Air Passages Research Articles

Free convective heat transfer induced inside a vented duct having two aligned hot and cold cylinders: An experimental study

AbstractFree convective heat transfer created from two aligned cylinders immersed inside a vented air duct is experimentally investigated. The experiments include the measurements of cylinders temperature and the air temperature inside the enclosure under steady, turbulent, and incompressible flow properties by using steady‐state heat equations. The studied parameters include Rayleigh number (), opening sizes at lower and upper enclosure surfaces (), and space size between cylinders () with the constant ratio of enclosure width to cylinder diameter equal to 6. The findings displayed that the average air temperature inside the enclosure for the low values of S and O is low, and it rises as S is raised. The behaviors of Nu differ with changing Ra values. An interaction between hot cylinder and cold cylinder inside the enclosure is observed that depends on O and S values, and hence, they have a large impact on fluid temperature. The data indicated that rises with the for all and values. The value of for each cylinder depends on the values of and . The maximum value has been obtained when and with maximum enhancement between 30% and 50% depending on Ra values as compared with and , whereas the minimum average has been indicated when and . The profiles of reveal that , , and have a considerable influence on heat transfer.

An Experimental Study for Air Temperature Distribution in a Conditioned Room Using Various Vertical Locations of Conditioned Air Ducts

The Air distribution phenomenon is most useful in thermal environment study and its effectiveness. The main aim of this investigation is to examine and discover the thermal properties of the inside area and its thermal environment. The experimental work for research was studied at the first-floor lab of the government women’s polytechnic, Bhopal. The experiment was conducted in the summer and winter seasons in a closed-conditioned room with the arrangement of a conditioned air discharge duct. The conditioned air was discharged through the circular pipe duct which was set vertically. The duct has arrangements to discharge the air through various vertical positions as the lower duct (L), middle duct (M), and upper duct (U). This experimental work investigates supply air velocity and vertical temperature variation effectiveness inside said test room. The experiment results were collected with lower, middle, and vertical duct opening conditions respectively. The vertical temperature variation and air velocity at the outlet of the duct were noted with considerable points at 1 m from each inside the test room space. The outcome of the results shows the indoor thermal environment and vertical temperature distribution were affected by the discharge air duct position and supply air velocity. The temperature profile vertically impacted when the measuring test point position was near the discharge air duct and it became quite consistent in respective measurements from a large distance.

Recycling kaolin from paper waste and assessment of its application for paper coating

In the cellulose industry, the paper coating process plays an essential role in reducing manufacturing costs while increasing the quality of the products. Given that cellulose products are being used increasingly, the ability to recycle and reuse these materials might be highly beneficial in this industry. Thus, kaolin—one of the most commonly utilized ingredients in the cellulose industry that has a major impact on the final quality—was recycled from paper waste for this study. Then, to confirm the successful recycling process, the particle distribution, morphology, and chemical composition of recycled kaolin were analyzed by DLS, SEM/EDS, FTIR, XRF, and XRD. The related results verified the recycled kaolin's high purity and crystallinity. Subsequently, coatings with thicknesses of 30, 60, 90, and 120 μm were applied to paper using a suspension of recycled kaolin. Their mechanical properties (burst strength and tensile strength), permeability (air passage, the amount of which indicates the porosity of the paper structure), wettability (the contact angle can reveal the wetting ability of the paper), and water absorbance (the Cobb test) were then assessed. The pertinent findings demonstrated that applying a coating considerably improves paper quality. So, a coating with a thickness of 30 µm is superior to uncoated paper. In addition, among all the coating thicknesses, the treatment with the best mechanical strength, permeability, contact angle, and Cob value values had a coating thickness of 120 µm. The corresponding values for the tensile index, burst index, air passage amount, and contact angle are 70 kNm/kgr, 3.61kPa m2/gr, 680 ml/min, and 46֯ ±2. Consequently, the 120 µm-thickness treatment was determined to be the most effective one in this investigation.

