Deep eutectic solvents (DESs) are a class of promising media for gas separation. In order to examine the potential application of DESs for natural gas upgrading, the solubilities of H2S, CO2, and CH4 ...in choline chloride (ChCl) plus urea mixtures were measured in this work. The solubility data were correlated with Henry's law equation to calculate the thermodynamic properties of gas absorption processes, such as Henry's constants and enthalpy changes. Grand‐canonical Monte Carlo simulations and quantum chemistry calculations were also performed to examine the mechanism of gas absorption processes. It is found that the absorption of H2S in ChCl + urea mixtures is governed by the hydrogen‐bond interaction between Cl of ChCl and H of H2S, whereas the absorption of CO2 and CH4 in ChCl+urea mixtures is governed by the free volume of solvents. Based on the different behavior of gas absorption, high H2S/CO2, H2S/CH4, and CO2/CH4 selectivities can be achieved by adjusting the ratio of ChCl/urea in mixtures.
En este trabajo, con la ayuda de las ecuaciones pertinentes y el software matemático se realizó una comparación de la medida de superficie de los cuerpos geométricos para un determinado volumen, ...entre estos están los poliedros, el cilindro y los prismas de base poligonal regular, el cono y las pirámides de base poligonal regular y algunas superficies de revolución como el paraboloide y el hiperboloide, con respecto a la más óptima es decir la de menor medida de superficie la esfera. Como resultado se registró que el Hiperboloide de una hoja es el de mayor medida de superficie. Adicionalmente se encontró que el cilindro y los prismas, así como el cono y las pirámides tienen proporcionalidades entre el radio de la base del cilindro y la medida de la arista de una base poligonal de n lados o el radio de la base del cono y la medida de la arista de la base poligonal de n lados que permitieron construir la tabla 3 y tabla 4. Este resultado permite dentro de la ingeniería proyectar de una manera rápida cuerpos geométricos óptimos, de manera que se pueda diseñar elementos respetando el ambiente, es decir utilizando solo los recursos necesarios y evitando reciclar mayor cantidad de materiales.
•Tube receiver with pin fin arrays inserting was introduced as tube receiver of PTR.•Average Nusselt number is increased up to 9.0% by using PFAI-PTR.•Overall heat transfer performance is increased ...up to 12.0% by using PFAI-PTR.
Tube receiver with pin fin arrays inserting was introduced as the absorber tube of parabolic trough receiver to increase the overall heat transfer performance of tube receiver for parabolic trough solar collector system. The Monte Carlo ray tracing method (MCRT) coupled with Finite Volume Method (FVM) was adopted to investigate the heat transfer performance and flow characteristics of tube receiver for parabolic trough solar collector system. To validate the feasibility of the developed MCRT and FVM combined method, the numerical results have been compared with experimental results conducted in the DISS test facility in Spain and the max relative error is less than 5%. The numerical results indicated that the introduction of absorber tube with pin fin arrays inserting design for the absorber tube of the parabolic trough receiver can effectively enhance the heat transfer performance. The average Nusselt number can be increased up to 9.0% and the overall heat transfer performance factor can be increased up to 12.0% when the tube receiver with pin fin arrays inserting was used.
Crosslinking is an effective method to improve the properties of high temperature proton exchange membranes based on polybenzimidazole. However, the compact structure of crosslinked polybenzimidazole ...hinders the phosphoric acid absorption of the membranes, resulting in a relatively poor fuel cell performance. Recently, we find that branched polymers can absorb more phosphoric acid with a larger free volume, but suffer from deteriorated mechanical strength. In this work, a new method is proposed to obtain excellent over-all properties of high temperature proton exchange membranes. A series of crosslinked polybenzimidazoles containing branching structure as membrane materials are successfully prepared for the first time. Compared with conventional crosslinked membranes, these crosslinked polybenzimidazole membranes containing branching structure exhibit a higher phosphoric acid doping level and proton conductivity, improved durability, lower swelling rate and comparable mechanical strength. In particular, the fuel cell base on the crosslinked and branched membrane with a 10% ratio of crosslinker in non-humidified hydrogen/air at 160 °C achieves a power density of 404 mW cm−2. The results indicate that the combination of crosslinking and branching is an effective approach to improve the properties of polybenzimidazole membrane materials.
•Silane-crosslinked polybenzimidazoles containing branching structure were prepared.•The membranes showed high proton conductivity and acceptable mechanical strength.•The best power density of 404 mW cm−2 was achieved at 160 °C under dry H2/air.•Reassembled fuel cell using the membrane showed no obvious performance degradation.
The aim of the current study is to investigate the natural convection heat transfer in a square enclosure with a wavy circular heater under magnetic field and nanoparticles. The governing equations ...that are expressed in dimensionless form are solved by means of control volume finite element method employing a validated FORTRAN code. The dimensionless controlling parameters of the present investigation are shape factor of nanoparticles (
m
), Hartmann number (
Ha
), Rayleigh number (
Ra
), and nanoparticle volume fraction (
ϕ)
. In this study, the amplitude
A
and number of undulations
N
are fixed at a constant value of 0.2 and 8, respectively. The obtained results portray that in the presence of waves on the inner wall of the annulus, the heat transfer rate is an ascending function of Rayleigh number, nanoparticle volume fraction and less obvious function of their shape factor, while it is a descending function of the Hartmann number.
