Air Balance Research Articles

Comparative Evaluation of HFC‐134a Decompositions Over Metal‐Impregnated γ‐Al2O3 Catalysts (M/γ‐Al2O3) (M = Mg, Ni, Co, Zn, Cu)

Al2O3, widely used in the catalytic decomposition of fluorocarbons, is known to be rapidly deactivated owing to its transformation to AlF3. Accordingly, in this study, metal‐impregnated γ‐Al2O3 catalysts (M/γ‐Al2O3) were synthesized and their long‐term stabilities for HFC‐134a decomposition were investigated under the conditions of 10,000 ppm HFC‐134a in air balance. Although γ‐Al2O3 and Mg/γ‐Al2O3 demonstrated long‐term activities, significantly longer than those of the other catalysts, activity of γ‐Al2O3 rapidly decreased, whereas that of Mg/γ‐Al2O3 gradually decreased. Although Mg/γ‐Al2O3 exhibited the smallest Brunauer‐Emmett‐Teller specific surface area among those of the synthesized catalysts, it demonstrated excellent long‐term stability and the lowest deactivation rate due to the high total amount of weak acid sites. Mg/γ‐Al2O3 exhibited considerably smaller crystal size of AlF3 compared to other catalysts. Additionally, after HFC‐134a decomposition, the morphology of Mg/γ‐Al2O3 was clearly less modified and metal agglomeration was lower than those of other catalysts. Finally, this was caused by the reaction of Mg with HF, forming MgF2, which inhibited the complete conversion of γ‐Al2O3 to AlF3 and produced AlOFX, an intermediate compound. These results suggest that Mg impregnation in γ‐Al2O3‐based catalysts is a suitable method for enhancing the performances of these catalysts in the long‐term decomposition of HFC‐134a.

A fast wide-range air balancing control method based on deep reinforcement learning

Air balancing is a crucial technology for reducing energy consumption in ventilation ducts and improving indoor environmental quality. Existing air balancing methods face challenges due to the complex and diverse internal duct topologies of ventilation duct systems, as well as the strong coupling of airflow between branches, making air balancing tuning difficult. To address the slow convergence speed and difficulty in precise control of air balancing in multi-branch ventilation systems, this paper proposes a fast wide-range air balancing control method based on deep reinforcement learning (DRL-AB). A system airflow control process with Markovian properties is designed, with state, action, and reward functions oriented towards reducing airflow errors. A dynamic single-branch target training mechanism is designed to reduce training costs while improving the agent’s training efficiency and its ability to generalize to different target airflow levels. The proposed method’s performance under various target airflow conditions is verified through experimental platforms. The results indicate that, in all test cases, the maximum percentage error is controlled within 3.33%, ensuring rapid and accurate convergence of a wide range of target airflows. This demonstrates strong universality, prevents waste of airflow energy, and enhances energy utilization efficiency.

How to improve the thermal performance of buildings with one simulation run? The heat exchange index applied to hot climates

Improvements in the thermal and energy performance of buildings usually involves techniques with high computational costs, such as multi-objective optimization and parametric simulation. However, sometimes, achieving the optimal case is not desirable, though only the refinement of thermal performance. Hence, methods that enable this analysis are helpful for designers and researchers. Then, this study proposed a framework based on the Heat Exchange Index to assist thermal performance analysis of buildings. The framework consists of two phases and begins by exploring air and surface heat balance derived from the base case building simulation. This analysis is based on the Heat Exchange Index, an index developed in this work, and its result indicates the impact of each heat exchange on the thermal performance. The next phase is the improvement, where strategies are defined and implemented, and the thermal performance of the improved case is evaluated against the base case. A single-family house was modeled using EnergyPlus to demonstrate the framework application. Results showed that the Heat Exchange Index could be used to enhance the thermal performance of buildings since the strategies adopted in the base case increased its thermal autonomy and decreased thermal load.