Integrated heat dissipation mechanism design of electronic equipment cabinet based on flow and sound analysis

The electronic equipment cabinet is the main bearing platform of radar back equipment, normally using a forced convection cooling form. With the continuous increase of radar function and processing capacity, the total heat consumption of electronic equipment is getting higher and higher, and the fan speed is constantly increasing. Besides the noise of electronic equipment cabinet shows a trend of gradually increasing. To reduce cabinet noise from the source, this paper presents three structural forms of integrated heat dissipation mechanism, and uses FloEFD fluid heat transfer analysis software and COMSOL acoustic module to analyze the cabinet flow field and the cabinet sound field respectively. By comparing the cabinet noise characteristics under different structural forms, the analysis results show that the noise reduction effect of bilateral air duct structure is best.

Physically based heat exchanger sizing method for the thermal management system of all-electric regional aircraft

Fully electric propulsion systems integrating hydrogen-powered fuel cells and batteries are promising options to reduce the overall climate impact of regional aircraft. However, the increase in low-temperature heat sources aboard the aircraft calls for advanced thermal management system solutions. To address this challenge, this study presents a sizing methodology for ram air heat exchangers in the nacelle-integrated cooling loop of an all-electric regional aircraft based on the ATR-72 platform. Different discretization schemes are compared to identify an optimal sizing method. The results highlight the simplicity and efficiency of the 0D ε-NTU model. Geometric design variables are optimized with respect to drag and mass during a hot-day take-off. The resulting Pareto front reveals a tendency for low airflow outlet temperatures and large diffuser area ratios to result in lightweight designs but in turn, induce high drag and require a large installation space. Comparative analyses of specific optimal ram air duct designs and equivalent skin heat exchangers demonstrate the potential of a second heat sink over a flight mission. The limited heat transfer area of the skin heat exchanger proves insufficient for hot-day take-off and climb but offers advantages during cruise and descent thanks to the reduced drag.

Characteristics, sources, and improvement measures regarding fine particulate matter in subway station office and the VAC system.

In order to study the characteristics and transport path of PM2.5 in the subway station office, three different types of typical subway station were selected for sampling and analysis. The PM2.5 of mechanical air duct and VAC (ventilation and air conditioning system) were tested simultaneously. Both the particulate matter in the station office and VAC exhibit highly enriched characteristics of metal elements. The mass balance equation with elemental Fe as the tracer element is established firstly in subway station, and the transport path of PM2.5 in the work area is revealed: if the work area is obviously under positive pressure compared to the station hall, metal-enriched fine particles come from the VAC system; otherwise, the particles come both from the VAC system and air infiltration from the station hall. The contribution of air infiltration to metal-enriched fine particles can reach 50%. Finally, following an investigation into the source of fine particles in the office, the measures to improve air quality are proposed and validated.

Study of air deionization factors

The object of research is the dynamics in the concentration of air ions and suspended particles in atmospheric air and in supply-exhaust ventilation systems. An urgent task is to determine the factors and obtain quantitative data on the deionization of the atmospheric air that enters the environment where people live. Quantitative data on changes in the concentration of air ions depending on the time of day, temperature, and relative air humidity have been established. It was shown that even in the absence of significant man-made influence on the concentration of suspended particles, this indicator is at least 7000 cm-3. In the presence of wind, this indicator reaches 30000 cm-3 and higher. Measurement of the spectrum of suspended particles in the range of 0,3–6,0 μm showed that the predominant fraction is particles with sizes of about 3 μm. Studies have been conducted on changes in the concentrations of air ions in supply-exhaust ventilation systems. It was established that in the air duct made of galvanized iron, which has a length of 16 m, the concentration of negative air ions is reduced by 67 %, and positive by 78 %. Laboratory studies of air deionization in air ducts made of different materials were carried out. There is significant air deionization in metal and cardboard ducts while it is absent in wooden ducts. This indicates the electrical nature of deionization. A calculation method for forecasting the aero-ionic mode of premises, taking into account the factors of air deionization, is proposed. For rooms with supply-exhaust ventilation, a calculation apparatus is proposed taking into account the air exchange rate (the number of complete air changes per unit of time). The results make it possible to choose the required performance of artificial air ionization devices for normalizing the aero-ionic regimes in the premises

Design of Automatic Seaming Machine for Fire Air Ducts with 3D Model and Its Experiment

