Decreasing Inclination Angle Research Articles

Impact of operational and geometrical factors on ejector performance with a bypass

The mechanical energy loss during the mixing process and the momentum waste in the diffuser are the main reasons for the relative low entrainment ratio. In the present study, the ejector with bypass is adopted to utilize the momentum in the diffuser, hoping to increase the entrainment ratio. The influence of operational and bypass geometrical factors on the entrained capacity is analyzed through CFD method. The results show that there is always an optimal location (around the place where the lowest pressure is) for the maximum entrainment ratio, and it moves downstream as the motive or induced pressure increases. Meanwhile, the increment enlarges as the motive pressure increases, and the improvement would enlarge from 10.7% to 32.8% when the motive pressure increases from 0.3 MPa to 0.4 MPa. Moreover, it is still an effective method to improve ejector performance by enlarging bypass inlet area when the bypass is installed in the optimal location. The same conclusion could be drawn when the inclination angle decreases, especially when the motive pressure is greater than the design value. Compared with the ejector without bypass, the maximum improvement could be high up to 48.7% while the inlet area is 4 mm × 8 mm and angle is 15°.

Saturation Boiling Critical Heat Flux of PF-5060 Dielectric Liquid on Microporous Copper Surfaces

Pool boiling experiments are performed to investigate potential enhancement of critical heat flux (CHF) of PF-5060 dielectric liquid on microporous copper (MPC) surfaces and the effect of surface inclination angle. The morphology and microstructure of the MPC surfaces change with thickness. The experiments tested seven 10 × 10 mm MPC surfaces with thicknesses from 80 to 230 μm at inclination angles of 0 deg (upward facing), 60 deg, 90 deg (vertical), 120 deg, 150 deg, 160 deg, 170 deg, and 180 deg (downward facing). CHF increases as the thickness of the surface increases and/or the inclination angle decreases. The values in the upward facing orientation are 36–59% higher than on smooth Cu. For all surfaces, CHF values in the downward facing orientation are approximately 28% of those in the upward facing orientation. A developed CHF correlation, similar to those of Zuber and Kutateladze, accounts for the effects of inclination angle and thickness of the MPC surfaces. It is in good agreement with experimental data to within ±8%. Still photographs of nucleate boiling on the MPC surfaces at different inclinations help the interpretation of the experimental results.

Mixed convection heat transfer in power law fluids over a moving conveyor along an inclined plate

We study the mixed convection boundary layer heat transfer of power law fluid over a moving conveyor along an inclined plate. The effects of shear flow and power law viscosity on the temperature field are taken into account according to a modified Fourier law. Approximate analytical solutions are obtained by the homotopy analysis method (HAM). Results indicate that heat transfer is strongly dependent on the values of power law exponent, inclination angle, boundary velocity ratio and Prandtl number. Three distinct characteristics are found for power law exponents 0<n<1, n=1 and n>1, especially the nonlinear behavior due to skin friction and local Nusselt number shown in Figs. 4 and 17, which has never been reported before. The decrease of inclination angle causes the loss of velocity boundary layer but the gain of temperature boundary layer. Heat transfer efficiency is enhanced but skin friction is diminished with the increase in velocity ratio (the ratio of conveyor velocity/mean velocity of flow field). Critical ratio (with skin friction zero) is obtained which strongly depends on the power law exponent. The effects of involved parameters on the velocity and temperature fields are analyzed.

Ga+ implantation in a PZT film during focused ion beam micro‐machining

AbstractThe objective of the present work was to study the impact of Focused Ion Beam (FIB) machining parameters on the thickness of the damaged layer within a thin film PZT. Therefore, different Ga+‐ ion doses and ion energies were applied to a standard PZT film (80/20 lead zirconium titanate) under two beam incidence angles (90° and 1°). The thicknesses of the corresponding Ga+‐implanted layers were then determined by cross‐sectional TEM in combination with energy dispersive spectroscopic (EDS) line‐scans and correlated with polarisation hysteresis loops. The results show a decrease of Ga+‐implanted layer thickness with decreasing inclination angle, whereas ion energy and ion dose could be correlated with gallium concentration in the implanted layers.. Under the most unfavorable conditions the depth of the affected zone was 26 nm, it was only 2 nm for the most favorable conditions. (© 2015 WILEY‐VCH Verlag GmbH &amp; Co. KGaA, Weinheim)

