Amount Of Air Leakage Research Articles

IMPROVEMENT OF METHODOLOGICAL BASIS OF DETERMINATION OF TIGHTNESS OF BUILDING COVER

Tightness and energy efficiency are among the most important parameters of buildings. The airtightness of the building ensures a reduction in energy consumption for heating, especially for buildings with a large heating volume. Currently, Ukraine does not have a regulatory framework for determining the tightness of buildings. The article analyzes the international standard for determining the airtightness of buildings ISO 9972:2015 Thermal characteristics of buildings − Determination of air permeability of buildings − Method of fan injection. On the basis of the international standard, the methodical bases for determining the tightness of the building envelope have been improved, and the methodology for determining the tightness of the building envelope has been adapted for Ukraine. The article presents the methods of measuring the tightness of the building, the rules for preparing the building for measurements, as well as the calculation of air permeability parameters. This technique contains the principle of determining the parameters of tightness in the conditions of fan injection. The hermeticity of the building, or its air permeability, is expressed by the amount of air leakage in cubic meters per hour per square meter of the area of ​​the outer shell of the building when the building is affected by a pressure drop of the internal air of 50 Pa. During the test, the fan creates a pressure drop of 50Pa. A differential manometer is used to record the pressure difference between the pressure in the room and the external pressure. Using the formulas given in the article, the volume flow of air through the enclosing structures is calculated, and the air leakage rate is also calculated. Based on the determined parameters, the air exchange rate n50 and the air exchange rate q50 at the created pressure drop ∆p were calculated. The method of determining the energy efficiency class based on the n50 parameter has been improved. Based on the results of the calculations, we have the opportunity to determine the energy efficiency class based on the determined air exchange ratio.

A Simple Method to Quantify Outward Leakage of Medical Face Masks and Barrier Face Coverings: Implication for the Overall Filtration Efficiency.

Face masking proved essential to reduce transmission of COVID-19 and other respiratory infections in indoor environments, but standards and literature do not provide simple quantitative methods for quantifying air leakage at the face seal. This study reports an original method to quantify outward leakage and how wearing style impacts on leaks and filtration efficiency. The amount of air leakage was evaluated on four medical masks and four barrier face coverings, exploiting a theoretical model and an instrumented dummy head in a range of airflows between 30 and 160 L/min. The fraction of air leaking at the face seal of the medical masks and barrier face coverings ranged from 43% to 95% of exhaled air at 30 L/min and reduced to 10–85% at 160 L/min. Filter breathability was the main driver affecting both leak fraction and total filtration efficiency that varied from 5% to 53% and from 15% to 84% at 30 and 160 L/min, respectively. Minor changes were related to wearing style, supporting indications on the correct mask use. The fraction of air leaking from medical masks and barrier face coverings during exhalation is relevant and varies according to design and wearing style. The use of highly breathable filter materials reduces air leaks and improve total filtration efficiency.

Seepage and Heat Transfer Characteristics of Gas Leakage under the Condition of CAES Air Reservoir Cracking

