Optimal Air Research Articles

Quality-based selection of the optimal hot air gradient drying method for anchovy and modeling of drying kinetics

The aim of this study was to investigate the effects of hot air gradient drying on anchovy drying quality and efficiency. Anchovies were initially dried at 40 °C to until their moisture content was 40%, 45%, 50%, 55%, 60%, and 65% respectively, followed by a second drying stage at an increased temperature of 60 °C until the moisture content reached 40%. Six drying models were selected to fit the anchovy drying curves, and the Page model was found to be conformed the anchovy drying model. The drying time decreased by a minimum of 8.3% and a maximum of 33.3% as the moisture content at the turning point rose. In addition, the rehydration rate of dried anchovies increased and then decreased with increasing moisture content, while the TBA and TVBN values decreased and then increased, and there were differences in the textural properties of drying at different moisture contents. Among them, the dried anchovies with a moisture content of 55% at the turning point had the highest rehydration ratio, the lowest TBA and TVBN values, and better textural characteristics.

Impact of modified ventilation strategies on water evaporation rate and thermal comfort in an indoor swimming pool by numerical study

The evaporation rate from a pool surface and the thermal comfort of bathers were evaluated numerically in a swimming pool enclosure in Canada while modifying the ventilation strategies, aiming to reduce trichloramine (NCl3) concentrations in the breathing zone. Air movement is required near the pool surface to remove NCl3 emanating from the water, but this airflow may cause unwanted thermal discomfort and water evaporation increase. A reference case based on the existing conditions and four simulated cases with varied ventilation strategies were evaluated to assess the impact on the water evaporation rate and thermal comfort. We implemented a water evaporation model in the Fire Dynamics Simulator (FDS) code to study how the modified airflow patterns may impact the evaporation rate. We also determined with a PMV modified index how thermal comfort of bathers with wet and dry skin is affected by the modified airflow of each case. Our findings show that adding deck level air extraction vents allow 41% NCl3 reduction without negatively impacting thermal comfort and with only a 4% water evaporation increase. Conversely, with commonly used dilution ventilation strategy and remaining within ASHRAE's recommendations for the airflow rate, we obtain only a 3% NCl3 reduction but up to 51% of dissatisfied bathers (with a local peak of 99%) for a “cool” environment. Water evaporation rate is also increased by 16%. Numerical airflow simulation is recommended as a tool to plan an optimal ventilation strategy balancing air quality, energy expenditure and thermal comfort in indoor aquatic environments.

Functional evaluation of air insoles and methodology for determining the optimal thickness according to weight group

This study evaluates the effectiveness of four air insoles with varying thicknesses and one typical insole by measuring the total muscle activity, total muscle fatigue, left/right foot pressure symmetry ratio, and subjective fatigue among participants in three weight groups (<50, 50–70, and >70 kg). To minimize cumulative fatigue among participants, only one type of insole was tested per day. The 0.6- to 1.0-cm thick air insoles have a positive impact on muscle activity, muscle fatigue, and subjective fatigue compared to the typical 0.8-cm insoles. In terms of subjective fatigue, the 0.6-, 1.0-, and 1.2-cm air insoles yielded lower fatigue levels in the <50 kg group; however, the 50–70 kg group exhibited the lowest fatigue level when wearing the 0.8-cm air insoles. The proposed methodology may provide reference for optimal air insole thickness for users of varying weight ranges.

Grey-box model-based demand side management for rooftop PV and air conditioning systems in public buildings using PSO algorithm