Proposal and examination of method of water removal from gas diffusion layer by applying slanted microgrooves inside gas channel in separator to improve polymer electrolyte fuel cell performance

The objective of this study was to improve the management of moisture from the gas diffusion layer (GDL) in the gas channel of a separator for PEFC. At the cathode-side, oxygen is transported as reactant gas from gas channel through GDL. When large quantity of moisture is generated during high power generation, moisture blocks transport of oxygen, and the cell voltage drops drastically. Narrow microgrooves with axes at tilt angle to the air flow were arranged inside channel walls. The water from GDL was discharged along microgrooves to facing top of GDL by forces of capillary and air flow shearing. Laser induced fluorescence method was used to measure water velocity in microgrooves. The effect of air velocity in the gas channel on water velocity in microgrooves was investigated. It was shown microgrooves manufactured inside gas channel worked properly. Water velocity in microgrooves increased with increasing air velocity, and moisture could be discharged from GDL by applying microgrooves. Furthermore, effective length of the microgrooves needed to remove water from the GDL surface increased with decreasing inclination angle of microgrooves in the range of 20°–45°. An effective length of approximately 200 mm was attained, which was overall length of experimental apparatus.

Experimental Investigation of Heat Transfer for a Jet Impinging Obliquely on a Flat Surface

An experimental study investigated the effects of the inclination of an impinging circular jet on heat transfer from a horizontal flat plate. Local Nusselt number distribution was determine depending on inclination angle, jet-to-plate distance, and Reynolds number. The results show that the maximum heat transfer point moves toward the uphill side of the plate and that the maximum heat transfer decreases as the inclination angle decreases. The correlations were conducted to predict maximum and local Nusselt number as a function of Re, θ, L/D, and x/D for three specific regions.

An experimental investigation on the effect of middle length and inclination angle of S-shaped channel on two-phase flow patterns

An experimental investigation is conducted to study the effect of middle length and inclination angle of an S-shaped channel on adiabatic two-phase flow patterns. To study this effect, three channel lengths of 0.25, 0.50, and 1.00m, and four bends at the angles of 22.5°, 45°, 67.5° and 90° were used along the test section which is 35.83m long. The channel cross section dimensions were 0.05×0.10m and the test fluids were air and water. The observed flow patterns in 12 cases were studied. Each flow pattern was identified by visual observation and recorded with video camera for further analysis of the collected data points. The momentum transfer phenomenon between the phases for passing the upward middle section along the S-shaped channel was closely investigated. Five flow patterns of vortex plug, vortex slug, vortex wavy-annular, churn and mist packet annular were observed. The vortex type flow patterns were recorded with high speed video camera. The physical mechanisms and momentum transfer related to formation of these flow patterns were explained in detail. Flow pattern maps were obtained and then compared for different middle lengths and inclination angles to perform a parametric study on the S-shaped channel. Moreover, effect of upstream/downstream of the S-shaped channel on the maps and transition lines were discussed. It was revealed that upstream effects reflect the interactions and momentum transfer between the phases. Therefore, flow pattern types mainly depend on upstream behavior. On the other hand, the amount of backward flow resulting in the establishment of countercurrent flow and creation of vortexes along middle section is determined by downstream effects. Increasing the middle length or inclination angle causes the transition to vortex plug flow pattern to occur at higher liquid velocities. It also causes the area with churn flow pattern on the map to expand ending in smaller vortex slug flow pattern area. However, increasing middle length or decreasing inclination angle, ends in smaller area of mist packet annular area. It is also observed that for higher middle lengths, increasing the inclination angle shifts the transition lines more remarkably.A dimensionless analysis of obtained flow pattern maps is also carried out. It is shown that effect of geometry changes along S-shaped pipeline on two-phase flow pattern transitions is determined by either inclination angle or elevation difference between two horizontal lines. The explained flow mechanisms, obtained flow pattern maps and the transition lines can be used to predict the particular flow pattern that will be established for a given mass flux, inclined length and angle along pipelines.

