Windy Conditions Research Articles

Uniformity Index as a Universal Air-Cooled Condenser Fan Performance Metric

Ambient wind has a negative effect on mechanical forced-draft direct air-cooled steam condenser (ACC) fan volumetric performance, and increases dynamic fan blade loading. Investigating these effects directly using on-site measurement or numerical analysis is complicated, and most previous work has focused on only one effect at the expense of the other. In this study, fan axial velocity inflow uniformity is identified as a single metric offering the potential to holistically qualify ACC fan operation under windy conditions. A 3 × 6 fan cell ACC was modelled with CFD using a blade element theory-based fan model, and clear relationships between the fan inflow uniformity index and both fan volumetric performance and dynamic blade loading were observed in the results. The same relationships were observed in on-site test data collected at a single ACC fan, thus validating the numerical results. The uniformity index can be used in both numerical and experimental work as a means of investigating both fan volumetric performance and dynamic blade loading with less computational and measurement complexity; it also offers a potentially useful means of quantifying the severity of fan operating conditions, to assist with more reliable case-specific fan design and selection.

Use of a drone-based sensor as a field-ready technique for short-term concentration mapping of air pollutants: A modeling study

While a network of low-cost sensors (LCS) boosts the capability in monitoring of air quality as covering a wide area, its fixed positioning hinders pinpointing of an unknown emitting source, its accuracy is variable over time, and its operation requires more periodic calibration than the USEPA's reference monitors. Alternatively, for short-term concentration mapping and regulatory compliance assessment, a drone equipped with a single reference sensor to detect the target air pollutant may provide a highly accurate concentration mapping tool as it offers flexibility to maneuver over hard-to-access terrains while addressing the abovementioned limitations. In this modeling study, we focused on a hypothetical point source emitting a certain air pollutant steadily inside a 1 km by 1 km study area. With respect to true concentrations generated from such source using USEPA's SCREEN3 Gaussian dispersion model and an inverse distance weighing (IDW) approach, we developed R and Python scripts to plot concentration and reliability maps for when a drone-based reference sensor/a stationary network of LCS is deployed to reconstruct the concentration maps. First, we compared the impact of the drone flight path on 1-hr-averaged concentration mapping of an air pollutant for locating a hidden point source or concentration accuracy determination at certain regions. Then, we conducted sensitivity analyses on the drone-based mapping reliability under different number of drone passes, wind speeds, and wind directions. Our results showed that compared to S-, N-, Z-, and diagonal-shape drone travel paths for the same travel total time, the time-averaged mapping accuracy of a zigzag drone flight is the best for pinpointing an unknown point source. For concentration mapping of known air polluting sources, which is intended to provide the utmost accuracy, an increase in the number of drone passes from the source to the downstream receptor points improves reliability of the projected dispersing plume. When flown under a windy condition (wind speeds above 3 m/s), concentration maps are underestimated for the most part, and the bias reduces when the drone travels in parallel to the wind direction. The outcomes of this study shed light on optimized development of the drone-based air quality sensors as proof-of-concept of a field-ready device to facilitate accurate short-term air quality monitoring or regulatory compliance of the air pollutants with hourly thresholds.

New multi-proxy record shows potential impacts of precipitation on the rise and ebb of Bronze Age and imperial Persian societies in southeastern Iran

The Achaemenids and Sasanian ‘Persian’ Empires were significant political, economic, and social forces in the Late Iron Age and Late Antiquity Eurasia, respectively, which have left marks on the heritage of the Mediterranean and Middle Eastern world. While attention is often focused on military and political conditions when discussing the prosperity and decline of these imperial powers, their realms, which crossed a variety of environmental settings, were highly dependent on the predictability of rainfall that drove agriculture and effective provisioning. Here, we present a multi-proxy sedimentological, geochemical, and palynological record from a 2.5-m long peat deposit near the excavation site in Konar Sandal near Jiroft in southeastern Iran, covering 4000-850 cal yr BP. Around 3950 cal yr BP a wet period prevailed based on elemental ratios, stable C isotope, pollen, and diagnostic lipids. Between 3900 and 3300 cal yr BP, wet/semi-wet conditions developed with the appearance of Cerealia-type pollen. Dry and windy conditions followed (ca. 3300-2900 cal yr BP), which coincided with the Siberian anticyclones and climatic shifts developing in the Eastern Mediterranean region. Consequently, the Bronze Age settlements around Jiroft, dependent on agriculture, underwent a steady decline. A prolonged wet period followed (ca. 2900-2300 cal yr BP) with the abundance of Sparganium-type pollen and the aquatic lipid proxy (Paq). This change coincided with intensive agricultural practices and the flourishing of the powerful Median and Achaemenid empires. The shift to high Ti/Al ratios coeval with the lowest δ13COM values suggests an increase in aeolian activity and dry conditions ca. 2100-1650 cal yr BP. The Jiroft valley again experienced wet conditions between 1550 and 1300 cal yr BP, which overlapped with the economic prosperity of the middle to late Sasanian empire. The paleoenvironmental reconstruction indicates that wet periods and intensive agriculture coincide with the Persian empires' zenith, political influence, and economic affluence. Therefore, contextualized and detailed paleoenvironmental records are desirable to explore the interplay of political and climatic factors in the development and fragmentation of the ancient settlements and imperial powers in Eurasian history.

