Triangle Channel Research Articles

Hydrodynamic processes that occur in a solar air heater collector with a triangle channel

In this article focuses on the hydrodynamic processes that occur in the solar air heater collector with a bottomless triangular channel working at the expense of solar radiation. Factors that directly affect the heat exchange processes in the working Chamber of the solar air collector with an overhead triangular shape have been analyzed, including air flow in the channels, heating surface structures, acceleration of the heat exchange process and methods for calculating the main indicators such as pressure loss. The solar air heater is one of the main and widely used equipment that can convert solar energy into useful thermal energy. Solar air heaters are economically efficient due to their simple structural structure and can be widely used in household and industrial sectors. The main area of application of solar air heater collectors is heating, in addition to agricultural, fruits and vegetables, including various products, the drying of technological products can be widely used.

Numerical Analysis of Liquid Potassium Flow and Heat Transfer in a Core for Space Nuclear Reactor Based on Entransy Dissipation Theory

AbstractThe research on the flow and heat transfer of alkali metals is an important technical means to strengthen the heat transfer of the core. In this paper, the 15 cooling channels with different structures are established. Under Re = 2.85 × 104–2.17 × 105, several operating parameters, such as core inlet temperature (T = 350 K, 390 K, 450 K, 550 K, 850 K), fuel rod pitch ratio (P = 1.2, 1.4, 1.6, 1.8, 2.0), and channel shape (triangle and square) on the heat transfer performance are numerically simulated. At the same time, this work introduces an evaluation criterion, entransy dissipation, to measure the irreversibility of the heat transfer process. The results show that the triangular channel has a stronger heat transfer capacity than the square. And the increase of the rod diameter ratio is a positive means to enhance the heat transfer. Among the studied channels, Model “I” (triangle channel, P = 2.0) has the best heat transfer performance. The above results have some guiding value to realize core heat transfer enhancement by adjusting fuel rod arrangement.

Targeted Synthesis of Isomeric Naphthalene‐Based 2D Kagome Covalent Organic Frameworks

AbstractTargeted synthesis of kagome (kgm) topologic 2D covalent organic frameworks remains challenging, presumably due to the severe dependence on building units and synthetic conditions. Herein, two isomeric “two‐in‐one” monomers with different lengths of substituted arms based on naphthalene core (p‐Naph andm‐Naph) are elaborately designed and utilized for the defined synthesis of isomerickgmNaph‐COFs. The two isomeric frameworks exhibit splendid crystallinity and showcase the same chemical composition and topologic structure with, however, different pore channels. Interestingly, C60is able to uniformly be encapsulated into the triangle channels ofm‐Naph‐COF via in situ incorporation method, while not the isomericp‐Naph‐COF, likely due to the different pore structures of the two isomeric COFs. The resulting stable C60@m‐Naph‐COF composite exhibits much higher photoconductivity than them‐Naph‐COF owing to charge transfer between the conjugated skeletons and C60guests.

Targeted Synthesis of Isomeric Naphthalene-Based 2D Kagome Covalent Organic Frameworks.

Targeted synthesis of kagome (kgm) topologic 2D covalent organic frameworks remains challenging, presumably due to the severe dependence on building units and synthetic conditions. Herein, two isomeric "two-in-one" monomers with different lengths of substituted arms based on naphthalene core (p-Naph and m-Naph) are elaborately designed and utilized for the defined synthesis of isomeric kgm Naph-COFs. The two isomeric frameworks exhibit splendid crystallinity and showcase the same chemical composition and topologic structure with, however, different pore channels. Interestingly, C60 is able to uniformly be encapsulated into the triangle channels of m-Naph-COF via in situ incorporation method, while not the isomeric p-Naph-COF, likely due to the different pore structures of the two isomeric COFs. The resulting stable C60 @m-Naph-COF composite exhibits much higher photoconductivity than the m-Naph-COF owing to charge transfer between the conjugated skeletons and C60 guests.