Saturation Nucleate Boiling and Correlations for PF-5060 Dielectric Liquid on Inclined Rough Copper Surfaces

Saturation pool boiling experiments of degassed PF-5060 dielectric liquid investigated nucleate boiling on 13 Cu surfaces with average roughness, Ra, of 0.039 (smooth polished) to 1.79 μm at six inclination angles, θ, from 0 deg (upward facing) to 180 deg (downward facing). Values of the nucleate boiling heat transfer coefficient, hNB, in the upward facing orientation increase with increasing surface roughness and are correlated in terms of the applied heat flux, q: hNB = A qB. The exponent “B” decreases from 0.81 to 0.69 as Ra increases from 0.039 to 1.79 μm, while the coefficient “A” increases with Ra to the power 0.24. The values of the maximum heat transfer coefficient, hMNB, which occurs near the end of the fully developed nucleate boiling region, increase with increasing Ra and decreasing inclination angle. In the upward facing orientation, hNB increases by ∼58% with increasing Ra from 0.134 to 1.79 μm, while hMNB increases by more than 150% compared with that on smooth-polished Cu. Values of hMNB in the downward facing orientation are ∼40% of those in the upward facing orientation.

Heat transfer from a flat surface to an inclined impinging jet

An experimental study was carried out to investigate the effect of the inclination jet on convection heat transfer to horizontal flat plate. Local heat transfer determined as a function is of three parameters including inclination angle of the air jet relative to the plate in range of 90° ≤ θ ≤ 45°, jet-to-plate spacing in range of 2 ≤ L/D ≤ 8 and Reynolds number in range of 1,500 ≤ Re ≤ 30,000. The results show that the maximum heat transfer point moves towards the uphill side of the plate and the maximum heat transfer decreases as the inclination angle decreases. The correlations were conducted to predict maximum and local Nusselt number as a function of Re, θ, L/D, and x/D for a specific three regions.

The Critical State Constitutive Model and Strain Localization for Hostun Sand

Aiming at the limitation of traditional constitutive theories which can not explain the decrease of inclination angle of shear bands correctly when confining pressure increases, a state-dependent critical state model is employed to analyze strain localization of Hostun sands. Firstly, the critical state formulation and model parameters are calibrated through available drained triaxial test results of Hostun sand. Then an analysis of strain localization is performed on the drained plane strain tests. The results show that the state-dependent critical state model is capable of simulating the effect of initial effective confining pressure on inclination angle of shear bands.

Experimental investigation of the effect of inclination angle on convection-driven melting of phase change material in a rectangular enclosure

This paper investigates the dynamic thermal behavior of phase change material (PCM) melting in a rectangular enclosure at various inclination angles. Lauric acid as a PCM with high Prandtl number (Pr≈100) is used. The enclosure is heated isothermally from one side while the other walls are thermally insulated. Experiments were performed with hot wall temperatures of 55, 60 and 70°C (3.6×108⩽Ra⩽8.3×108) for different inclination angles of 0°, 45° and 90°. Image processing of melt photographs along with recorded temperatures were used to calculate the melt fractions, Nusselt numbers and the local interfacial heat transfer rates at the solid–liquid interface. Qualitative time-dependent natural convection flow structures were deduced indirectly from the instantaneous shape of the solid–liquid interface which were confirmed by quantitative data from temperature measurements. The results reveal that the enclosure inclination has a significant effect on the formation of natural convection currents and consequently on the heat transfer rate and melting time of the PCM. As the inclination angle is decreased from 90° to 0°, the convection currents in the enclosure increases and chaotic flow structures appear. When melting commences in the horizontally inclined enclosure, the solid–liquid interface line becomes wavy which implies the formation of Benard convection cells in the liquid PCM. For the same hot wall temperatures, a decrease in inclination angle leads to a considerable enhancement in energy transport from the hot wall of the enclosure to the PCM. It is found that the heat transfer enhancement ratio for the horizontal enclosure is more than two times higher than that of the vertical enclosure.

Numerical and experimental study of the flow through a geometrically accurate porous wind barrier model

A method in which the complex flow near and through the openings of a porous wind barrier is treated at a detailed level. The flow characteristics of the turbulent wake behind the barrier are experimentally and numerically investigated. The wind barrier is accurately geometrically represented with a three-dimensional model in the numerical simulation. Barrier models consisting of horizontal bars with different inclination angles are considered. The unsteady Reynolds-averaged Navier–Stokes (URANS) computation is applied because the flow is not statistically stationary. The shear stress transport (SST) k–ω turbulence model is used because it shows good behavior in adverse and separated flows. In addition to the three-dimensional URANS numerical study, an experimental study is performed to confirm the numerical data. The aim is to conduct an experimental and numerical study of a fluid flow through the geometrically accurate three-dimensional barrier model and analyze the bar inclination effect on the wake characteristics behind the barrier. As the bar inclination angle decreases, the bleed flow gets stronger, which results in a smaller reduction of the mean streamwise velocity. In addition, the turbulence intensity decreases in the shelter wake with a decreasing bar inclination angle.