Honeybees modify flight trajectories in turbulent wind

In windy conditions, the air is turbulent. The strong and intermittent velocity variations of turbulence are invisible to flying animals. Nevertheless, flying animals, not much larger than the smallest scales of turbulence, manage to maneuver these highly fluctuating conditions quite well. Here we quantify honeybee flight with time-resolved three-dimensional tracking in calm conditions and controlled turbulent winds. We find that honeybee mean speed and acceleration are only weakly correlated with the strength of turbulence. In flight, honeybees accelerate slowly and decelerate rapidly, i.e., they break suddenly during turns and then accelerate again. While this behavior is observed in both calm and turbulent conditions, it is increasingly dominant under turbulent conditions where short straight trajectories are broken by turns and increased maneuvering. This flight-crash behavior is reminiscent of turbulence itself. Our observations may help the development of flight strategies for miniature flying robotics under turbulent conditions.

Improved reference evapotranspiration methods for regional irrigation water demand estimation

Temperature- and radiation-based methods are widely used for reference evapotranspiration (ETo) estimates and in regional irrigation water demand studies, especially in areas with limited weather data. A major limitation is that without local calibration, the constant parameters used in these methods usually cannot ensure the same reliability in regional analysis. On the other hand, the controlling variables of ETo under different climatic conditions and how they are related to the structures of these methods have not been adequately addressed yet. Herein, we evaluated the performance of three commonly used temperature-based methods, i.e., Thornthwaite (Th_T), Blaney-Criddle (BC_T), and Hargreaves and Samani (HS_T), and five radiation-based methods, i.e., Makkink (Ma_R), Priestley-Taylor (PT_R), Jensen and Haise (JH_R), Turc (Tu_R), and Abtew (Ab_R), for regional ETo estimates and calibrated them using the Penman-Monteith method. Monthly meteorological data (1961–2010) from 15 weather stations in Texas, United States, covering humid, subhumid, semiarid, and arid climates, were used. The HS_T method is recommended for regional analysis if reliable wind speed and relative humidity data are not available. The radiative component was the driving factor of ETo, accounting for 72− 84% of its variation in the warm season in all climates. Therefore, temperature- and radiation-based methods performed well and showed little variation in the warm season. However, we demonstrated that the vapor pressure deficit impact on ETo variations could be as high as 43–49% in the cool season in subhumid, semiarid, and arid climates, and wind speed impact on ETo variations was 4–12% and 10–16% in humid, semiarid, and arid climates, respectively. To accurately reflect these impacts, we adjusted the HS_T and PT_R methods by multiplying a calibration-free coefficient. By doing so, the accuracy of ETo under cool, dry, and windy conditions is considerably improved compared with the locally calibrated methods. The adjusted HS_T and PT_R methods can significantly improve the efficiency and accuracy of applying the less data-intensive ETo methods to predict regional or global irrigation water demand.

Effect of Rotor Tilt on the Gust Rejection Properties of Multirotor Aircraft

In order to operate safely in windy and gusty conditions, multirotor VTOL aircraft require gust resilience. This paper shows that their gust rejection properties can be improved by applying a small amount of fixed outward rotor tilt. Standard aerodynamic models of the rotors are incorporated into two dynamic models to assess the gust rejection properties. The first case is a conceptual birotor planar VTOL aircraft. The dependence of the trim and stability on the tilt angle are analyzed. The aircraft is stabilized using a pole-placement approach in order to obtain consistent closed-loop station-keeping performance in still air. The effect of gusts on the resulting response is determined by simulation. The second case study is for a quadrotor with a 10° outward rotor tilt. The aerodynamic coefficients are analyzed for trimmed station-keeping over a range of steady wind speeds. An LQR controller is used to apply station-keeping that includes integral action, and the gust responses are again obtained using simulation. The results show that the outward rotor tilt causes the aircraft to pitch down into a lateral gust, providing lateral force that opposes the gust and so significantly improving the gust rejection properties.

