Smooth Channel Research Articles

Effect of Baffles in Flow Channel on the Performance of Vanadium Redox Flow Battery

For a PEMFC to work better, adding baffles to a flow channel can improve reactant transfer. As a result, the work starts by developing a 3-D numerical model for the vanadium redox flow battery (VRFB) using COMSOL Multiphysic Simulation Software. By incorporating baffles into the serpentine flow channel, it is possible to simulate changes in ion concentration and terminal voltage. The findings indicate that the battery efficiency will be impacted by adding baffles. The authors also studied the effect of baffle height and baffle count. The baffle height of 0.9 times the channel height and baffle number of 9 has a better performance on the battery. There are four cases for installing nine baffles and four arranging types in the entire serpentine flow using such baffle height and number. In Case 4, baffles are placed uniformly at the location of channel numbers 1, 9, and 17 in the serpentine flow path. It has a better voltage and ion concentration reaction than the other cases. The unit tests for cell performances were experimentally analyzed for a smooth-serpentine channel and a baffled-serpentine one. According to the experimental findings, a higher volume rate (300 mL/min) and lower current per area (40 mA/cm2) acquire the best energy efficiency. Case 4 has a higher energy efficiency than the smooth channel.

Aldosterone activates cerebrovascular smooth muscle BK channels in absence of β1 subunits, yet these potentiate steroid action and thus facilitate aldosterone-induced dilation of cerebral arteries.

Calcium/voltage-gated, big conductance K+ channels (BK α subunits or slo1 proteins) modulate smooth muscle (SM) tone and thus cerebral artery diameter. In cerebral arteries, the BK current phenotype is conditioned by regulatory β1 subunits which fine-tune channel activity to tissue-specific physiology. Several physiological steroids modify BK function and may modify cerebral artery function. Thus, cholesterol and pregnenolone inhibit SM BK and evoke middle cerebral artery (MCA) constriction through recognition by slo1 whereas estradiol and cholanes activate SM BK through recognition by β1. Aldosterone is a steroid with documented vasoactive properties, yet the involvement of BK in aldosterone's cerebrovascular action and the contribution of distinct channel subunits to this action remain unknown. Here, we first used nanoscale differential scanning fluorimetry to test whether aldosterone (0.3-100 μM) could directly bind BK α or β1 subunits. Changes in temperature of onset and inflection point (indicators of protein-steroid binding) were evident at 10 and 1 µM aldosterone for α and β1. Next, MCA SM cells were enzymatically isolated from mice, and cell-free recordings were conducted to determine changes in BK activity by aldosterone. Increased activity by aldosterone was concentration-dependent: EC50 = 3 μM; ECMAX = 10 μM, at which activity increased by 20%. Consistently with this small yet reproducible SM BK activation, 10 μM aldosterone dilated MCA by 2%, independently of circulating and endothelial factors. In SM cells and MCA segments from β1-/- mice, aldosterone activated BK with reduced potency and efficacy, and vasodilation by the steroid was evoked by very high concentrations (>>10 µM). Therefore, aldosterone is able to activate SM BK in absence of β1, yet this regulatory subunit potentiates aldosterone action and thus enables subµM-µM aldosterone to dilate MCA.

Experimental and Numerical Study of Heat Transfer and Turbulent Flow in a Rotating channel with V Rib-Dimple Hybrid Structures

Heat transfer and turbulent flow structure of novel hybrid structures with V rib-dimple arrays in channels with a sudden contraction have been investigated through experimental and numerical studies for the Reynolds number (Re) from 10,000 to 200,000 and Rotation number (Ro) from 0 to 0.413, which are also compared with those of a smooth and a dimpled only channel. For rotating smooth channels, sudden contraction can significantly enhance heat transfer in the entrance region for the first 4 times Dh of the channel, and heat transfer rates for trailing and leading walls are higher compared with those of static channels. For the rotating V rib-dimple channel at Re = 10,000, heat transfer rates of the trailing wall significantly increase by about 39.13% at Ro = 0.413 compared with those under the non-rotating state, which is because the longitudinal vortex on the trailing side becomes stronger with the actions of the Coriolis force produced by the rotation, thus significantly enhancing heat transfer there. It is also noted that strong longitudinal vortex pairs from inside the dimples of the V rib-dimple structure can partially offset influences of the rotation effects. Therefore, the maximum heat transfer difference between leading and trailing sides of rotating V rib-dimple channels is just 22.57%, which is much smaller than the difference of 107.25% of the rotating dimpled only channel.