The fire air duct is one of the important components of the ventilation system in large buildings, which is is a unit system for ventilation and smoke exhaust. The ventilation system is a customized system with a wide range of applications and a high demand, resulting in the use of multiple sizes and specifications of fire air ducts. At the same time, fire air ducts are generally made of thin galvanized iron sheets, which have poor rigidity and are prone to deformation. For the two above-mentioned reasons, the seaming process of the fire air duct is currently mainly completed by manual tapping, resulting in low processing efficiency, high labor intensity, and high cost. Therefore, it is necessary to design an automated equipment that can complete the fire air duct seaming process. Firstly, a 3D model for automatic seaming machine for fire air ducts to demonstrate the working principle and a double head positioning and clamping mechanism is proposed to improve the pipe rigidity; Secondly, to adapt to most specifications for rectangular fire air ducts, a system was designed that utilizes the two right angle ends of the stitching edge for positioning and clamping without many special toolings. Thirdly, a set of automatic seaming prototype has been manufactured based on the above design ideas. The experimental results on the prototype show that the fire air duct automatic stitching machine can seam a fire air duct within 1 minute. Compared with manual processing, the processing efficiency is improved by more than 80%.

A Five-Hole Pressure Probe Based on Integrated MEMS Fiber-Optic Fabry-Perot Sensors.

The five-hole pressure probe based on Micro-Electro-Mechanical Systems (MEMS) technology is designed to meet the needs of engine inlet pressure measurement. The probe, including a pressure-sensitive detection unit and a five-hole probe encapsulation structure, combines the advantages of a five-hole probe with fiber optic sensing. The pressure-sensitive detection unit utilizes silicon-glass anodic bonding to achieve the integrated and batch-producible manufacturing of five pressure-sensitive Fabry-Perot (FP) cavities. The probe structure and parameters of the sensitive unit were optimized based on fluid and mechanical simulations. The non-scanning correlation demodulation technology was applied to extract specific cavity lengths from multiple interference surfaces. The sealing platform was established to analyze the sealing performance of the five-hole probe and the pressure-sensitive detection unit. The testing platform was established to test the pressure response characteristics of the probe. Experimental results indicate that the probe has good sealing performance between different air passages, making it suitable for detecting pressure from multiple directions. The pressure responses are linear within the range of 0-250 kPa, with the average pressure sensitivity of the five sensors ranging from 11.061 to 11.546 nm/kPa. The maximum non-linear error is ≤1.083%.

Pengukuran Efisiensi Proses Produksi Castable Guna Mengidentifikasi Wasting Time di PT Benteng Api Technic

PT Benteng Api Technic was founded in 1997 and produces refractory bricks, refractory cement and various refractory materials. Refractory cement or castable currently still uses a pre-order system before the production process is carried out. During observations for seven days with 38 observations, there were activities that were felt to be less efficient, then the value stream mapping method was carried out to streamline waste. The result is a defect when the production process is finished, there is a repetition of the production process because it does not pass the feasibility test, processing because a lot of leftover material falls in the bagging section and the material is no longer used. Waiting is the average part of weighing materials/products of 1.54 seconds (waiting for the material composition recipe and weighing platform trouble/error). Material mixing section with an average/product of 1.82 seconds (waiting for machine repairs due to leaking air duct). Total production lead time is 3396 seconds. Once the waste is identified, the next step is to eliminate the activity by testing data adequacy and testing data uniformity. The results of the analysis of the castable production process contained 2 analyses, the first analysis by reducing activity time with an average total time of 3285 seconds/44 cement and the second analysis by reducing and eliminating the cement weighing activity in the bagging section with a total time of 2873 seconds/44 cement

Gas-Solid Flow Characteristics of Airflow and Dust Particles in Blasting Excavation of Underground Metal Mine Tunnels.