Numerical modeling of the thermal characteristics of a fan spray cooling tower

The work constructs a mathematical model of the heat and mass transfer process in a spray cooling tower. The mathematical model consists of the equations of motion and heat and mass transfer of water droplets and the equations of thermal and material balance of moist air, considers the polydispersity of the droplet flow and allows to calculate the cooling capacity of the cooling tower depending on the parameters of the droplet flow. The mathematical model is confirmed by the results of industrial tests of irrigation-free cooling towers. The simulation results show that the cooling capacity of a spray fan cooling tower significantly depends on the atomization dispersion and the height of the water cutting nozzles. Reducing the average diameter of the droplet flow to less than 2 mm and increasing the height of the nozzles H > 4…5 m make it possible to achieve the cooling performance of known cooling towers with nozzle. The mathematical model allows to calculate the cooling capacity of the cooling tower and determine the necessary individual parameters of the droplet flow for each type of equipment and consumers for which the specific energy costs for cooling is minimal.

Impact of air entrapment on capillary absorption in porous building materials

When the water content of a porous material is high, air entrapped in the pore space is expected to affect water transfer through the pores. To understand the effects of air entrapment on water transfer in porous building materials in the high-water-saturation region, we examined the water transfer characteristics corresponding to significantly small air entrapment effects. First, we conducted two sets of water uptake experiments. In the first experiment, using three building materials, the time evolution of the amount of water absorption was measured at a low air pressure near vacuum (several kPa). In the second experiment, the water content profile during water uptake was measured using the gamma-ray attenuation method. The experimental results showed that low air pressure accelerated the water uptake by the brick and aerated concrete specimens, whereas water uptake by the calcium silicate board specimens was not significantly affected. These differences among materials were analyzed from a pore structure viewpoint. Moreover, gamma-ray attenuation measurements confirmed that the obtained water content profile was qualitatively similar at atmospheric and low air pressures, although the low air pressure increased both the water content of the material after capillary absorption and the wetting front propagation rate. Finally, simultaneous water and air transfer calculations based on the air and liquid water balance in a material reproduced the measured water absorption rates well, confirming that air entrapment and pressure development in the pores can significantly reduce the rate of water uptake and water content after capillary absorption. The calculation results also indicated that the air pressure in a material did not significantly increase at early water uptake stages where local water content was not high, which supported the general assumption that treating the liquid-water transfer in porous building materials as a one-component flow is valid in most cases.

Calculation of a heat exchanger using heat pipes in the exhaust air heat recovery system

Objective. The purpose of the work is to develop practical recommendations for the design and manufacture of a heat exchanger using heat pipes, which could find widespread use in heating, ventilation and air conditioning systems at facilities for various purposes. Method. The research is based on methods of thermodynamic analysis, full-scale and computational modeling of processes and objects of refrigeration and cryogenic technology, air conditioning and life support systems. Result. The implementation of the practical recommendations studied in the work on the use and design of heat exchangers using heat pipes in ventilation, heating and air conditioning systems will provide significant savings in energy spent on heating and/or cooling the air supplied to the room served by the HVAC system. To reduce heat loss in a building, it is rational to maintain air balance and compensate for the exhaust air with an organized influx of outside air, to heat which the heat of the removed exhaust air is utilized. Conclusion. Compared to a heat exchanger based on a glycol recuperator, a regenerator using heat pipes is less energy-intensive, requires virtually no maintenance, and is also more energy efficient due to the absence of a pumping device that requires electricity in the design. At the same time, the ability to completely separate the supply and exhaust ventilation flows of the regenerator on heat pipes is preserved, which is extremely in demand in medical institutions, due to the need to comply with strict sanitary standards.

Role of Rhizosphere on the Soil Fertility and Availability Nutrient

The review summarizes the literatures which focus on the role of rhizosphere at soil fertility and availability nutrient. Most researchers agreed that the rhizosphere could important in mediating the interactions between plant roots, soil, and microorganisms. Soil fertility and efficient nutrient acquisition are vital factors governing plant growth and productivity. The review begins by examining the physical and chemical attributes of the rhizosphere that influence nutrient availability and uptake. It delves into the intricate mechanisms of nutrient release, mobilization, and uptake, elucidating the impact of root exudates, symbiotic associations, and mycorrhizal networks on nutrient cycling. Therefore, the majority of researchers established that the rhizosphere has an equalizing influence on annual/seasonal changes regarding soil heat, air, and water balance, the availability of plant nutrients, and consequently, crop yields. Additionally, increasing soil microbial diversity through the rhizosphere and activity is explored, shedding light on the crucial symbiotic relationships that develop between plants and microorganisms to support nutrient acquisition and soil health. Furthermore, the review assesses the responses of the rhizosphere to various environmental factors such as soil types, moisture levels, and temperature fluctuations, and how these factors influence nutrient dynamics and availability.