Efficient Tuning of the Opto-Electronic Properties of Sol-Gel-Synthesized Al-Doped Titania Nanoparticles for Perovskite Solar Cells and Functional Textiles.

The efficient electron transport layer (ETL) plays a critical role in the performance of perovskites solar cells (PSCs). Ideally, an unobstructed network with smooth channels for electron flow is required, which is lacking in the pristine TiO2-based ETL. As a potential solution, here we tuned the structure of TiO2 via optimized heteroatom doping of Al. Different concentrations (1, 2, and 3 wt%) of Al were doped in TiO2 and were successfully applied as an ETL in PSC using spin coating. A significant difference in the structural, opto-electronic, chemical, and electrical characteristics was observed in Al-doped TiO2 structures. The opto-electronic properties revealed that Al doping shifted the absorption spectra toward the visible range. Pure titania possesses a bandgap of 3.38 eV; however, after 1, 2, and 3% Al doping, the bandgap was linearly reduced to 3.29, 3.25, and 3.18 eV, respectively. In addition, higher light transmission was observed for Al-doped TiO2, which was due to the scattering effects of the interconnected porous morphology of doped-TiO2. Al-doped titania shows higher thermal stability and a 28% lower weight loss and can be operated at higher temperatures compared to undoped titania (weight loss 30%) due to the formation of stable states after Al doping. In addition, Al-doped TiO2 showed significantly high conductivity, which provides smooth paths for electron transport. Thanks to the effective tuning of band structure and morphology of Al-doped TiO2, a significant improvement in current densities, fill factor, and efficiency was observed in PSCs. The combined effect of better Jsc and FF renders higher efficiencies in Al-doped TiO2, as 1, 2, and 3% Al-doped TiO2 showed 12.5, 14.1, and 13.6% efficiency, respectively. Compared to undoped TiO2 with an efficiency of 10.3%, the optimized 2% Al doping increased the efficiency up to 14.1%. In addition, Al-doped TiO2 also showed improvements in antibacterial effects, required for photoactive textiles.

Effect of arc-shaped twisted-baffles on augmented heat transfer in a rectangular duct

In this current work, the effect of utilizing arc-shaped twisted-baffles (T-ABs) in a rectangular air channel on thermal performance factor (TPF) has been experimentally studied. In these experiments, the influence of the changes in parameters such as dimensions of pitch ratio (p/w), attached arc-shape angle (α), and Reynolds number (Re) are explored. The comparisons demonstrate that a channel mounted with arc-shaped twisted-baffles yielded considerably greater Nusselt numbers than a smooth channel, possibly attributable to multiple-impinging jets near the channel surface. Heat transfer enhancements of twisted arc-shaped baffles (T-AB) having larger attack angles were superior to those having smaller attack angles. The one with α = 90o offered greater heat transfer rates than the ones with α = 20o, 40o, 60o, and 80o by approximately 8%, 7%, 4%, and 2%, respectively. The superior heat transfer was attributed to the better contact between the working fluid and heat transfer surfaces. In addition, utilizing arc-shaped twisted-baffles with the lowest p/w of 4.0, in a channel produced stronger vortices and multiple impinging jets, which caused better fluid mixing than other p/w. The optimum condition is achieved using T-ABs at an attached arc-shape angle of α = 90o, p/w = 4.0 and Re = 4000, where the heat transfer rate (Nu), friction factor (f) and TPF are found to be, respectively, 3.31, 4.68 and 1.98 times greater than those of a plain channel.

