Preventing surgical site infections and prosthetic joint infections is crucial for patient safety after total joint arthroplasty. Microbial air contamination has been suggested as a risk factor. ...Therefore, the ventilation system that will reduce air contamination most effectively in operating theatres (OTs) has been discussed.
To determine whether laminar airflow (LAF) ventilation is superior to turbulent airflow (TAF) ventilation by looking at the colony forming units (cfu) count during live total hip and knee arthroplasties. Furthermore, to explore whether the number of OT personnel, door and cabinet lock openings and technical parameters of the ventilation systems have an impact on the number of cfu.
Active air sampling and passive sedimented bacterial load were performed in 17 OTs, equipped with either LAF or TAF ventilation, during 51 live surgeries while observations were noted.
LAF OTs reduced cfu counts compared with TAF OTs during live surgery (P<0.001). All LAF OTs provided ultraclean air whereas TAF had nine procedures exceeding the threshold of 10 cfu/m3. Door and cabinet lock openings and number of personnel did not influence the cfu count, while it decreased with increasing volume and total air change per hour (P<0.05).
All LAF OTs had cfu counts within recommendations and provided lower cfu counts compared with TAF OTs. The number of OT personnel and total openings did not have an influence on cfu counts. Increased volume of the OT and total air change per hour showed a decrease in active cfu counts.
Effects of sequential increase in airway resistance: no, low (5 kPa.s/l), high (24 kPa.s/l), and complete block in the inspiratory or expiratory phase of mechanically induced cough on the cough motor ...pattern were studied in 16 anesthetized (pentobarbital) spontaneously breathing cats (3.70±0.15 kg, 11♂, 5♀). Esophageal pressure and electromyographic activities of the diaphragm during inspiration and abdominal muscles during expiration were analyzed. No significant changes in the number of coughs occurred. Inspiratory occlusion caused a prolongation of cough inspiratory phase, cough inspiratory diaphragm activity, and all cough-related activity. Inspiratory occlusion along with high resistance increased inspiratory esophageal pressure amplitude, total cough cycle duration and the time between maximum activity of the diaphragm and abdominal muscles. High expiratory resistance and occlusion resulted in increased cough expiratory esophageal pressure amplitude, a longer active portion of cough expiration, and cough abdominal activity. Expiratory occlusion also prolonged cough expiratory phase, all cough activity, and total cough cycle. Significantly increased airway resistance and occlusion induce secondary, in addition to mechanical, changes in cough by significantly modulating the generated cough motor pattern. A certain level of resistance appears to be successfully compensated, resulting in minimal changes in coughing characteristics, including expiratory airflow and the rising time of the airflow. Afferent feedback from the respiratory tract, particularly volume feedback, represents a significant factor in modulating cough, mainly under various pathological conditions in the respiratory system.
•Alterations in airflow markedly influence the generation of the cough motor pattern.•Partially increased airway resistance allows the production of efficient coughing.•High airway resistance leads to highly impaired coughing.•Both mechanical factors and feedback effects enhance the occurrence of impaired coughing.
Atmospheric microplastics have been widely reported and detected in remote mountain areas and oceans, indicating that they can be transported over long distances through the atmosphere. Regional ...transport and deposition processes of atmospheric microplastics have a significant impact on the source and sink patterns, as well as the flux mechanisms of microplastics in terrestrial and marine environments. However, few studies have been conducted on the deposition of atmospheric microplastics. Thus, in this study, we collected atmospheric microplastic samples from the northwestern South China Sea and estimated that in the fall the dry deposition of atmospheric microplastics into the ocean was 1.4 × 103 t, which had a greater contribution than riverine inputs of microplastics in this region, suggesting that atmospheric microplastics are non-negligible sources of marine plastic litter with high environmental risk. Additionally, we reported on the abundance (0.035 ± 0.015 n/m3), morphological characteristics, composition, and sources of atmospheric microplastics in the northwestern South China Sea. Smaller-sized microplastics had a high abundance that decreased with increased proximity from the coast. Most of the detected microplastics were fibers, which accounted for approximately two-thirds of the total quantity. The spectral analysis detected seven polymer types, and polyester was predominant (29%). Combined with the cluster analysis of the backward trajectories of airflow, we demonstrated that the airflow affecting the northwestern South China Sea originated mainly from the northeast, potentially carrying microplastics from cities located in southeastern Chinese provinces to the South China Sea.
•Dry deposition of atmospheric MPs into the northwestern SCS in the fall was 1400 t.•The number of MPs gradually increased and peaked as the particle size decreased.•The airflow may carry MPs over cities in southeastern China into SCS in the fall.•Long-term monitoring of atmospheric MPs and making evaluation standards are needed.
The optimal type of ventilation in operating theatres for joint arthroplasty has been debated for decades. Recently, the World Health Organization changed its recommendations based on articles that ...have since been criticized. The economic and environmental impact of ventilation is also currently an important research topic but has not been well investigated.
To compare how large, high-volume, laminar airflow (LAF) and turbulent airflow (TAF) ventilation systems perform during standardized simulated total hip arthroplasty (THA), as they pertain to colony-forming units (cfu), particle counts, and energy consumption.
