Horizontal Air Research Articles

Multiple models and neural networks based adaptive PID decoupling control of mine main fan switchover system

Mine main fan switchover system (MMFSS) consists of two main fans, which are equipped with a horizontal air door and a vertical air door, respectively. The purpose of operating MMFSS is to ensure small fluctuation of the underground airflow quantity and to guarantee safe operations of both fans simultaneously by controlling the four air doors during switchover from working to standby fan. MMFSS has time-varying dynamics under different operating conditions, strong coupling, high non-linearities and uncertainty in character, applying conventional control methods can not lead to satisfactory performances. In this study, an adaptive intelligent decoupling proportional–integral–derivative (PID) control method is proposed, where the unmodelled dynamics are estimated and compensated by neural networks, the coupling effect is eliminated by the designed decoupling compensator, and a switching mechanism among multiple models is employed to deal with the effect of time-varying dynamics. By inspiring from the generalised minimum variance control law concept, the parameters of the developed controller are determined. The stability of the close-loop system and the convergence of tracking error are examined. Finally, simulations of MMFSS show the feasibility and effectiveness of the obtained results.

Comparative study of fire resistance and acoustic performance of ceramic brick walls in concern to NBR 15575 in residential buildings in Brazil

Con la publicación de la norma NBR 15575 (ABNT, 2013), ha sido necesario que los sistemas constructivos utilizados en edificios residenciales se sometiesen a ensayos para el cumplimiento de los requisitos de desempeño. En el ámbito de los requisitos de seguridad solicitados por la norma, existe la necesidad de la evaluación de la resistencia al fuego de los sistemas de aislamiento vertical. Dentro de la habitabilidad, la norma recomienda que estos sistemas tienen un desempeño acústico adecuado. Dentro de este escenario, el objetivo de este trabajo es evaluar el desempeño acústico de dos sistemas de pared compuestos por diferentes tipos de bloques cerámicos con agujeros horizontales. Para este análisis, fueron realizados ensayos de laboratorio de acuerdo con las normas NBR 10636 (ABNT, 1989) y ISO 10140-2 (ISO, 2010). Se verificó que el sistema con mayor densidad presentó desempeño sensiblemente mejor acerca la resistencia al fuego, con desempeño prácticamente idéntico en el análisis del aislamiento acústico.

Experimental analysis on particle fluctuation velocity in a horizontal air–solid two-phase pipe flow having a dune model

ABSTRACTTo further elucidate the mechanism of energy-conserving conveying in horizontal pneumatic conveying with the dune model, the high-speed particle image velocimetry is applied to measure particle fluctuation velocity near the minimum conveying velocity of the conventional pneumatic conveying. This study focuses on the effect of mounting dune models on the horizontal pneumatic conveying in terms of power spectrum, autocorrelation coefficients, two-point correlation coefficients, fluctuation intensity of particle velocity, skewness factor, and probability density function. It is found that the power spectrum peaks with the dune model are larger than those of the nondune system, suggesting the acceleration and suspending efficiency of the dune model, especially dune models mounted at the bottom of the pipe. Meanwhile, the profiles of particle fluctuation velocity intensity indicate that the large particle fluctuating energy is generated due to mounting the dune model so that the particles are more easily accelerated and suspended. This is one of the important reasons why the mounted dune model results in a low pressure drop and low minimum conveying velocity. Based on the distribution of skewness factor and probability density function, it is found that the particle fluctuation velocities of all cases follow the Gaussian distribution in the lower and middle parts of the pipe. The particle fluctuation velocities in the case of the dune models mounted at the bottom of the pipe obey the Gaussian-type fluctuation more.