A novel air balancing method based on an improved perceptron under multiple constraints for the energy conservation of ventilation system

Air balancing is a key technology for improving indoor environmental quality and reducing ventilation system energy consumption. Existing air balancing methods just considered damper angles and fan control voltages, combined as single constraint strategy to balance air. Fan power, as the direct parameter affecting system electricity consumption, has not been included in air balancing modelling. On the other hand, single constraint strategy makes current methods inflexible to maintain airflow accuracy and energy efficiency together. This paper proposes a novel air balancing energy-saving model with multiple constraint control strategy. Damper angle, fan control voltage, and fan power are combined by an improved perceptron model. It is aimed at minimizing ventilation system energy consumption, by achieving optimal airflow accuracy and energy conservation. The proposed improved perceptron under multiple constraints (IPMC) method is validated on the experimental system with 5 terminals, air balancing relative errors within 6.0 %. Compared with the current high-precision and energy-saving methods in references, IPMC reduces energy consumption by 12.0 % and 7.6 %, respectively, with improved airflow prediction accuracy. The proposed air balancing method has three innovation: 1) Constrained by the fan power, the IPMC method improves ventilation energy efficiency; 2) Independent and flexible constraints enable more accurate airflow control; 3) Integrated by an improved perceptron, multiple constraints consider airflow prediction accuracy and energy conservation at the same time. This method is expected to better satisfy airflow demand and reduce effectively energy consumption of ventilation system, thus improving building ventilation energy utilization efficiency without losing thermal comfort and indoor air quality.

Fuzzy prediction of the mine's ventilation structure's tunnel air volume

For the problem that it is difficult to accurately measure the air volume in the tunnel where the mine ventilation structure is located. Firstly, the tunnel air volume value is expressed by the interval number, and the air volume value of the tunnel where the ventilation structure is located is obtained by the law of nodal air balance. Then the interval number is transformed into a triangular fuzzy number to represent the tunnel air volume, the generalized induced ordered weighted average operator is introduced, the minimum-maximum closeness is used as the optimal quasi-measure, and the preference coefficient is introduced to transform the multi-objective nonlinear optimization problem into a single-objective optimization problem. And consider the temporal characteristics of the error series and the trend of the error value change for the error correction of air volume prediction error, and construct the interval combination type air volume fuzzy prediction model. Using the air volume data of a mine tunnel in Inner Mongolia, the example calculation of the model shows that the interval combination type prediction method can effectively improve the accuracy of air volume prediction in the tunnel of ventilation structures. Keywods: Error correction, Interval combination type, Interval number, Preference coefficient, Triangular fuzzy number

Elimination of the main damage of the ventilation system of the boiler premise

AbstractThe article is devoted to solving of urgent problem: creation of staff work safety in the boiler room due to ensure of required conditions by natural ventilation. The aim of the work is to eliminate the main damage of the natural ventilation system of the boiler premise by using of compact air jet due to correction coefficients and updated results. Static and dynamic air pressure, difference of static pressure due to wind, aerodynamic coefficients and air balance for necessary nature ventilation of the boiler premise as well temperature correction coefficient are established. The update calculation dependencies for determining of the air static pressure and its volume flow rate in the boiler room have been obtained. Updated graph, monogram, and analytical equations for natural ventilation calculation of boiler room are presented.

A two-phase online air balancing method for multi-zone ventilation systems based on distributed finite-time control

Air balancing (AB) is a commonly used technique to control and balance the air flow of multi-zone ventilation systems. The performance of air balancing is associated with occupant thermal comfort, indoor air quality (IAQ) and system energy consumption, which is critical to the ventilation system. However, the existing air balancing methods suffer low convergence and some even require shutdown period of the ventilation system for offline operation, causing big inconvenience and degraded ventilation performance. To fix the above issues, this paper proposes a novel air balancing method based on distributed finite-time control (DFTC). The proposed DFTC-AB method is an online method which can be performed during system operation without interrupting the ventilation service. It achieves the balance of air flow by two phases, i.e. to first proportion the ventilation system and then finely regulate the absolute quantity of each terminal flow. A revised DFTC control protocol is proposed to accelerate the convergence of terminal flow given any initial state, which significantly improves the efficiency of the air balancing process. To validate the proposed DFTC-AB method, a 5-terminal duct system is fabricated in the lab. The experimental results demonstrate that the proposed DFTC-AB method can balance the 5-termial ventilation system under various cases with satisfactory dynamic performance. The whole process of air balancing can be fulfilled within 20 min, with the highest accuracy achieving 3.2% among the tested cases.

