energy content and thereby efficiency of fuels, such as coals. There exist a number of correlations for estimating the GCV of a coal sample based upon its proximate and/or ultimate analyses. These correlations are mainly linear in character although there are indications that the relationship between the GCV and a few constituents of the proximate and ultimate analyses could be nonlinear. Accordingly, in this paper a total of seven nonlinear models have been developed using the artificial neural networks (ANN) methodology for the estimation of GCV with a special focus on Indian coals. The comprehensive ANN model developed here uses all the major constituents of the proximate and ultimate analyses as inputs while the remaining six sub-models use different combinations of the constituents of the stated analyses. It has been found that the GCV prediction accuracy of all the models is excellent with the comprehensive model being the most accurate GCV predictor. Also, the performance of the ANN models has been found to be consistently better than that of their linear counterparts. Additionally, a sensitivity analysis of the comprehensive ANN model has been performed to identify the important model inputs, which significantly affect the GCV. The ANN-based modeling approach illustrated in this paper is sufficiently general and thus can be gainfully extended for estimating the GCV of a wide spectrum of solid, liquid and gaseous fuels.