An equivalent source method for removal of attitude-induced responses in drone-towed magnetic scalar gradiometry data

SUMMARY Drone-towed scalar field gradiometry surveys conducted in windy conditions or under self-excited oscillations generate attitude-induced responses that can hinder the geological interpretation. Here, we present a gradiometric equivalent source method (GESM) to remove these attitude-induced responses by interpolating and continuing the measured gradiometry data to new idealized pseudo-sensor positions free of any attitude deviations. In addition, we present transverse horizontal difference (THD) data from a precisely positioned drone-towed horizontal gradiometry survey collected in Nautanen, northern Sweden. Analysing the Nautanen survey’s positional data revealed that the gradiometer system exhibited directional-dependent yaw deviations with periods of unpredictable attitude deviations. Based on synthetic THD data created using the Nautanen survey’s positional data, these deviations manifest as line-to-line striping and short-wavelength oscillations in the THD maps. Applying GESM to the synthetic THD data removes these attitude-induced THD responses with satisfactory accuracy compared to the true THD values. Furthermore, on the actual THD data collected in Nautanen, applying GESM improved the continuity of anomalies, significantly improving the interpretation of the data. The results suggest that including GESM in the data processing of drone-towed gradiometry surveys, given precise positional information via an onboard GNSS-IMU system, ensures high-quality geological interpretation even in windy conditions or in high-gradient areas.

Experimental Verification of Windshields in the Measurement of Low Frequency Noise from Wind Turbines

Measuring noise from wind turbines is a problematic metrological task due to the significant interference caused by the wind, especially in the low-frequency range. In the audible band, especially A-weighted, the impact of interference from wind is considerably less than in the low-frequency and infrasound bands. In the audible band, especially the A-weighted curve, the impact of interference from wind is significantly less than in the low-frequency and infrasound bands. For this reason, methods are still being sought to reduce interference from wind in the lowest frequency bands effectively. Experimental tests within the scope of the work were carried out using several windshields, with a single standard windscreen at 1.5 m and 4 m height, with an additional microphone shield (tent), and on the board with a double windscreen at a ground level according to IEC 61400-11. Experimental verification of a windshield’s effectiveness and impact under real conditions was carried out using a low-frequency noise source, which was the main fan station at the salt mine shaft. This source generates noise with similar spectral characteristics to wind turbines and can operate in windless conditions. This allowed noise measurements to be made without interference from the wind. Signals were recorded in windless and windy conditions at different wind speeds using tested windshields. An effectiveness analysis of the proposed measurement methods was also carried out on the wind farm. Performed research indicates that the best of the tested variants, when measuring wind turbine noise in the low-frequency range, is to place the microphone on the board with a double windscreen according to IEC 61400-11. At wind speeds of less than 5 m/s at 1.5 m above the ground, the shield effectively eliminates disturbances in the band above 4 Hz. Still, as the wind speed increases above 6 m/s, the level of disturbance increases, and its bandwidth in the lowest frequencies expands.

PULMONARY NOCARDIOSIS AS A CONSEQUENCE OF DOMESTICALLY GROWN MARIJUANA

PULMONARY NOCARDIOSIS AS A CONSEQUENCE OF DOMESTICALLY GROWN MARIJUANA

Quadrotor Model for Energy Consumption Analysis

In this paper, a quadrotor dynamic model’s energy efficiency was investigated. A method for the design of the dynamic model which assures energy consumption estimation was presented. This model was developed to analyze the energy efficiency of the quadrotor during each maneuver. A medium-class quadrotor (4.689 kg) was used as a test platform. Thrust force correction factors obtained with FLIGHTLAB software were used to predict object behavior in forward flight. Model validation and long-duration flight tests in outdoor windy conditions are also presented. Monte-Carlo simulation was used to study the influence of uncertainties in model parameters on the simulation reliability. The developed model might be used for practical purposes (for example, energy-efficient coverage path planning).