Novel hybrid active greenhouse solar dryer with evacuated tube solar collector: energy and exergy analysis

A novel hybrid active greenhouse solar dryer (HAGSD) attached with an evacuated tube solar collector is developed for faster drying of high moisture crops. Bottle gourd is taken as the drying product and dried to 10% moisture content. The energy balance of the greenhouse room air, crop surface, floor, and PV module has been established using the first law of thermodynamics. The exergy balance is also established to predict the heat loss through the dryer more accurately. The maximum exergy efficiency of the dryer is 7.92%, and the overall thermal efficiency of the setup is 7.88%.

A Chemical Invasion on Waters and Aquatic Organisms: Bisphenol A

The main reason for the intense discharge of chemical pollutants into nature is the increase in the world population. These pollutants disrupt the natural balance in soil, water and air. However, this effect is most prominent in the aquatic ecosystem. These pollutants are considered to be predominantly endocrine disruptors (EDCs) and which well known EDC is Bisphenol A. Bisphenol A is a chemical used in making polycarbonate plastics and epoxy resins. Also it is one of the most produced chemicals worldwide and it cause serious problems to health of aquatic population. This review provides information about the discharge routes of BPA, its effects in the aquatic system and its mechanisms of action.

Winter season Southern Ocean distributions of climate-relevant trace gases

Abstract. Climate-relevant trace gas air–sea exchange exerts an important control on air quality and climate, especially in remote regions of the planet such as the Southern Ocean. It is clear that polar regions exhibit seasonal trends in productivity and biogeochemical cycling, but almost all of the measurements there are skewed to summer months. If we want to understand how the Southern Ocean affects the balance of climate through trace gas air–sea exchange, it is essential to expand our measurement database over greater temporal and spatial scales, including all seasons. Therefore, in this study, we report measured concentrations of dimethylsulfide (DMS, as well as related sulfur compounds) and isoprene in the Atlantic sector of the Southern Ocean during the winter to understand the spatial and temporal distribution in comparison to current knowledge and climatological calculations for the Southern Ocean. The observations of isoprene are the first in the winter season in the Southern Ocean. We found that the concentrations of DMS from the surface seawater and air in the investigated area were 1.03 ± 0.98 nmol−1 and 28.80 ± 12.49 pptv, respectively. The concentrations of isoprene in surface seawater were 14.46 ± 12.23 pmol−1. DMS and isoprene fluxes were 4.04 ± 4.12 µmol m−2 d−1 and 80.55 ± 78.57 nmol m−2 d−1, respectively. These results are generally lower than the values presented or calculated in currently used climatologies and models. More data are urgently needed to better interpolate climatological values and validate process-oriented models, as well as to explore how finer measurement resolution, both spatially and temporally, can influence air–sea flux calculations.

Single-screen Bark Particle Separation Can be Used to Engineer Stratified Substrate Systems

