Polypropylene/Silica Aerogel Composite Incorporating a Conformal Coating of Methyltrimethoxysilane-Based Aerogel.

Silica aerogels possess low thermal conductivity but have a brittle nature, while their polymers tend to exhibit enhanced mechanical properties. In this study, we introduce a new approach to overcoming this brittle property of silica aerogels. Polypropylene/silica aerogel composites were prepared by thermally induced phase separation followed by a supercritical CO2 drying method. Silica aerogel was formed onto a polypropylene scaffold using a two-step sol-gel process with methyltrimethoxysilane as the silica precursor. Enhancement of the mechanical properties of the polypropylene/silica aerogel composite compared with a pristine methyltrimethoxysilane-based silica aerogel was observed. The effects of the latter on the microstructure and physical properties of the polypropylene/silica aerogel (hereafter referred to as the polymer matrix aerogel) composite were investigated. Compared with the polypropylene monolith, the polymer matrix aerogel composite demonstrated enhanced surface-chemical and microporous-structural properties such as higher hydrophobicity (135°), pore volume (0.18 cm³/g), average pore diameter (12.55 nm), and specific surface area (57.2 m²/g). This novel approach of incorporating methyltrimethoxysilane-based silica aerogel onto polypropylene when synthesizing the polymer matrix aerogel composite shows great potential as a durable superhydrophobic and corrosion resistant thermal insulating material.

A study of cover slope effect on productivity of solar still under Tunisian winter and summer conditions.

The Tunisian country will suffer from the scarcity of clean and healthy drinking water in the near future. Solar still-based water distillation is one of the simplest cheap technologies that may solve this problem. The present study addresses this problem through experimentally and numerically investigating the feasibility of water desalination with a passive solar still in actual Tunisia Sfax central region climate conditions as well as the glass cover angle effect on the productivity of the solar still. The study was conducted for 2 days so that 1 day is in the summer and another day in the winter for comparison purpose. The flow solution was obtained with the Fluent solver Eulerian multiphase model coupled to a developed C + + mass transfer code based on the Dunkle model. The considered glass cover angles are 5°, 10°, 20°, 30°, 45°, and 60°. The deviation between the numerical results and test data does not exceed 15% which ensures the validity of the calculation method. Both experimental and numerical results showed that the solar still productivity in summer is by far better than that in winter. The optimal glass cover angle was found to be of 20° in both summer and winter seasons. The maximum daily water yield is of 535.64 ml on January 15, 2021 and 3083.11 ml on June 15, 2021. The results proved that the solar still can be an efficient device for solar desalination in Tunisia central region.

Corrigendum: Numerical study of perforated obstacles effects on the performance of solar parabolic trough collector.

[This corrects the article DOI: 10.3389/fchem.2022.1089080.].

Thermal Study of Carbon-Fiber-Reinforced Polymer Composites Using Multiscale Modeling.

The layered fibers of carbon-fiber-reinforced polymer (CFRP) composites exhibit low thermal conductivity (TC) throughout their thickness due to the poor TC of the polymeric resin. Improved heat transmission inside the hydrogen storage tank during the filling process can reduce further compression work, and improved heat insulation can minimize energy loss. Therefore, it is crucial to understand the thermal properties of composites. This paper reports the thermal behavior of plain-woven CFRP composite using simulation at the micro-, meso-, and macro-scales. The TC was predicted numerically and compared to experimental findings and analytical models. Good results were found. Using the approach of multi-scale modeling, a parametric study was carried out to analyze in depth the influence of certain variables on thermal properties. The study revealed that both fiber volume fraction and temperature significantly influenced the TC of the composite, with the interphase fiber/matrix thickness following closely in terms of impact. The matrix porosity was found to have a relatively slighter impact, particularly within the porosity range of 5 to 15%.

Natural Convection within Inversed T-Shaped Enclosure Filled by Nano-Enhanced Phase Change Material: Numerical Investigation.

Energy saving has always been a topic of great interest. The usage of nano-enhanced phase change material NePCM is one of the energy-saving methods that has gained increasing interest. In the current report, we intend to simulate the natural convection flow of NePCM inside an inverse T-shaped enclosure. The complex nature of the flow results from the following factors: the enclosure contains a hot trapezoidal fin on the bottom wall, the enclosure is saturated with pours media, and it is exposed to a magnetic field. The governing equations of the studied system are numerically addressed by the higher order Galerkin finite element method (GFEM). The impacts of the Darcy number (Da = 10-2-10-5), Rayleigh number (Ra = 103-106), nanoparticle volume fraction (φ = 0-0.08), and Hartmann number (Ha = 0-100) are analyzed. The results indicate that both local and average Nusselt numbers were considerably affected by Ra and Da values, while the influence of other parameters was negligible. Increasing Ra (increasing buoyancy force) from 103 to 106 enhanced the maximum average Nusselt number by 740%, while increasing Da (increasing the permeability) from 10-5 to 10-2 enhanced both the maximum average Nusselt number and the maximum local Nusselt number by the same rate (360%).