Effective dust removal has long been a challenge in the blasting mining of underground metal mine tunnels, and uncontrolled dust diffusion seriously endangers workers' respiratory systems and the underground space safety environment. However, the vast majority of existing numerical studies on dust diffusion are focused on coal mine fully mechanized mining, which is different from metal mine blasting excavation in terms of stope structure and dust properties. Furthermore, the mechanism by which the forced and exhaust ventilation modes affect the diffusion characteristics of inhalable particles is unclear. In this work, gas-solid flow characteristics for dust diffusion in a typical metal mine blasting tunnel were numerically investigated based on the Euler-Lagrange method, where the blasting face instantly released 6.37 × 107 particles with 100 different sizes, ranging from 0.8 to 200 μm. The interphase forces between airflow and dust particles are comprehensively modeled, and the particle diffusion effect caused by fluid turbulence is described by a discrete random walk model. Detailed information for airflow turbulence and particle migration was revealed, and dust removal efficiencies for inhalable particulate matter (PM10) by forced, exhaust, and hybrid ventilation were analyzed. Numerical results predict a complex airflow pattern in the working roadway, including the jet-flow region, return airflow core region, airflow disorder region, and secondary flow region. Dust diffusion temporal characteristics can be divided into three stages, namely, the initial stage of dust generation, the efficient ventilation and dust removal stage, and the later stage of dust diffusion. Dust diffusion spatial characteristics indicate that under the Coanda wall attachment effect, the dust concentration exhibits nonuniform distribution in both vertical and horizontal directions of the return air roadway. The dust removal efficiency of hybrid ventilation on inhalable particles above respiratory height is better than that of forced ventilation, especially in the return air roadway. The additional exhaust air duct based on forced ventilation can discharge more inhalable particles from the tunnel.

The augmentation of the heat recovery by using evaporative cooling in HVAC applications: Experimental study

An experimental study was conducted to investigate the impact of evaporative cooling on heat recovery within HVAC systems. This study involved the development of a specialized test rig comprising two air passages connected by a wickless heat pipe heat exchanger (wickless HPHE). Additionally, an evaporative cooling pad was integrated into the cold air return duct. The evaporative cooling process effectively lowered the temperature of the cold air, which was subsequently directed through the wickless HPHE condenser. This occurred at a variable mass flow rate ratio, in contrast to the constant mass flow rate of warm air passing through the wickless HPHE evaporator section. The study encompassed a range of mass flowrate ratios, specifically 1, 1.5, and 2. The thermosiphon heat pipe was charged with acetone at a 60 % filling ratio. The results clearly demonstrated that evaporative cooling played a pivotal role in enhancing the heat exchanger's performance. Notably, the temperature differential observed in the wickless HPHE evaporator surpassed that in the HPHE condenser, primarily due to the influence of evaporative cooling. The highest temperature difference recorded in the HPHE evaporator was 17.8 °C, indicative of the most substantial heat recovery achieved. Importantly, the effect of evaporative cooling significantly improved the performance of the wickless HPHE by more than 48 %.

Experimental and parametric analysis of a novel hybrid thermal management strategy for cylindrical lithium‐ion cells

AbstractThis paper reports on a novel hybrid thermal management strategy. It uses secondary coolants (air and liquid) to withdraw heat simultaneously from the composite phase change material, resulting in increased heat extraction capability of the composite phase change material and improved thermal environment of the battery module. The significance of this strategy is that the fluid used in the liquid cooling stays stationary. Comprehensive experimental and numerical studies are performed, and parametric studies are conducted to reduce the volume of the phase change material, size of the air duct, and airflow Reynolds number. The numerical results showed that the maximum temperature was limited to 27.8°C, and a high‐temperature uniformity of 0.4°C was obtained. Furthermore, the required volume of the composite phase change material is reduced by ~50%. Additionally, beyond a 6 mm height of the air duct, the reduction in maximum pressure drop is not significant enough, and it is considered the optimal height, and a Reynolds number of 1950 is considered the optimal airflow Reynolds number. Therefore, the proposed thermal management concept for the battery module can sustain the thermal environment needed for the effective operation of Lithium‐ion batteries.

Study of the enhancement in the performance of a hybrid flat plate solar collector using water and air as working fluids

AbstractA hybrid flat solar collector was manufactured from basic materials to combine the effects of both water and air solar heaters. The reason is to increase the amount of heat delivered to water by doubling the heat sources, one from the direct beam of sun and the other from the hot air delivered by the air solar heater. In addition, the flow of water inside the solar heater is made in a thin layer so that much heat can be gained by water per unit time. The outlet hot air of the solar air heater enters air ducts that pass through the solar water heater. With a constant water flowrate of 0.0167 kg/s, three different air velocities (1.7, 2.1, and 2.4 m/s) were applied to determine the optimum air velocity that results in the maximum outlet water temperature and the maximum removal factor FR for the solar water heater. The experiment was run from 10:00 a.m. to 2:00 p.m. every day during June 2023 and the data was recorded every 15 min. The data obtained from the experiment showed that the lowest air speed (1.7 m/s) results in the highest outlet water temperature (63°C) and heat removal factor FR (0.74).