Two identical operating theatres were used to perform simulated THA. The only difference was that one was equipped with LAF and the other with TAF. Cfu and particles were collected from key points in the operating theatre, and energy was measured for each simulation. Thirty-two simulations were done in total.
LAF had significantly reduced cfu and particle count when compared with TAF, at both 100% and 50% air influx. Furthermore, it was shown that lowering the air influx by 50% in LAF did not significantly affect cfu or particles, although reducing the fresh air influx from 100% to 50% significantly lowered the energy consumption. Most simulations in TAF did not meet the cleanroom requirements.
Cfu were significantly lower in LAF at both 100% and 50% air influx. It is possible to reduce fresh air influx in LAF operating theatres by 50%, significantly reducing energy consumption, while still maintaining cfu and particle counts below the ISO classification threshold required for THA surgery.
The existing grape drying technology and equipment often have problems such as poor hygiene conditions, high drying costs, and large drug residues. Therefore, the market urgently needs grape drying ...equipment with low energy consumption, high efficiency, and a green-clean processing process. To solve the above problems, a piece of integrated drying equipment combining the two technologies of air impingement blanching and air impingement drying for multi-layer grape material drying is designed. The dried product quality is directly affected by the airflow field distribution. Therefore, obtaining good airflow distribution and airflow velocity uniformity in the drying chamber via parametric studies is essential to ensure uniform drying of products. Since parametric and optimization investigations by physical experiments are usually expensive and time-consuming, computational fluid dynamics (CFD) being a flexible and less expensive tool can be employed to perform such studies. In the current work, the airflow velocity distribution and uniformity of the drying material room are analyzed by Ansys Fluent software. The airflow velocity non-uniformity coefficient is used to evaluate airflow uniformity. Results show that the original design has poor uniformity and needs to be optimized. The influence of air inlet chamber deflection device and material truck airflow baffles on the flow field of the material drying room is investigated to improve the uniformity of airflow distribution. Considering drying efficiency and uniformity, drying material room structure with the addition of deflection device design with the structural parameters of L = 50 mm and
θ
= 76°, airflow baffle design with the structural parameters of h = 0 mm,
θ
2
= 20° is chosen as the final optimized design. After optimization, the velocity of airflow between material layers has improved overall, and the maximum difference of average airflow velocity between material layers has been reduced from 0.73 m/s to 0.69 m/s, improving the drying uniformity of dried materials. In comparison to other drying equipment, the current integrated drying equipment combing air impingement blanching and drying has the advantages of being efficient and energy-saving, suitable for large-scale drying of grapes with better drying quality. The current results could guide the drying equipment design for grapes and develop the grape drying industry with high-dried quality.
Ultra-Clean-Air (UCA) operating theatres aim to minimise surgical instrument contamination and wound infection through high flow rates of ultra-clean air, reducing the presence of Microbe Carrying ...Particles (MCPs). This study investigates the airflow patterns and ventilation characteristics of a UCA operating theatre (OT) under standard ventilation system operating conditions, considering both empty and partially occupied scenarios. Utilising a precise computational model, quasi-Direct Numerical Simulations (qDNS) were conducted to delineate flow velocity profiles, energy spectra, distributions of turbulent kinetic energy, energy dissipation rate, local Kolmogorov scales, and pressure-based coherent structures. These results were also complemented by a tracer gas decay analysis following ASHRAE standard guidelines. Simulations showed that contrary to the intended laminar regime, the OT’s geometry inherently fosters a predominantly turbulent airflow, sustained until evacuation through the exhaust vents, and facilitating recirculation zones irrespective of occupancy level. Notably, the occupied scenario demonstrated superior ventilation efficiency, a phenomenon attributed to enhanced kinetic energy induced by the additional obstructions. The findings underscore the critical role of UCA-OT design in mitigating MCP dissemination, highlighting the potential to augment the design to optimise airflow across a broader theatre spectrum, thereby diminishing recirculation zones and consequently reducing the propensity for Surgical Site Infections (SSIs). The study advocates for design refinements to harness the turbulent dynamics beneficially, steering towards a safer surgical environment.
•Detailed CFD analysis by qDNS of airflow and ventilation of an UCA operating theatre.•Regions of UCA operating theatres developing turbulent flow and recirculation zones.•Transition from laminar to turbulent flow in locations within operating theatres.•Turbulence and velocity profiles used for assessment of indoor airflow quality.•Operating theatres occupancy improves ventilation efficiency and indoor air quality.
In this study, experiment was carried out with a solar chimney model with large gap-to-height ratios between 0.2 and 0.6. The experimental results show that the existing prediction method available ...in the literature overpredicts the airflow rate for chimney geometry investigated in this work, especially for vertical solar chimney with large gap-to-height ratios. An improved prediction method, which takes into account the variation of pressure loss coefficient for different flow conditions at the chimney outlet, is presented and compared with the experimental results obtained in this work and available in the literature. It is shown that the improved prediction method are in better agreement with the experiment results than the existing prediction method available in the literature for both narrow and wide chimneys. On the other hand, it is also found that the temperature and velocity distribution of air and airflow rate in chimney are highly dependent on heat flux and chimney gap. Experimental results show that an optimum gap-to-height ratio that maximizes the airflow rate in chimney is around the gap-to-height ratio of 0.5.