Effect of LVAD Outlet Graft Anastomosis Angle on the Aortic Valve, Wall, and Flow

Left ventricular assist devices (LVADs), which pump blood from the left ventricle to the aorta are an important therapy option for patients with end-stage cardiovascular diseases. Recent publications show that even with optimized LVADs fatal complications can occur because of the blood deformations around the inflow cannula or through the LVAD outlet graft-aorta anastomosis. This study investigates the effects of the anastomosis geometry on the flow through the aorta, on the pressure and wall shear stress (WSS) distributions on the aortic wall and on the total entropy generation in the anastomosis region. Anastomosis geometry is defined with two angles, one on the coronal plane and the other on the transversal plane. Turbulent flow simulations are performed for each geometry. Results indicate that 3% to 5% of the work given by the LVAD is dissipated because of the viscous losses in the anastomosis region. The entropy generation, as well as the maximum WSS, increases as the inclination angle decreases. Some portion of the blood streaming out of the LVAD conduit flows toward the aortic valve; therefore the reverse-flow region extends up to the aortic valve in some cases, which may be one of the causes of aortic-valve dysfunction. Results of this study provide insight on the importance of the anastomosis geometry on the hemodynamics in the aorta and downstream the aortic valve, stresses on the aortic wall, and viscous losses.

Experimental study on the liquid slug of cryogenic slug flow in inclined tubes

An experimental study was carried out to understand the phenomena of the boiling flow of liquid nitrogen in inclined tubes with closed bottom by using a high speed motion analyzer. The experimental tubes are 0.018 and 0.014 m inner diameter (ID) and 1.0 m in length. The range of the inclination angle is 45°–90° from the horizontal. The experimental observation on the liquid slug was carried out along the tubes. Statistical method was employed to analyze the experimental data. The experiment analyzed the influences of the inclination angle and the tube diameter on the liquid slug length and velocity. The results show the liquid slug propagation velocity increases with the decrease of inclination angle θ. For all cases, the maximum values of the mean liquid slug lengths were obtained at θ = 60°. The mean liquid slug lengths were greater for large tube at higher tube position. These conclusions provide a basis for further study liquid slug of cryogenic two-phase undeveloped slug flow.

Heat transfer effects on dusty gas flow past a semi-infinite inclined plate

Heat transfer effects on dusty gas flow past a semi-infinite isothermal inclined plate are considered here-with. The governing boundary layer equations for the above problem are set up and non-dimensionalised. The non-dimensional governing equations are solved by an implicit finite difference scheme of Crank–Nicolson method, which is fast convergent and unconditionally stable. Gas-velocity, dust particle-velocity, temperature, skin friction and Nusselt numbers are calculated numerically for various parameters occurring into the problem and are shown graphically. It is observed that the velocity of the dusty-gas decreases with decreasing inclination angle ϕ to the horizontal. An increase in the mass concentration of dust also causes a fall in the gas-velocity.

Three-dimensional convection flow adjacent to inclined backward-facing step

Simulations of three-dimensional laminar forced convection adjacent to inclined backward-facing step in rectangular duct are presented to examine effects of step inclination on flow and heat transfer distributions. The step height is maintained as constant while its inclination angle is changed from 15° to 90°. The inlet flow is hydrodynamically steady and fully developed with uniform temperature. The bottom wall is heated with constant heat flux, while other walls are maintained as being thermally adiabatic. Velocity, temperature, Nusselt number, and friction coefficient distributions are presented. The “jet-like” flow and its impingement do not appear as the inclination angle of backward-facing step is small ( α = 15°). At the center width of the duct and close to the stepped wall, the location where the streamwise velocity component is zero changes from a saddle point to a nodal point as the step inclination angle decreases. The downwash adjacent to the sidewall becomes stronger as the step inclination angle increases. The maximum Nusselt number on the stepped wall is located near the sidewall for α ⩾ 30° and it appears near the center width of duct for small step inclination angle ( α = 15°). The friction coefficient inside the primary recirculation region increases with the increase of the step inclination angle. Downstream of the primary recirculation region, increase of the friction coefficient becomes slower as the step inclination angle increases.