Experimental study of interfacial structure of horizontal air-water two-phase flow in a 101.6 mm ID pipe

The current work seeks to investigate the interfacial structure and establish an extensive experimental database in horizontal air–water two-phase flow in a 101.6 mm inner diameter pipe. A wide range of flow configurations are studied including bubbly, plug and slug flows. A flow visualization study using the high-speed video camera enables qualitative description of bubbly-to-plug and bubbly-to-slug transitions, while the database of local time-averaged two-phase flow parameters obtained by the four-sensor conductivity probe enables quantitative study on the evolution of the flow. Detailed measurements across the flow area are performed for nine test conditions at three different axial locations downstream of the inlet. Using this database, the effects of superficial liquid and gas velocities, and development length on the evolution of interfacial structure are investigated. Similar characteristics are observed as in a counterpart 38 mm ID horizontal two-phase flow facility, which include (1) the bubbles are found to be more concentrated near the top wall in bubbly flow as superficial liquid velocity decreases at a constant superficial gas velocity, while increasing superficial gas velocity promotes the growth of bubble layer thickness; (2) in bubbly-to-plug transition, the void fraction of small bubbles decreases and the size of small bubbles increases, while in bubbly-to-slug transition, opposite trends are observed. Meanwhile, different characteristics on the evolution of the interfacial structure are also observed, which indicates the effect of increasing pipe diameter. The bubbly-to-plug/slug transition is found to shift to higher superficial liquid velocities as pipe diameter increases. It is observed that the gas phase is more concentrated near the top wall in the large diameter pipe. As a result, the distance between bubbles is smaller and there is a higher chance for bubbles to coalesce into large bubbles. The critical void fraction where the bubbly-to-plug/slug transition initiates decreases as pipe size increases.

Experimental study of the flame geometrical characteristics of the crude oil boilover fire under cross air flow

This paper presents an experimental investigation of the flame geometrical characteristics of the crude oil boilover fire under cross air flows. Circular crude oil boilover fire are burned under the horizontal cross air flows ranged in 0–1.5 m/s. The flame geometrical characteristics are recorded by a CCD (Charge-Coupled Device) digital camera. Results indicate that the crude oil boilover fire under cross air flow can be divided as initial growth stage, steady stage, boilover stage and decay stage. The average flame length in the both steady stage and boilover stage decreases with the increasing cross air flow speed when the speed (u) is less than 1.0 m/s and then increases. Furthermore, the initial fuel layer thickness (h0) has a stronger influence on the average flame length in the boilover stage. The flame tilt angle increases fast when u rose from 0 to 1.0 m/s and then increases slowly. The tilt angle decreases with the pool diameter but weakly influenced by h0. A new correlation equation based on the Richardson number is introduced to predict the flame tilt angle, which collapses the tangent value of the flame tilt angle well.

Temperature and Relative Humidity Vertical Profiles within Planetary Boundary Layer in Winter Urban Airshed

The planetary boundary layer is a dynamic system with turbulent flow where horizontal and vertical air mixing depends mainly on the weather conditions and geomorphology. Normally, air temperature from the Earth surface decreases with height but inversion situation may occur, mainly during winter. Pollutant dispersion is poor during inversions so air pollutant concentration can quickly rise, especially in urban closed valleys. Air pollution was evaluated by WHO as a human carcinogen (mostly by polycyclic aromatic hydrocarbons) and health effects are obvious. Knowledge about inversion layer height is important for estimation of the pollution impact and it can give us also information about the air pollution sources. Temperature and relative humidity vertical profiles complement ground measurements. Ground measurements were conducted to characterize comprehensively urban airshed in Svermov, residential district of the city of Kladno, about 30 km NW of Prague, from the 2nd Feb. to the 3rd of March 2016. The Svermov is an air pollution hot-spot for long time benzo[a]pyrene (B[a]P) limit exceedances, reaching the highest B[a]P annual concentration in Bohemia – west part of the Czech Republic. Since the Svermov sits in a shallow valley, frequent vertical temperature inversion in winter and low emission heights of pollution sources prevent pollutant dispersal off the valley. Such orography is common to numerous small settlements in the Czech Republic. Ground measurements at the sports field in the Svermov were complemented by temperature and humidity vertical profiles acquired by a Vaisala radiosonde positioned at tethered He-filled balloon. Total number of 53 series of vertical profiles up to the height of 300 m was conducted. Meteorology parameters were acquired with 4 Hz frequency. The measurements confirmed frequent early-morning and night formation of temperature inversion within boundary layer up to the height of 50 m. This rather shallow inversion had significant influence on air quality due to inversion cap over the valley. Nevertheless, formation of an inversion showed strong diurnal variability. For example, on the 18th Feb. early morning shallow inversion quickly disappeared within less than 2 hours. According to this study tethered balloon measurements has proved to be a good tool for completion comprehensive ground air quality measurements.