Substrate stratification is an emerging substrate management strategy involving layering multiple substrate materials within a single container to modify physiochemical characteristics of the substrate system. Specifically, stratifying allows growers and researchers to rearrange the air–water balance within a container to modify hydraulic characteristics. Moreover, fertilizer can be incorporated into just the upper strata to reduce leaching. Research to date has shown benefits associated with resource efficiency, production timing, and weed control. With the associated benefits for substrate stratification, interested growers will need pragmatic solutions for onsite trials. Therefore, the objective of this study was to identify a cost-effective solution for growers interested in exploring stratification options. As such, this research was designed to identify a single-screen bark separation to generate fine and coarse bark textures suitable for use as the top and bottom substrate strata. Loblolly pine bark (Pinus taeda) was screened with either a 4.0-mm, 1/4-inch, or 3/8-inch screen, with the particles passing through the screen (unders) separated from retained particles (overs). Stratified substrate systems were engineered with an individual screen wherein the fines were layered atop the coarse particles from the same screen. ‘Natchez’ crepe myrtle (Lagerstroemia indica) liners were planted in either of the three stratified substrate treatments or a nonstratified control. Substrate physical characteristics were assessed for each strata by pre- and postproduction properties to identify changes of substrate. The final growth index of the crop was unaffected by the substrate treatment (P = 0.90); however, stratified substrates did increase dry root weight (P = 0.02), with the smallest screen (4.0 mm) resulting in the greatest root weight. Separation of roots between the two strata indicated the presence of more roots in the upper strata in all substrates. However, the stratified substrates resulted in a greater shift in root location, encouraging increased rooting in the upper strata with fine particles, with the largest screen (3/8 inch) resulting in the greatest differentiation between upper and lower rooting. Each stratified treatment had increase in water-holding capacity in the lower (coarser) strata without changes in the upper strata. Thus, we conclude that single screens can be used to build stratified substrate systems. Moreover, screen aperture size may be used to achieve different outcomes with regard to root growth and development as well as water–air balance. Further research may indicate that screen selection may be used to target specific crop needs.

Air balancing method of multibranch ventilation systems under the condition of nonfully developed flow

Air balancing is one of the cornerstones of the building environment. Research on air balancing aims to ensure the efficient operation of ventilation systems. However, there are two challenges in the air balancing process. The first issue is accurately calculating the duct resistance under the condition of nonfully developed flow. The other obstacle is calculating the damper adjustment degree when the operating flow characteristics of the dampers are affected. Based on these two challenges, this study first proposes a pressure balance model under the condition of a nonfully developed flow for the resistance calculation. The problem of parameter identification in the model is converted into a multiobjective optimization problem and solved by the elitist nondominated sorting genetic algorithm II (NSGA-II). In contrast to the traditional pressure balance model, the average error of the resistance calculation can be reduced by 78.83%–82.24%. Second, based on the resistance characteristics (degree, airflow, pressure difference) of the dampers in the duct system, XGBoost is used for machine learning to achieve accurate adjustment of the dampers. Compared with the traditional method that requires checking manuals, the average error of the damper degree calculation can be reduced by 62.27%–94.6%. Finally, the air balancing method proposed in this study is experimentally verified, which has an average relative error of airflow of only 4.11% and a maximum relative error that does not exceed 10%. • A Pressure balancing model suitable nonfully developed flow is proposed. • The identification of parameter is converted into a multi-objective optimization. • The machine learning method of XGBoost is used to predict the damper degree.

The impact of heating, ventilation, and air conditioning design features on the transmission of viruses, including the 2019 novel coronavirus: A systematic review of ventilation and coronavirus.

Aerosol transmission has been a pathway for the spread of many viruses. Similarly, emerging evidence has determined aerosol transmission for Severe Acute Respiratory Syndrome coronavirus 2 (SARS-CoV-2) and the resulting COVID-19 pandemic to be significant. As such, data regarding the effect of Heating, Ventilation, and Air Conditioning (HVAC) features to control and mitigate virus transmission is essential. A systematic review was conducted to identify and comprehensively synthesize research examining the effectiveness of ventilation for mitigating transmission of coronaviruses. A comprehensive search was conducted in Ovid MEDLINE, Compendex, Web of Science Core to January 2021. Study selection, data extraction, and risk of bias assessments were performed by two authors. Evidence tables were developed and results were described narratively. Results from 32 relevant studies showed that: increased ventilation rate was associated with decreased transmission, transmission probability/risk, infection probability/risk, droplet persistence, virus concentration, and increased virus removal and virus particle removal efficiency; increased ventilation rate decreased risk at longer exposure times; some ventilation was better than no ventilation; airflow patterns affected transmission; ventilation feature (e.g., supply/exhaust, fans) placement influenced particle distribution. Few studies provided specific quantitative ventilation parameters suggesting a significant gap in current research. Adapting HVAC ventilation systems to mitigate virus transmission is not a one-solution-fits-all approach. Changing ventilation rate or using mixing ventilation is not always the only way to mitigate and control viruses. Practitioners need to consider occupancy, ventilation feature (supply/exhaust and fans) placement, and exposure time in conjunction with both ventilation rates and airflow patterns. Some recommendations based on quantitative data were made for specific scenarios (e.g., using air change rate of 9 h-1 for a hospital ward). Other recommendations included using or increasing ventilation, introducing fresh air, using maximum supply rates, avoiding poorly ventilated spaces, assessing fan placement and potentially increasing ventilation locations, and employing ventilation testing and air balancing checks. Trial registration: PROSPERO 2020 CRD42020193968.