Particle characterization in commercial buildings: A cross-sectional study in 40 offices in Singapore

There is a knowledge gap in understanding how existing office buildings are protecting occupants from exposure to particles from both indoor and outdoor sources. We report a cross-sectional study involving weekly measurements of size-resolved indoor and outdoor particle concentrations in forty commercial building offices in Singapore. The outdoor and indoor particles size distributions were single mode with daytime peak number concentrations at 36.5 nm and 48.7 nm. Outdoor concentrations were significantly greater than indoors for all particle diameters. Indoor particle concentrations were generally low due to: 1) relatively high indoor particle removal (IPR) rates; 2) low indoor source strengths; and 3) low indoor particle of outdoor proportion (IPOP). We found that the ventilation system type had a substantial effect on indoor particle levels, IPR and IPOP. Through linear mixed model analyses, we identified dependencies of IPR rates with the use of MERV13 filters in supply air and filter maintenance frequency, IPOP with the use of MERV13 filters in the fresh air and supply air ducts and low particle source strength with regular daily cleaning presumably due to dust reservoir removal. Lastly, the contribution of outdoor sources was mainly seen for ultrafine and fine particles but less pronounced for coarse particles. This study provided detailed understanding of particle exposure in building offices and their influencing factors, facilitating future research on health impact of particle exposures.

Comprehensive Review on the Relationship between Duct Cleanliness and Airborne Contaminants

This study investigates the relationship between Indoor Air Quality (IAQ) and air duct cleanliness, addressing the rising concern for human well-being. Airborne contaminants like dust, mold, and bacteria are identified as significant threats to IAQ, with potential health consequences. The study will also explore the several established safety and health guidelines and duct characteristics that influenced IAQ. Consequently, the primary research goal is to examine the relationship between duct cleanliness and airborne contaminants in the building environment and determine whether air duct cleaning effectively reduces these contaminants. By thoroughly reviewing studies and established standards, we examine IAQ contaminants and explore the effects of duct cleaning, along with its potential health advantages. Findings emphasize duct cleaning's potential to enhance IAQ, reduce exposure to pollutants, and its importance for building owners, facility managers, and stakeholders in safeguarding occupants' health and comfort.

Analysis of the alternative air ductwork by Numerical airflow behavior combined with the New Economic index and standard

This research studies the numerical modelling using computational fluid dynamics with a k-Epsilon turbulence model to analyze airflow behaviors inside the alternative compared with conventional air ductwork combined with a comprehensive analysis of the economic parameter created by the author called Reveal Comparative Advantage Cost index. All alternative air ductwork has lower pressure drop and a higher ability to maintain the temperature inside, showing that alternative air duct systems have a significant advantage over conventional air ductwork. The fabric ductwork has a lower pressure drop than galvanized steel perforated ductwork, which is 69.15 %. The pre-insulated ductwork can keep the best temperature inside, with a different temperature value between the air inlet and air outlet of 0.06°C. The Reveal Comparative Advantage Cost of construction costs of the galvanized steel ductwork and the galvanized steel perforated ductwork are 1.02 and 1.06, which means the conventional air ductwork is initially cost-effective in terms of investment and operating costs. However, alternative air ductwork is the better option for long-term use. They have cost-effective electrical energy and maintenance costs with a high Reveal Comparative Advantage Cost index. Significantly, the pre-insulated ductwork has the Reveal Comparative Advantage Cost index of maintenance, electrical energy, and construction costs of 1.38, 1.09, and 0.95, respectively. The results of the airflow behaviors study combined with the Reveal Comparative Advantage Cost index study show that the galvanized steel perforated ductwork is not a selectivity that qualifies either for airflow behaviors or is unsuitable for investment. Pre-insulated ductwork is the appropriate option due to the high airflow behaviors and cost, which makes it suitable for investment. However, the Thailand Authority should develop alternative air ductwork Thai standards for engineering design and safety building.