Cellulose/PET humidifying elements having horizontal air and vertical water channels

New material and shape of a humidifying element were developed, which outperformed the widely- used criss-cross glasswool element. The new material consists of 50% cellulose and 50% PET. A parallel channel configuration was devised to reduce excessive pressure loss caused by the decreased height (5.0mm) from that (7.0mm) of the criss-cross configuration. For the same criss-cross configuration, the humidification efficiency of the cellulose/PET element was 26% higher than that of the glasswool element. For the same cellulose/PET material, humidification efficiency of the parallel channel configuration was 14% higher than that of the criss-cross configuration. As for the pressure drops, those of the glasswool element were 2–52% higher than those of the cellulose/PET element. For the same cellulose/PET material, the pressure drop of the parallel channel configuration was 14% higher than that of the criss-cross configuration. Data were compared with the predictions by existing correlations and those by the proposed model.

Numerical and experimental study of conjugate heat transfer in a horizontal air cavity

The demand for general reduction of the energy consumption in civil engineering leads to more frequent use of insulating materials with air gaps or cavities. Heat transfer through a constructional part can be decreased by adding an air gap and low emissivity reflective foils to the structure. In the first part of this paper, the impacts of cavity thickness and inner surface emissivity on combined conduction, convection and radiation heat transfer was experimentally explored in the case of constructional part with a horizontal cavity subjected to constant downward heat flux. The heat flow meter Netzsch HFM 436 Lambda was used for steady-state measurements. Results suggest that the studied parameters seriously affect the combined heat transfer in the composed structure. In the second part the paper reports the numerical study of two-dimensional conjugate heat transfer in closed horizontal cavity having air as the intervening medium. Numerical models validated by related experimental results were performed to further investigate the effect of radiation heat transfer. It was found that in general, the total heat flux through the composed structure decreases with increasing air cavity thickness, which is significant especially when low emissivity inner surfaces are taking into account. The direction of heat flow (downward or upward heat flow) has a significant impact on the convection heat transfer. An important contribution from the present work is the analysis of the optimal thickness of the cavity at different boundary conditions. The optimal thickness of the enclosure with low emissivity surfaces is 16 mm when subjected to upward heat flux.

An innovative solution to increase the performances of an Air-Cooled Heat Pump by Horizontal Air-Ground Heat-Exchangers

This work presents the performances of an Air-Cooled Heat Pump combined with Horizontal Air Ground Heat Exchanger. The Horizontal Air Ground Heat Exchanger has been used not for the direct ventilation of the room, but for the treatment of the outside air flux of an Air-Cooled Heat Pump; consequently, the heat pump works with colder and warmer air than outside one in summer and winter, respectively. The results are exposed in terms of the Coefficient of Performance and Energy Efficiency Ratio of the Air-Cooled Heat Pump.

Vertical air motion retrievals in deep convective clouds using the ARM scanning radar network in Oklahoma during MC3E

