Air Speed Research Articles

Designing Body Life Bag Using Reusable Ice Gel As A Curative Measure To Handle Heat Stroke Cases Of Indonesian Hajj Jamaah

Hajj is the fifth pillar of Islam which is carried out physically, activities in the outside environment can reach 30 hours exposing pilgrims to hot temperatures [3]. The Indonesian Ministry of Health recorded that 430 Indonesian pilgrims died each year between 2012 and 2019 due to heat stroke. The Indonesian Ministry of Health for Hajj 2022 uses body bags as a medium for storing ice water, creating fear among pilgrims and making it difficult to get ice water. The body life bag is an innovative immersion device using ice gel. Testing of three alternative body life bag designs (Salamon, Arabiyan, Camel Poc) was carried out by three subjects aged 42 years. Subjects were selected based on the similarity in appearance of fatigue due to exposure to environmental heat with elderly Indonesian pilgrims. The criteria of BMI are 30.45 kg/m2, 26.93 kg/m2, and 27.64 kg/m2. The test was carried out during the day under exposure to environmental heat with an ambient temperature of 28.3oC, an air speed of 1.5 m/s, and an air humidity of 43 g/m2. This test was based on ISO 9920 and ISO 11079 standards. There were three alternative designs of the Body Life Bag, the fastest cooling time was 5 minutes 41 seconds and the subject's final temperature was obtained at 33.2oC. So the most effective design for lowering body temperature is the Salamon design.

Comparison of low air speed facilities

Main textSupplementary interlaboratory comparison between European low air speed calibration facilities. Two thermal anemometers have been used as transfer standards and circulated between five participants. The transfer standards selection was based on stable behaviour and sensitivity at very low air speeds. The first anemometer was calibrated by the participants at nominal velocities from 0.05 m/s to 1.0 m/s. The second anemometer was calibrated at nominal velocities from 0.15 m/s to 1 m/s.To reach the main text of this paper, click on Final Report. Note that this text is that which appears in Appendix B of the BIPM key comparison database https://www.bipm.org/kcdb/.The final report has been peer-reviewed and approved for publication by the CCM, according to the provisions of the CIPM Mutual Recognition Arrangement (CIPM MRA).

A Fixed-Wing UAV Formation Algorithm Based on Vector Field Guidance

The vector field method was originally proposed to guide a single fixed-wing Unmanned Aerial Vehicle (UAV) towards a desired path. In this work, a non-uniform vector field method is proposed that changes in both magnitude and direction, for the purpose of achieving formations of UAVs. As compared to related work in the literature, the proposed formation control law does not need to assume absence of wind. That is, due to the effect of the wind on the UAV, one can handle the UAV air speed being different from its ground speed, and the UAV heading angle being different from its course angle. Stability of the proposed formation method is analyzed via Lyapunov stability theory, and validations are carried out in software-in-the-loop and hardware-in-the-loop comparative experiments. Note to Practitioners—The software-in-the-loop and hardware-in-the-loop experiments, which are done with PX4 autopilot software and hardware, show that the proposed method can be implemented on board of UAVs and integrated with the control architecture of existing autopilot suites. Comparisons with standard formation algorithms show that the proposed method is effective in achieving formation in different path scenarios.

Разработка параметрической модели определения газового состава воздушной среды (аммиак, сероводород, углекислый газ) животноводческого помещения