As the major power consumer in buildings, Heating, ventilation and air conditioning (HVAC) systems can significantly contribute to the economical operation of the power system during the peak periods in summer or winter, by flexibly responding to the grid demands. Indoor air temperature set-point resetting is a typical passive demand response (DR) control strategy that have potentials to be widely implemented by inverter air conditioners in residential buildings. However, in the existing small and medium-size public buildings, the compressor motor of HVAC systems mostly does not allow for stepless speed changes. This means that the indoor temperature set-point resetting strategy may results in frequent on/off switching of the chiller plant, leading to a compromised lifespan. Although rooftop photovoltaic systems (PVs) are expected to be widely adopted in new buildings, their potential for peak load shaving or valley load filling has received limited investigation. This study proposes a grey-box model-based demand side management (DSM) method for variable air volume systems (VAVs) and rooftop PVs in public buildings. The DSM method utilizes the particle swarm optimization (PSO) algorithm to determine optimal indoor air temperature and/or evaporator outlet water temperature set-point schedules for the VAVs, as well as optimal charging/discharging schedules for the storage battery of rooftop PVs. This approach aims to reduce the peak power demands of the integrated system without causing severe thermal discomfort, increasing chiller mechanical costs (refers to frequent on/off switching of the chiller plant in this paper), or overcharging/over-discharging of storage batteries. The results of case studies demonstrate that the strategy of co-resetting indoor air temperature – evaporator outlet water temperature set-points outperforms the indoor air temperature set-point resetting strategy in terms of both peak power demands reduction and mechanical cost saving when applied to the VAVs in low performance buildings. In comparison, for the VAVs installed in normal buildings, both the strategies yield significant decreases in peak power demands and mechanical cost by fully utilizing the thermal capacity of the building internal thermal mass. Furthermore, by implementing the DSM method for rooftop PVs, the integrated system can achieve zero or near-zero net power demands during the DR periods. The proposed DSM method can also be utilized in valley load filling programs to facilitate the accommodation of renewable energy.

Design and performance analysis on a breathing-type instant heat recovery module for fresh air ventilation

The process of air exchange in buildings is essential for maintaining optimal indoor air quality. However, this process results in the loss of thermal energy in the form of sensible heat carried by the air, thereby increasing the energy demand of the buildings. In order to recover this thermal energy, the present study introduces a breathing-type instant heat recovery module for fresh air ventilation, inspired by the biological nasal breathing process. The performance of this module was thoroughly investigated through Fluent simulation and experimental tests. Based on the simulation results, the module exhibits the capability to decrease the outdoor air temperature by an average of 7.5 ℃ prior to its entry into the room. Consequently, this leads to a daily energy conservation of approximately 2.354 kW·h, accompanied by an energy recovery rate of 62.9 % under typical summer conditions. Notably, the heat recovery performance is more favorable during winter, resulting in daily energy savings of about 5.446 kW·h and an energy recovery rate of 62.2 %. The conducted experiments substantiate that the module is able to recuperate approximately 70 % of heat when the indoor temperature is set at 22 °C, while the outdoor temperature reaches its lowest point at 6 °C. The study describes an effective heat recovery technology for building air exchange using a breath-type instant heat recovery module. This could offer a new energy-saving solution for the renovation of fresh air systems.

Numerical simulation of the dust pollution characteristics and the optimal dustproof air volume in coal washing plant screening workshop

Dust pollution generated during the working process of a screening workshop in a coal washing plant seriously threatens the occupational health of workers. To improve the working environment for workers, we investigated the effects of various airflow parameters on the diffusion of dust particles and pollutants. We established a proportional model of the screening workshop and conducted spatiotemporal analysis of the evolution laws of airflow and particulate matter. We used numerical simulation and on-site measurements to obtain the optimal dust removal air flow rate in a coal washing plant workshop. When the air flow rate is between 360 and 1260 m³/min, the overall dust concentration in the workshop and the average dust mass concentration in the breathing zone decrease significantly as the air flow rate increases. However, if the air flow rate is too high, this can cause re-entrainment of dust, which will pollute the operation area again. The optimum dust removal airflow for the inlet air was 1260 m³/min. This air flow rate decreases the dust at the height of the breathing zone in the working area, and the dust concentration at the sidewalk in the working area decreases by 58.82%. This air flow rate can act as a reference value for workshop ventilation design to provide a clean and safe production environment for coal miners. Our methodology and results are of value the formulation and development of effective dust control and clean production technologies.

Thermal behavior of flexible and breathable sandwich fibrous polyethylene glycol (PEG) encapsulations