Numerical study of perforated obstacles effects on the performance of solar parabolic trough collector.

The current work presents and discusses a numerical analysis of improving heat transmission in the receiver of a parabolic trough solar collector by introducing perforated barriers. While the proposed approach to enhance the collector's performance is promising, the use of obstacles results in increased pressure loss. The Computational Fluid Dynamics (CFD) model analysis is conducted based on the renormalization-group (RNG) k-ɛ turbulent model associated with standard wall function using thermal oil D12 as working fluid The thermo-hydraulic analysis of the receiver tube with perforated obstacles is taken for various configurations and Reynolds number ranging from 18,860 to 81,728. The results are compared with that of the receiver without perforated obstacles. The receiver tube with three holes (PO3) showed better heat transfer characteristics. In addition, the Nusselt number (Nu) increases about 115% with the increase of friction factor 5-6.5 times and the performance evaluation criteria (PEC) changes from 1.22 to 1.24. The temperature of thermal oil fluid attains its maximum value at the exit, and higher temperatures (462.1 K) are found in the absorber tube with perforated obstacles with three holes (PO3). Accordingly, using perforated obstacles receiver for parabolic trough concentrator is highly recommended where significant enhancement of system's performance is achieved.

Numerical simulation and experimental validation of the ventilation system performance in a heated room.

The time spent by the occupant indoor the building is significant; therefore, the central objective of the major research was the evaluation of the thermal sensation for the existing people. This study examines the numerical simulation in a room containing a manikin sitting in front of a computer. The computational fluid dynamics (CFD) tools were considered using ANSYS Fluent 16.2 software. This software exploits the finite volume method that is based on the resolution of the Navier-Stokes equations. The distribution of the temperature, velocity, static pressure, turbulent kinetic energy, turbulent viscosity, and turbulent dissipation is tested in different planes and different directions to characterize the airflow indoor a heated room. Equally, the thermal comfort is examined by calculating the predicted mean vote (PMV). The comparison between the numerical results and the experimental data founded from the literature prove that the supply of airflow was affected by the presence of the heat sources and the thermal climate is considered as a slightly hot. The use of the adequate meshes is in a good agreement with the experimental data and confirms the validity of the numerical approach.

Enhancement of the performance of hemispherical distiller via phosphate pellets as energy storage medium.

In this experimental work, the performance of hemispherical distiller has been enhanced via phosphate pellets. To investigate the best approach to the phosphate pellet utilization in a basin of hemispherical distiller to achieve the highest performance, the present study was carried out in two stages. In the first stage, 250 g of phosphate pellets was arranged in a layer of 5 mm thickness placed at the bottom of the basin. In the second stage, the phosphate pellets were distributed in a homogeneous manner in basin salt water with two concentrations 1% (10 g/L) and 2% (20 g/L) without aggregation on the basin. To achieve this idea, in the first test stage, two distillers were compared, the first is the conventional hemispherical distiller which represents the reference distiller (CHSS) and the second is the modified hemispherical distiller with a phosphate layer (MHSS-PL). In the second test stage, three distillers were compared, the first is the CHSS which represents the reference distiller, the second is the modified hemispherical distiller which contained 1% phosphate (MHSS-1), and the third is the modified hemispherical distiller which contained 2% phosphates (MHSS-2). The experimental results show that the cumulative yield was 4.6, 6.32, 6.15, and 6.85 L/m2·day for CHSS, MHSS-PL, MHSS-1, and MHSS-2, respectively. The results showed that the utilization of the phosphate pellets as a storage medium enhanced the performance of the hemispherical distiller. The enhancement in the distiller productivity was 37.4, 33.7, and 47.9% for MHSS-PL, MHSS-1, and MHSS-2, respectively, compared to conventional hemispherical solar still (CHSS). The peak enhancement in the productivity was achieved in the case of modified hemispherical solar still with 2% (20 g/L) phosphate pellets (MHSS-2).

A comparative energy and exergy efficiency study of hemispherical and single-slope solar stills.

In this experimental work, a comparative energy and exergy efficiency study of hemispherical solar still and a single-slope solar still has been carried out. The experiments were conducted in southeast Algeria on 25-5-2020 and 3-6-2020 in the natural climatic environment, and daily accumulation of distilled water produced for both distilleries was measured. The maximum obtained cumulative yield of distilled products is equal to 5.38 kg/m2/day for the hemispherical solar still, and 3.64 kg/m2/day for the single-slope solar still. The overall daily productivity was improved by 47.96% for the hemispherical solar still compared to the single-slope solar still. The maximum daily energy efficiency of the single-slope solar still is 25.81%, and hemispherical solar still is 38.61%. Similarly, the maximum daily exergy efficiency of single-slope solar still is 1.8%, and hemispherical solar still is 3.1%. The main conclusion from the study is the hemispherical distillery greatly enhances productivity as compared to the single-slope distillate and gives more efficiency. Thus, the hemispherical solar still is recommended to be used to provide safe drinking water from salty water.