Indoor climate parameters influence the productivity of animals and their physiological condition. Exceeding permissible concentrations of gases leads to animal diseases, loss of productivity, and the mortality of young cattle. Therefore, it is reasonable to predict the concentration of gas composition in the livestock houses. To determine and distribute harmful gases (ammonia, hydrogen sulphide, and carbon dioxide) in the livestock house, the authors performed the 3D modeling of a fragment of the farm in the SolidWorks 2020 software package. Parametric models of gas movement under different conditions were created and optimal measurement points of gas concentration in the livestock house were determined. The simulations made it possible to determine the direction of air flows and detect accumulations and clouds of gases. The maximum concentration of carbon dioxide was detected at 0.9m (an air speed of 0 m/sec) and at 1.3m (a speed of 0.75 m/sec). The highest concentration of hydrogen sulphide was found in the area bordering the ridge space (an air speed of 0 m/s) and at the level of 2.25 m (a speed of 2 m/s). The highest concentration of ammonia was observed under the roof and in the area under the ridge (an air speed of 2 m/s). It is recommended to install hydrogen sulphide and ammonia sensors under the ridge, while carbon dioxide, hydrogen sulphide and ammonia sensors – in the stall, carbon dioxide and hydrogen sulphide sensors – near the feed table. Concentrations should be measured at heights of 500, 1500, and 3000 mm. When the concentration of emitted gas increases and other conditions are equal, the concentration of gas in the cloud increases, but the structure of the cloud changes insignificantly. Parameter interrogation sensors should be installed in enclosed ventilated boxes in the same manner as in weather stations.

Optimizing airfoil shape for small, low speed, unmanned gliders: A homemade investigation

Motivated by an interest to increase the efficiency of static airfoils, the objective of this study was to optimize airfoil lift generation based solely on airfoil shape. Enhancing the lift generated by airfoils without flaps can lead to longer flight times for unmanned gliders and possibly reduce fuel requirements for ground and air vehicles (1,2,3). We employed a Bernoullian model of airfoil lift generation to predict an optimized wing shape which was then constructed and compared with five others in a wind tunnel. We assembled airfoils from Styrofoam and conducted experiments in a small wind tunnel, measuring air speeds with a handheld anemometer. Our Bernoullian model related lift generation to the ratio of surface areas above and below an airfoil’s chord, and because this ratio was maximized in our optimal airfoil, we predicted that this wing would generate more lift force than the other tested wings with lower ratios. However, we identified a variety of confounding variables including imperfections in wing constructions, turbulent airflow and air resistance within the wind tunnel, and low resolution of the anemometer, all of which contributed to unpredicted and unreliable results. Moreover, we concluded that our mathematical model was not rigorous enough to be generalized to a wider set of experimental conditions. Despite these shortcomings, our results did point to a correlation between airfoil shape and lift generation, and will allow for more informed, less error prone future studies.

Parameter Optimization of Intercalated Meltblown Nonwovens Based on NSGA-II

The preparation process parameters of intercalated meltblown nonwoven materials are complicated, and the relationship between process parameters, structural variables, and product performance needs to be investigated to establish a good mechanism for product performance regulation. In this study, we first used Wilcoxon test and Pearson correlation analysis to investigate the effect of intercalation rate on structural variables and product performance. Then, regression models were constructed to predict the values of each structural variable under different combinations of process parameters. Finally, we constructed a multi-objective constrained optimization problem based on the stepwise regression model and the product variable conditions. The problem was solved using the NSGA-II algorithm. The optimal was achieved when the acceptance distance was 2.892 cm and the hot air speed was 2000 r/min.

Recent advances in solar drying technologies: A Comprehensive review

Preservation of food and vegetable products is an age-old practice for the retention of flavor, appearance, and quality. From ancient times, driers for drying food grains work on direct sun rays, firewood, fossil fuels, and coals causing carbon release. These available methods are expensive, unreliable, and unhygienic; thereby the use of a solar dryer working on free and clean energy is better for higher value addition to food preservation. The objective of this exploration is to study the recent developments in the use of different types of solar dryers for drying foods, vegetables, seafood, etc. There exist many studies on the effects of the parameters such as temperature, relative humidity, and speed of air, turbulence effect, sun irradiation, and the latitude of the location in the solar drying process. The findings show that the climate conditions such as solar radiation and atmospheric air play an important role in the drying efficiency of the solar dryer. A phase change material stores thermal energy during the daytime and releases heat during the nighttime. This process improves thermal efficiency and reduces heat loss during the drying period. On the one hand, a hybrid dryer integrated with a solar panel produces electricity for the operation of a DC blower circulating hot air inside the drying chamber for better drying. In addition, a critical review has been performed on the usage of different absorbing plates increasing heat transfer rate, use of various phase change materials for heat storage, and analysis of CFD simulation.