Textiles incorporating phase change material have attracted increasing attention due to their temperature regulating function. Although a great progress has been made in the development of phase change material textiles, it has been found that the loading amount of phase change materials is limited by other final properties. Recently, we have proposed a sandwich fibrous phase change material encapsulation with a relatively high phase change material loading amount, which is a multi-layer fabric structure containing phase change material. However, the breathability of sandwich fibrous phase change material encapsulation should be improved because there is no path for air to penetrate through. In this work, the sandwich fibrous phase change material encapsulation structure with polyethylene glycol as phase change material is modified by introducing different air pockets in the thermal function layer ranging from 19% to 64%. The leakage phenomenon, phase transition behavior, thermal energy storage, breathability, T-history and practicality of the breathable sandwich fibrous phase change material encapsulations are investigated. As a result, the maximum polyethylene glycol loading amount of the phase change materials pocket is 83 wt%, and there is no leakage of polyethylene glycol during working time. The overall enthalpy value of the breathable sandwich fibrous phase change material encapsulation ranges from 27 J/g to 48 J/g. The optimal air permeability and water vapor resistance of the breathable sandwich fibrous phase change material encapsulation is 9 mm/s under 100 Pa and 34.5 m2 Pa W−1. Furthermore, the heterogeneous heat transfer through the breathable sandwich fibrous phase change material encapsulation is found due to the complicated thermal resistances of the hybrid thermal functional layer. In addition, for breathable sandwich fibrous phase change material encapsulation, the flexibility, hydrophobicity, self-cleaning property, abrasion resistance, and stability after water immersion are found. We believe the research has a great potential in various applications related to phase change material.

Simulation-Driven Strategies for Improving Natural Ventilation in Educational Spaces: A Case Study of An Educational Building in Sari

Any architectural space, especially the architecture of an educational complex, should provide comfort for human beings in the face of geographical and climatic characteristics. Climatic factors have always profoundly affected the formation of the physical environment of buildings. Energy demand has always been one of society’s most critical issues. Saving resources is one of the architectural design goals to achieve a suitable environment-friendly architecture. This architectural approach, which comes from the concepts of sustainable development, is one of the basic human needs in the current world due to its compatibility with the environment. The goal is to build constructions that can improve the climate, prevent the waste of energy consumption, and avoid the adverse effects of construction on the environment. In traditional Iranian architecture, there are numerous passive methods; natural ventilation is an essential part of Iranian conventional building design, which is being ignored today. Since humid and moderate climates have high relative humidity on most days of the year, one important goal is to move the stagnant moisture inside to establish a suitable thermal environment for occupants. The research method of the present study is descriptive-analytical, which has been experimented with according to library studies in addition to climate and meteorological data. Then, analysis of the data is provided by an energy simulator. It is concluded that the best orientation of the educational building is south, which can provide proper natural ventilation and solar heat gain. In other words, optimal interior air quality is achieved in this orientation.

Machine Learning-based Calibration Approach for Low-cost Air Pollution Sensors MQ-7 and MQ-131

Air quality is a vital concern globally, and Sri Lanka, according to WHO statistics, faces challenges in achieving optimal air quality levels. To address this, we introduced an innovative IoT-based Air Pollution Monitoring (APM) Box. This solution incorporates readily available Commercial Off-The-Shelf (COTS) sensors, specifically MQ-7 and MQ-131, for measuring concentrations of Carbon Monoxide (CO) and Ozone (O3) ,Arduino and "ThingSpeak" platform. Yet, those COTS sensors are not factory-calibrated. Therefore, we implemented machine learning algorithms, including linear regression and deep neural network models, to enhance the accuracy of CO and O3 concentration measurements from these non-calibrated sensors. Our findings indicate promising correlations when dealing with MQ-7 and MQ-131 measurements after removing outliers.

Indoor pollution control based on surrogate model for residential buildings

Individuals typically spend most of their lives indoors, predominantly in spaces like offices and residences. Consequently, prolonged indoor exposure underscores the critical significance of maintaining optimal indoor air quality (IAQ) to safeguard one's health. The primary impediment to attaining efficient regulation of Indoor Air Quality (IAQ) is the challenge of monitoring the IAQ parameters, particularly within the immediate vicinity of an individual's breathing space. Current heating, ventilation, and air conditioning systems lack the ability to rapidly predict and optimize the quality of indoor air. The objective of this study is to acquire the distribution features of indoor pollutants and precise indoor environment data in order to efficiently forecast and enhance the IAQ. To achieve this objective, a proposed surrogate model was developed using computational fluid dynamics (CFD). Notably, the Kriging surrogate model can rapidly predict IAQ while using a limited number of CFD runs. CFD are widely used as numerical simulation methods to obtain the accurate information. Surrogate models can rapidly forecast indoor environmental conditions using CFD simulation data simultaneously. Optimization algorithms can efficiently achieve desirable indoor ambient conditions, offering highly effective and intelligent control techniques for indoor atmospheric ventilation.