Abstract. The US Department of Energy (DOE) Atmospheric Radiation Measurement (ARM) program's Southern Great Plains (SGP) site includes a heterogeneous distributed scanning Doppler radar network suitable for collecting coordinated Doppler velocity measurements in deep convective clouds. The surrounding National Weather Service (NWS) Next Generation Weather Surveillance Radar 1988 Doppler (NEXRAD WSR-88D) further supplements this network. Radar velocity measurements are assimilated in a three-dimensional variational (3DVAR) algorithm that retrieves horizontal and vertical air motions over a large analysis domain (100 km × 100 km) at storm-scale resolutions (250 m). For the first time, direct evaluation of retrieved vertical air velocities with those from collocated 915 MHz radar wind profilers is performed. Mean absolute and root-mean-square differences between the two sources are of the order of 1 and 2 m s−1, respectively, and time–height correlations are of the order of 0.5. An empirical sensitivity analysis is done to determine a range of 3DVAR constraint weights that adequately satisfy the velocity observations and anelastic mass continuity. It is shown that the vertical velocity spread over this range is of the order of 1 m s−1. The 3DVAR retrievals are also compared to those obtained from an iterative upwards integration technique. The results suggest that the 3DVAR technique provides a robust, stable solution for cases in which integration techniques have difficulty satisfying velocity observations and mass continuity simultaneously.

Numerical investigation of the effect of air gap orientations and heterogeneous air gap in thermal protective clothing on skin burn

Numerical model for heat transfer through air gap in thermal protective clothing was coupled with bio-heat transfer model for multi-layer human skin. Coupled CFD-radiation heat transfer model was used for heat transfer through air gap and Pennes' bio-heat transfer model was used for heat transfer through human skin. First and second degree skin burn times were calculated using Henriques' burn integral. Effect of air gap width and air gap orientations were analyzed on heat transfer through air gap and skin burn injuries. Significant impact of air gap width and air gap orientations were observed in first and second degree burn times. First and second degree burn times and hence the thermal protection were found to be higher in case of vertical air gap orientations as compared to horizontal air gap orientations. Air gap orientation influences the thermal protection more at higher air gap widths. Analysis were also performed for determining outcome of heterogeneous air gaps on heat transfer through air gap and protective performance. Heterogeneous air gap cases results in more heat transfer and lower thermal protection as compared to homogeneous air gap cases for both the air gap orientations. Further, effect of fold aspect ratio was also analyzed on first and second degree burn times in case of the heterogeneous air gap.

Thermal regime of annual air temperature in Bosnia and Herzegovina

Horizontal air temperature is defined by the value of the mean air temperature for a certain surface area unit. It is defined by the value of horizontal thermal gradient, i.e. the value of average change of horizontal temperature per unit area. In order to define the horizontal change of air temperature in Bosnia and Herzegovina, a GRID thermal model was constructed whose spatial resolution is 20 m. Based on obtained thermal model geo-database it was determined that the mean annual air temperature for the whole area of Bosnia and Herzegovina is about 10.9 °C, keeping in mind that there are significant thermal differences with respect to the two existing climate zones. More specifically, on the territory of the northern temperate climate zone the average annual temperature is about 9.7 °C, while in the Mediterranean climate zone the said value is 12.1 °C. In this work, it was also found that thermal contrasts are very pronounced as well, due to the fact that average annual temperature in the highest mountain peak zones in southeastern Bosnian highlands is negative and is found to be -1.4 °C (Maglić peak), while at the Neum coastal zone it is measured at 15.9 °C. The above stated pronounced thermal contrasts are determined on a small horizontal distance, as a consequence of climactic position of Bosnia and Herzegovina as well as highly pronounced terrain dynamics.

Three-pattern decomposition of global atmospheric circulation: part II—dynamical equations of horizontal, meridional and zonal circulations

The three-pattern decomposition of global atmospheric circulation (TPDGAC) partitions three-dimensional (3D) atmospheric circulation into horizontal, meridional and zonal components to study the 3D structures of global atmospheric circulation. This paper incorporates the three-pattern decomposition model (TPDM) into primitive equations of atmospheric dynamics and establishes a new set of dynamical equations of the horizontal, meridional and zonal circulations in which the operator properties are studied and energy conservation laws are preserved, as in the primitive equations. The physical significance of the newly established equations is demonstrated. Our findings reveal that the new equations are essentially the 3D vorticity equations of atmosphere and that the time evolution rules of the horizontal, meridional and zonal circulations can be described from the perspective of 3D vorticity evolution. The new set of dynamical equations includes decomposed expressions that can be used to explore the source terms of large-scale atmospheric circulation variations. A simplified model is presented to demonstrate the potential applications of the new equations for studying the dynamics of the Rossby, Hadley and Walker circulations. The model shows that the horizontal air temperature anomaly gradient (ATAG) induces changes in meridional and zonal circulations and promotes the baroclinic evolution of the horizontal circulation. The simplified model also indicates that the absolute vorticity of the horizontal circulation is not conserved, and its changes can be described by changes in the vertical vorticities of the meridional and zonal circulations. Moreover, the thermodynamic equation shows that the induced meridional and zonal circulations and advection transport by the horizontal circulation in turn cause a redistribution of the air temperature. The simplified model reveals the fundamental rules between the evolution of the air temperature and the horizontal, meridional and zonal components of global atmospheric circulation.