Security Analysis of Triangle Channel-Based Physical Layer Key Generation in Wireless Backscatter Communications

Ambient backscatter communication (AmBC) enables ultra-low-power communications by backscattering ambient radio frequency (RF) signals and harvesting energy simultaneously. It has emerged as a cutting-edge technology for supporting a variety of Internet of Things (IoT) applications. However, existing research lacks effective secret key sharing schemes for safeguarding communications between resource-constrained backscatter devices (BDs) in AmBC systems. In this paper, we present, Tri-Channel, a novel physical layer key generation scheme between two BDs by multiplying downlink signals and backscatter signals to obtain the information of a triangle channel as a shared random secret source for key generation. In particular, we analyze the security of our scheme under both passive and active attacks, concretely Eavesdropping Attack (EA), Control Channel Attack (CCA), Signal Manipulative Attack (SMA), and Untrusted RF-Source Attack (URSA). Through theoretical analysis and simulations by comparing with a traditional scheme (named Tradi-Channel), we found that our scheme consistently outperforms the Tradi-Channel under the EA and two active attacks (CCA and SMA). In addition, it shows better security performance under URSA, which is proposed based on the unauthenticated characteristic of BDs in Tri-Channel, even though URSA is more vital than SMA. Concretely, Tri-Channel’s secret key rate (SKR) outperforms Tradi-Channel’s under the above four passive and active attacks. This implies that our scheme is advanced in terms of both security and efficiency of key generation. Numerous extensive simulations further prove our theoretical analysis results.

Numerical study on the heat and mass transfer in charging and discharging processes of a triangular honeycomb thermochemical energy storage reactor

• A triangular honeycomb reactor has been designed and experimentally investigated. • A 3-D numerical model of this reactor has been developed and validated. • Relationships between heat transfer and mass diffusion are determined. • The thermal efficiency of triangular honeycomb reactor can achieve around 20% Adsorption heat storage based on porous adsorbents attracts considerable attention for the high energy storage density and long storage duration compared to sensible and latent heat storage methods. However, one of the critical challenges is the poor heat and mass transfer performance of thermochemical reactors. This study presents a triangular honeycomb reactor using zeolite 13X-H 2 O working pair and investigates the heat and mass transfer performance. To do this, a three-dimensional transient heat and mass transfer model has been built in COMSOL to simulate the adsorption and desorption processes of the new reactor. A detailed numerical model and the corresponding modelling methods are critical to the investigation while most of the recent studies are based on one-dimensional and two-dimensional models. The model has been experimentally validated thoroughly to a close agreement in both adsorption and desorption processes (mean sum of percent errors of 0.6% to 8.91% for air temperature and relative humidity). The reactor thermal efficiency from the simulation and experiment are 19.57% and 21.93%, respectively, which are achieved by the fast and controllable charging and discharging performance along with the reduced air pressure drop benefited from the reactor design. To add value of the charging and discharging details, this study also presents the contour diagrams with detail discussions for the air velocity, temperature, water concentration, and heat and mass flux variations of the triangular honeycomb channel during desorption and adsorption processes. The results show that the side of triangle channel has larger and stronger moisture desorption in a charging process and stronger moisture adsorption in a discharging process than that of the triangle corner areas.

ГАЗОДИНАМИЧЕСКИЙ АНАЛИЗ ПРОЦЕССА ВПУСКА С РАЗНЫМИ КОНСТРУКЦИЯМИ КАНАЛА В ГОЛОВКЕ БЛОКА ЦИЛИНДРОВ В АВТОМОБИЛЬНОМ ДВИГАТЕЛЕ

Piston engines remain main power installation for many products of transport mechanical engineering. The aim of the paper is to study a structure of air flows in an admission system and a cylinder of an automobile engine at various designs of channels in a head of a cylinder block on the basis of physical and mathematical modeling. Results of modeling are qualitatively confirmed by experimental data of thermograms gained with the use of a thermal imaging photography method. The paper presents description of a mathematical model and a method of conducting laboratory experiments. The paper shows that the application of square and triangle channels leads to significant change of dynamics of flow in the admission system. In particular, in profiled channels of the cylinder head vortex structures are formed. It is established that the use of profiled channels in the admission system leads to large-scale turbulence in the engine cylinder. Common influence of mentioned gas dynamics phenomena may insignificantly decrease hydraulic resistance in the admission system and also may enhance processes of mixture formation and combustion in the cylinder of the piston engine.

Crowding-induced polymer trapping in a channel.

In this work, we report an intriguing phenomenon: crowding-induced polymer trapping in a channel. Using Langevin dynamics simulations and analytical calculations, we find that for a polymer confined in a channel, crowding particles can push a polymer into the channel corner through inducing an effective polymer-corner attraction due to the depletion effect. This phenomenon is referred to as polymer trapping. The occurrence of polymer trapping requires a minimum volume fraction of crowders, ϕ^{*}, which scales as ϕ^{*}∼(a_{c}/L_{p})^{1/3} for a_{c}≫a_{m} and ϕ^{*}∼(a_{c}/L_{p})^{1/3}(a_{c}/a_{m})^{1/2} for a_{c}≪a_{m}, where a_{c} is the crowder diameter, a_{m} is the monomer diameter, and L_{p} is the polymer persistence length. For DNA, ϕ^{*} is estimated to be around 0.25 for crowders with a_{c}=2nm. We find that ϕ^{*} also strongly depends on the shape of the channel cross section, and ϕ^{*} is much smaller for a triangle channel than a square channel. The polymer trapping leads to a nearly fully stretched polymer conformation along a channel corner, which may have practical applications, such as full stretching of DNA for the nanochannel-based genome mapping technology.