Air exchange rate as a means of ensure requirements to air purity on the basis of high-efficiency filters

In the context of a constant increase in air pollution, the question arises of creating safe air zones with quality control of the air environment in places where people stay. The constant deterioration of air quality caused by military operations and their consequences, as well as the need to reduce the consumption of available energy resources, requires studying the recommendations on the optimal air exchange rate of existing European and American air quality requirements in residential and office buildings to achieve the required air quality with minimal energy consumption. The objectives of the study were to obtain data on the efficiency of air purification in a given volume at different air exchange rates. A separate task was to check the data declared by the manufacturer on the pressure drop across the filter with an increase in the volume of air passing through it. CleanZone5300 filtration systems with F9 class filter and HEPA H12/13 class filter were considered, which can provide an air exchange rate of 2 to 10 times. In a room volume of 225.9 m3, at a temperature of 18 ˚C, a relative humidity of 57-59 % and an initial number of particles in the room air of 533,440 particles/ft3 (15105 particles/m3), the ability of filtration units to purify the air at different rates was studied. It was concluded that even with a factor of 2, the filtration system can provide air purification up to 40 % when using the F9 filter and up to 60 % when using the HEPA H12/13 filter in a short period of time. Recirculation filter units are considered as the easiest way to increase the air exchange rate in the room, in our climatic conditions. With the possibility of avoiding the processing of air for heating or cooling when using outside atmospheric air. In the installations used in the study, the electrical power consumption of the fans is 300 W per hour. The conclusions of the study need to be tested in office premises with an existing ventilation system to determine the optimal multiplicity of achieving a given air quality when using filters or portable filter units.

Determining optimal air leak resolution criteria when using digital pleural drainage device after lung resection

ObjectiveThere is limited clinical evidence to support any specific parenchymal air leak resolution criteria when using digital pleural drainage devices following lung resection. The aim of this study is to determine an optimal air leak resolution criteria, where duration of chest tube drainage is minimized while avoiding complications from premature chest tube removal. MethodsAirflow data averaged at 10-minute intervals was collected prospectively using a digital pleural drainage device (Thopaz; Medela) in 400 patients from 2015 to 2019. All permutations of air leak resolution criteria from <10 to 100 mL/minute for 4 to 12 hours were applied retrospectively to the pleural drainage data to determine air leak duration, and air leak recurrence frequency and volume. Air leak recurrence indicates potential for rather than occurrence of adverse events. Descriptive statistics were used to identify the optimal criteria based on patient safety (low frequency and volume of air leak recurrences), and efficiency (shortest initial air leak duration). ResultsThe majority of the 400 patients underwent lobectomy (57% [227 out of 400]), wedge resections (29% [115 out of 400]), or segmentectomies (8% [32 out of 400]) for lung cancer (90% [360 out of 400]). An airflow threshold <50 mL/minute resulted in longer air leak duration before meeting the criteria for air leak resolution (P < .0001). Air leak recurrence frequency and volume were greater in patients with a monitoring period <8 consecutive hours (P < .0001). ConclusionsWhen using a digital pleural drainage device, a postoperative air leak resolution criteria <50 mL/minute for 8 consecutive hours was associated with the best safety and efficiency profile.

The effect of tree shading on soil temperature at Arabica coffee plantation (Coffea arabica L.)

Coffee is a group of plants that require partial light (C3), whose cultivation combines the use of shade trees and cultivated plants with the aim of increasing production and maintaining the microclimate around the cultivated plants. The shade provided by shade trees will have a significant effect on soil temperature and water content. The growth and development of a cultivated plant is strongly influenced by water content, on the other hand, water content also affects soil temperature. The optimal air temperature needed by Arabica coffee plants is 18-21°C, while the soil temperature suitable for Arabica coffee plants is 21°C. The research was needed to determine the effect of shade tree type on the soil temperature of Arabica coffee plants. This research was at the Koperasi Ribang Gayo Musara, Pantan Musara Village, Pegasing Subdistrict, Central Aceh District, Aceh Province. This research used a non-factorial randomized block design with five treatments and four replications. Treatments consisted of shade tree type on coffee plants were control/no shade, small lamtoro shade (Leucaena leucocephala ssp. leucocephala), big lamtoro shade (Leucaena leucocephala subsp. glabrata), banana shade (Musa paradisiaca L.), avocado shade (Persea americana Mill.). The results showed that the shade tree type had a significant effect on soil temperature at a depth of 0, 10, and 20 cm. Coffee plants that were shaded by avocado trees have better temperatures for coffee plants and can reduce soil temperature until they reach optimal temperatures.