CSM-CERES-Wheat Sensitivity to Evapotranspiration Modeling Frameworks under a Range of Wind Speeds

Crop modeling uncertainty is expected to be high under weather data limitations; thus, jeopardizing decision-making on food-water security. Missing near-surface wind speed (u2) data required to accurately estimate reference evapotranspiration (ETo) seemed to significantly affect both the potential evapotranspiration (ETP) and yield simulations for data-scarce windy regions. In this study, the uncertainty in crop modeling based on different ETP approaches was assessed. In this regard, wheat yield and evapotranspiration were simulated with the CSM-CERES-Wheat model using either the Priestley-Taylor/Ritchie (PT) or the Penman-Monteith DSSAT (PM) methods under “rain-fed, low-nitrogen stress”, “rain-fed, high nitrogen stress”, “full irrigation, low nitrogen stress”, and “full irrigation, high nitrogen stress” scenarios for a u2 range from 0.8 to 3.5 m s−1. The daily weather data required to run the model were retrieved from 18 semi-arid areas located in western Iran. The statistically significant differences in mean yield and cumulative distribution were determined by the non-parametric Wilcoxon signed-rank and the Kolmogorov-Smirnov tests, respectively. The deviation in evaporation and transpiration simulated by applying PT and PM was lower under rain-fed condition. Under “rain-fed, low-nitrogen stress”, the PT-simulated yield deviated significantly (p < 0.05) from PM-simulated yield by more than 26% for the sites with u2 above 3 m s−1. The deviation in ETP estimates did not, however, lead to statistically significant difference in yield distribution curves for almost all sites and scenarios. Nitrogen deficiency resulted in a smaller difference in yield for rain-fed condition. The yield results showed a deviation below 6% under full irrigation condition. Under windy rain-fed condition, high deviation in leaf area index (LAI) and ETP estimates caused a large difference in the actual transpiration to potential transpiration ratio (Ta/TP), and yield. However, the deviation between PT- and PM-simulated LAI and Ta/TP for the full irrigation scenarios was less than 6%. Overall, the results from this study indicate that when soil moisture is depleted, resembling rain-fed condition, simulation of yield appears to be highly sensitive to the estimation of ETP for windy areas.

The Effect of Wind Screens on the Performance of an Induced Draft Air-Cooled Condenser Under Windless and Windy Conditions

Abstract Wind generally reduces the thermal effectiveness of air-cooled condensers (ACCs). Therefore, this study investigates wind screens as a means to improve the performance of a 20-fan induced draft ACC under windy conditions. Two wind-screen configurations are tested: walls extending above the fan platform (termed wind walls) and walls extending below the fan platform (termed wind skirts). The performance of this five-by-four ACC is evaluated using the open-source computational fluid dynamics code, OpenFOAM. The performance is first analyzed under windless operating conditions and then when the ACC is subjected to wind speeds of 3, 6, and 9 m/s directed along the shorter and longer axes of the ACC. Under windless conditions, wind walls increase the ACC’s thermal effectiveness by 1.0%. Wind skirts, however, reduce the effectiveness by 1.8%. Depending on the wind speed and direction, wind walls increase the mean thermal effectiveness of the ACC by 0.3–3.9% under windy conditions. Wind skirts, on the other hand, are only beneficial at higher wind speeds: At 3 m/s, the effectiveness declines by 1.4–2.1%; at 6 m/s, the change in effectiveness ranges from −0.4% to 2.2%; and at 9 m/s, the effectiveness increases by 2.4–3.8%. Wind walls are therefore considered more effective than wind skirts for the tested range of wind speeds.

A Tutorial and Review on Flight Control Co-Simulation Using Matlab/Simulink and Flight Simulators