A microporous metal–organic framework with triangular channels for C2H6/C2H4 adsorption separation

For separation of ethylene (C2H4) and ethane (C2H6), pressure swing adsorption (PSA) with C2H6-selective porous materials is considered as an ideal alternative to traditional energy-intensity cryogenic distillation. Inspired by the geometry complement feature between molecular lock and target in molecular imprinting recognition system, herein, we select the microporous metal–organic framework Fe2(BDP)3 with triangular channels as study object and investigate its adsorption separation performance for C2H6/C2H4. The experiment results indicate that Fe2(BDP)3 exhibits the higher C2H6 uptake than C2H4 and a considerable C2H6/C2H4 selectivity (2.1). Theoretical calculations reveal the better geometry complementarity between triangle channels and configuration-variable trifurcate C2H6 than rigid plane-like C2H4 play a key role for reversed adsorption relationship. The breakthrough experiments demonstrate the effectiveness of Fe2(BDP)3 for C2H6/C2H4 adsorption separation under ambient conditions.

PEM fuel cell cathode-side flow field design optimization based on multi-criteria analysis of liquid-slug dynamics

Since the Gas Diffusion Layer (GDL) clearance and the residence time of produced water in gas channels remarkably affect the proper operation of proton exchange membrane (PEM) Fuel Cells, the water management in this part plays a key role. To this end, the present study aims to introduce novel and optimized gas channels through geometrical modifications that act efficiently in terms of GDL clearance and liquid residence time. For this purpose, the VOF (Volume of Fluid) model was employed to numerically simulate two-phase flow by means of a finite volume method. Several decisive parameters including superficial gas velocity, channel surface wettability, and channel cross-section geometry were considered to find their effects on the liquid removal behavior. The liquid removal performance was analyzed by two-phase pressure drop, area coverage ratio (ACR), and liquid removal time. Results have been compared with previous works done on the conventional rectangular channels. Interestingly, it was found out that for the analyzed segment of the gas flow channels, the channel with triangle cross-section has superior performance in reducing ACR by 64% for inlet superficial air velocity of 0.5 ms and 8–24.45% reduction for higher velocities (1, 1.5 and 2.5 ms). Also, the transition from slug flow to film flow also stable two-phase pressure drop were only seen in this type of channel. The ranking of channels based on their residence time merit is as: hexagon>pentagon>rectangular>triangle. Increment of the contact angle of hydrophilic walls causes fluctuations in the two-phase pressure drop and decreases liquid water residence time. For triangle channel, surface with a contact angle of ∼120° and for the hexagon and pentagon channels 85–120° is suggested for the best fuel cell performance.

Influence of design anode and cathode channel on (PEMFC) fuel cell performance

Abstract This paper is focussed on investigating into some key aspects relating to design of an integrated proton exchange membrane fuel cell. Analysis of all currently utilised storage mediums was undertaken. High and low inlet operating conditions were studied by determining the distributions of over potentials, velocity distribution, and pressure. At entrance and exit, a triangle channel flow-field was predicted to have better polarization performance and regular velocity distribution, whereas for rectangular that was performance differences among four serpentine flow-fields for hydrogen and air. The pressure in the triangle channels were monitored to have periodically similar plots and showed important low pressure drop. Considering low pressure drop of rectangular channel has mid effect between triangles and rectangular for the same dimension that depends on the hydraulic diameter, these flow-fields would be beneficial for the larger inlet channel area. The study found that the triangular channels produced a better performance than their square flow path counterparts.

