Gas Flow in Occluded Respiratory Tree: A New Matrix-Based Approach

Studies suggest that both the size of airways and the number of bifurcations of the respiratory tree provide the best structural design to accomplish its function. However, constrictions and occlusions due to inflammation and pulmonary edema of the airways can inhibit normal air flowing through the respiratory tree, affecting gas exchange. It results in heterogeneity in gas exchange (and pulmonary perfusion) with adverse risk factors. In this study, we propose a methodology based on the airway tree admittance (reciprocal of impedance) to study this problem. This methodology is distinct from the traditional quantification, based on overall impedance using lump parameter models, and applies to a matrix formed by admittances of each airway of the entire conducting part of the bronchial tree. The generated system admittance matrix is highly sparse in nature, and thus to solve the same system, a modified block-based LU decomposition method is proposed to improve the space-time trade-off. Our approach enables the determination of the local ventilation pattern and reduces the mis-evaluation, mainly in the cases that characterize the early-stage obstructive disorders. The key finding of the present study is to show that how the position and intensity of local obstruction in an airway can affect the overall as well as regional ventilation which can lead to impaired gas exchange.

The question of determining installation sites for the Air purification of pig premises local system elements

The allocation of intake air stream in pig premises is not evenly. The existence of engineer-ing networks and equipment, the breaching of montage technologies of air ventilation, incorrect maintenance of air ventilation system – all these factors bring to many breaches and problems. This problem such as air exchange violation in all premises, appearing zones of stasis (aero stasis), and others. As a result of which the differential of temperature and humidity has appeared. These also appear excess maximum per-mitted concentration of dust and gases. The all-exchanged ven-tilation system can’t solve all problems in local zones in pig premises. In this local air-ventilation system become more demand. For effective work of local air ventilation, the question of deter-mining installation sites for the air purification of pig premises local system elements should be solved. Keywords: LOCAL VENTILATION, AIR CLEANING FROM DUST, DUST RELEASE, HARMFUL GAS CLEANING

Assessment of exposure determinants and exposure levels by using stationary concentration measurements and a probabilistic near-field/far-field exposure model

Background: The Registration, Evaluation, Authorization and Restriction of Chemicals (REACH) regulation requires the establishment of Conditions of Use (CoU) for all exposure scenarios to ensure good communication of safe working practices. Setting CoU requires the risk assessment of all relevant Contributing Scenarios (CSs) in the exposure scenario. A new CS has to be created whenever an Operational Condition (OC) is changed, resulting in an excessive number of exposure assessments. An efficient solution is to quantify OC concentrations and to identify reasonable worst-case scenarios with probabilistic exposure modeling. Methods: Here, we appoint CoU for powder pouring during the industrial manufacturing of a paint batch by quantifying OC exposure levels and exposure determinants. The quantification was performed by using stationary measurements and a probabilistic Near-Field/Far-Field (NF/FF) exposure model. Work shift and OC concentration levels were quantified for pouring TiO2 from big bags and small bags, pouring Micro Mica from small bags, and cleaning. The impact of exposure determinants on NF concentration level was quantified by (1) assessing exposure determinants correlation with the NF exposure level and (2) by performing simulations with different OCs. Results: Emission rate, air mixing between NF and FF and local ventilation were the most relevant exposure determinants affecting NF concentrations. Potentially risky OCs were identified by performing Reasonable Worst Case (RWC) simulations and by comparing the exposure 95th percentile distribution with 10% of the occupational exposure limit value (OELV). The CS was shown safe except in RWC scenario (ventilation rate from 0.4 to 1.6 1/h, 100 m3 room, no local ventilation, and NF ventilation of 1.6 m3/min). Conclusions: The CoU assessment was considered to comply with European Chemicals Agency (ECHA) legislation and EN 689 exposure assessment strategy for testing compliance with OEL values. One RWC scenario would require measurements since the exposure level was 12.5% of the OELV.

