Green nano-encapsulation technique for preparation of phase change nanofibers mats with core-sheath structure

Nanoencapsulated phase change material in a trapezoidal prism wall under the magnetic field effect for energy storage purposes

Recently, Nano-encapsulated phase change materials (NEPCM) have attracted the attention of researchers due to their promising application in thermal management. This research investigates magnetohydrodynamic mixed convection of NEPCM contained within a lid-driven trapezoidal prism enclosure containing a hot-centered elliptical obstacle. The upper cavity wall is moving at a constant velocity; both inclined walls are cold, while the rest of the walls are insulated. The Galerkin Finite Element Method was used to solve the system's governing equations. The influence of Reynolds number (Re 1-500), Hartmann number (Ha = 0-100), NEPCM volumetric fraction φ (0-8%), and elliptical obstacle orientation α (0-3π/4) on thermal fields and flow patterns are introduced and analyzed. The results indicated that the maximum heat transfer rate is observed when the hot elliptic obstacle is oriented at 90°; an increment of 6% in the Nu number is obtained in this orientation compared to other orientations. Reducing Ha from 100 to 0 increased Nu by 14%. The Maximum value of the Bejan number was observed for the case of Ha = 0, α = 90° and φ = 0.08.

Preparation and Analysis of Sheath-Core Intelligent Thermo-Regulating Fiber

In this work, a skin-core composite intelligent temperature-adjusting fiber was prepared using the composite melt spinning method, with polypropylene as the skin layer and T28-type paraffin as the core layer, in order to obtain clothing fibers with a bidirectional temperature adjustment function. A differential scanning calorimeter was used to test the phase-change latent heat of fibers with different amounts of paraffin injections, and an infrared thermal imager was used to monitor the skin-core composite intelligent temperature-adjusting fiber bundles and ordinary polypropylene fiber bundles under the same heating and cooling conditions. The temperature of the fiber bundle was considered to be a function of time. The results showed that with the increase in the amount of the paraffin injections, the proportion of the paraffin component in the fiber and the latent heat of the fiber phase transition also increased. When the paraffin injection amount was 1.5 mL/min, the melting enthalpy and the crystallization enthalpy reached 65.93 J/g and 66.15 J/g, respectively. Under the same conditions, the heating speed of the intelligent temperature-adjusting fiber bundle was found to be slower than that of the ordinary polypropylene fibers, and the maximum temperature difference between the two reached 8.0 °C. Further, the cooling speed of the former was also observed to be slower than that of the latter, and the maximum temperature difference between the two reached 6.7 °C.

Evidence for bicomponent fibers: A review

Recently, bicomponent fibers have been attracting much attention due to their unique structural characteristics and properties. A common concern was how to characterize a bicomponent fiber. In this review, we generally summarized the classification, structural characteristics, preparation methods of the bicomponent fibers, and focused on the experimental evidence for the identification of bicomponent fibers. Finally, the main challenges and future perspectives of bicomponent fibers and their characterization are provided. We hope that this review will provide readers with a comprehensive understanding of the design and characterization of bicomponent fibers.

Controllable Crimpness of Animal Hairs via Water-Stimulated Shape Fixation for Regulation of Thermal Insulation

Animals living in extremely cold plateau areas have shown amazing ability to maintain their bodies warmth, a benefit of their hair's unique structures and crimps. Investigation of hair crimps using a water-stimulated shape fixation effect would control the hair's crimpness with a specific wetting-drying process thereafter, in order to achieve the regulation of hair thermal insulation. The mechanism of hair's temporary shape fixation was revealed through FTIR and XRD characterizations for switching on and off the hydrogen bonds between macromolecules via penetration into and removal of aqueous molecules. The thermal insulation of hairs was regulated by managing the hair temporary crimps, that is, through managing the multiple reflectance of infrared light by hair hierarchical crimps from hair root to head.