Vent Pipe Research Articles

Modeling the vertical transmission of bioaerosols in residential building drainage systems

The vertical transmission of bioaerosols in building drainage systems is an understudied route of disease spread. This research examines how the position of drainage floors, flush volume, pipe type, and building story number affect the dynamics and reach of bioaerosols in such systems. Our findings show that drainage points positioned lower in a building amplify the number of the affected floors above, with recorded pressure differences at various drainage points ranging from 900 to 3200 Pa, depending on flush volume and floor position. The transition to a double pipe system significantly reduced pressure differences (to as low as 330 Pa in vent pipes), thereby diluting bioaerosol concentrations but increasing their dispersion across more floors. Building story number further influenced bioaerosol spread, with higher buildings exhibiting negligible pressure differences across stories (1400–2300 Pa) but a pronounced increase in affected floors above the drainage site.

Compliance of private ventilated improved pit latrines to odour and fly control guidelines: A technical audit in selected regions of Ghana

The ventilated improved pit (VIP) latrine offers a promising route to safely managed sanitation to many households in developing countries. However, some technical guidelines must be followed in order to realise the technology's advantage of odour and fly nuisance control. This study sought to audit private VIP latrines in selected regions of Ghana to assess their compliance to conventional technical guidelines and to understand the major factors that influence the latrine designs. An inspection checklist was developed to assess 296 private VIP latrines in the Central, Ashanti and Northern Regions of Ghana while semi-structured interviews were conducted among the latrine owners to enquire the factors that influenced the designs of their latrines. The results show that provision of a window in the superstructure (86 %), and the avoidance of an insect screen in the window(s) (77 %) were the most complied guidelines. The use of 150 mm diameter vent pipe was the least satisfied guideline (5 %). On the average, a latrine satisfied about half (3.6) of the technical guidelines that were assessed. The decision or advice of local artisans is the most influential factor in the design of the latrines. Cost was the least mentioned factor cited by the latrine owners. There is the need to establish information desks at the various Metropolitan, Municipal and District Assemblies (MMDAs) to guide prospective owners on the proper design and construction of the VIP latrine. In addition, toilet construction should be incorporated in the curriculum for the basic training of building and construction students in Technical and Vocational Education and Training (TVET) institutions in Ghana. Further research is required to ascertain the basis of the decisions of local artisans and the potential impact of the use of accessories that are ‘borrowed’ from the WC toilet on odour and fly control in the latrine.

Numerical Simulation on Dispersion of Hydrogen Leaked in Particle Layers of Glass Beads and Soil

In order to understand the dispersion of hydrogen (H2) leaked in packed beds of nonporous/porous particles in a partially open space practically, the dispersion of H2 in the particle layers of glass beads and soil was analytically studied using a computational fluid dynamics code to be compared with the experiments and to elucidate the effects of the particle layer. The packed beds in the partially open space can be considered as a basic model for all processes of transfer, treatment, storage, and disposal of radioactive materials containing fuel debris in the decommissioning of nuclear facilities after a severe accident. The H2 flowing out from a single leak point in the particle layer of nonporous glass beads was affected by buoyancy around the leak point and diffused directly above the leak point in an elliptical shape faster than in the horizontal direction. After that, when it reached the air layer in the head space above the particle layer, the H2 spread horizontally, formed a large concentration gradient near the boundary between the particle layer and the air layer, and further diffused in the air layer until the H2 concentration became about 1/3 or less of the concentration near the surface of the particle layer. When the particle diameters were 512 μm and 1200 μm, this tendency was more pronounced when the porosity was the same and the particle diameter was smaller. The calculations largely reproduced the experimental concentration distributions. When the particle layer was porous decomposed granite soil, the diffusion behavior of H2 in the particle layer proceeded in the same manner as in the case of the glass beads. However, a large concentration gradient was formed near the boundary between the particle layer and the air layer, and then H2 diffused in the air layer until the H2 concentration became below the lower combustion limit. It was suggested through sensitivity analysis that the air permeability coefficient had a large effect on the time course of the H2 concentration distribution. Based on this information, we further simulated H2 behavior in the vessel containing the H2 leaked particle layer. By inserting multiple vent pipes without considering H2 generation distribution and particle properties in the particle layer, H2 accumulated from one pipe was discharged by buoyancy without depending on the H2 generation distribution and particle properties in the particle layer and air flowed in from the other pipe. It was suggested that such a natural ventilation process would reduce the H2 concentration in the container.

Research on Dynamic Venting Characteristics of City Gas Pipeline Networks and Analysis of Software Development

As an important part of the gas pipeline safety system, the venting pipe plays a role in protecting the safe operation of the network and reducing the consequences of accidents, and its design feasibility, rationality and safety are particularly important. In China, most of the online simulation software used for gas pipeline network venting simulation is limited to expensive, poorly controllable software and difficult to design for specific working conditions, so the application of dynamic simulation software for gas pipeline networks is of great importance. In this paper, simulation software is developed for city gas pipeline venting systems, simulations are carried out using a programming language, the usability of the developed software is verified and the influence of different influencing factors on the venting process is investigated using the control variable method of analysis.