•Experiments are carried out for solar chimney with large gap-to-height ratios.•Presenting the overprediction of airflow rate for vertical solar chimney.•Presenting an improved prediction method for airflow rate in solar chimney.•The improved prediction method is supported by the experimental results.
•Numerical modeling of an integrated refrigerated container.•Different cargo pallet arrangements and cargo packaging boxes are tested.•Airflow short-circuiting has both positive and negative effects ...on cargo cooling.•Improving vertical airflow in cargo pallets enhances cargo cooling than air gaps.
Improving the performance of a refrigerated container is crucial in effectively preserving thermal-sensitive cargo. The combined effect of vertical airflow resistance and airflow short-circuiting in air gaps play a vital role in cargo cooling. This study numerically investigates the effects of cargo vertical airflow resistance and air gaps between cargo pallets using two commonly used apple packaging boxes, each stacked in six different cargo pallet arrangements. A heat transfer enhanced refrigerated container design and a numerical model developed from the present authors’ previous studies are used. The numerical model uses the porous medium model to incorporate the refrigeration unit and cargo within the refrigerated container. Additionally, the numerical domain includes the T-bar floor in the refrigerated container. Initially, the airflow characteristics based on vertical airflow resistance and air gaps are discussed. Then, the corresponding effects on cargo cooling are addressed. Results show that the air gaps between the cargo pallets have positive and negative effects on cargo cooling. In cargos with lower vertical airflow resistance, an increase in air gaps leads to reduced cargo cooling and elevated temperature non-uniformity. Conversely, cargos with higher vertical airflow resistance experience increased cooling rates and reduced temperature non-uniformity with the increase in air gaps. However, avoiding airflow short-circuiting through the air gaps between the cargo pallets and improving the vertical airflow inside the cargo pallets can provide better cargo cooling, which outweighs the positive cooling effect of the air gap.
The risk of healthcare-associated infections (HAIs) is higher in patients admitted to intensive care units (ICU) and high dependency units (HDU). Currently, most ventilation studies focus on ...specialized areas, mainly isolation rooms and operating rooms. This paper focuses on the ventilation of multiple-bed hospital wards in developing countries. This study uses computational fluid dynamics (CFD) simulation to model and investigate airflow and the spread of pollutants. The study aims to investigate ICUs with various ventilation system designs. These predicted behaviors and characteristics were compared numerically to determine compliance with the requirements of airflow patterns, airborne contaminant distribution, and current international standards. The case study simulations were carried out using ANSYS Fluent simulation software as a solution tool. Three different ventilation systems, Vertical Laminar Airflow Ventilation (VLAF), Horizontal Laminar Airflow Ventilation (HLAF), and Temperature-Controlled Airflow Ventilation (TcAF), were modeled within five different designs to determine the most effective possible distribution of air inside the patient's room, based on different categories, primarily temperature distribution, CO2 concentration, and airflow distribution. The authors applied the TcAF technique in an ICU room, comparing the results of the proposed technique with those of other common techniques (HLAF and VLAF). It was found that TcAF showed the most effective airflow distribution around patients, isolating each patient from the others. However, the temperature distribution was excluded from the ASHRAE standard. HLAF with two exhausts is the most suitable option, with a lower CO2 concentration than the alternatives and a temperature that meets ASHRAE standards.
•Numerical investigation of airflow and pollutant spread in ICU.•Three ventilation strategies of airflow were carried out using CFD simulation in ICU.•A novel application of Temperature-controlled airflow in ICU was carried out.•Measuring and analyzing the concentration of CO2 in ICU rooms.
A stockpile heated and ambient air dryer (SHAD) was developed as an alternative to conventional almond windrow drying. Previous experiments showe that the drying air produced by SHAD was undesirably ...distributed through the almond stockpile. Therefore, an air distributor was developed containing 12 outlets, arranged in 4 rows of 3 outlets each. This study describes the comprehensive process of the air distributor design, manufacturing, and its optimization. The optimization process employed both computational fluid dynamics simulations and in-field airflow validation measurements. Initial 4-row air distributor in-field validation measurements indicated airflow distribution percentages were 4.1%, 30.8%, 44.9%, and 20.2% for the outlets in rows 1 through 4. This showed that almonds located around row 1 would not receive sufficient air to properly dry. Thus, an optimized 3-row air distributor configuration was developed and validated to yield an airflow distribution percentage of 31.3%, 44.4%, and 24.3% for outlets in the second to fourth rows, respectively. The 3-row air distributor configuration is therefore desirable, as the middle and tallest section of the stockpile will receive the highest airflow. The air distributor therefore markedly enhanced the SHAD's air supply distribution.
•Drying air supplied by SHAD was unevenly distributed in the almond stockpile.•A multi-outlet air distributor was developed to improve air delivery.•Optimized air distributor design contained 3 rows, with 3 outlets on each row.•Air supply was highest in the middle row, where there are most almonds to dry.•The SHAD with air distributor significantly improved the air distribution supply.
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