Air Tightness Research Articles

The dynamic partitioning of airborne phthalates in indoor environment: effects of ventilation

Low energy consumption buildings with strong air tightness such as passive buildings are the development trend in the world. However, ventilation directly affects the emission and dynamic transport of indoor phthalates. A transient partition model considering the dynamic behavior of size-resolved particle was utilized to investigate the influence of ventilation on the airborne Di-2-ethylhexyl phthalate (DEHP). The air exchange rate (a) was set to 0.15 h-1, 0.3 h-1, 0.6 h-1, 2h-1 for the different conditions. The predicted gas-phase concentration of DEHP in the initial 70 days is unaffected for different a and constant hms, whereas it raises until the a increases to 2 h-1. The equilibrium gas-phase concentration decreases from 0.257 to 0.203 μg/m3. Meanwhile, the higher a also reduced the particle-phase concentration of DEHP. Furthermore, the changes of airborne DEHP were analyzed by considering the impact of a on hms caused by ventilation. The results indicates that more ventilation leads to higher gas-phase concentration for the whole stage. The gas-phase concentration at equilibrium increases from 0.237 to 0.440 μg/m3. The total airborne (gas-phase + particle-phase) concentration decreases with the higher ventitation rate, which indicates that the ventitation has a positive effect on indoor airborne DEHP.

Research progress of water-based release agents

A mould release agent is an additive that makes the moulded product easy to detach from the mould, it forms a protective film on the product to ensure the surface quality of the mould. Mold release agents are divided into water-based release agents, oil-based release agents and powder-based release agents. Water-based release agents are widely used because they have the advantages of low price, good release effect, green environment protection, smooth casting surface, good air tightness and good automaticity operation. According to the effective release material in the mold, release agent can be divided into silicone oil type, wax and fatty acid type water-based mold release agent. In this paper, the composition, properties and application characteristics of various water-based release agents were analyzed, and the future development direction of water-based release agents was forecasted.

Особливості проєктування поздовжньо-співвісних хвилеводно-мікросмужкових з’єднувачів

The authors justify the use of combined longitudinal-coaxial connectors — waveguide-coaxial or waveguide-microstrip type — in new modern antenna-feeder microwave paths. Using the example of a basic coaxial waveguide-coaxial connector based on a section of a regular rectangular waveguide, the study considers the process of converting an electromagnetic wave of a regular waveguide of the main waveguide type H10 into a transverse electromagnetic wave of a coaxial line with a wave resistance (impedance) Z0 = 50 Ohm. Such a connector allows implementing good electrical parameters — matching (standing wave ratio, SWR) and linear losses — but its design is difficult to configure and cannot be reliably reproduced. However, the basic operation principles of this connector make it possible to use it as a prototype when creating modern coaxial waveguide-coaxial or waveguide-microstrip connectors. One example of such a modern connector is the sealed longitudinal-coaxial waveguide-microstrip connector based on a segment of H-shaped waveguide, shorted by an end wall on one end. Correcting the reactive component of both inductive and capacitive nature will allow achieving the required parameters of the wave impedance of the connector. With this in mind, the author has built an inductive-capacitive system consisting of a matching element in the form of a staggered fin and a corrective element in the form of a rectangular parallelepiped. To ensure the air tightness of the connector design, the segment of the coaxial line was replaced by a sealed coaxial insert, which is a serial electronic component. Particular attention was paid to the layout and design of this sealed waveguide-microstrip connector, as well as to the calculation of the overall dimensions of its elements. The article proposes an original technique for measuring the main parameters of both waveguide-coaxial and waveguide-microstrip connectors. The author forms a mathematical model of combined type connectors based on the scattering wave matrix and presents the parameters of real hermetically sealed longitudinally coaxial waveguide-microstrip connectors based on waveguide segments of various standard sizes and measured at various frequencies.