Relationships between Air Pollutants and Meteorological Factors during Southwest and Northeast Monsoon at Urban Areas in Peninsular Malaysia

People who currently live in urban areas are subjected to significantly higher levels of exposure to air pollution. Pollutant concentrations in the air change according to the weather, the locations of the many sources of pollution, and the topography of the area. This study examines the link between meteorological parameters (ambient temperature, relative humidity, and wind speed) and daily air pollutant concentrations in four monitoring stations at Peninsular Malaysian cities (Seberang Perai, Pasir Gudang, Batu Muda, and Kemaman) during southwest and northeast monsoon. Pearson Correlation Analysis analyzed air quality data over two years (January 2016 - January 2018). The study found that PM10 concentrations were highest at all monitoring locations. At all monitoring locations, climatic parameters correlated with NO2, PM10, and CO. Air pollution and meteorological conditions correlate weakly to moderately during the southwest monsoon. The investigation found that weather conditions affect O3 most during the dry season. CO and climatic parameters correlated weakly at all four monitoring stations during the northeast monsoon. PM10 correlated positively with ambient temperature and negatively with relative humidity and wind speed at all four stations. The northeast monsoon correlation values were weak to moderate. This study will help officials identify optimal air pollution controls for metropolitan areas during monsoon seasons in line with SDG-11, which promotes sustainable cities and communities.

Optimizing slug bubble size for application of the ultra-thin flat sheet membranes in MBR: a comprehensive study combining CFD simulation and experiment.

Optimizing the slug bubble size specifically for ultra-thin flat sheet membranes in MBR systems can effectively enhance the scouring force and improve fouling control efficiency, thereby further advancing their targeted and widespread application. In this study, a three-dimensional model was developed based on the practical application to investigate the impact of slug bubbles on scouring performance in ultra-thin flat sheet MBR systems, encompassing their evolution, disturbance level, and shear stress. A membrane fouling probability index for quantifying the distribution of membrane fouling, along with a turbulence intensity index have been proposed. The findings revealed that the 20-mL slug bubble induced the highest disturbance level in the surrounding fluid, characterized by an instantaneous peak velocity of 0.63m/s at the local system level, conducive to bubble scouring. And exerted the greatest shear stress effect, achieving the most effective reduction in membrane contamination, with a maximum shear stress of 1.82Pa. The experimental validation conducted during the operational cycles confirmed that the scouring effect of 20-mL slug flow yielded in a maximum proportion of 48.16% within the low fouling probability region. The results provided evidence supporting the assertion that specific aeration conditions producing 20mL of bubbles resulted in minimal membrane fouling, ensuring a more pronounced scouring effect. The combination anythsis of slug bubble characteristics and behaviors, integrating theoretical and experimental approaches, implied that 20mL was the optimal bubble size in ultra-thin flat sheet MBR, which fulfilled the optimal air scouring effect.

Filter Cleaning System Modification to Improve Dust Colletor

The filter cleaning system is part of the dust collector which functions as a filter between dirty air and clean air. Blockage of the dust collector is due to a lack of maintenance to control the performance of filter cleaning components such as valves, jetspray tubes and bagcloth. Another cause is the less than optimal air pressure from the jetspray to dislodge the dust adhering to the bagcloth. So it is necessary to recondition both the layout of the filter cleaning components and the optimization of jet spray pressure. Determination of the capacity of the jetspray tube is adjusted to the specifications of the compressor and uses the ASME VIII Div I (Pressure Vessel) standard with dimensions of 1400mm x 8inch SCH20. The feasibility test of the jetspray tube is carried out by calculating the allowable thickness and the factor of safety based on the pressure operated on the jetspray tube. Determining the location of the filter cleaning components is based on aspects that make it easier for the operator to carry out the maintenance so that the performance of the filter cleaning components can be controlled properly. Based on the stress simulation using solidworks 2020 for the SCH20 pipe which has a thickness of 6.35mm operated with a pressure of 7 bar it is categorized as safe to use.