Model of the software and hardware complex of automated flight instruction for cadets based on the reference flight pattern

Information is provided regarding the developed model of the software-hardware complex of the automated flight instruction of cadets based on the reference image of the flight. It is proposed to model the movement of a helicopter between two support points as the movement of a material point that has mass and is affected by gravity. The movement model is represented by a system of differential equations of the first order, which describes the movement parameters: air speed, angle of inclination of the trajectory, flight height and distance of movement. Based on the existing regulatory rules for the operation of aircraft, a system of restrictions on movement parameters has been defined. The set of basic flight control bodies is substantiated, the laws of pilot control and restrictions on control parameters, which are also determined by the rules of helicopter operation, are set. The task of finding optimal control parameters at the stage of acceleration of a helicopter at a constant altitude has been formalized. The general structure of the adaptive search system has been built. Procedures for finding optimal parameters have been created using a combined method of finding optimal control parameters based on single-criteria conditional and vector optimization methods. Based on the model experiment, the optimal value of the parity criterion in the method of adaptive convolution of the optimal criterion vector is determined. The calculated data of the proposed model made it possible to find in real time the parameters of the movement of the helicopter under the control of the pilot, the history of the deviation of this movement from the ideal, and the dynamic forecast of such deviation. The possibility of obtaining predicted solutions in the case of existing linear control laws or approximate to linear control laws has been established experimentally. The parameters of the model were determined experimentally. A system of commands of an electronic instructor in verbal form is proposed for correcting the pilot's behavior and bringing his actions closer to optimal ones. Recommendations regarding the practical application of the developed model are substantiated.

2D numerical model of downward push pull ventilation for protecting workers against airborne infection

Industrial clusters contributed significantly to the spread of Covid-19 worldwide, including in Indonesia. One of the causes is that maintaining a minimum distance of 1 to 2 meters between workers is often challenging due to the plant layout and work system design limitations. Therefore, an intervention to the workstation is needed to protect industrial workers from potential exposure to Covid-19 and other airborne infections. One technology that has a high potential to be applied to solve this problem is the air curtain/personalized ventilation. This research analyzes the effectiveness of downward push-pull air curtain in protecting workers from inhaling the infected microdroplet. The extent to which the downward push-pull ventilation can withstand the burst of microdroplets was studied by varying the air speed ratios of the air curtain. A 2D simulation was carried out with Salome, OpenFOAM, and ParaView softwares. Two scenarios were tested, i.e., the distance between the person who is coughing is 0,5 and 1 meter from the air curtain. For the distance of 0,5 meter, the results showed that the optimum velocity ratio between the pushed and pulled air was 0,17 with a droplet penetration percentage of 8,98 %. While for 1 m, the optimum velocity ratio was 0,25 with a droplet penetration percentage of 5,67 %.

Akçakatık Peynirinin, Tasarımı ve İmalatı Yeni Yapılan Peynir Kurutma Makinesinde Kurutulması

Burdur’un yöresel peynirlerinden olan Akçakatık peynirine, geleneksel yöntemlerle yapılan kurutma işlemi, tasarımı ve imalatı yeni yapılan, kurutma sıcaklığı 25°C, kurutma hava hızı 1,5 m/s, kurutulmuş üründe nem tayini %20’yi sağlayacak parametrelerle çalışan bir peynir kurutma makinesi ile kurutma işlemi gerçekleştirilmiştir. Geleneksel yöntemle, peynir hijyen koşullarında temizlenen ve kurutulan karın içine basılarak, açık havada ve gölgede 3-4 ay olgunlaştırılarak veya güneşte kurutulmaktadır. Kurutma işlemi 3 gün süreyle, her gün 3 saatlik kurutma yapılarak, kurutma işlemi bittikten sonra peynir tekrar yoğurularak ve kurutma işlemi bitince ertesi gün aynı kurutma saatine kadar peynir +4°C’de dinlendirilerek tamamlanmıştır. Kurutma işlemi tamamlanan peynirde, kuru madde oranı %34,44’den %62,55’ ye yükselmiş, yağ oranı %18-19,5 arasında değişim göstermiştir. Kuru maddedeki yağ oranları %52,26’dan %31,17’ ye düştüğü görülmüştür. Çalışmada elde edilen örneklerin, kuru madde değerleri, en az 2-3 ay olgunlaşma geçiren peynirlerinkine oldukça yakın bir düzeyde bulunmuştur.