Cooling performance in a minichannel heat sink with different triangular pin-fins configurations

With the continuous progress of automotive new energy technology, the motor has become an important part of the power system, and the heat dissipation of insulated-gate bipolar transistors (IGBT) determines the reliability of the power system. Minichannel structure can be added to the thermal management system of new energy vehicles to improve the heat transfer capacity. Due to the growth of the boundary layer in the smooth minichannel flow channel, the cooling performance improvement was limited. Pin-fins and rib structures were used to break the boundary layer and increased the heat transfer area to enhance the heat transfer capacity. In this study, a numerical simulation model of minichannel with triangular pin-fins with different rotation angles was established and calculated using the SST k-omega method. The temperature field, velocity field, pressure, and vortex distribution under different configurations were discussed in detail. The jet area formed by the prism wall and the side wall of the minichannel would impact the wall and reduce the growth of the boundary layer. However, the stagnation area generated in the center and corner will reduce the improvement of heat transfer capacity. The thermo-hydraulic characteristics of different configurations at different Reynolds numbers (Re), such as Nusselt number (Nu), Darcy friction resistance coefficient (f), and performance evaluation criterion (PEC), were analyzed. As Re increased, the best and worst configurations changed, the best configuration changed from the 90°–120° structure to the 120°–120° structure, and the worst configuration changed from the 75°–60° to the 60°–60° structure. When the Re = 663, the influence of the front and rear rotation angle on the cooling performance was explored. When the rotation angle was closer to 60°, the cooling performance of the minichannel was better. And the closer the rotation angle was to 120°, the cooling performance was better. This has a reference effect on the design of minichannel heat sinks.

"Molecular and Cellular Emerging Role of Arterial Vascular Smooth Muscle Cells Potassium Channels in Chronic Hypertension"

"Molecular and Cellular Emerging Role of Arterial Vascular Smooth Muscle Cells Potassium Channels in Chronic Hypertension"

"Molecular and Cellular Emerging Role of Arterial Vascular Smooth Muscle Cells Potassium Channels in Chronic Hypertension"

"Molecular and Cellular Emerging Role of Arterial Vascular Smooth Muscle Cells Potassium Channels in Chronic Hypertension"

Effects of pyrolysis on heat transfer enhancement for hydrocarbon fuel flow in unilateral heated channels with dimples

• Pyrolysis aggravates the non-uniformity of secondary flow intensity by two times. • Pyrolysis causes nonlinear correspondence between heat flux and wall temperature. • Dimples weaken the stratification of secondary flow intensity for pyrolysis fuel. • Dimple cannot disturb aggravated non-uniformity of properties for pyrolysis fuel. • Dimple cannot effectively enhance heat transfer for cracking fuel at high heat flux. Heat transfer enhancement of hydrocarbon fuel is essential to improve the regenerative cooling performance for scramjet engines, especially under hypersonic flights ( Ma >6). Aiming to investigate the effects of fuel pyrolysis on heat transfer enhancement design in the channel, this study exploits the local secondary flow intensities for non-pyrolysis and pyrolysis fuel flow. Flow and heat transfer characteristics of pyrolysis n-Decane in smooth and dimpled channel are compared at 0∼4 MW/m 2 . Parametric analysis of dimple geometry is conducted. Among five dfferent dimensions dimples, h p =0.3 mm, d p =1.5 mm, p =3 mm obtains the best heat transfer performance but it still cannot effectively reduce wall temperature compared with smooth channel. Fuel pyrolysis intensively aggravates the non-uniformity of fluid properties and secondary flow intensities. Besides, the deep-degree pyrolysis in near wall region causes nonlinear correspondence between fluid temperature and heat flux. Above two factors brings enormous difficulties for heat transfer enhancement design in the cooling channel. Dimples weaken the secondary flow intensities stratification and significantly improve the adaptability for the heat transfer of pyrolysis fuel to the changing heat conditions. But dimples cannot sufficiently disturb the strengthened properties stratification induced by severe pyrolysis non-uniformity. Therefore, under high heat flux, dimples cannot perform good heat transfer enhancement for pyrolysis hydrocarbon fuel.