The contradiction between supply and demand of energy leads to more and more attention on the large-scale energy storage technology; Compressed Air Energy Storage (CAES) technology is a new energy storage technology that is widely concerned in the world. The research of coupled heat transfer and seepage in fractured surrounding rocks is the necessary basis to evaluate the operation safety and effectiveness of CAES. Current studies point to the possibility of cracking in concrete liner seals, but the thermodynamic processes and leakage characteristics of compressed air in the presence of cracking and the heat transfer characteristics of seepage have not been addressed and reported. In order to investigate the leakage, the gas seepage and heat transfer law in fractured rock when the hard rock CAES gas reservoir seal cracks, the COMSOL fracture Darcy module, and the non-Darcy Forchheimer model are used as the constitutive seepage. The global ODE is used to calculate the thermodynamic process of compressed air in gas storage with coupled seepage and heat transfer process. The pressure and temperature of compressed air are obtained as the unsteady boundary of the seepage heat transfer model. A program for calculating the seepage and heat transfer characteristics of fractured surrounding rock in the CAES gas reservoir is established. On this basis, with the proposed Suichang CAES cavern as the background, the seepage and heat transfer characteristics of the fractured surrounding rock of the gas storage are studied. The results showed that when there are fewer cracks in the lining and surrounding rock of the air reservoir, the air pressure decreases due to a small amount of air leakage after 30 operation cycles, and the leakage rate of each cycle is 0.7% of the gas storage capacity, but it still meets the engineering requirements. If the plant is operating under these conditions, the charging rate will need to be increased by 1.2 kg/s per cycle charging stage. In the discharging and power generation phase, the high-pressure air that previously percolated into the rock mass cracks could flow back into the air storage through the lining cracks. Therefore, it is incorrect and unreliable to consider the gas which flows out from the inner surface of the lining as unusable. When the lining crack width is less than 0.3 mm, the seepage flow is Darcy flow and the non-Darcy effect can be ignored; when the lining crack width is greater than 0.5 mm, the non-Darcy effect of seepage cannot be ignored. The gas velocity in the surrounding rock fracture medium is on the order of 0.01 m/s with an influence range of over 100 m, and the gas velocity in the pore medium is on the order of 10-6 m/s with an influence range of 50 m. The findings of this study contribute to a better understanding of the interaction between the thermodynamic properties of compressed air and the seepage heat transfer process in compressed air storage underground reservoirs, as well as the gas leakage process in the event of liner seal cracking.

Quantifying airtightness in Brazilian residential buildings with focus on its contribution to thermal comfort

ABSTRACT Airtightness refers to the amount of air leakage through a building’s envelope. This uncontrolled exchange of air between inside and outside, either infiltration or exfiltration, may lead to thermal discomfort. Nevertheless, little or no attention has been given to airtightness in some countries including Brazil. In Brazil, a range of different strategies are suitable to achieve thermal comfort depending on the several climatic regions. In those regions where winter conditions are noticeable, such as in São Paulo, airtightness is a key parameter, but it has been historically overlooked. In this work, the authors deployed the innovative Pulse test methodology to determine airtightness levels for the first time in Brazil, in the city of São Paulo. Three representative multifamily residential buildings dating from the 1970s, 1980s and 2000s were measured, and the results’ values widely ranged from 1 to 5.7 h−1, at 4 Pa. Next, dynamic building simulations were conducted using measured and representative airtightness values (converted to infiltration) to understand the contribution of this variable on the thermal comfort. The results suggested that up to 9% improvement in the thermal comfort levels could be achieved by adopting 1 h−1 as maximum infiltration, and up to 14% by adopting 0.5 h−1.

Dependent Competing Failure Modeling for the GIL Subject to Partial Discharge and Air Leakage With Random Degradation Initiation Time

Confronted with the ever-growing demand for electricity delivery over long distances, the gas insulated transmission line (GIL), as an advanced underground technology, has been under rapid development recently. Physics-of-failure analysis for the GIL indicates that it experiences two competing failure modes: 1) Once the amount of air leakage is greater than a predetermined threshold level, a deterioration-based soft failure happens. 2) The arrival of a partial discharge with overlarge voltage will result in a shock-based hard failure. Furthermore, statistical analysis of some engineering projects shows that the beginning of the GIL degradation, i.e., the inner air begins to leak, occurs after an initiation time. In addition, the flashover voltage decreases considerably as the SF6 in the GIL leaks outside and the moisture penetrates inside, which reflects that the hard failure threshold level is related to the degradation process. Confronted with these problems, a new dependent competing failure model is presented for the GIL, with the consideration of degradation initiation time. The GIL reliability assessment is obtained through theoretical derivation, and the numerical calculation method with controllable approximation accuracy. Finally, a case study is carried out to show the implementation of the proposed model.