Аnаlysis of efficiency of using heаt pump units for heаt recovery from ventilаtion emissions

The system analysis of the current state of quality of functioning of ventilation systems of industrial and public buildings in terms of volumes and modes of fuel and energy resources consumption has been carried out. The analysis of energy efficiency of using a steam-compression heat pump system for utilization of heat of ventilation emissions for heating the supply air has been carried out. Direct-flow ventilation systems with and without the heat pump unit are compared. A mathematical model and a calculation algorithm of the considered ventilation systems are offered. The model can calculate operation modes of one of the arrangement options both with fixed values of parameters affecting the result and with variables, which allows carrying out multivariate calculations and numerical research quickly and with minimum labour inputs. The results of comparative analysis are given on the example of a specific production room. Heat, moisture and air balance data obtained from regulatory documents and reference data, as well as the results of research by other authors are used as source data. Depending on the chosen arrangement, the contents of the calculations and the results obtained are different.In addition, the developed model allows, depending on the considered arrangement and the need, to obtain a large number of output parameters, such as surface areas of heat exchangers, heat transfer coefficients, all thermophysical properties of working media in all nodal points of the flowing process, etc. The principles of a comprehensive approach to assessing the efficiency of ventilation systems based on a system analysis, taking into account the parameters of heat and cold consumers, environmental parameters, the impact of aerodynamic characteristics of the air duct on energy costs and the tariff index in different climatic zones of Russia are substantiated.

Klasifikasi Dehidrasi Tubuh Manusia Berdasarkan Citra RGB Pada Warna Urine Menggunakan Metode K-Nearest Neighbor

Dehydration is a condition in the body where the amount of fluid that comes out is more than the amount of fluid that enters so that the body experiences a lack of fluids. The simplest way to find out if you are dehydrated is to check the color and amount of urine. If it is very dark and there is little water, then the body needs a lot of air. If the urine is clear, it means the body is in normal air balance. The level of dehydration between each person is different, so we need a system that can classify the level of dehydration objectively through urine, so that it can facilitate the process of early detection and diagnosis before being enforced. Based on the research that has been done, it is found that the Matrix Laboratory (Matlab) can classify dehydration in the human body, by utilizing urine images through several processes, namely preprocessing, segmentation, feature extraction of Red Green Blue and then the K-Nearest Neighbor method to classify a person's level of dehydration. From 30 urine image training data and 15 urine image test data with 3 classes of urine color levels, namely not dehydrated, mild dehydration and severe dehydration, the results obtained from the accuracy of the dehydration level classification using the K-Nearest Neighbor method of 93.3% obtained from 14 test data with accurate classification, and 1 test data with inaccurate classification.

Edukasi Bahaya Limbah Tekstil pada Kesehatan di MAS Al-Washliyah 22 Tembung

The process of industrial pollution of hazardous and toxic waste (B3), especially in the textile industry, can occur directly or indirectly. The direct process is that the pollutant has a direct impact on poisoning so that it interferes with the health of humans, animals and plants or disrupts the ecological balance of water, air and soil. Indirect process, some chemical substances react in the air, water and soil, causing pollution. Batik waste also contains wax (wax). contains chemical compounds that are harmful to health, starting from itching on the skin, interfering with breathing, digestion and cancer. The purpose of this Community Service is to find out the description of knowledge about waste and its health hazards for students at MAS Al-Washliyah 22 Tembung. The method used is a lecture about the impact of waste and its dangers on health and questions and answers as well as the provision of brochures and measuring instruments using a questionnaire. The results of the measurement of knowledge before education resulted in good knowledge of 60%, 20% enough and 20% less. After good education 75% and 25% enough. There is a significant relationship between before and after education p = 0.000. The conclusion in this service activity is that there is an increase in students' knowledge after education.