Experimental investigation on thermal efficiency augmentation of solar air heater using copper wire for discrete roughened absorber plate

Solar air heaters are used to heat the air, however their thermal efficiency is low due to the weak thermal conductivity between the air and the absorber plate. The thermal efficiency of solar air heaters can be improved by artificially roughening the absorber plate, which elevates the temperature of the plate and results in maximum thermal losses to the atmosphere.The performance of solar air heaters (SAH).is improved by using the largest range of solar flux and discharging heat energy from the absorber plate through air working fluid. In the outdoor experiment described in this article, artificial rib elements were added to the surface of the absorber plate to increase the heat transfer coefficient. In a recent study and outdoor experimental laboratory work done in view of the investigation of heat transfer coefficient and thermal efficiency parameters, a novel discrete double arc reverse form artificial roughness has been developed on the underside of the absorber plate. The roughness range of parameters used in the outdoor work are channel aspect ratio (W/H) of 8, relative roughness pitch (p/e) of 6.67–8.33, relative roughness height (e/Dh) of 0.027, angle of arc (α) of 60° and Reynolds number (Re) of 3000–14000, The test was run from morning 11 am until afternoon 2 pm, and the solar heat flux (I) was between 850 and 890 W per square metre. Under comparable working conditions, the artificially roughened channel performs well in comparison to the smooth channel. Over the smooth channel, the maximum ranges of thermal efficiency and heat transfer coefficient were noted to be 288 % and 129 %, respectively.

Effective construction of a CuCo MOF@graphene functional electrocatalyst for hydrogen evolution reaction.

Electrochemical water splitting is considered a green and sustainable method of producing hydrogen energy. Herein, to pursue a highly efficient hydrogen evolution reaction, we fabricated high-performance electrocatalysts, by utilizing a bimetallic (Cu and Co) metal-organic framework to modify rGO through a one-step in situ approach. The synthesized CuCoOC@rGO presents a highly ordered structure with a defect-rich porous surface for the hydrogen evolution reaction (HER). Specifically, the appropriate adjustment of metal (Cu and Co), 1,3,5-benzenetricarboxylic acid (H3BTC), and rGO ratios leads to a well-defined morphology, which creates a defect-rich porous surface. Characterized by XRD, SEM, EDS, FT-IR spectroscopy, Raman spectroscopy, XPS, and BET, the morphology exposes more active sites, strong evidence for the promotion of electrocatalytic efficiency. Upon the analysis of the experimental data, the obtained CuCoOC@rGO catalyst exhibits excellent activity in alkaline media with a low overpotential of 120 mV at a current density of 10 mA cm-2, and a Tafel slope of 124 mV dec-1 for the hydrogen evolution reaction (HER). Guided by the structure-activity relationship, the superior HER activity of CuCoOC@rGO in alkaline electrolyte could originate from many sources, including: (1) as a self-supported substrate, CuCoOC@rGO not only leads to profitable electrical contact and mechanical stability but also firmly roots into the rGO without extra binders. (2) The highly ordered structure provides smooth ion and electron transport channels, which are conducive to electrolyte infiltration and gas release. (3) The abundance of defective pores on the surface of the nanoarrays, which offers more active sites for the catalytic process. This study provides new prospects for the rational design and fabrication of advanced hierarchical functional electrocatalysts for application in electrochemical energy devices.

The Last “Green Field” of Enterprise's Competitive Advantages: A Discussion on Human Capital and Human Resource Management

Every company has its own tangible assets (financial and physical assets, etc.) and intangible assets (trademarks, customer relationships, employees, etc.). In the past, tangible assets were the main source of competitive advantage, but they are increasingly unable to reflect their particularity or special advantages that distinguish them from others. Smooth and multi-level financing channels such as debt financing, equity financing, can no longer give a company any competitive advantage, nor can it distinguish it from competitors. The same happens with technological means and tools. The company that adopts the new technology first has a competitive advantage that can last for several years, but now, the advantage brought by the new technology is fleeting, and the technology of one company can be easily obtained by other companies, imitation or surpassing, which makes technology no longer an advantage, but gradually becomes a necessity, such examples are too numerous to mention. At the same time, increased competition is causing things that were previously unimaginable: small companies competing with large companies, and new companies competing with established companies.