Flight testing in a realistic three-dimensional virtual environment is increasingly being considered a safe and cost-effective way of evaluating aircraft models and their control systems. The paper starts by reviewing and comparing the most popular personal computer-based flight simulators that have been successfully interfaced to date with the MathWorks software. This co-simulation approach allows combining the strengths of Matlab toolboxes for functions including navigation, control, and sensor modeling with the advanced simulation and scene rendering capabilities of dedicated flight simulation software. This approach can then be used to validate aircraft models, control algorithms, flight handling chatacteristics, or perform model identification from flight data. There is, however, a lack of sufficiently detailed step-by-step flight co-simulation tutorials, and there have also been few attempts to evaluate more than one flight co-simulation approach at a time. We, therefore, demonstrate our own step-by-step co-simulation implementations using Simulink with three different flight simulators: Xplane, FlightGear, and Alphalink’s virtual flight test environment (VFTE). All three co-simulations employ a real-time user datagram protocol (UDP) for data communication, and each approach has advantages depending on the aircraft type. In the case of a Cessna-172 general aviation aircraft, a Simulink co-simulation with Xplane demonstrates successful virtual flight tests with accurate simultaneous tracking of altitude and speed reference changes while maintaining roll stability under arbitrary wind conditions that present challenges in the single propeller Cessna. For a medium endurance Rascal-110 unmanned aerial vehicle (UAV), Simulink is interfaced with FlightGear and with QGroundControl using the MAVlink protocol, which allows to accurately follow the lateral UAV path on a map, and this setup is used to evaluate the validity of Matlab-based six degrees of freedom UAV models. For a smaller ZOHD Nano Talon miniature aerial vehicle (MAV), Simulink is interfaced with the VFTE, which was specifically designed for this MAV, and with QGroundControl for the testing of advanced H-infinity observer-based autopilots using a software-in-the-loop (SIL) simulation to achieve robust low altitude flight under windy conditions. This is then finally extended to hardware-in-the-loop (HIL) implementation on the Nano Talon MAV using a controller area network (CAN) databus and a Pixhawk-4 mini autopilot with simulated sensor models.

The Interaction of Wind Velocity and Air Gap Width on the Thermal Comfort in Naturally Ventilated Buildings with Multiple Skin Facade

A Multiple (MSF) or Double Skin Facade (DSF) is a building envelope system. It has an external and internal layer that contains buffer space used for controlled windy conditions, ventilation and solar protection. Employing a multiple or double-skin facade for natural ventilation is not an innovative idea, but the background on this mechanism and the impacts of these environmental and designing factors on its performance are still unknown and critically needed. Therefore, with this study, the influences of the Multiple or Double Skin Facade with different width air gaps configurations, alongside the environmental factor on buoyant-driven natural ventilation, are discussed. Naturally ventilated MSFs are often very intriguing in terms of a microclimatic comfort, but an optimum design is crucial to enhance the microclimatic comfort and therefore the proper operation of the entire system. Especially, the development of the system is important when working in a hot climate. There is a significant lack of data within the current literature to demonstrate the complexity and challenges in designing large, naturally ventilated buildings. For these sorts of buildings, it is important to possess the tools to gauge a design’s predicted performance to realize successful natural ventilation concepts. However, with the utilization of glass, heat loss during the winter and solar gain during the summer will increase energy loads. At the same time, this will also negatively effect the microclimatic comfort. Through this study, both the effect of the utilization of multiple facades on indoor comfort conditions and thus the effects of distances at different distances from the facade on wind flow and therefore microclimatic comfort at the situation of the Multiple Skin Facades were investigated. This paper demonstrates through a sensitivity analysis, an optimal strategy for completing a CFD simulation of this special building envelope. This study also attempts to research a mechanically ventilated building with DSF configuration—a building in terms of indoor microclimatic thermal comfort. The aim of this study is to work out the effect of wind velocity and wind distribution on naturally ventilated buildings with DSF configuration, to work out if a DSF configuration will provide a far better microclimatic thermal comfort through natural ventilation. This study not only defines and analyzes the dimensional parameters of the air gap to maximize airflows, but also explores the importance of design decisions on system performance, such as the interaction between thermal mass and air gap distances and the building facade. Keywords: double skin facade, microclimatic thermal performance, airflow modelling, ındoor microclimatic thermal comfort, wind velocity, wind distribution, CFD, natural ventilation performance simulation

DRL-RNP: Deep Reinforcement Learning-Based Optimized RNP Flight Procedure Execution.

The required navigation performance (RNP) procedure is one of the two basic navigation specifications for the performance-based navigation (PBN) procedure as proposed by the International Civil Aviation Organization (ICAO) through an integration of the global navigation infrastructures to improve the utilization efficiency of airspace and reduce flight delays and the dependence on ground navigation facilities. The approach stage is one of the most important and difficult stages in the whole flying. In this study, we proposed deep reinforcement learning (DRL)-based RNP procedure execution, DRL-RNP. By conducting an RNP approach procedure, the DRL algorithm was implemented, using a fixed-wing aircraft to explore a path of minimum fuel consumption with reward under windy conditions in compliance with the RNP safety specifications. The experimental results have demonstrated that the six degrees of freedom aircraft controlled by the DRL algorithm can successfully complete the RNP procedure whilst meeting the safety specifications for protection areas and obstruction clearance altitude in the whole procedure. In addition, the potential path with minimum fuel consumption can be explored effectively. Hence, the DRL method can be used not only to implement the RNP procedure with a simulated aircraft but also to help the verification and evaluation of the RNP procedure.