TEST AND SIMULATION OF THE ELECTRONIC CONTROL SUSPENSION SYSTEM OF SEMI-TRAILER BASED ON SIMULINK

Aiming at the poor matching of the existing semi-trailer air suspension system, such as vehicle roll, airbag leakage and airbag response time after single airbag failure, the semi-trailer electronic control air suspension system is designed. The three-dimensional model and simulation model of semi-trailer electronic suspension system are established by using Creo and Simulink simulation software. The existing air suspension electronic control logic (ECAS), system layout and configuration are optimized to improve the turning stability, airbag response speed, static air tightness and NVH of semi-trailer air suspension. Through Simulink and ADAMS/car simulation analysis and vehicle carrying test, the simulation results and test data are analyzed, and finally the closed-loop control logic with supercharger is determined to adapt the novel control logic and system layout. The simulation and test results show that when the air compressor opening time is 3.5 s, the solenoid valve frequency is 22 kHz and the air pressure difference is 5.6 bar, the system response is the fastest and the energy consumption is the lowest.

Experimental Study on Mechanical Properties of Integrated Wall Panels of Grain Warehouse with “Thermal Insulation”

The walls of grain cottage silos are still being built by clay brick masonry featured with single‐structure form, poor air tightness, large workload of manual masonry on site, and huge consumption of raw materials and burning materials, which is not conducive to energy saving and environmental protection. In order to study the mechanical function of the new wall under the action of grain side pressure, the static loading test was conducted on the model of scaled‐down wall panel under the action of side pressure. The damage process, the damage pattern, and the bearing capacity of the wall panel were studied through the analysis of the crack development process and distribution law to reveal the force characteristics of the wall panel. The test results show that the span deflection of the “structure‐insulation” integrated wall panel under the lateral pressure meets the requirement of the limit state of normal use; the inner and outer leaf wall panels can work together under the action of the joint; the ratio of the load borne by the inner and outer leaf wall panels is equal to the ratio of their stiffness; the flexural stiffness of the wall panels after cracking is proposed based on the combined effect analysis. Based on the analysis of the combined effect, the degradation factor of the wall panel after cracking is proposed, and the deflection calculation formula of the inner and outer leaf wall panel is established, which provides a theoretical basis for the design and the promotion of the “structure‐insulation” integrated wall panel.

Research on air tightness of image intensifier tube during laser sealing

采用高功率YAG激光焊接机对高性能三代像管管壳后端（4J34可伐合金）与荧光屏屏环（4J49可伐合金）进行封接试验。研究了激光功率、脉冲宽度对焊接接头成型及表面热扩散的影响规律。研究表明：4J34合金与4J49合金表面成型质量在设备最大工作电流100 A，激光功率195 W及脉宽1.7 ms时最好，相对于激光功率，脉冲宽度对焊缝熔宽和熔深的影响更加显著，接头焊接中心区硬化最为严重，其硬度最大，热影响区次之。

Transcatheter Closure of Atrial Septal Defect

Background: Over the past decade, percutaneous atrial septal defect (ASD) closure has been the preferred treatment option in many clinical programs for ASD. Percutaneous ASD closures with advanced device architecture and distribution have established user experience and process security. The ability to diagnose has also improved. The devices have evolved from the larger fixtures to the reset zone, being easily eliminated with little residual mesh material and comfortable fitting with the surrounding structures. Biodegradable technology has been introduced and will be considered as a future option. The emergence of the use of the ASD closure device over the last forty years includes improvements that reduce the incidence of adverse effects reported over the years. Issues reported in the literature include thrombus formation, air tightness, device insertion, abrasion, residual shunts and nickel hypersensitivity. Modern tools hold medium and long-term data with excellent results. Multi-sized devices securely close simple and complex ASDs that can re-scan, reset, and detect percutaneous advanced delivery procedures. In this review, the most widely used tools and distribution processes are discussed and the tools that show promise for the future.
 Conclusion: As the field of transcatheter treatment of atrial septal defects (TC-ASD) and congenital interventional cardiology develops, real-world design studies provide valuable developmental information on aspects of care where there is disagreement about best practices and more research is needed.

Design of Low-Pressure Sand Casting Process for Water-Cooled Motor Shell in Electric Vehicle

Aluminium alloy motor shell is the core part of the new energy vehicle powertrain. It has a complex structure with an average wall thickness of 4∼5mm, a side wall with 6∼7mm spiral water jacket, and the bottom of the shell inlaid with cast steel bearing bushing. Because of its complex structure characteristics, as well as higher internal quality requirements and air tightness requirements, the casting process of motor housing is very difficult. This paper introduces the structural characteristics and common casting defects of the motor shell. On this basis, the typical casting process scheme of motor shell with sand core casting technology and the application of computer simulation technology in the development of motor shell casting process are discussed and shared.