ON AIR FLOW STRUCTURE IN STATION VENTILATION CONNECTIONS OF SUBWAYS

One of the important microclimatic criteria for the comfort and safety of passenger transportation in subways is dust concentration in passenger and staff area. It is known that fine dust concentration in subways is significantly exceeded relative to the permissible regulatory level. To reduce the dust concentration to the maximum allowable level, it is necessary to filter the tunnel air not only for the systems of local ventilation of staff rooms, but also for tunnel ventilation and general ventilation of passenger rooms at the stations. It is better to install filters in station ventilation connections, since significant circulating air flows pass through them. To determine the type and parameters of filters, it is required to know the magnitude and direction of an airflow rate, i.e. the structure of its velocity field. Due to the complex topology and presence of separation zones, the airflow structure, gradient of air velocities in the cross-section of ventilation connections and, accordingly, justification of filter installation locations in a ventilation connection requires a separate study. The paper substantiates a decomposition approach to mathematical modeling of aerodynamic processes by transition from a linear open-loop model of the subway line to a closed circular one; geometric parameters of the adopted design model; mathematical statement of the problem. Computational aerodynamics methods allowed determining the minimum, average and maximum projections of air velocity on the normal to the cross section of a ventilation connection and air flows through this cross section. This makes it possible to justify the requirements for the placement and operating parameters of the filtration equipment.

NUMERICAL SIMULATION OF DUST-AIR FLOWS NEAR THE LOCAL VENTILATION EXTRACTION FROM DRILLING EQUIPMENT

A significant amount of dust is released during the drilling process. It negatively affects the cleanliness and ecology of the surrounding space, as well as human health. The design of a local extraction nozzle is proposed for dedusting the process of drilling concrete with standard drills. A computer model of the dust-air flow in the developed nozzle is created in the software package SolidWorks Flow Simulation. The dynamics of dust particles formed during drilling is numerically studied. The behavior of dust particles of different sizes is considered. It is proposed to use the value of the maximum diameter of dust particles completely captured by the suction channel as a criterion for the efficiency of dust particle capture. Three variants of the drilling plane arrangement are considered: floor, ceiling and vertical wall. The dependences of the maximum diameter of dust particles on the intake air flow rate, the distance of the extraction channel on the side surface of the nozzle to the place of its abutment to the drilling plane, and the radius of the suction channel are determined. The results obtained can be used to design and improve systems for capturing dust pollution generated during drilling. The formulated further directions of research are useful for researchers engaged in identifying the processes of capturing dust particles from mobile technological equipment.

Local ventilation and its impacts on urban heat islands and outdoor thermal comfort

<p>Many cities are facing urban overheating issues where the reduction of urban ventilation is one of the key drivers. To address the urban overheating problems, this study concentrates on the analysis of local-scale urban ventilation and its impacts of urban heat islands and outdoor thermal comfort, in order to support wind-sensitive urban planning and design. To achieve this, this study develops a framework for analysing local ventilation, urban heat islands and outdoor thermal comfort with the consideration of local morphological characteristics, external meteorological conditions, local ventilation performance, urban heat islands and outdoor thermal comfort. In particular, the consideration of local morphological characteristics is supported by the development of precinct morphology classification scheme based on three-component protocol of building height, street structure and compactness. Based on the three-component protocol, 20 types of the local ventilation zones were identified in the context of Greater Sydney, Australia.</p><p>Field measurement was conducted in three typical local ventilation zones, including open low-rise gridiron, open midrise gridiron and compact high-rise gridiron among the 20, to examine the local ventilation performance, urban heat islands and outdoor thermal comfort in summer 2019. The results indicate that the open midrise gridiron precinct underwent the best precinct ventilation performance, followed by the low-rise gridiron precinct and then the compact high-rise gridiron precinct. The local ventilation created by the sea breeze can help alleviate urban heat islands in the open low-rise gridiron and compact high-rise gridiron precincts with every 0.1 increase in relative wind velocity ratio leading to a 0.09-0.12 °C reduction in UHI intensity. However, in the open midrise gridiron precinct, the local ventilation created by the sea breeze made no difference for urban heat islands. However, the precinct ventilation of the open midrise gridiron precinct still partially exhibited UHI alleviation potential with every 0.1 increase in relative wind velocity ratio leading to a 0.06-0.1 °C reduction in UHI intensity depending on the approaching wind temperature and shading conditions.</p><p>Only the precinct ventilation of the open low-rise gridiron precinct leads to outdoor thermal comfort improvement with every 0.1 increase in relative wind velocity ratio leading to 0.29 °C and 0.50 °C physiological equivalent temperature reductions under sea breeze and varying wind conditions, respectively. The results also indicate that within ‘gridiron’ precincts, street orientation is not critical to precinct ventilation performance and its impact on urban heat islands and outdoor thermal comfort. Under wind conditions, trees do not always alleviate urban heat islands and improve outdoor thermal comfort as trees can block sea breeze penetration and inhibit wind cooling potential. These key findings will serve to inform urban heat island mitigation strategies and future planning and design decisions in the built environment.</p>