Experimental investigation of horizontal air–water bubbly-to-plug and bubbly-to-slug transition flows in a 3.81 cm ID pipe

The present study seeks to investigate horizontal bubbly-to-plug and bubbly-to-slug transition flows. The two-phase flow structures and transition mechanisms in these transition flows are studied based on experimental database established using the local four-sensor conductivity probe in a 3.81cm inner diameter pipe. While slug flow needs to be distinguished from plug flow due to the presence of large number of small bubbles (and thus, large interfacial area concentration), both differences and similarities are observed in the evolution of interfacial structures in bubbly-to-plug and bubbly-to-slug transitions. The bubbly-to-plug transition is studied by decreasing the liquid flow rate at a fixed gas flow rate. It is found that as the liquid flow rate is lowered, bubbles pack near the top wall of the pipe due to the diminished role of turbulent mixing. As the flow rate is lowered further, bubbles begin to coalesce and form the large bubbles characteristic of plug flow. Bubble size increases while bubble velocity decreases as liquid flow rate decreases, and the profile of the bubble velocity changes its shape due to the changing interfacial structure. The bubbly-to-slug transition is investigated by increasing the gas flow rate at a fixed liquid flow rate. In this transition, gas phase becomes more uniformly distributed throughout the cross-section due to the formation of large bubbles and the increasing bubble-induced turbulence. The size of small bubbles decreases while bubble velocity increases as gas flow rate increases. The distributions of bubble size and bubble velocity become more symmetric in this transition. While differences are observed in these two transitions, similarities are also noticed. As bubbly-to-plug or bubbly-to-slug transition occurs, the formation of large elongated bubbles is observed not in the uppermost region of bubble layer, but in a lower region. At the beginning of transitions, relative differences in phase velocities near the top of the pipe cross-section to those near the pipe center become larger for both gas and liquid phases, because more densely packed bubbles introduce more resistance to both phases.

Estimation of water-surface deformation by vortices in a viscous horizontally decelerating air flow

The maximum height of a disturbance on the water surface, which occurs when a spatial (non-point) vortex departs from a viscous layer of a horizontal air flow that decelerates in the direction of motion, is estimated. The dependence of the initial disturbance parameters on the air flow speed over the water surface is derived. It is shown that the height of the disturbance increases and its width decreases with an increase in the air flow speed. The suggested model is verified experimentally.

C&C efficiency of canopy hood exposed to horizontal air stream in commercial kitchen calculated by CFD analysis

ABSTRACTAs one of the commercial kitchen ventilation researches, the mechanism of capture phenomenon and containment one of a canopy hood has to be investigated. Several experiments intended to change the Capture and Containment (C&C) efficiency of combustion gas and cooking effluence were conducted under the conditions of different suction wind velocity at the bottom of a hood, sometimes called face velocity, which is caused by the different hood size. The overall C&C efficiency was analyzed by means of computational fluid dynamics (CFD). The C&C efficiency from the experiment and CFD analysis showed good agreement, and it was assumed that the disturbing ambient airflow around the hood can influence on the C&C efficiency. Therefore the kitchen space was assumed which includes the disturbing airflow over the counter between a dining hall and a kitchen. As a result, the C&C efficiency of the larger hood decreased more under the disturbing airflow.