Mathematical modelling of blood flow in curved arteries

We study the mixed convection boundary layer heat transfer of power law fluid over a moving conveyor along an inclined plate. The effects of shear flow and power law viscosity on the temperature field are taken into account according to a modified Fourier law. Approximate analytical solutions are obtained by the homotopy analysis method (HAM). Results indicate that heat transfer is strongly dependent on the values of power law exponent, inclination angle, boundary velocity ratio and Prandtl number. Three distinct characteristics are found for power law exponents 0 < n < 1, n = 1 and n > 1, especially the nonlinear behavior due to skin friction and local Nusselt number shown in Figs. 4 and 17, which has never been reported before. The decrease of inclination angle causes the loss of velocity boundary layer but the gain of temperature boundary layer. Heat transfer efficiency is enhanced but skin friction is diminished with the increase in velocity ratio (the ratio of conveyor velocity/mean velocity of flow field). Critical ratio (with skin friction zero) is obtained which strongly depends on the power law exponent. The effects of involved parameters on the velocity and temperature fields are analyzed.

Direct Numerical Simulation of Jet Mixing Control Using Combined Jets(Numerical Simulation)

To develop efficient method of jet mixing, direct numerical simulations of combined jets are carried out. The Reynolds number is defined with a nozzle diameter, is Re=1500. The spatial discretization is performed with hybrid scheme in which sixth order compact scheme in streamwise direction and Fourier series in cross section are adopted. The distance between two jets is fixed at 6 times jet diameter, and the inclination angle of jet is changed from 45 to 70 deg. As a results, it reveals that the turbulence intensity is strengthened with decreasing inclination angle, and that the jet width increases via the excitation of jets. These findings suggest that the combination of jets flexibly meet the diversified needs of jet mixing control.

Diagnosis of Faraday Rotation with Video Vector Magnetograph at Huairou

Over the wavelength interval of 150 mÅ redward of line center of the FeI λ5324.19 Å to 150 mÅ to the blue, in steps of 10 mÅ, observations of a simple sunspot were obtained with the Video Vector Magnetograph at Huairou Solar Observing Station (HSOS) of National Astronomical Observatories. In this paper, we present results of the inversion of stokes polarization profiles of this sunspot to recover the vector magnetic field parameters of the spectral line forming region using the FeI λ5324.19 Å using a nonlinear least-squares fitting. At the same time, curves of the observed variation of azimuth with wavelength were compared with model calculations for the azimuth at each wavelength as derived the inverse Zeeman effect modified by Faraday rotation. Hagyard, et al. (2000, Solar Phys. 191, 309) find it is difficult to separate two effects of Faraday rotation and π —σ rotation. However, π —σ rotation relates to the Landé factor of a spectral line. For the spectral line FeI λ5324.19 Å, its Landé factor g = 1.5. In the solar magnetic field atmosphere, its Zeeman split is less than that of line FeI 5250.22 Å which has larger Landé factor g = 3. The correlations in Figure 1 show that the azimuth rotation increases as the field strength increases and inclination angle decreases. The results show that rotation of the azimuth is less significant in observation taken near the center of the FeI λ5324.19 A than that of FeI λ5252.22 Â line.

Removal of batteries from solid waste using trommel separation

This paper describes the design and testing of a trommel for separation of batteries from solid waste. A trommel is a cylindrical separation device that rotates and performs size separation. It has also been used in areas such as municipal solid waste (MSW) processing, classifying construction and demolition debris, screening mass-burn incinerator ash and compost processing. A trommel has been designed based on size separation to separate household batteries from solid waste, which can then be used as feedstock for alternative applications of solid waste combustion, particularly where the metal content of the product is also a critical parameter, such as the Co-Co process for integrated cement and power production. This trommel has been tested with batches of university office and restaurant wastes against various factors. The recovery efficiency of batteries increases with decreasing inclination angle of the trommel and decreasing rotational speed. A physical characterization of the university solid waste has been performed with a 20-kg sample of the tested waste. It was found that there is a trend of decreasing recovery of batteries with increasing paper composition, and a trend of increasing recovery of batteries with increasing organic materials composition.