Microclimate measurements in ventilated air gaps – instrumentation and first results

To achieve energy efficient buildings, the requirements for air tightness in Norway were strengthened in the recent years. Thus, the use of tape for tightening connections and overlaps in the wind barrier and vapour barrier layer has become more and more common. Since these products are covered by a façade cladding and hence difficult to access, they need to maintain their performance level over many years, usually 25 to 30 years. To design test methods to ensure the performance of tapes and other products used in the ventilated air gap, more knowledge on the climatic conditions, especially temperature conditions, is needed. The recently finished ZEB Lab building in Trondheim, Norway, has been instrumented with thermocouples to monitor the temperature conditions in the air gap. This study presents the instrumentation set up and first findings from the start of the experiment in summer 2020. First results show temperature levels up to 76°C in the upper part of the roof construction.

Semi-empirical model of internal pressure for a high-speed train under the excitation of tunnel pressure waves

To study the transmission of air pressure from external to internal carriage of high-speed trains, an internal pressure model excited by tunnel pressure wave is established. Firstly, factors affecting the air pressure transmission are analysed. Then, the semi-empirical models of the internal pressure caused by a single factor are established based on both the theoretical analysis and experimental data: (1) by applying the finite element method, effects of carbody deformation are studied; (2) based on the static air tightness test, the transmission from the gaps is modelled and (3) the model of the air ducts are surveyed on the base of the characteristics of the ventilation fans and valves. Finally, three routes are comprehensively considered and a coupling model of the internal pressure is established. Simulation results shows the model is adaptable in predicting the internal pressure under excitation of tunnel pressure waves. Besides, the effect of the factors on internal pressure are studied based on the models. Among the factors, the deformation has the least effect. Meanwhile, the air ducts are the dominant factor that affects the internal pressure at high opening degree, while the gaps will become the dominant factor when the opening degree of air ducts is relatively low.

Influence of Salt Rock Creep on Integrity of Cement Sheath Gas Seal

Salt rock is soluble and plastic. Plastic deformation or creeping flow is easy to occur in the process of drilling and cementing, which leads to irregular shape of wellbore, deformation or collapse of casing, and affects the wellbore air tightness in salt rock section, thus affecting the normal production and safety of oil (gas) wells. In order to provide a theoretical basis for the evaluation of wellbore air tightness in salt rock formation, based on petrophysical experiments and three-dimensional finite element method, the influence of the first and second interfaces of cementing in salt rock formation on wellbore air tightness was analyzed. The results show that the gas sealing ability of the first interface is stronger than that of the cement paste itself, and the salt rock creep can enhance the gas sealing ability of the second interface; the gas sealing ability of the salt rock mainly depends on the gas sealing ability of the second interface and the cement paste itself; the gas sealing ability of the salt rock has a complex positive correlation with the contact pressure of the interface; the second boundary is obtained The quantitative evaluation model of gas seal pressure is established. The quantitative evaluation model of gas seal pressure at the second interface of cementing can provide practical guidance for the evaluation of salt rock formation air tightness in the target area, and also has reference value for similar formations in other areas.

Adiabatic compressed air energy storage technology

Adiabatic compressed air energy storage technology

Wireless Leak Detection System as a Way to Reduce Electricity Consumption in Ventilation Ducts

This article presents a proposal for a wireless diagnostic system for checking the air tightness of the ventilation network. The solution is designed to increase crew safety in underground mining plants and increase the energy efficiency of the ventube ventilation system. The system is based on sensors measuring the pressure inside the ventilation duct in relation to the barometric pressure in the immediate vicinity of the duct. The flow of diagnostic data is based on a cascade transfer. The data from the first sensor are transferred successively to the last one. Based on the prior calibration of alarm thresholds in each device, the leakage or factor influencing the increase of air flow resistance is located. The article presents the genesis of the creation and discusses the principle and purpose of the system. In the following chapters, the progress of work related to testing the system in laboratory, industrial, and underground conditions at the Velenje Premogovnik mine (Slovenia) is presented. The authors analyze the test results and indicate the directions of possible further work on improving the system. The proposed leak detection system is based on a network of pressure sensors that communicate with each other to clearly pinpoint the leak location. The system has been designed for operation in underground mining plants with limited space.