Adrenaline and Anesthesia - Clinical Review

Abstract Adrenaline or epinephrine is one of the primarily important catecholamines in the general stress response and is manufactured in the adrenal medulla. In stress, it is secreted into the blood circulation and evokes many bodily transformations which prepare the body for the fight or flight response, some of which include tachycardia and hypertension, dilation of the air passages, and mobilization of energy reserves. This catecholamine surge can, however, cause myocardial stress, as evidenced during acute ischemia, hence an implication of increased risk of myocardial injury. In terms of functioning at the molecular level, adrenaline interacts with adrenergic receptors, which trigger intracellular processes associated with the readiness of a body to act fast as well as affecting more general forms of cardiac activity. Adrenaline stimulates beta-adrenergic receptors, enhancing heart rate and contractility, vital under stress but harmful with constant exposure. It is metabolized in the liver and may also cause dysrhythmias when used together with some inhaled anesthesia such as halothane. In anesthesia, adrenaline gets used to increase the local anesthetic action of the drug by constricting blood vessels and thereby increasing the duration and extent of analgesia besides reducing the uptake of the anesthetic into the systemic circulation. The common dose schedule is 1 in 2 lakh of adrenaline which means 5 μ/mL. The usual dose should not increase to 3 μ/kg. Preferably, the dose can be supplemented after 10–15 min. The use of adrenaline also creates a plane to dissect. The duration of action of local anesthetic drug is prolonged following the addition of adrenaline. Epidural test doses detect accidental intravascular catheterization. There is evidence that adrenaline belongs to anesthetic protocols, enabling deeper anesthesia, which, in turn, contributes to more effective outcomes of the surgery and easier recovery. Adrenaline by way of its alpha 2 agonism is likely to increase the effects of local anesthetic drugs and inhalational agents. Still, practitioners must address those benefits against possible side effects since minor, albeit significant, changes in the electrocardiographic characteristics have been recorded with lignocaine–adrenaline mixtures. Adrenaline nebulization is used for acute respiratory conditions like croup postextubation. The dose is 0.5 mg/kg, max 5 mg, diluted in 2–3 mL saline, repeated every 30 min if needed, with monitoring for tachycardia and hypertension. For perioperative anaphylaxis, administer 0.5 mg intramuscular for adults, adjusted by age for children. Hence, adrenaline is extremely useful in local anesthesia because of its vasoconstrictive effects, which must, however, be monitored continuously for patient and operational safety.

Распределение осевой и радиальной скорости вблизи с круглым раструбом в воздуховоде

The purpose of the article is to increase the energy efficiency of ventilation systems in mining enterprises using a round socket installed in the air duct. The article presents numerical and experimental results of studying the outlines of vortex zones formed at the installation site of a round bell. Numerical studies were carried out using the Ansys Fluent software package. We obtained graphical and analytical dependences of the distribution of the axial and radial components of the velocity near the bell, depending on its radius and angle of inclination

A UAV-Borne Six-Vessel Negative-Pressure Enrichment Device with Filters Designed to Collect Infectious Fungal Spores in Rice Fields

Fungal spores that cause infectious fungal diseases in rice are mainly transmitted through air. The existing fixed, portable or vehicle-mounted fungal spore collection devices used for rice infectious diseases have several disadvantages, such as low efficiency, large volume, low precision and incomplete information. In this study, a mobile fungal spore collection device is designed, consisting of six filters called “Capture-A”, which can collect spores and other airborne particles onto a filter located on a rotating disc of six filters that can be rotated to a position allowing for the capture of six individual samples. They are captured one at a time and designed and validated by capturing spores above the rice field, and the parameters of the key components of the collector are optimized through fluid simulation and verification experiments. The parameter combination of the “Capturer-A” in the best working state is as follows: sampling vessel filter screen with aperture size of 0.150 mm, bent air duct with inner diameter of 20 mm, negative pressure fan with 1500 Pa and spore sampling of cylindrical shape. In the field test, the self-developed “Capturer-A” was compared with the existing “YFBZ3” (mobile spore collection device made by Yunfei Co., Ltd., Zhengzhou, China). The two devices were experimented on at 15 sampling points in three diseased rice fields, and the samples were examined and counted under a microscope in the laboratory. It was found that the spores of rice blast disease and rice flax spot disease of rice were contained in the samples; the number of samples collected by a single sampling vessel of “Capturer-A” was about twice that of the device “YFBZ3”in the test.