Numerical investigation on NOX formation in oxygen-CH4 MILD combustion with air leakage

In this paper, we focus on formation of NOX under oxy-fuel MILD combustion using JHC (jet-in hot co-flow) burner. The effect of the different oxygen dilution ratio in the co-flow is analyzed for MILD combustion formation and also for characterizing NOX emission. RANS (Reynolds averaged Navier Stokes) with the modified k-e equation and EDC (eddy dissipation concept) model were applied for 2D-axisymmetric computational domain using the Ansys Fluent. It is found that the effect of the oxygen concentration rather than the composition of dilution gas is more significant for the formation of the MILD combustion and as the oxygen concentration of the dilution gas increases under MILD combustion conditions, the region with Da < 1 expressed as MILD regime tends to be decreased. The effect of a diluted oxygen concentration in the oxy-fuel combustion on NOx emission under MILD condition is found to be much greater than the amount of air leakage into co-flow, and NO emissions are almost unaffected by the increase of N2 concentration in case of MILD combustion condition within practical air leak ranges.

Influence of air leakage from building façade on the energy efficiency of air conditioning system in Tropic Asia

Many buildings are being built in Southeast Asian cities due to rapid economic growth. Because large-scale buildings, such as office buildings, in particular, consume a large amount of energy, it is essential to construct environmental buildings for global climate change. Despite the improving airtight performance of building envelopes for effective energy saving, almost no research regarding them in Southeast Asia is done at present. Therefore, this paper aims to determine the current state of energy conservation effects of office buildings in Asian cities. This research adopts on-site measurement and energy-simulation methods to evaluate the sealing performance of the office building envelope in Bangkok, Hanoi, Hong Kong, Singapore, and Taipei. In the field survey, the CO2 leakage rate from the building envelope, covered with a vinyl cloth, is investigated using the tracer gas method. In addition, air quality, internal and external differential pressure, and energy consumption are measured. Furthermore, indoor environmental quality such as temperature, humidity, wind speed, CO2 density, clo value and MRT are measured. The evaluation of the energy conservation performance of the target buildings is multifaceted. In the energy simulation part of this study, actual data are used with simulation software to calculate the energy performance of the heating and cooling load. This research is focused on energy conservation in Hanoi because the amount of air leakage was higher there than the other cities in Tropical Asia. Furthermore, we verified how much of the energy conservation is realized by changing the performance of the air leakage in the model. This paper discusses the current situation of Asian buildings in terms of the results and suggests an appropriate energy conservation model for Asian tropical office buildings.

Analysis on the Calculating of Air Leakage Threshold which Caused the Condenser Vacuum Deterioration

There is an air leakage threshold under certain condenser heat load and air ejector output. When the amount of air leakage is less than the threshold, the condenser pressure is essentially the same, we can maintain a stable condenser vacuum, once exceed the threshold, condenser pressure begin to gradually larger, condenser vacuum will deteriorate. Considered the air leakage influences on the heat transfer coefficient of condenser, this paper had been established the one-dimensional steady-state heat transfer model of condenser to obtain the condenser pressure curve along with the amount of air leakage, the turning point on the curve is the air leakage threshold.

Effects of coal properties on ventilation air leakage into methane gas drainage boreholes: Application of the orthogonal design

Ventilation air leakage into underground to inseam drainage boreholes is a common issue observed during gas drainage in underground coal mines. This air leakage adversely affects the gas drainage efficiency. Despite the extensive research conducted on air-leakage prevention strategies, the effects of coal properties on the air leakage has not yet been properly investigated. This paper presents a fully-coupled numerical study on the effects of coal properties such as Young's modulus, Poisson's ratio and porosity on the air leakage into drainage boreholes. This was achieved through an integrated approach of the orthogonal design method and the F-test theory. The results show that there is a direct correlation between the Young's modulus and the amount of air leakage. Furthermore, the F-test theory was used to examine the significance of the above-mentioned properties' effects. It is found that the impact of Young's modulus on the air leakage is the most significant among those three properties. The Poisson's ratio is the next significant factor with an inversely proportional relationship. Porosity is found to have the least effect on the air leakage. This study provides a systematic approach to examine the air leakage performance for various site conditions and coal properties. Research outcomes offer the mining researchers and engineers a guidance to develop appropriate leakage-prevention strategies and enhance gas drainage performance.