STUDY OF THE HEAT VENTILATION WITH INCLINED CHIMNEY IN THE ATTIC

This paper proposes the design of inclined chimney with horizontal outlets that integrated with a triangular roof. Utilize solar radiation to heat and induce air through natural ventilation in the interior of the house. For achieving this goal, Solidworks Flow Simulation software is used to visualize and simulate the 3-D flow plane performance of the chimney, by modeling using Navier-Stokes (RANS) for numerical investigations. The effect of depth the channel of solar chimney investigated in six configurations under the roof with a slope of 45o. The simulation is performed on steady-state, to predict the dynamics of heat transfer, velocity distribution, and mass flow rate. The results showed that the greater the depth of the chimney, the higher the airflow and quite effective in reducing the temperature of the interior space, but would result in a decrease in heat in the solar chimney channel. Solar chimney airflow is mainly caused by buoyancy due to differences between ambient temperature and in the channel. They confirmed that the more significant the difference in temperature inside and the environment, the more efficient the performance of ventilation. However, the triangle channel output is still a place to collect hot air and high airflow. Natural ventilation using a solar chimney in the roof cavity seems to be effectively applicable to solar incidence discharges in traditional homes in the Indonesian climate.

Shear Yield Stress of Magnetorheological Fluids between Characteristic Surfaces of Different Materials

Abstract Magnetorheological fluids (MRFs) have a wide range of applications in automotive and other industrial fields. As one of the main performance parameters of MRFs, static yield stress is the demarcation point of solid–liquid performance conversion. Therefore, yield stress is important to the study of MRFs. In this work, a new type of MRF testing device was designed. Three types of material blocks, namely, steel, copper, and aluminum, were tested to determine wall slippage using MRF-122E and MRF-132D. The results indicate that the best pulling blocks were the 1-mm copper rectangular channel and the 2-mm aluminum triangle channel. Identity distance was also tested, and the result indicated that the 1-mm copper pulling block and identity distance of 5-mm curve were nearest to the Lord Corporation yield curve with a maximum relative error within 5 %.

Effect of tube shape on the condensation patterns of R1234ze(E) in horizontal mini-channels

In this paper, the condensation characteristic of R1234ze(E) in horizontal circular, square and triangle channels were numerically investigated. The detailed liquid-vapor interfaces, local film thickness and stream traces were presented for better understanding the condensation process in circular and non-circular tubes. Under the same hydraulic diameter, the void fraction in square and triangle tubes was lower than that in circular tubes at the same vapor quality. The square tube exhibited higher heat transfer coefficients than that of the circular tube, while the triangle tube showed similar heat transfer performance with the circular tube. The tube shape had no significant effects on the pressure gradients. The gravity played a dominant role in local film distribution in the circular tube, but was almost negligible in the square tube. Both the surface tension and gravity played an important role in film distribution in the triangle tube. The number and structure of vortexes in the square and triangle tube were very different from that in the circular tube. The tube shape has a significant effect on the liquid phase velocity at different circumference positions. Under the same external perimeter, either the heat transfer coefficients or the pressure gradients of the square or triangle tube were larger than that of the circular tube. The numerical data of heat transfer coefficients and pressure gradients were also compared with the predicted values from the available well-known correlations. The results of this paper are important for the industrial applications of alternative refrigerants.

Three dimensional numerical investigations on the heat transfer enhancement in a triangular facing step channels using nanofluid

In this paper, laminar flow for the distilled and SiO2-water nanofluid flow and heat transfer were numerically investigated in three-dimensional triangular facing-step channel. The nanoparticle volume fraction and Reynolds number considered are in the range of 0-1% and 100-1500, respectively. Numerical solutions are obtained by using finite difference method to solve the governing equations. The effects of the volume fraction of nanoparticle, triangular facing-step channel amplitude height, wavelength and Reynolds number on local skin-friction coefficient, average Nusselt number and enhancement of heat transfer are presented and discussed. The results show that the Nusselt number and friction coefficient increases as the amplitude height of triangle channel increases. As the nanoparticle volume fraction increases, the Nusselt number is also found to be significantly increased, accompanied by only a slight increase in the friction coefficient. In addition, it is found that the heat transfer enhancement mainly depends on the amplitude height of the triangle wall, nanoparticle volume fraction and Reynolds number rather than the wavelength.

Experimental investigation of heat transfer in helium-xenon mixtures in triangle channels

Correlations are obtained for resistance and heat transfer of a helium-xenon mixture with a helium mass fraction of 9.1% in a triangle channel for Reynolds numbers from 103 to 2.4 × 104 and thermal fluxes up to 9.3 kW/m2. It is shown that the resistances of the turbulent dependence are in agreement and the heat transfer corresponds to the Tetelbaum dependence.