Numerical assessment on aerodynamic free area of natural smoke and heat exhaust ventilator without and with side wind

As a convenient means for modeling the dynamics of fluids, computational fluid dynamics has not yet been fully applied in the refined quantitative analysis of the effectiveness of individual smoke ventilator. Previous related numerical simulation studies were short of the overall consideration of various verification scenarios involving all aspects of performance of testing device and accuracy of testing results without and with side wind. In this paper, a comprehensive numerical assessment process containing seven typical simulation scenarios is established for determining the aerodynamic free area of a roof mounted ventilator without and with side wind. Compared with related on-site testing platform, the geometric construction of testing apparatus is reasonably optimized to obtain more uniform flow field inside the settling chamber and more appropriate coverage of side-wind field acting on the ventilator; some measurement positions of air speed, which are unspecified in the testing standard, are designed properly in the simulation. Six types of regression equations on the relationship between discharge coefficient and pressure difference are established and compared for exploring the best goodness of fit of curve fitting. Good agreement of simulation results with reference data demonstrates the feasibility and validity of the numerical assessment process developed in this study.

Influence of military actions on the process of the formation of precipitation

This work concerns the study of the influence of military actions on the development of global ecological processes, in particular, the fall of acid rain from individual single explosions. A mathematical model is proposed, which takes into account the emission of pollutants into the subcloud washout zone and the kinetics of the condensation process. The concentration of combustion products in the atmosphere at the level of three to five diameters of the explosion area (the area of the formed explosion funnel) is found using the theory of a convective jet from a warm source to the environment. At the same time, we determined the speed of warm air that rises above the area of the explosion, the average temperature in the transition section of the convective jet, and the flow rate of polluted air in the upper part of the jet. The paper presents a system of dimensionless non-stationary differential equations for a high unshaded source, which can be used to determine the dispersion of the main acid-forming substances in the Boussinesq approximation with the variables "eddy velocity – current function – temperature – concentration" with appropriate initial and boundary conditions. Sulfuric anhydride was considered as an example of the main acid-forming substances and the most dangerous and toxic compounds of explosion products. The proposed mathematical model can be used to forecast the possible fall of acid rain on the territories adjacent to single explosions, thereby making a forecast of changes in environmental risk as a result of military operations for the environment and the population. and will make it possible to determine the zones of influence and dispersion from the place of the explosion.

Features of Replacement of the ТГМП-314 Boiler Heating Installation

Thermal power stations play the main role not only in carrying the base load, but also in ensuring the coverage of peak and semi-peak loads of electricity consumption. Improving the operational maintenance of energy equipment gives a greater economic effect, since the costs of modernization of regenerative air heaters, which improve their density and thermal efficiency, are repaid in a short time. The efficiency and cost-effectiveness of the operation of regenerative air heaters was increased by the reconstruction of the heating installation. The results of the reconstruction of the design heaters of the TГМП-314 boilers with sections of sanitary-technical heaters КФСО -II and КФБО -II with replacement by sections of energy heaters (СО-110) are presented. The improved heating installation is installed in front of each regenerative air heater of the ТГМП-314 boiler and is made of two walls placed sequentially according to the air movement, in each of which 12 sections of reconstructed CO-110 heaters with a downward movement of the heating steam flow are installed. An important advantage of the proposed sequential installation of radiators is an increase in the uniformity of the temperature field in the box in front of the regenerative air heater due to two-stage air heating. Sequential installation of radiator walls increases the heat transfer coefficient approximately 1.6 times compared to parallel connection, which makes it possible to double the air speed in the radiators for the same number of sections. The possibility of formation of stagnant zones of sections of CO-110 heaters is excluded. In this case, it is recommended to reconstruct single-pass radiators with the installation of a pipe board and heating steam condensate removal chambers. The high efficiency of the improved heating installation made it possible to carry out all boiler ignitions with the possibility of supplying flue gases immediately through the RAH.

