The Analysis of the Possibility of Feeding a Liquid Catalyst to a Coal Dust Channel

This article presents the concept of a method of improving the dynamics of combustion in boilers operating in power plants, cogeneration plants, and heating plants by introducing a catalyst that is fed with a carrier in the form of droplets. Thanks to the proposed method, a greater degree of fuel burnout can be obtained, which, in turn, results in lower energy consumption in the case of producing the same amount of power. The parameters of the emitted exhaust gases and ash are also improved. The method described in the article involves the adding of a catalyst to the dust pipe of the boiler, which improves the combustion parameters. The catalyst was implemented using a sprayer/nebulizer. In order to obtain the correct flow parameters, the sprayer was modeled using CFD calculations. The calculations include trajectories, velocities and concentrations with regards to various flow parameters. Particular attention should be paid to the model of the evaporation of moving droplets. The results of these calculations enable the parameters that guarantee that the catalyst reaches the dust channel outlet in the desired form to be assessed. The analysis is an introduction to experimental research that is carried out on a medium and large scale.

Experimental study of sediment supply control on step formation, evolution, and stability

We present results from an experimental campaign conducted in a steep flume subject to longitudinal width variations and different sediment feed rates. The experiments were designed to study how sediment supply influences step formation, step location, and step stability. Our results show that steps are more likely to form in segments of the channel where the width narrows because of particle jamming, and these steps are also more stable. Sediment feed increases particle activity which generates a dynamic channel morphology with steps forming and collapsing. A comparison with experiments without sediment feed shows that sediment supply does not inhibit step formation. Time series of step formation, evolution, and destruction show that the maximum number of steps is achieved when the sediment feed is larger than zero but smaller than the transport capacity. We summarize this outcome in a conceptual model where the dependence of step frequency on sediment supply is expressed by a bell curve. Sediment yield measured at the channel outlet followed the sediment feed at the inlet closely, even when we fed 50 % more and 50 % less than the calculated transport capacity. This outcome challenges the applicability of the concept of transport capacity to steep channels and highlights the key role played by sediment feed in dictating sediment yield and channel response. Finally, we detected a positive correlation between sediment concentration and step destruction, which stresses the importance of particle interactions for step formation and stability.

Experimental and Numerical Analysis of Fluid Flow Through a Micromixer With the Presence of Electric Field

Fluid flows in a microchannel with highly ordered laminar fashion. For this reason, two different fluid streams cannot mix easily, or it takes a very long time. The problem becomes intense for large molecules such as peptides, proteins, and nucleic acids during rapid mixing for biochemical applications in a microfluidic device. Many researchers tried to solve this problem by applying an electric potential. In this work, a numerical simulation was performed on a 2D micromixer. Four symmetric electrodes were placed on the wall of a straight microchannel of width 19 μm. The electroosmotic slip velocity boundary condition was used to create the turbulence on the laminar fluid stream. It was found that this model creates a well-mixed flow at the channel outlet. Then the input parameters were changed to compare the mixing performance in terms of concentration distribution at the channel outlet. Channel width, inter-electrodes gap, the magnitude of electric potential, frequency of the electric potential and asymmetricity of the electrodes were changed and results were compared. An experimental micromixer like the numerical model was fabricated by dc magnetron sputtering machine. Four gold electrodes (thickness, 120 nm) were sputtered on top of a silicon substrate. The value of the input parameters was chosen based on the results obtained from the numerical simulation. To test the mixing functionality of our device the movement of tracer particles was tracked down on the zone surrounded by four electrodes. The micro-PIV (Particulate Image Velocimetry) system was used to analyze the movement of the tracer particles and visualize the flow field in the mixing zone. The magnitude of the AC electric potential and frequency was changed to find out the optimum input parameters for the micromixer. These results could play an important role to design and improve a micromixer design using an AC electric field. A micromixer has many potential applications in biology (DNA analysis, enzyme Screening), chemistry (synthesis, polymerization) and detection (drug discovery, diagnosis).

On how sediment supply affects step formation, evolution and stability in steep streams: an experimental study

We present results from an experimental campaign run in a steep flume subject to longitudinal width variations and different sediment feed rates. The experiments were designed to study how sediment supply influences step formation, step location, and step stability. Our results show that steps are more likely to form in narrowing areas (i.e., where the channel width is getting smaller moving downstream) because of particle jamming, and these steps are also more stable. Sediment supply increases particle activity generating a more dynamic channel morphology with more steps forming and collapsing. However, sediment supply does not inhibit step formation, since more steps are generated in experiments with sediment feed than without it. Time-series of step formation, evolution, and destruction show that the maximum number of steps is achieved for average values of sediment supply. We summarize this outcome in a conceptual model where the dependence of step frequency on sediment supply is expressed by a bell curve. Sediment yield measured at the channel outlet followed the sediment feed at the inlet closely, even when we fed 50 % more and 50 % less than the transport capacity. This outcome challenges the applicability of the concept of transport capacity to steep channels and highlights the key role played by sediment supply for channel stability and sediment transport. Finally, we detected a positive correlation between sediment concentration and step destruction, which highlights the key role played by granular jamming for step formation and stability.