CFD simulation and optimization of the flow field in horizontal turbo air classifiers

This paper mainly presents a numerical study of the gas flow in horizontal turbo air classifiers. The effect of the air-inlet direction on the performance of classifier was also investigated through powder classification experiments. The simulated results show that the vertical vortex is the dominant flow in conical part of the classifier and there exists the horizontal vortex in the classifying chamber. The tangential velocity profile resembles a Rankine vortex inside the rotor cage. The vertical vortex intensity increases with increasing the inlet air velocity, while the rotor cage speed has limited effect on the control of gas pathlines in the classifying chamber. Horizontal turbo air classifiers are divided into four quadrants according to the air-inlet direction. For classifiers in quadrants I and III, a double-layer flow with opposite directions generates around the rotor cage which causes a secondary vortex. The secondary vortex is eliminated and the airflow becomes uniform in the classifier that belongs to quadrant Π or IV. The experimental results with fluidized catalytic cracking catalysts and fly ash demonstrate that cut sizes of this classifier decrease averagely by 5μm and 2.2μm respectively, and the classification accuracy increases by 7.5–10.3%.

Optimization of Operational Parameters in a Cyclone Type Pneumatic Rice Polisher

A pneumatic rice polishing system has been developed to minimize broken content (BP) and maximize the degree of polishing (DP). This polisher consists of a metallic cyclone coated with hard abrasive material, a blower, a collection system. Brown rice is feed vertically at the rate of 1.5 kg/min that flows towards the abrasive cyclone through horizontal air flow at 72.2 m/s. Experiments were carried out at different moisture content (M) and grit size of abrasive material (E) at fixed number of passes. Degree of polishing and broken content varied with both M and E. System showed DP from 4.224 ± 0.02% (13% M and 60 E) to 13.250 ± 0.56% (12% M and 36 E) whereas BP from 2.146 ± 0.14% (10% M and 60 E) to 49.717 ± 2.64% (13% M and 36 E). Effect of M and E and their square were found significant (p < 0.05 and p < 0.01) on DP and BP. Optimum values of DP and BP were achieved at 100 E and 11.70% M (wet basis) respectively with a value of 10.359% and 0.476%.

Measurement of horizontal air showers with the Auger Engineering Radio Array

The Auger Engineering Radio Array (AERA), at the Pierre Auger Observatory in Argentina, measures the radio emission of extensive air showers in the 30-80 MHz frequency range. AERA consists of more than 150 antenna stations distributed over 17 km$^2$. Together with the Auger surface detector, the fluorescence detector and the under-ground muon detector (AMIGA), AERA is able to measure cosmic rays with energies above 10$^{17}$ eV in a hybrid detection mode. AERA is optimized for the detection of air showers up to 60$^{\circ}$ zenith angle, however, using the reconstruction of horizontal air showers with the Auger surface array, very inclined showers can also be measured. In this contribution an analysis of the AERA data in the zenith angle range from 62$^{\circ}$ to 80$^{\circ}$ will be presented. CoREAS simulations predict radio emission footprints of several km$^2$ for horizontal air showers, which are now confirmed by AERA measurements. This can lead to radio-based composition measurements and energy determination of horizontal showers in the future and the radio detection of neutrino induced showers is possible.

Research on simulation and experimental of thermal performance of LED array heat sink

This study presents experimental study and numerical simulation on thermal analysis and design of array heat sink under natural convection conditions. Based on computational fluid dynamics (CFD) method, the thermal performances of LED array heat sink have been studied. The numerical results show that both the average convection heat transfer coefficient and the heat resistance decrease with the increase of the number of fins. The heights of the fins have the same effect on LED array thermal performance with the number of fins. The heating power and horizontal air inlet volumes can lead to the decrease of the thermal resistance and the increase of the average convection heat transfer coefficient. And according to the regression analysis method, the average Nusselt criterion correlations were derived. Furthermore, the numerical results are also compared to the experimental dates, this study suggest that the established mathematical models can be predicted the heat transfer characteristics of this type heat sink.