Outcome of pleurodesis using different agents in management prolonged air leakage following lung resection.

Prolonged air leaks (PAL) are a common problem after pulmonary resection. PAL can be a source of significant complications. One of the treatment options is chemical pleurodesis. The efficiency of three methods of treatment of PAL after lung resection was evaluated. In Iodine_ group aqueous iodine solution (lat.Tinctura Jodi) was applied intrapleurally (30 patients); in Doxycycline_group (34 patients) 200 mg of Doxycyclin was given and in Drainage_group 35 patients were applied Lidocaine solution only. The group investigated was similar with regard to age [F = 0.04, P = 0.96] and the amount of air leakage (approx. 462 mL/min). The shortest drainage time and hospital stay was observed in the Iodine_group [10.57, P < 0.001]. However, this therapy was connected with strongly perceptible chest pain (P < 0.0001]). The number of case of pneumothorax recurrence was low and it was the same was seen in other methods of treatment [F = 0.87, P = 0.42]. Allergic reactions were not observed. The number of episodes of tachycardia, hypotension, dyspnea, pneumonia, subcutaneus empyema, fluid collection, emphysema, pneumothorax recurrence and number of re-thoracotomies were statistically similar in all three methods of treatment. Iodine pleurodesis can be considered as one of possible treatment methods of PAL after lung resection as it showed favorable results compared with Doxycycline pleurodesis or drainage alone regarding duration of air leakage, hospitalization and pneumothorax recurrence with only slightly increased pleural pain.

肺切除後のエアリーク量に対するThopaz吸引器（Thopaz™）による定量的評価と従来型持続吸引器による定性的評価の比較

肺切除後のエアリーク量に対するThopaz吸引器（Thopaz™）による定量的評価と従来型持続吸引器による定性的評価の比較

Research on the Air Leakage Law and the Control Technology of the Main Air Doors of the Mine

Air leakage of the main air doors in the mine deteriorates the underground working environment and threatens both the safety production and the physical and mental health of workers. Based on the complex air-leaking problems of the main air doors, this paper has worked out a method by combining SF6 tracer technique and pressure energy test together. In this way, the air leakage law of the main air doors between the intake and the return airway of SHAOYAO coal mine has been determined: the total air leakage of the 10 sets of main air doors amounts to 499. 33m3/min; the amount of air leakage has positive correlation with the differential pressure of air leakage; on the basis of the law of air leakage resistance, the windage resistance of the main air doors has been calculated. According to the air leakage features of the main air doors, this paper also puts forward the control technology, such as spraying polyurethane foam, keeping the tightness of doorframe, etc. After field application, the amount of air leakage has decreased 56.1% on average. And accordingly, the air leakage of the main air doors has been effectively controlled and the underground working environment has been greatly improved.

Infiltration as ventilation: Weather-induced dilution

The purpose of outdoor air ventilation is to dilute or remove indoor contaminants to which occupants are exposed. It can be provided by mechanical or natural means. In most homes, especially older homes, weather-driven infiltration provides the dominant fraction of the total ventilation. As we seek to provide good indoor air quality at minimum energy cost, it is important to neither over-ventilate nor under-ventilate. Thus, it becomes critically important to evaluate correctly the contribution that infiltration makes to the total outdoor air ventilation rate. Because weather-driven infiltration is dependent on building air leakage and weather-induced pressure differences, a given amount of air leakage will provide different amounts of infiltration. Varying rates of infiltration will provide different levels of contaminant dilution and, hence, effective ventilation. This article derives these interactions and then calculates the impact of weather-driven infiltration for different climates. A new “N-factor” is introduced to provide a convenient method for calculating the ventilation contribution of infiltration for over 1000 locations across North America. The results of this work could be used in indoor air quality standards (specifically ASHRAE 62.2) to account for the contribution of weather-driven infiltration toward the dilution of indoor pollutants.