EVALUATING THE EFFECT OF MASHRABIYA AND PERFORATED MALAY CARVING WINDOW ON THE INDOOR NATURAL VENTILATION PERFORMANCE OF LIVING SPACE

This study focuses on natural cross-ventilation improvements in terms of internal air velocity, measured in meter per second in the living room space in Malaysia, using two types of perforated windows namely, Mashrabiya window as well as perforated Malay carving window element to determine the performance of their internal air velocity. Cross ventilation has been proposed as one of the most effective natural ventilation methods for thermal comfort by several studies. It is, however, one of the most misunderstood aspects of passive design's approach to regulating interior temperature. In this study, the proposed design solution is by introducing the Mashrabiya (W1) and perforated Malay carving window (W2) as two predominant indigenous solutions for traditional houses that can be further developed and utilized in modern houses. The research involves three stages. The first stage includes the inventory exercise on five (5) different reference case studies of perforated windows. This is to ascertain the most fundamental and common pattern, as well as the dimensions of each W1 and W2. The second step involves computer simulations utilising Computational Fluid Dynamics (CFD) software known as Ansys fluent R2 2021. This program is used to simulate and evaluate natural air velocity and its performance in an interior context, and to determine the viability of a recommended design solution. Finally, an empirical method is used to predict the internal air velocity. The result shows that W1 and W2 represent effective passive design strategies for energy saving. The air velocity using W1 is three times higher than the normal speed which is 4.5/1.5 m/s, while using W2 makes the air velocity two times higher than the actual air speed which is 3/1.5 m/s. The simulation test and results are discussed based on the Malaysian region with a 1.5m/s wind speed. Understanding the different effects of the size of the voids and the placement of the patterns are significant to improve the indoor natural ventilation performance in a living room space.

High actuation capability and smooth-deformation piezo morphing wing based on multi-layer parallel pre-compressed MFC bimorph

A single macro-fiber composite (MFC) unimorph or bimorph wing can only be applied to micro aerial vehicles (MAV) at speeds lower than 20 m/s owing to its relatively small output work. In this study, a high-actuation MFC pre-compressed bimorph actuator (MFC-PBA) multilayer parallel morphing wing is proposed for application in high-speed miniature unmanned aerial vehicles (mini-UAVs). The morphing wing adopts the proposed ribs with an arc groove and three parallel layers of MFC-PBAs to improve the output work and guarantee smooth morphing wing surface. The large deformation finite element (FE) models of a single MFC-PBA and its multilayer parallel morphing wing are established to evaluate the output deformation and output force. Subsequently, a prototype of the morphing wing is fabricated, and the actuation capabilities of the single MFC-PBAs and morphing wing are tested. The experimental and FE simulation results satisfactorily agree. The results show that at the peak driving voltage, with axial compression forces of 18 and 27 N applied to the side and middle MFC-PBAs, respectively, the deflection angle of the morphing wing reaches ±12°, which is twice that of the morphing wing without compression; and its blocking force is maintained at 1.682 N; thus, its output work has doubled. The multiphysics model of the proposed morphing wing under airflow is established to evaluate the deformation capability. The results show that the present morphing wing achieves a deflection of 5.04° on the side of the incoming flow direction, and a unit lift of 249.1 N/m at an air speed of 40 m/s and angle of attack of 15°. Consequently, the proposed morphing wing exhibits a high deformation capability. We expect the proposed morphing wing will be used for the flight control of mini-UAVs at higher speeds and larger sizes.