Effects of Channel Outlet Configuration and Dimple/Protrusion Arrangement on the Blade Trailing Edge Cooling Performance

The trailing edge regions of high-temperature gas turbine blades are subjected to extremely high thermal loads and are affected by the external wake flow during operation, thus creating great challenges in internal cooling design. With the development of cooling technology, the dimple and protrusion have attracted wide attention for its excellent performance in heat transfer enhancement and flow resistance reduction. Based on the typical internal cooling structure of the turbine blade trailing edge, trapezoidal cooling channels with lateral extraction slots are modeled in this paper. Five channel outlet configurations, i.e., no second passage (OC1), radially inward flow second passage (OC2), radially outward flow second passage (OC3), top region outflow (OC4), both sides extractions (OC5), and three dimple/protrusion arrangements (all dimple, all protrusion, dimple–protrusion staggered arrangement) are considered. Numerical investigations are carried out, within the Re range of 10,000–100,000, to analyze the flow structures, heat transfer distributions, average heat transfer and friction characteristics and overall thermal performances in detail. The results show that the OC4 and OC5 cases have high heat transfer levels in general, while the heat transfer deterioration occurs in the OC1, OC2, and OC3 cases. For different dimple/protrusion arrangements, the protrusion case produces the best overall thermal performance. In conclusion, for the design of trailing edge cooling structures with lateral slots, the outlet configurations of top region outflow and both sides extractions, and the all protrusion arrangement, are recommended.

Kühlkanalaustrittsbedingungen bei Bohrern*/Cooling channel outlet conditions for drills. Influence of the cooling channel diameter and second tool orthogonal clearance on the cooling lubricant’s efficiency

Die Kühlschmiereffizienz von innengekühlten Bohrern lässt sich durch eine Optimierung der Kühlkanalaustrittsbedingungen steigern. In dem Beitrag wird der Einfluss des Kühlkanaldurchmessers und des zweiten Freiwinkels auf den Bohrprozess mittels VHM (Vollhartmetall)-Wendelbohrern, welche auf Basis einer numerischen Simulation ausgelegt wurden, experimentell untersucht. Es wird gezeigt, dass im Besonderen der Kühlkanaldurchmesser einen Einfluss auf die Kühlung hat.   The cooling lubricant efficiency of internally cooled drills can be increased by optimizing the cooling channel outlet conditions. In this paper, the influence of the cooling channel diameter and the second tool orthogonal clearance on the drilling process is experimentally investigated using cemented carbide drills based on numerical simulations. It will be shown that the cooling channel diameter in particular has an influence on cooling lubrication.

ANALISIS PENGARUH LEBAR CELAH UDARA PADA CHANNEL OUTLET TERHADAP KONDISI RUANGAN DAN DAYA LISTRIK DENGAN MEMANFAATKAN PANEL SURYA

Only a Part of the energy of sunlight is absorbed by solar panels during the day will be converted into electrical energy, the rest will be converted into thermal energy that conducted to the solar panel surface with high surface temperatures. High temperatures on the surface of solar panels can be combined as a trombe wall to produce a temperature gradient in the channel outlets or vents. The produced gradient temperature will create air flow velocity in the chamber and will increase due to the difference in density gradient. So heat in the room will be pushed out. This study will vary, the air gap width 3 cm, 4.5 cm and 6 cm by comparing the indoor temperature, humidity and electric power by using solar panels and without 450 tilted solar panel facing north. Room dimensions are 0.5x0.5x0.5 m, with solar panels 150x180x18 mm dimensions. Collecting data every 10 minutes from 07:00 until 19:00. The sensor used is LM35, DHT11, Voltage Sensor, and ACS712. Air condition obtained will be compared with the standard of comfort of air in the tropical building. Results obtained from the research is a widening gap Outlet Channel or ventilation in the room conditions will increase the temperature, the humidity, increase power and decrease the comfort in the room. Otherwise the narrow width of the gap or ventilation Outlet Channel it will lower the temperature, increase humidity, lower power and increased comfort in the room.

Right heart dilatation in a fetus with an abnormal foramen ovale valve: an indicator of interatrial communication restriction

Aims: Foramen ovale (FO) valve with a shape or motion abnormality is frequently detected during routine obstetric ultrasonic examinations. However, the hemodynamics mechanism of this entity remains unclear. The purpose of the study is to determine the relevance of interatrial communication restriction and resultant morphological modifications.Materials and methods: We reviewed the echocardiographic records of fetuses with isolated abnormal FO valve evaluated between January of 2010 and december of 2016. The size (DFO) of the FO orifice, opening angle (α) of the FO valve, and dimensions of cardiac chambers, FO channel outlet (DOUT) and inferior vena cava (DIVC) were measured. We evaluated their (DFO, DOUT, α) relationships to the diameters of RA and DIVC. Five hundred and seventy normal fetuses were selected to establish the normal range of the DOUT/DIVC ratio so as to provide a criterion for restriction.Results: An abnormal FO valve was identified in 89 fetuses without congenital heart disease, with restriction noted in 62 fetuses (45 fetuses with RA dilatation, 12 fetuses with RA and RV dilatation, and 5 fetuses with no RA dilatation). There were no significant correlations between RA/LA and DFO/DIVC, RA/ LA and α. RA/LA was negatively correlated with DOUT/DIVC (R2=0.97, p<0.01).Conclusions: For a fetus with an abnormal FO valve, right heart dilatation could be considered as an indicator of interatrial communication restriction, which could be assessed by evaluating the FO channel outlet. The degree of right atrium dilatation indicates the severity of the restriction.

Temperature and Current Distribution Along the Air Channel in Planar SOFC Stack: Model and Asymptotic Solution

We report a model for coupled temperature and current distributions along the single channel in planar solid-oxide fuel cell stack. Approximate analytical solution to model equations is derived; the solution predicts that air and stack temperatures are close to each other and linearly increase with the distance along the channel. Maximal temperature at the channel outlet is proportional to the average stack current and inversely proportional to the air flow velocity. This means that temperature oscillations due to variable load can be compensated for by the respective variation in air flow velocity.