ON GAS AND HYDRAULIC TIGHTNESS OF LINAC ACCELERATING SECTIONS

A technique for calculating the required impenetrability of brazing linac accelerating sections cooled by water and for control of their hydraulic tightness based on the total helium leakage rate is given. Three types of cooling systems: a water stream in tubes soldered on the outer surface of the sections, a water stream along the outer surface and along the internal cooling channels in sections are considered. It is shown that the contact of accelerating sections surface with cooling water requires increasing the tightness of their soldering at least by 66 times. As an example, requirements for hydraulic and air tightness of accelerating sections for the developed accelerator LU-10 NSC KIPT are given.

Local synergies and antagonisms between meteorological factors and air pollution: A 15-year comprehensive study in the Sydney region

Associated with rapid urbanization and escalation of bushfire events, Sydney has experienced significant air quality degradation in the XXI century. In this study, we present a 15-year retrospective analysis on the influence of individual meteorological factors on major air pollutants (NO2, O3, PM10 and PM2.5) at 14 different sites in Greater Sydney and Illawarra. By applying a newly developed “zooming in” approach to long-term ground-based data, we disclose general, seasonal, daily and hourly patterns while increasing the level of spatial associativity. We provide evidence on the pivotal role played by urbanization, sprawling dynamics, global warming and bushfires on local meteorology and air pollution. We strike associations between temperature and O3, both as average trends and extremes, on account of increasing heat island effects. The role of wind in a coastal-basin environment, influenced by a vast desert biome inland, is investigated. A steady trend towards stagnation is outlined, boosted by enhanced urban roughness and intensified heat island circulation. Relative humidity is also crucial in the modulation between NO2 and O3. With a sharp tendency towards drier and hotter microclimates, NO2 levels dropped by approximately 50% over the years at all locations, while O3's median levels almost doubled in the last 10 years. Further, O3 and PMs shifted towards more frequent extreme events, strongly associated with the exacerbation of bushfire events. Such results suggest an urgent need to prioritize emission control, building air tightness improvement and urban heat mitigation, towards a future-proof governance in Sydney and similar regions in the world.

Assessment of mussel shells building solutions: A real-scale application

The construction sector is a key generator of greenhouse emissions, so the use of alternative low-emission building materials is a growing tendency. This work describes and analyses an innovative sustainable building that includes mussel shells in all its constructive elements. This material is a by-product of the canning industry that is nowadays landfilled. Mussel shells were used as aggregate in the concrete strip footing (foundation) and in the exterior and interior coating mortars (walls), and as loose-fill material for the whole envelope insulation (floor, walls, and roof). The results from both the laboratory and the constructive process were useful to improve the solutions and to develop a building with low energy consumption. Finally, the energy demand of the building was assessed using the Passive House Planning Package (PHPP) software and the blower door test was carried out to measured air tightness. It can be concluded that mussel shell materials meet the requirements of Passive House standard for energy efficient buildings: simulation results showed a primary energy consumption of 86 kWh/(m2yr), that is a 28.3% lower than the value fixed by the standard.

Airtightness of cross-laminated timber envelopes: Influence of moisture content, indoor humidity, orientation, and assembly

Decrease in the relative humidity (RH) of the indoor air causes cracks in the cross-laminated timber (CLT) surface resulting in air leakages in the CLT panel. The effect of construction moisture on CLT air tightness properties is not clearly defined, which is important for moisture safe construction. The aim of this study was to investigate the effect of high MC on CLT air tightness properties compared to conventional factors such as indoor RH change, insulation type and façade orientation. An air permeability test was carried out on 12 different test walls with CLT as the airtight layer exposed to indoor environmental conditions. Test walls were constructed from CLT panels with two different initial moisture content (MC) values, ≈13%, and ≈26%, and in addition, different insulation materials were used in the wall assemblies: mineral wool, cellulose wool and polyisocyanurate (PIR) plates. Air leakage measurements were carried out at two different times, first in mid-autumn and second at the end of winter. Based on the results of this research it was concluded that high initial moisture content in the CLT panels significantly weakens the airtightness of the external wall. CLT exposure to water and wetting the CLT panels during construction carries more than a risk of moisture damage, and the planning and implementation of moisture safety in the construction of CLT buildings is therefore essential if the CLT is to be considered as an airtight layer. The effect of a change in indoor RH is small on the air permeability properties of the CLT wall. Therefore the 5-layer CLT panel can be considered and used as an air-tight layer in external wall construction as long as its initial low moisture content (about 13%) is maintained during both construction and service life.