Towards an accurate CFD prediction of airflow and dispersion through face mask

Given the difficulty of experimental measurement of respiratory airflow and dispersion through a face mask, accurate numerical simulation is an important method to increase the understanding of the health effect of face masks and to develop high-performance ones. The objective of this study is to develop such an accurate modeling framework based on computational fluid dynamics (CFD) theory and method. For model validation, the flow characteristics through the face mask were tested experimentally, and the air speed and exhaled pollutant concentration in the breathing zone were measured with human subjects. The influence of gird division, time step size, and turbulence model on simulation accuracy were investigated. The result shows that the viscous resistance coefficient and inertial resistance coefficient of face masks (surgical masks) were 3.65 × 109 and 1.69 × 106, respectively. The cell size on the surface of face masks should not be larger than 1.0 mm; the height of the first layer cells near the face masks should not be larger than 0.1 mm; and the time step sizes discretizing the breathing and coughing periods should not be more than 0.01 s and 0.001 s, respectively. The results given by LES model show closer agreement with the experimental data than RANS models, with approximately 10% relative deviation for the air speed near the face mask. Overall, the SST k-ω model performs the best among the RANS models, especially for the air speed. The findings obtained form a CFD modeling framework for an accurate prediction of airflow and dispersion problems involving face masks.

A Semi-Automatic Data Management Framework for Studying Thermal Comfort, Cognitive Performance, Physiological Performance, and Environmental Parameters in Semi-Outdoor Spaces

Semi-outdoor space can be used as an alternative to short-term office activities to save office energy consumption and promote a healthy and nature-based working environment. This study evaluated the suitability of semi-outdoor space in four aspects including environmental measurements, physiological measurements, subjective measurements and cognitive performance tests. However, the manual processing and analysis of such multidimensional data can be time-consuming and error-prone. Hence, the objective of this study was to develop a semi-automatic method to manage and analyze the data from different instruments and platforms and two open-source applications (a stroop color and word test and a digit span test) for cognitive performance tests. These codes were critical to the success of the project, providing an effective framework for data extraction, data pre-processing, data analysis and performance tests. Eighty-nine people participated in the experiment of evaluation of thermal comfort, cognitive performance, physiological performance and environmental parameters in semi-outdoor spaces in a tropical setting. Each participant received cognitive tests to assess their selective attention, short-term memory, concentration and creativity quotient. Concurrently, qualitative measurements were conducted to assess thermal sensation, thermal comfort and thermal acceptability. The heart rate, skin temperature, and skin conductance of participants were measured throughout the experiments. Microclimatic variables such as illuminance, noise levels, dry-bulb air temperature, global temperature, relative humidity, air speed, and air direction were monitored simultaneously. To understand the effects of semi-outdoor spaces on participant performance, this study recorded participant performance in different environments through controlled experiments. Data related to participants in different settings include those shared (e.g., environmental measurement), and data unique to each participant (e.g., physiological performance). The results revealed that the subjects’ cognitive and physiological performance did not change significantly after switching to the semi-outdoor space due to the availability of natural and mechanical ventilation, suggesting that short-term office activities in the semi-outdoor space are feasible in the tropics.

Methods for detecting heat stress in hutch-housed dairy calves in a continental climate

Dairy calves exposed to solar radiation, elevated ambient temperature, and humidity are at risk of impaired welfare and productivity. Initial detection of thermal discomfort requires determination of optimal heat stress indicators and thresholds. Such values have recently been established in calves in chronic, subtropical, and acute continental environments but not in continuous, temperate conditions. Herein, the objectives were to determine associations between animal-based and environmental heat stress indicators and establish environmental breakpoints for hutch-raised dairy calves during a continental summer. From June to August, dairy calves (n = 63; 14 to 42 d of age) were individually hutch-housed and managed according to the dairy standard operating procedures in Arlington, Wisconsin. Calf respiration rates (RR), rectal temperatures (RT), shaved or unshaved skin temperatures (ST), and hutch internal and external air speed were measured thrice weekly at 0700 and 1400 h after a 15 min hutch restriction. Environmental indices including dry bulb temperature (Tdb), black globe temperature, and relative humidity were measured every 15 min, averaged hourly, and used to calculate temperature-humidity index (THI) using 8 different equations (THI1-8). Correlation and linear regression models were used to determine relationships within and between animal-based and environmental indicators. Environmental breakpoints were established using segmented regression models to estimate THI and Tdb thresholds for abrupt changes in animal responses. There were strong, positive correlations between animal-based indicators and Tdb or THI1-8, with the strongest association observed between unshaved ST and Tdb (r = 0.80). The linear regression of animal-based indicators with the best fit included Tdb or Tdb plus relative humidity and air speed. The threshold at which RR and RT began to rise was at a THI of 69 for both or at a Tdb of 21.0 or 21.5°C, respectively. No threshold was established for ST. Together, these outcomes indicate that Tdb is an appropriate measurement to detect thermal discomfort for calves in a temperate summer climate and individual hutch housing. Monitoring of calves is warranted before ambient temperature reaches 21.0°C, corresponding to RR of 40 breaths per minute and RT of 38.5°C, to promote calf comfort and reduce the risk of hyperthermia-related welfare and productivity consequences.