Holocene environmental changes in the fuegian forest and steppe, Argentina

Environmental changes were reconstructed from a multiproxy synthesis of over 30 localities from the Isla Grande de Tierra del Fuego and Isla de los Estados, southernmost South America. At a local scale, the results from the mountain forest and gently undulating steppe areas were integrated as well as those from the marine environments of the Beagle Channel and the Atlantic coasts. At a regional scale, the results were integrated with those published for the southernmost Andean and Extra-Andean Patagonia and the Antarctic Peninsula. This study focuses on the environmental evolution during the Late Glacial-Holocene transition, the Middle to Late Holocene transgressive-regressive hemicycle and wet-dry oscillations, the Medieval Climate Anomaly, the Little Ice Age, the tephra inputs from the Patagonian Andes, and the recent climatic warming. Most paleoenvironmental changes are related to variations in the latitudinal position and intensity of the Southern Westerly Winds (SWW) while others are associated with astronomical or endogenous forcings. At a strong intensity of the SWW, a greater contribution of humidity to the forest areas and an increase in the rainfall gradient create windy and arid conditions in the steppe. At a weak intensity of the SWW, lower humidity input in the forest areas and the advection of air masses from the Atlantic Ocean promoted humid and slightly windy conditions in the steppe. Similar environmental trends are observed between terrestrial and marine environments in the center and south of Tierra del Fuego, Isla de los Estados and the Antarctic Peninsula, and between the Fuegian steppe and Extra-Andean Patagonia. The paleoclimatic evidence reveal high environmental variability in the last 10,000 years for this sector of the Southern Hemisphere.

Characterization of winter air pollutant gradients near a major highway

Traffic-related air pollutants (TRAP) including nitric oxide (NO), nitrogen oxide (NOx), carbon monoxide (CO), ultrafine particles (UFP), black carbon (BC), and fine particulate matter (PM2.5) were simultaneously measured at near-road sites located at 10 m (NR10) and 150 m (NR150) from the same side of a busy highway to provide insights into the influence of winter time meteorology on exposure to TRAP near major roads. The spatial variabilities of TRAP were examined for ambient temperatures ranging from −11 °C to +19 °C under downwind, upwind, and stagnant air conditions. The downwind TRAP concentrations at NR10 were higher than the upwind concentrations by a factor of 1.4 for CO to 13 for NO. Despite steep downwind reductions of 38 % to 75 % within 150 m, the downwind concentrations at NR150 were still well above upwind concentrations. Near-road concentrations of NOx and UFP increased as ambient temperatures decreased due to elevated emissions of NOx and UFP from vehicles under colder temperatures. Traffic-related PM2.5 sources were identified using hourly PM2.5 chemical components including organic/inorganic aerosol and trace metals at both sites. The downwind concentrations of primary PM2.5 species related to tailpipe and non-tailpipe emissions at NR10 were substantially higher than the upwind concentrations by a factor of 4 and 32, respectively. Traffic-related PM2.5 sources accounted for almost half of total PM2.5 mass under downwind conditions, leading to a rapid change of PM2.5 chemical composition. Under stagnant air conditions, the concentrations of most TRAP and related PM2.5 including tailpipe emissions, secondary nitrate, and organic aerosol were comparable to, or even greater than, the downwind concentrations under windy conditions, especially at NR150. This study demonstrates that stagnant air conditions further widen the traffic-influenced area and people living near major roadways may experience increased risks from elevated exposure to traffic emissions during cold and stagnant winter conditions.