Flow pattern map and time–frequency spectrum characteristics of nitrogen–water two-phase flow in small vertical upward noncircular channels

We experimentally investigate the vertical upward gas–liquid two-phase flow in a 2×0.81mm small rectangular channel and an equilateral triangle channel with a 2mm side length. The two channels have same hydraulic diameters (Dh=1.15mm). We first present an experimental flow pattern map with nitrogen and water superficial velocities ranging from 0.08m/s to 11.82m/s and 0.12m/s to 1.52m/s, respectively. We also compare the flow pattern transition criteria between the triangle and rectangular cross sections by using the same hydraulic radius. We employ the influence rule that small passage geometry limits the flow pattern transition criteria. Thereafter, we comparatively analyze the transition boundaries of experiment flow patterns with other results in literature and classical prediction models. Results show that the cross-sectional shapes and experimental conditions of the experimental pipeline significantly affect the changes in the flow regime. Given the differential pressure signal of the two-phase flow, we propose two effective quadric time–frequency representations, namely, the adaptive optimal kernel time–frequency representation (AOK TFR) and data reduction sub-frequency band wavelet (DA SFBW) to investigate the complex behavior of vertical upward gas–liquid flows. We extract the positive power spectral density of the singular value–frequency entropy, singular value–frequency entropy, damping ratio, and vibration mode to characterize the evolution of flow patterns. The results suggest that the AOK TFR method can reveal flow dynamic details, whereas the DA SFBW based method is a powerful tool for characterizing the dynamical characteristics of different vertical upward gas–liquid flow patterns.

Optimal Design of Round Bottomed Triangle Channels

In optimal design concept, the geometric dimensions of a channel cross-section are determined in a manner to minimize the total construction costs. The Direct search optimization method by using MATALAB is used to solve the resulting channel optimization models for a specified flow rate, roughness coefficient and longitudinal slope. The developed optimization models are applied to design the round bottomed triangle channel and trapezoidal channels to convey a given design flow considering various design scenarios However, it also can be extended to other shapes of channels. This method optimizes the total construction cost by minimizing the cross-sectional area and wetted perimeter per unit length of the channel. In the present study, it is shown that for all values of side slope, the total construction cost in the round bottomed triangle cross-section are less than those of trapezoidal cross-section for the same values of discharge. This indicates that less excavation and a lining are involved and therefore implies that the round bottomed triangle cross-section is more economical than trapezoidal cross-section.

Interpenetrated Three‐Dimensional MnIIMIII Ferrimagnets, [Mn(4dmap)4]3[M(CN)6]2⋅10 H2O (M=Cr, Mn): Structures, Magnetic Properties, and Pressure‐Responsive Magnetic Modulation

Two novel cyanide-bridged ferrimagnets, [Mn(4dmap)(4)](3)[M(CN)(6)](2)- 10 H(2)O (4dmap=4-dimethylaminopyridine, M=Cr (1) and Mn (2)), have been prepared from the reaction of MnCl(2)4 H(2)O, a monodentate coligand (4dmap), with K(3)[M(CN)(6)]. X-ray crystallographic results show that these are isomorphous, and form a unique twofold interpenetrated three-dimensional framework with a triconnected 6.10(2) net. The framework contains two types of one-dimensional channel: hexagonal channels based on a cyanide-bridged Mn(6)M(6) hexagon, and triangle channels segmented by CN-Mn-NC linkages, which are filled with lattice water molecules. The dimethylamino groups of the 4dmap coligands are located around a pore and form the basic inner space. Variable-temperature X-ray powder diffraction and thermogravimetric analysis results show that the frameworks of both compounds are susceptible to dehydration through the loss of strongly hydrogen-bonded lattice water molecules. Magnetic measurements on both compounds show a ferrimagnetic ordering occurs at low temperature, T(C)=17 K for 1 and 6 K for 2. Application of hydrostatic pressure showed a positive effect on the magnetic ordering. Both values of T(C) increased linearly, to 25 K for 1 and 15 K for 2 at 1.0 GPa. The magnetic properties of both compounds were reversibly modulated by the external stress.

Numerical investigations of electro-osmotic flows in triangle microchannels

Small triangle channels are frequently encountered in microelectromechanical systems (MEMS). In this paper, the mixed electro-osmotic/pressure-driven flows in triangle microchannels are numerically investigated. Poisson and Navier–Stokes equations were numerically solved employing the Galerkin algorithm. The accuracy of the numerical algorithm was validated by refining the grids and using Richardson extrapolation. The numerical results show the mass flux of electrolytic solution increases with the increase of imposed positive pressure gradient. At small pressure gradients, the relative mass flux increment induced by the imposed positive pressure gradient is sensitive to the change in the pressure gradient. However, when the pressure gradient increases beyond a critical value, the relative mass flux increment increases smoothly with the increase of pressure gradient. It is also found that the mass flux increases with increasing the length ratio, κD h, at a given pressure gradient.