Study on Convective Heat Transfer of Supercritical Water in Annular Square Channel

Supercritical water, known for its abrupt changes in fluid properties near the pseudocritical region, has always posed a design challenge, leading to enhancement or deterioration in heat transfer. Additionally, the lack of complete understanding of the thermodynamic behavior of supercritical water near the pseudocritical zone, unlike in the subcritical zone, highlights the necessity of a systematic study. Hence, this paper focuses on characterizing the convective upward flow and heat transfer characteristics inside a vertical smooth annular square channel. The numerical analysis uses a steady-state, pressure-based, compressible, Newtonian solver with body force term and two-equation turbulence model to study the influence of variation in pressure, heat flux, and heat-to-mass flux ratios. The flow characteristics and heat transfer behavior of deteriorated, normal, and enhanced heat transfer modes are studied. The heat transfer deterioration is suppressed with the increase in pressure; however, it increases with the increase in inlet bulk temperature. The supercritical boiling number that determines the heat transfer mode is calculated and analyzed for the square annulus section. The evolution of the flow in different heat transfer modes differs based on the effect of buoyancy on the velocity field and the turbulence. The calculated Nusselt numbers match the existing Jackson and Hall correlation well with a maximum absolute error of 9.91%.

Thermal-hydraulic characteristics of FLiBe in annuli with helical wire

A fully tight-fitting triangular wire coil is used to enhance heat transfer of FLiBe in the annular channel for the first time. The numerical simulations of annular channels with triangular wire coil were performed with three helical pitches, three annular widths, and one equilateral triangle corresponding to Reynolds number of 4000–10000. It is found that adding triangular wire coil generates a vortex and reduces significantly the lengths of flow and thermal entrance regions of the annular channel. The local Nusselt number for peripheral point is extremely non-uniform. The Nusselt number decreases with annular width and helical pitch increase. The Nusselt number of enhanced annular channel is 1.45–1.98 times that of smooth annular channel. The overall performance of annular channel with helical pitch of 15 mm and annular width of 10 mm is best by using the principle of entropy generation. However, by using the performance evaluation criteria, the annular channel with helical pitch of 15 mm and annular width of 19.4 mm is best when the Reynolds number is less than or equal to 5500. And the annular channel with helical pitch of 20 mm and annular width of 19.4 mm is best at the high Reynolds number.

Factors Affecting Vegetable Marketing Channel In Rangamati Hill District of Bangladesh

50 respondents were chosen randomly for primary data collection. In this study, principal component method was applied to estimate the factor loadings and communalities. ‘Varimax’ factor rotation was used to estimate factor loadings. The Kaiser-Meyer-Olkin (KMO) and Bartlett's Test were also applied. Besides, to identify the factors coefficient value and significance level multiple logistic regression model was applied. The study identified two major vegetable marketing channels, viz. Farmer- Local Market- Consumer and Farmer- Local Market- Local Retailer- Consumer; and three value addition activities, viz. washing, grading and bundling of vegetables. Problems associated with marketing channels were identified as lack of proper irrigation system, better transportation, diversified market, market infrastructure, storage facility, knowledge about new technology and marketing skill, proper guidance and training. The study recognized four factors that affect vegetable marketing channels. These are: Marketing factor (Factor 1), Economic factor (Factor 2), Social factor (Factor 3) and External factor (Factor 4). The study recommended that policy makers should come forward to ensure dissemination of appropriate technologies, adequate training for indigenous farmers, better transportation system, well established market infrastructure and integrate all activities of participants like farmers, local retailers, government, NGOs etc. to ensure a smooth, fair and profitable vegetable marketing channel.
 Bangladesh J. Agril. Res. 45(4): 445-454, December 2020

Construction of PdS@MIL-125-NH2@ZnS type-II heterostructure with efficient charge separation for boosted photocatalytic hydrogen evolution

A new photocatalyst, PdS@NH2-MIL-125(Ti)@ZnS (PdS/M125/ZnS) heterojunction is fabricated for photocatalytic H2 generation for the first time, where PdS nanoparticles are anchored in the pore of M125 by utilizing its confinement effect, and the ZnS is closely wrapped on the surfaces of the MOFs. The optimal photocatalyst exhibits a significantly enhanced H2 generation rate of 1164.2 μmol/g/h, while the pure M125 only displays a H2 generation rate of 16.7 μmol/g/h. The resultant improvement can be ascribed to the following comprehensive advantages. The hierarchical structure built by PdS, M125, and ZnS can form lots of intimate interfaces, offer abundant sites for reaction, and smooth channels for charge carriers due to the porous characteristics of MOFs. Moreover, M125 and ZnS with inner defect levels form an analogous type-II heterojunction assisted by PdS co-catalyst, which greatly promotes charge separation. This work may supply a new avenue to design MOFs photocatalysts for energy conversion.