Mechanistic relations between the evolution of the starch/flour structure, dough rheology and bread quality were investigated using the most common flours and starches in gluten-free bread-making. ...Micrographs showed that the small wheat starch granules filled the spaces of the big granules, forming a uniform starch-hydrocolloid matrix. This granular advantage decreased the consistency and increased the uniformity of wheat-starch based doughs throughout fermentation, as shown by micrographs and the higher critical strain. The viscoelastic properties of the different doughs strongly influenced the bread volume and the crumb texture. Thus, starch-based breads showed higher specific volume and lower hardness, especially those made with wheat starch, whose lower pasting temperature also reinforced the continuous phase of the crumb. On the other hand, the large potato starch granules did not form a continuous starch-hydrocolloid matrix, resulting in breads with the lowest specific volume, elasticity, cohesiveness and resilience, and the highest hardness.
•The rheological evolution of gluten-free doughs during fermentation was studied.•The textural evolution of gluten-free breads during baking was studied.•Mechanistic relations among starch, dough rheology and bread quality were obtained.•Doughs with low consistency and uniform continuous phase provided high volume breads.•Wheat starch was prone to form a continuous phase that increased bread quality.
In this study, epoxy (EP)/binary spherical alumina (S-Al2O3) composites with a high loading of 50 vol% were fabricated by incorporating different sizes of S-Al2O3 into EP to increase the thermal ...conductivity and yet retain the flowability of the composites. Notably, a distinctly reduced viscosity (21.8 Pa·s) and a highly increased thermal conductivity (1.364 W/m·K) were achieved by a binary S-Al2O3 mixture with 80% 30 μm and 20% 5 μm alumina that would have a theoretical maximum packing volume, thus permitting larger available free volume for the motion of particles and hence reducing the friction between them. Also, these EP/S-Al2O3 binary composites possessed superior electrical insulation, high thermal stability, significantly reduced thermal expansion coefficient and good mechanical properties. These combined desirable properties indicate that binary S-Al2O3 mixtures with an optimized size distribution and maximum packing volume are best candidates to develop high-performance epoxy-based underfill materials which would improve the flip-chip reliability.
Two trifunctional bromomethyls containing crosslinkers, 1,3,5-tris(bromomethyl)benzene (B3Br) and 1,3,5-tris(bromomethyl)-2,4,6-triethylbenzene (Be3Br), are employed to covalently crosslink ...polybenzimidazole (PBI) membranes for the high temperature proton exchange membrane fuel cell. The presence of three bromomethyl groups in each crosslinker molecule is expected to create more free volume for acid doping while enhancing the adhesive strength of the PBI chains. In addition, the influence of the two crosslinker structures on the property of the crosslinked membranes is compared and analyzed. All the crosslinked PBI membranes exhibit longer morphology durability over the pristine PBI membrane toward the radical oxidation. Moreover, the crosslinked PBI membranes with the crosslinker Be3Br containing three ethyl groups display superior acid doping level, high conductivity and excellent mechanical strength simultaneously, over those with the crosslinker B3Br and the pristine PBI membrane. Single cell measurements based on the acid doped membrane with a crosslinking degree of 7.5% by Be3Br demonstrate the technical feasibility of the prepared membranes for high temperature proton exchange membrane fuel cells.
•Crosslinked PBI with crosslinkers containing trifunctional bromomethyls.•Low swelling of the crosslinked membranes by acid doping.•The membrane electrolyte possesses high conductivity and strength simultaneously.•Demonstration of the technical feasibility of the membrane for use in HTPEMFCs.
Sprouting is a natural process that enhances the nutritional and sensory profile of cereal-based foods. The present work addressed the possibility of using refined flour from sprouted wheat (SWF) to ...improve the bread-making performance of some flours in place of conventional improvers - i.e. enzymatic improver (EI) and malt (M). Either 0.5% EI or M was added to the control flour (CTRL), as conventionally used in bakeries, whereas SWF was used up to 2%. Unlikely EI and M, 1.5% SWF showed a gluten aggregation strength similar to that of the CTRL, suggesting no worsening of the protein network characteristics. As for the leavening properties, dough development increased, thanks to the enrichment with 1.5% SWF. In addition, presence of SWF improved the amount of gas production during leavening-resulting in bread with high specific volume - and the crumb softness during storage. Addition of SWF may represent a valid alternative to enzymatic improvers or malt for improving the technological performance of wheat flours.
•Sprouting was carried out in an industrial plant under controlled conditions.•Sprouting enhanced the enzymatic activities of the flour.•Sprouted wheat flour (SWF) improved dough properties even at low percentage (1.5%).•SWF can replace conventional processing aids, as malt or other enzymatic improvers.
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