Choked Flow Characteristics of Subcritical Refrigerant Flowing Through Converging-Diverging Nozzles

Hydrophobic and breathable nanofiber membranes have attracted considerable attention owing to their applications in various fields. In this study, we fabricated superhydrophobic and breathable nanofiber membranes using solution blow spinning. We optimized the spinning process parameters by analyzing their effects on the structure and properties of the nanofiber membranes. And the nanofiber membranes achieved superhydrophobicity through hydrophobic modification treatment. The average fiber diameter and pore size of the obtained membrane were 0.51 and 13.65 μm, respectively. The membranes exhibited superhydrophobicity, breathability, and mechanical properties: water vapor transmission of 12.88 kg/m 2 /day, air permeability of 10.97 mm/s, water contact angle of 150.92°, maximum tensile stress of 5.36 MPa, and maximum elongation at break of 12.27%. Additionally, we studied the impact of heat treatment on the nanofiber membranes. The membranes prepared in this study can be applied to protective garments, outdoor clothing, antifouling materials, etc. Because of its relatively higher production efficiency, solution blow spinning is a prospective method for producing functional nanofibers.

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“…Sample 18 exhibits a desirable morphology because the precursor solution jet is sufficiently stretched. 27 , 28 …”

Section: Resultsmentioning

confidence: 99%

“…Sample 18 exhibits a desirable morphology because the precursor solution jet is sufficiently stretched. 28,29 With increase in the nozzle diameter, the fibers first become thinner and then thicker (Figure 12a). The fiber diameter decreases when the nozzle diameter is increased from 0.26 to 0.34 mm.…”

Section: Ncdmentioning

confidence: 99%

Superhydrophobic and Breathable Polyacrylonitrile/Silica/Perfluoroalkyl Ethyl Methacrylate Nanofiber Membranes Prepared by Solution Blow Spinning

et al. 2022

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“…The effect of shock structures on the fibre formation has not been determined, however it is likely that the rapidly changing conditions before and after the shock will have a detrimental effect on the fibre morphology [32]. To avoid choking, nozzle diameter, feed rate and air pressure must be carefully optimized [32,33].…”

Section: Resultsmentioning

confidence: 99%

Solution Blow Spinning of High-Performance Submicron Polyvinylidene Fluoride Fibres: Computational Fluid Mechanics Modelling and Experimental Results

et al. 2020

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Computational fluid dynamics (CFD) was used to investigate characteristics of high-speed air as it is expelled from a solution blow spinning (SBS) nozzle using a k-ε turbulence model. Air velocity, pressure, temperature, turbulent kinetic energy and density contours were generated and analysed in order to achieve an optimal attenuation force for fibre production. A bespoke convergent nozzle was used to produce polyvinylidene fluoride (PVDF) fibres at air pressures between 1 and 5 bar. The nozzle comprised of four parts: a polymer solution syringe holder, an air inlet, an air chamber, and a cap that covers the air chamber. A custom-built SBS setup was used to produce PVDF submicron fibres which were consequently analysed using scanning electron microscope (SEM) for their morphological features. Both theoretical and experimental observations showed that a higher air pressure (4 bar) is more suitable to achieve thin fibres of PVDF. However, fibre diameter increased at 5 bar and intertwined ropes of fibres were also observed.

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“…The effect of shock structures on the fiber formation has not been determined; however, it is likely that the rapidly changing conditions before and after the shock will have a detrimental effect on the fiber morphology. To avoid choking, nozzle diameter, feed rate and air pressure must be carefully optimized [103].…”

Section: Air Pressure and Velocitymentioning

confidence: 99%

Solution Blow Spinning of Polyvinylidene Fluoride Based Fibers for Energy Harvesting Applications: A Review

et al. 2020

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Polyvinylidene fluoride (PVDF)-based piezoelectric materials (PEMs) have found extensive applications in energy harvesting which are being extended consistently to diverse fields requiring strenuous service conditions. Hence, there is a pressing need to mass produce PVDF-based PEMs with the highest possible energy harvesting ability under a given set of conditions. To achieve high yield and efficiency, solution blow spinning (SBS) technique is attracting a lot of interest due to its operational simplicity and high throughput. SBS is arguably still in its infancy when the objective is to mass produce high efficiency PVDF-based PEMs. Therefore, a deeper understanding of the critical parameters regarding design and processing of SBS is essential. The key objective of this review is to critically analyze the key aspects of SBS to produce high efficiency PVDF-based PEMs. As piezoelectric properties of neat PVDF are not intrinsically much significant, various additives are commonly incorporated to enhance its piezoelectricity. Therefore, PVDF-based copolymers and nanocomposites are also included in this review. We discuss both theoretical and experimental results regarding SBS process parameters such as solvents, dissolution methods, feed rate, viscosity, air pressure and velocity, and nozzle design. Morphological features and mechanical properties of PVDF-based nanofibers were also discussed and important applications have been presented. For completeness, key findings from electrospinning were also included. At the end, some insights are given to better direct the efforts in the field of PVDF-based PEMs using SBS technique.

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Choked Flow Characteristics of Subcritical Refrigerant Flowing Through Converging-Diverging Nozzles

Cited by 12 publications

References 23 publications

Superhydrophobic and Breathable Polyacrylonitrile/Silica/Perfluoroalkyl Ethyl Methacrylate Nanofiber Membranes Prepared by Solution Blow Spinning

Superhydrophobic and Breathable Polyacrylonitrile/Silica/Perfluoroalkyl Ethyl Methacrylate Nanofiber Membranes Prepared by Solution Blow Spinning

Solution Blow Spinning of High-Performance Submicron Polyvinylidene Fluoride Fibres: Computational Fluid Mechanics Modelling and Experimental Results

Solution Blow Spinning of Polyvinylidene Fluoride Based Fibers for Energy Harvesting Applications: A Review

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