Гума як перспективний конструкційний матеріал для створення вузлів стикування системи термостатування

In integrated launch vehicles, one of the systems responsible for successful launch preparation and support is a ground thermal conditioning system supplying low-pressure thermostatic air to the “dry” compartments and head blocks of a launch vehicle. To connect the thermal conditioning system to the launch vehicle, a special interface is used. The proper functioning of the interface is critical to the reliability of the ground equipment of the system, the launch vehicle, and the space complex as a whole. This article describes key requirements to the interfaces of the thermal conditioning system and the drawbacks of their existing designs. The article proposes a new concept of interface design, according to which the pipeline of the ground thermal conditioning system is connected to the inlet tube of the launch vehicle via a corrugated rubber hose composed of three basic parts. The hose is attached to the inlet tube of the launch vehicle with the help of a metal lock/unlock device. The proposed solution provides good air tightness, ease of operation, easy multiple connections to the launch vehicle at different angles, and an automatic disconnection at launch or a manual disconnection in the case of a cancelled launch. Using rubber, which is a high-elasticity structural material, in the manufacturing of hoses makes it possible to minimise the effort required to disconnect the interface from the launch vehicle. In a high elasticity state, rubber can absorb and dissipate mechanical energy over a wide range of temperatures, which precludes the vibration caused by the engine operation from being transmitted to the ground thermal conditioning system. The article presents the key properties of rubber used as a structural material and its features to be considered in the design of similar devices. In contrast to metal, which shows two types of deformation (elastic and plastic), rubber can exhibit three types (elastic, superelastic, and plastic). During the design of interfaces, two types of deformation were taken into account: elastic and superelastic. Experimental tests of the interface presented in the article showed its full compliance with the requirements specification.

A Bayesian strategy for forecasting the leakage rate of concrete containment buildings – Application to nuclear containment buildings

The forecast of large concrete structures behavior such as Nuclear Containment Buildings (NCB) is a critical safety issue, whether for the structure itself or for its surrounding environment. Over the past few decades, complex finite element models have been developed for assessing the mechanical behavior and the leak tightness of large concrete structures. These models involve numerous parameters known with uncertainties, which importance could jeopardize the reliability of forecasts. Therefore, this contribution aims to present a weakly coupled Thermo-Hydro-Mechanical-Leakage methodology to forecast the evolution of dry air tightness of large concrete structures. The proposed approach is based on a Bayesian updating strategy aiming to reduce uncertainties on forecasts by combining information provided by both a physical model and in situ observations acquired up to date. The Bayesian strategy is coupled with a scale reduction method for ensuring applicability at the scale of large structures. The methodology is applied to a 1:3 scale NCB, in order to improve confidence level of leakage rate forecasts by taking advantage of monitoring measurements. The forecasted leakage rates are in good agreement with the measurements, and the proposed methodology enables to significantly reduce the uncertainty throughout the operational phase of the structure, even with a limited amount of monitoring data.

Development of the selective pressure neutralization method – An air tightness test method for exterior pressure boundary characterization in high-rise residential buildings

This paper presents a novel method for characterizing the exterior envelope air tightness of high-rise multi-unit residential building suites, the “Selective Pressure Neutralization” (Selective PN) method. Through the neutralization of air flow across the corridor-suite pressure boundary, this method can improve accuracy compared to the typically implemented “Whole Suite” method, while halving the time and equipment requirements of on-site testing compared to the Pressure Neutralization method. A CONTAM model was developed using field data from eight case study suites and then used to simulate the effectiveness of the proposed method in fourteen suite configurations. Sensitivity study simulations were also carried out where individual suite pressure boundary air tightness characteristics were varied. The case study results showed average absolute exterior boundary characterization errors of 16% and 51% for the Selective PN and Whole Suite methods, respectively. The sensitivity study results showed that the Selective PN method meets or exceeds the accuracy of the Whole Suite method by up to 78% in buildings with leakier exterior boundaries, like those in buildings with punched windows (as opposed to window wall configurations). Thus, the Selective PN method shows promise as an alternative air tightness testing method.