Determine Coverlay Thickness According to Air Leakage Characteristics in Open Pit to Underground Overlay

During surface-underground combined mining, the method to control the ground air leakage is adopted by the capping layer using the fragmented rocks and the discarded tailings. In order to study the air leakage characteristic with the capping, the porosity of the rock particles of seven sizes and the air leakage characteristics of the capping were studied and the relationship between the air leakage coefficient and amount of air leakage with the capping height were found basing on the laboratory analogue simulation tests. It can provide the theoretical basis for determining the capping height of iron mine.

Research on Relationship Between Porosity of Coal, Amount of Air Leakage and Gradient of Wind Pressure

Abstract About half of China's underground mining coal seams have risks of spontaneous combustion, and the condition of airflow in coal directly influences coal's nature of spontaneous combustion. In the experiment, through putting pulverized coal of certain porosity into ventilating tube and attracting wind with pipe-type ventilator at an end, the differential pressure of both ends of the ventilating tube and the ventilating volume in tube are determined. Results of experiment show that the ratio of gradient of wind pressure and amount of air leakage per unit area is stationary for coal sample of certain porosity. In the process of porosity increasing from 0.4 to 0.6 and corresponding p/q increasing from 7.248 2 to 1 840.4, as long as any one of value of p/q and porosity is fixed, the other one can be fixed. This has certain referencing value for further improving the theory of spontaneous combustion of coal and preventing technology against spontaneous combustion of coal.

A case of thoracic degloving injury with flail chest

A 75-year-old male patient suffered a chest degloving injury when he fell on his back and was run over by a small farm tractor he was pulling. At the time of patient admission, the paradoxical motion of the right chest wall was remarkable; and he had an open fracture of the right humerus, a dislocation of the right ankle, and a laceration of the right forearm. Chest computed tomography revealed fractures of the fifth to seventh ribs and detachment of both the right pectoralis major muscle and serratus anterior muscle from the chest wall, with a disconnected right thoracic cavity. Because the right flail chest was severe and there was a large amount of air leakage that continued under positive-pressure ventilation for pneumatic stabilization, we performed surgical fixation of the ribs and repaired the lung injury on the fifth hospital day. The patient's postoperative course was uneventful.

Measurement of Ventilation Airflow Rates of 39 Houses by Three Different Methods

This paper reports on the measurement results of ventilation rates in existing occupied houses in the northern region of Japan. A total of 61 measurements were made over a period of 4 years on 39 houses. Some houses were measured once a year over the four years investigation period. The ventilation systems equipped in some of the investigated houses were improved during the course of this investigation period. The effect of the improvement on ventilation airflow volume was reported. The ventilation rates were measured by three different methods, namely constant concentration method, measurement of airflow rate at inlets/outlets and passive homogeneous emission method. Through this investigation, the measurement results indicated that the ventilation rate was insufficient in many houses and some of the ventilation systems were not operated properly. In addition, the amount of air leakage in the house envelope and the amount of air change due to occupant behaviour were also determined.

Heat Transmission in Surface Condensers

The paper deals with the resistance to heat flow on the steam side of surface condenser tubes, and begins with a brief reference to theoretical and experimental work on the subject. The separation of the total resistance from steam to water into its component resistances and the estimation of the resistance from steam to tube by the remainder method is then discussed, an example of the procedure used by the author in the preparation of the paper being given in Appendix I. The probable factors in the conditions of operation which produce the variations observed in apparent resistance to heat flow from steam to tubes, as estimated by the remainder method from the results of condenser tests, are then considered. The validity of the assumptions made with regard to these factors is tested by a re-examination of the results of four well-known condenser tests in which the amount of air leakage was recorded. The conclusions and observations to which this examination would appear to give rise are then stated. An alphabetical list of references is given in Appendix II.