Heat transfer enhancement in a regenerative cooling channel using porous media

The endothermic hydrocarbon fuels play an important role in the thermal management of hypersonic scramjet. However, there often involve serious thermal stratifications in the regenerative cooling channel. The present work conducts a two-dimensional cooling channel numerical simulation with the addition of porous media using a unique global chemical kinetics model to clarify the increase of the total heat sink of hydrocarbon fuels. It is proposed that the addition of porous media is a coupling process, which not only enhances heat transfer, but also will bring resistance to heat. Therefore, the energy source term is included in the numerical simulations, which makes our calculations closer to the actual working condition compared to the previous numerical modeling. The simulated results indicate that compared to the smooth channel, the thermal stratifications are relieved in the cooling channel with the addition of porous media, while the thermal cracking of n-decane is inhibited due to the decrease of the wall temperature. In addition, with the decrease of porosity of porous media, the total heat sink of fuel increases. The heat transfer coupling rule of porous media is studied by placing porous media at different positions, and the optimal placement position is found.

Heat transfer enhancement in the novel wavy shaped heat exchanger channel with cylindrical vortex generators

The enhancement characteristics of heat transfer in conjunction with a low pressure drop were experimentally and numerically investigated for the novel geometry wavy shaped heated channel with cylindrical vortex generators. To visualize the temperature distribution there was used the holographic interferometry method while the Ansys Fluent software was used to evaluate the temperature, velocity, and pressure field in the wavy channel. The study is focused on the analysis of the heat transfer coefficients, Nusselt numbers, thermal performance, Colburn factor, and friction factor for the wavy channel and the wavy channel with cylindrical vortex generators of 15 mm diameter located in five different horizontal positions. Moreover, we have performed a comparison with the smooth channel. The results are presented for the surface temperature Ts = 318.15 K, Reynolds number 778 ≤ Re ≤ 7,930, and channel height 0.04 m ≤ H ≤ 0.06 m. At the wavy channel with position “2” of cylindrical vortex generators for the channel height of 0.04 m and Re = 1,669 was noticed the maximum thermal performance factor TPF́ = 0.8167. For this configuration, the novel asymmetric curve geometry in combination with cylindrical vortex generators at position “2” brought the enhancement of the Colburn factor j by 2.48 and 3.28 times compared to the wavy and smooth channels, respectively. The new correlating equations for all investigated channel height and volumetric flow rate in the range of 10 m3/h to 50 m3/h were created. The results show that inserting cylindrical vortex generators into the investigated channels is significant to achieve more efficient heat transfer and thus reducing energy consumption.

Heat transfer enhancement in a square channel with a set of triangular prisms: an experimental study

ABSTRACT In this study, heat transfer behavior in a channel adapted with a set of equilateral triangular prisms was investigated experimentally in a turbulent flow regime, with a range of Reynolds numbers corresponding to 1x104<Re<8x104. The cross-section of the channel is square, and the triangular prisms were installed in the middle of the channel. In the test section of the channel, only the bottom wall was heated with constant heat flux. The square channel geometry and the triangular obstacle dimensions were assumed as fixed. Multiple equilateral triangular prisms were used with three different tandem arrangements and four different attack angles in the cross-flow of air. The heated wall temperatures, and channel inlet and outlet temperatures were measured using thermocouples on the test section. The triangular prisms changes flow structure in the flow field by cross-flow interaction, and increases the heat transfer from the heated surface. It was observed that compared to the smooth channel, the heat transfer was enhanced by about 22% for a single triangular prism. The obtained results are given as dimensionless parameters and discussed in this study. Results are compared with the existing literature and show strong similarities. Overall, in our study, triangular prisms showed a more noticeable increase in heat transfer for channel flows.

Insight into the effects of smooth channels, sharp channels and channel bending angles on intra-droplet mass transfer behavior

Insight into the effects of smooth channels, sharp channels and channel bending angles on intra-droplet mass transfer behavior