Occupant's preferred indoor air speed in hot-humid climate and its influence on thermal comfort

As an energy-efficient and high-comfort indoor environment control method, the rational application of airflow in modern buildings has brought renewed attention, especially in hot and humid areas. Chamber experiments were conducted to examine occupants’ preferred air speed and its effects on thermal comfort in hot-humid climate, and the extended thermal comfort zone limit was obtained. Three temperature levels (26 °C, 29 °C, and 32 °C) and two relative humidity levels (40%–60% and 70%–90%) were set, achieving six experimental conditions. During each condition, thirty-six participants were sequentially exposed to two stages with still air and personal controlled stable mechanical airflow produced by electric fans, each lasting 30 min. Their subjective perceptions were collected repeatedly, and skin temperature was measured continuously. For the six conditions, the average preferred air speeds were estimated to be 0.53 m/s, 0.62 m/s, 1.06 m/s, 1.31 m/s, 1.28 m/s, and 1.48 m/s respectively. The preferred air speed at high humidity (70%–90%) was approximately 0.15 m/s-0.3 m/s higher than that at moderate humidity (40%–60%), and such difference increased with air temperature. Elevated air speeds may be used to offset thermal discomfort, as indicated by a 0.2°C–0.5 °C significant decrease in the mean skin temperature and improvements in subjective perceptions. However, for extremely hot and humid conditions including 29 °C/85%, 32 °C/55%, and 32 °C/85%, the discomfort cannot be completely eliminated. When local control of airflow is provided to occupants, the acceptable operative temperature range could be extended by approximately 1 °C regardless of humidity, compared with that under near still air speed below 0.1 m/s.

Event-Specific Transmission Forecasting of SARS-CoV-2 in a Mixed-Mode Ventilated Office Room Using an ANN.

The emerging novel variants and re-merging old variants of SARS-CoV-2 make it critical to study the transmission probability in mixed-mode ventilated office environments. Artificial neural network (ANN) and curve fitting (CF) models were created to forecast the R-Event. The R-Event is defined as the anticipated number of new infections that develop in particular events occurring over the course of time in any defined space. In the spring and summer of 2022, real-time data for an office environment were collected in India in a mixed-mode ventilated office space in a composite climate. The performances of the proposed CF and ANN models were compared with respect to traditional statistical indicators, such as the correlation coefficient, RMSE, MAE, MAPE, NS index, and a20-index, in order to determine the merit of the two approaches. Thirteen input features, namely the indoor temperature (TIn), indoor relative humidity (RHIn), area of opening (AO), number of occupants (O), area per person (AP), volume per person (VP), CO2 concentration (CO2), air quality index (AQI), outer wind speed (WS), outdoor temperature (TOut), outdoor humidity (RHOut), fan air speed (FS), and air conditioning (AC), were selected to forecast the R-Event as the target. The main objective was to determine the relationship between the CO2 level and R-Event, ultimately producing a model for forecasting infections in office building environments. The correlation coefficients for the CF and ANN models in this case study were 0.7439 and 0.9999, respectively. This demonstrates that the ANN model is more accurate in R-Event prediction than the curve fitting model. The results show that the proposed ANN model is reliable and significantly accurate in forecasting the R-Event values for mixed-mode ventilated offices.