Influence of pressure recovery on the performance of an induced draught air-cooled condenser under windless and windy conditions

This research aims to enhance the performance of a 20-fan induced draught air-cooled condenser (ACC) by increasing the airflow rate and heat rejection rate of the ACC. These improvements are achieved through pressure recovery, which is the conversion of the dynamic pressure loss at the fan outlets into static pressure. Two different conical diffusers are attached to the outlets of the ACC’s fans to facilitate pressure recovery. The shorter diffuser has a length equal to 20% of the fan diameter and an included angle of 2 θ = 40° ; the longer diffuser is 40% the length of the fan diameter with 2 θ = 32° . The performance of this five-by-four ACC is analysed with and without these diffusers through numerical simulation in OpenFOAM. The analysis is performed under windless and windy conditions. The added diffusers increase the volumetric and thermal effectiveness of the ACC by 2.5% and 2.0%, respectively, under windless conditions. At wind speeds of 3, 6 and 9 m/s, the gain in volumetric effectiveness declines to 1–2%, while the gain in thermal effectiveness varies in the range of 0–5%. The longer of the two diffusers yields greater improvements, especially at higher wind speeds. • Discharge conical diffusers can increase the effectiveness of an induced draught ACC. • Under windless conditions, the mean volumetric effectiveness increases by 2.5%. • Under windless conditions, the mean thermal effectiveness increases by 2.0%. • Under windy conditions, the mean volumetric effectiveness increases by 1–2%. • Under windy conditions, the mean thermal effectiveness increases by 0–5%.

Numerical study on the effects of layout compactness of the annular-aligned moist media on thermo-hydraulic performance of an indirect dry cooling tower

• A 3D numerical model integrating a dry cooling tower and moist media was built. • Annular-aligned moist media conduct air precooling and flow field reconstruction. • Effects of media layout compactness on tower performance were revealed. • Media in dry (wet) mode maximize cooling capacity of the tower by 17.7% (26.9%). • Water loss for unit cooling capacity increment of the tower is within 0.6–0.8 kg/MJ. It is necessary to address the low-efficiency operation of an indirect dry cooling tower (IDCT) under adverse ambient conditions. Annular-aligned moist media outside the tower base is an integrated solution by performing inflow air precooling and flow field reconstruction to improve thermo-hydraulic performance of the tower. In this work, a three-dimensional (3D) numerical model was developed to evaluate the synergy between the air precooling effect and windbreak-like effect of moist media with varied interval angles. The results indicate that under moist media scheme of any interval angle, the air precooling effect enhances steadily with wind speed, but the windbreak-like effect or the combined effect of the moist media turns to decline as wind speed exceeds 8 m/s. The air precooling effect is stronger than windbreak-like effect in improving tower performance at low and ultra-high wind speeds. Under the identical windy condition, the windbreak-like effect of the moist media enhances with the interval angle, while the air precooling effect varies little. The media with an interval angle of 10° working in dry (wet) mode maximize cooling capacity of the IDCT by 17.7% (26.9%). Water consumption for unit cooling capacity increment of the IDCT generally ranges from 0.6 kg/MJ to 0.8 kg/MJ.

Biocrust Amendments to Topsoils Facilitate Biocrust Restoration in a Post-mining Arid Environment.

Soil cryptogamic biocrusts provide many ecological functions in arid zone ecosystems, though their natural reestablishment in disturbed areas is slow. Accelerating reestablishment of biocrusts may facilitate the establishment of vascular plant communities within the timeframes of restoration targets (typically 5–15 years). One technique is to inoculate the soil surface using slurries of biocrust material harvested from another site. However, this is destructive to donor sites, and hence the potential to dilute slurries will govern the feasibility of this practice at large spatial scales. We conducted a replicated experiment on a disturbed mine site to test the individual and combined effects of two strategies for accelerating soil cryptogamic biocrust reestablishment: (1) slurry inoculation using biocrust material harvested from native vegetation; and (2) the use of psyllium husk powder as a source of mucilage to bind the soil surface, and to potentially provide a more cohesive substrate for biocrust development. The experiment comprised 90 experimental plots across six treatments, including different dilutions of the biocrust slurries and treatments with and without psyllium. Over 20 months, the reestablishing crust was dominated by cyanobacteria (including Tolypothrix distorta and Oculatella atacamensis), and these established more rapidly in the inoculated treatments than in the control treatments. The inoculated treatments also maintained this cover of cyanobacteria better through prolonged adverse conditions. The dilute biocrust slurry, at 1:100 of the biocrust in the remnant vegetation, performed as well as the 1:10 slurry, suggesting that strong dilution of biocrust slurry may improve the feasibility of using this technique at larger spatial scales. Psyllium husk powder did not improve biocrust development but helped to maintain a soil physical crust through hot, dry, and windy conditions, and so the potential longer-term advantages of psyllium need to be tested.