Performance enhancements of conventional solar still using reflective aluminium foil sheet and reflective glass mirrors: energy and exergy analysis.

Many researchers are seeking simple and successful solutions to increase the output from the solar distiller. In this research work, reflective mirrors and reflective aluminium foil sheet were fixed on inner surfaces of the single-slope solar distiller, leading to more water production. The presence of reflective mirrors and reflective aluminium foil sheet on inner surfaces of the solar distillate permits the reflection of solar radiation falling inside the basin. Experiments were carried out on three stills: the first distiller is conventional solar still with black painted walls (CSS-BPW); the second distiller is conventional solar still with reflective aluminium foil sheet walls (CSS-RAFW); and the third distiller is conventional solar still with reflective glass mirror walls (CSS-RGMW). The maximum total drinking water productions from the CSS, CSS-RAFW and the CSS-RGMW are 3.41, 5.1 and 5.54 kg/m2, respectively. Compared to the CSS-BPW, the production of drinking water was increased by 68.57% when using the reflective glass mirrors and 48.57% when using the reflective aluminium foil sheet.

Phosphate bags as energy storage materials for enhancement of solar still performance.

In this experimental work, the effect of cotton bags filled with phosphate on solar distillery performance has been investigated. In this study, 25 phosphate bags are evenly distributed (5 × 5) with a length equal to 50 cm in a wooden box called the modified solar still (MSS). This system was compared with the conventional solar still (CSS) in the same climatic conditions. Phosphate bags are placed vertically to increase the energy storage capacity, and the water's surface area since the capillaries inside the phosphate bags play an important role in increasing the energy storage capacity. Experiments were conducted at El Oued University in Algeria during April and May 2020, with 1 cm and 2 cm of saltwater depth. The cumulative yield of 5.27 and 4.87 kg was produced from the MSS at 1 cm and 2 cm of saltwater, respectively, while the cumulative yield of the CSS was 3.8 kg. The MSS's overall efficiency at 1 cm and 2 cm of saltwater was enhanced by 28 and 22.5%, respectively compared with the CSS. The presence of calcium and copper in phosphate stores the heat energy during morning and afternoon, and stored heat energy was released during evening. Finally, it can be concluded that increasing phosphate bags significantly enhances the productivity in solar distillation, increasing efficiency and productivity.

Facile Synthesis of SnO2 Aerogel/Reduced Graphene Oxide Nanocomposites via in Situ Annealing for the Photocatalytic Degradation of Methyl Orange.

SnO2 aerogel/reduced graphene oxide (rGO) nanocomposites were synthesized using the sol⁻gel method. A homogeneous dispersion of graphene oxide (GO) flakes in a tin precursor solution was captured in a three-dimensional network SnO2 aerogel matrix and successively underwent supercritical alcohol drying followed by the in situ thermal reduction of GO, resulting in SnO2 aerogel/rGO nanocomposites. The chemical interaction between aerogel matrix and GO functional groups was confirmed by a peak shift in the Fourier transform infrared spectra and a change in the optical bandgap of the diffuse reflectance spectra. The role of rGO in 3D aerogel structure was studied in terms of photocatalytic activity with detailed mechanism of the enhancement such as electron transfer between the GO and SnO2. In addition, the photocatalytic activity of these nanocomposites in the methyl orange degradation varied depending on the amount of rGO loading in the SnO2 aerogel matrix; an appropriate amount of rGO was required for the highest enhancement in the photocatalytic activity of the SnO2 aerogel. The proposed nanocomposites could be a useful solution against water pollutants.

Immobilization of His-tagged recombinant xylanase from Penicillium occitanis on nickel-chelate Eupergit C for increasing digestibility of poultry feed.

Recombinant xylanase 2 from Penicillium occitanis expressed with an His-tag in Pichia pastoris, termed PoXyn2, was immobilized on nickel-chelate Eupergit C by covalent coupling reaction with a high immobilization yield up to 93.49%. Characterization of the immobilized PoXyn2 was further evaluated. The optimum pH was not affected by immobilization, but the immobilized PoXyn2 exhibited more acidic and large optimum pH range (pH 2.0-4.0) than that of the free PoXyn2 (pH 3.0). The free PoXyn2 had an optimum temperature of 50 °C, whereas that of the immobilized enzyme was shifted to 65 °C. Immobilization increased both pH stability and thermostability when compared with the free enzyme. Thermodynamically, increase in enthalpy and free energy change after covalent immobilization could be credited to the enhanced stability. Immobilized xylanase could be reused for 10 consecutive cycles retaining 60% of its initial activity. It was found to be effective in releasing reducing sugar from poultry feed. Immobilization on Eupergit C is important due to its mechanical resistance at high pH and temperature. Hence, considerable stability and reusability of bound enzyme may be advantageous for its industrial application.