Optimization of Air Supply Conditions for Large Space Radiant Air Conditioning Based on Response Surface Analysis

In large spaces, the comfort control of radiant air conditioning systems still has deficiencies. Mainly reliant on traditional parameter control methods, the interaction effects of diverse operating conditions are not taken into account, and the control results are still in need of optimization. To improve indoor air conditioning comfort control and address gaps in existing research, the response surface analysis method combined with numerical simulation is applied to determine the optimal air supply conditions for large-space radiant air conditioning. With the real model as a reference, simulations are carried out in Airpak, selecting four factors: supply air temperature, supply air humidity, air supply volume, and air supply angle for the response surface design. Discussions on interaction effects are carried out based on the simulated results of various scheme designs, determining eight groups of air supply schemes with the highest comfort. The research concludes that the response surface analysis method, considering the interactive effects of impacting factors, can lead to the strategy of high comfort and reasonable air supply conditions. Additionally, a set of recommendations are proposed for future practical application and promotion.

Control of Aerodynamic Characteristics of Thick Airfoils at Low Reynolds Numbers Using Methods of Boundary Layer Control

The article explores flow behavior around thick airfoils at low Reynolds numbers and the potential application of energy methods to manipulate the flow field for increased lift and reduced drag. The study relies on a set of propulsion airfoils calculated using a combined approach of solving the inverse problem of aerodynamics and applying stochastic global optimization methods. The calculations consider the transition from laminar to turbulent flow regimes, which significantly affects lift and airfoil drag. The suitability of different turbulence models for airfoil modeling in low Reynolds numbers is discussed, and numerical simulation results determine the lift coefficient dependence on angle of attack and the optimal air flow rate taken from the airfoil surface for each angle of attack. The accuracy of different turbulence models is analyzed by comparing numerical simulation results to physical experiment data.

Multi-objective optimization of thermal management system for multiple heat source arrays electronic chassis in a noiseless environment

Effective thermal management of electronic chassis is currently a critical concern. A heat sink with fins and heat pipes is suggested in this paper. It is intended to handle the heat produced by numerous sources within an electronic case and enhance its functionality. The parameters have been examined and improved in order to work quietly. Response surface methodology (RSM) was employed to examine the influence of fin length, fin thickness, fin spacing and Re on the junction temperature, temperature uniformity and thermal resistance of the heat sink for a printed circuit board array (PCBA). The parameter combinations were optimized using a genetic algorithm. The results indicated that the optimal fin spacing is 11 mm, optimal length is 199 m, and optimal thickness is 2.9 mm when the Reynolds number falls within the range of 2000 ≤ Re ≤ 7000. Compared to the original fins, the combined finned heat pipe heat sink decreases the temperature of the PCBA junction by approximately 10 K, enhances the temperature uniformity by around 49 %, and diminishes the total thermal resistance by nearly 48 %. The optimal air velocity is approximately 0.41 m/s. The improved heat sink can efficiently enhance the thermal management of electronic casings.

Performance analyses of basic cogeneration basic cogeneration plants in agriculture and food production

Energy in agriculture and in food production have vital importance that affect directly the cost and the quality of the products. Micro cogeneration plants are widely used in the World to produce heat and electricity at the same time in a same plant. The aim of this study, to analyze the performance of the production of power and heat for the food production process and the agricultural needs. For that reason, a basic cogeneration plant is taken to analyze the performance by using 1st and 2nd laws of thermodynamics and exergy analysis method. The electric-heat exergy rates, the energy and exergy efficiencies, the combustion chamber and the gas turbine outlet temperatures, the total electric and heat energies and exergies, and the specific works were calculated for various ambient temperatures and for various excess air rates of the basic cogeneration plants fueled with methane. The effects of the various ambient temperatures and the various excess air rates on the performance of the basic cogeneration plants were obtained, discussed and analyzed. For the best performance and for the best working conditions of the basic cogeneration plants in agriculture and food production process and food industry recommendations were done. It was found that, lower ambient temperatures give higher electric efficiency, but lower heat efficiency. However, an optimum excess air rates for the best performance was found at the value 2.3 of the excess air rates of the basic cogeneration plants fueled with methane.