Analysis of the Impact of Lateral Conduit and Metal Wire Mesh on Methane Explosions

To enhance the deflagration efficiency and protection level of combustible mixed gases in narrow spaces, a small square experimental pipeline system was designed. Experiments were conducted to investigate the effects of lateral vent pipes and metal wire meshes on the explosion characteristics of methane gas. This study examined the influence of changing the positions of the lateral vent pipes and metal wire meshes in the pipeline on the variation of parameters such as the flame shape, leading speed, and pressure of the methane/air premixed gas in the pipeline. The results indicated that the lateral vent pipes could effectively release part of the energy from the methane explosion, and the release effect was stronger the closer they were to the ignition end. This was significantly more effective in releasing the flame and pressure than when the vent pipes were placed in the middle or at the end of the pipeline. For lateral vent pipes close to the ignition source, their effective release of the not yet fully developed premixed flame allowed the heat absorption, wave absorption, and quenching performance of the installed metal wire mesh in the pipeline to fully exert their effects on the slow-spreading premixed flame. Furthermore, when a metal mesh was installed in the pipeline and the flame could not be extinguished, the flame penetrated the mesh structure, causing the flame front to become unstable and exhibit “irregular wrinkles”. That is, the flame front was no longer smooth, the wrinkles became more pronounced, and the degree of turbulence was enhanced.

LES model of flash-boiling and pressure recovery phenomena during release from large-scale pressurised liquid hydrogen storage tank

The paper presents large eddy simulations (LES) model of two-phase (liquid-gas) hydrogen behaviour during pressurised tank venting. The results of simulations are compared against published experiment on flash-boiling of liquid hydrogen (LH2) in a large-scale tank of 7.622 m height, 2.3 m internal diameter, filled with LH2 to 6.248 m (80% tank filling) at pressure 321.8 kPa gauge. The volume-of-fluid model is applied for tracking phases and Lee's model is used to simulate evaporation and condensation. The effect of various Lee's model evaporation-condensation coefficients on the process dynamics is assessed. The simulations are compared against experimental pressure dynamics monitored at the venting pipe and experimental temperature measured by thermocouples in gaseous and liquid phases during the first 15 s of venting. The LES model reasonably predicts physical phenomena during depressurisation of LH2 storage tank, including the pressure recovery phenomenon, LH2 level and temperature dynamics in the tank.

Experimental research on the venting characteristics of methane and coal dust two-phase system mixture explosions

This research focused on the venting characteristics and influence factor of methane and coal dust mixture explosions. The corresponding relationship between the venting parameters was analyzed and the effect of methane concentration was obtained. Results indicate that the venting flame propagation and pressure rise of vessel interior and exterior presented the clear corresponding relationship. The venting flame underwent the evolution process of “mushroom”, “spherical” and “strip” structures. At 6% methane concentration, the venting flame was longest and its propagation velocity was fastest. During the extinguishing stage, the flame exhibited an obvious oscillation. The venting flame appeared a secondary venting phenomenon at 6% and 8% methane concentrations, and the phenomenon was more evidently at 8% methane concentration. The pressure at the venting pipe was the greatest and its change was also most significant, even appeared a larger negative value. Compared with the vessel interior, the pressure of vessel exterior was continuously decreased as the venting distance increased. The venting pressure was the greatest at 6% methane concentration, followed by 8% methane concentration. The pressures of four points at 4% methane concentration were respectively reduced by 25.0%, 34.9%, 43.8% and 81.8%. The corresponding flame temperature also presented the same change trend. Besides, the venting flame image showed a good correspondence with the temperature field distribution and the highest temperature appeared in the center of spherical flame. The secondary venting resulted in the recurrence of high temperature flame at the venting port (500℃-650℃) and was affected by the methane concentration inside the vessel.

Ventilated improved pit latrine: a theoretical evaluation of conventional design guidelines, user adaptations and prospects for improvement

The ventilated improved pit latrine has the potential of meeting the sanitation needs of many households in developing countries and enhance the chances of attaining the Sustainable Development Goal (SDG) 6. However, some user adaptations of the technology appear to conflict with conventional design guidelines and may compromise the ventilation rate in the vent pipe. This would negatively affect the odour control function of the technology. This paper seeks to evaluate existing conventional design guidelines that are aimed at controlling odour and fly nuisance in the latrine to highlight their relevance and possible conflicts with existing and emerging user adaptations. It also identifies potential structural modifications that may be adopted to accommodate emerging user preferences without compromising the odour control mechanism. The review shows that, indeed, some construction practices such as provision of windows in multiple sides of the superstructure adversely affect the ventilation rate and could lead to odour problems. However, the effects of some suspected unfavourable user adaptations such as use of closed-top vent caps and ceramic seats with covers have not been investigated. Furthermore, recent studies have demonstrated the possibility of compensating for the negative effect of some user preferences with favourable environmental conditions such as high wind speed and structural modifications using a mathematical model. However, the existing model fails to account for some key design criteria and needs to be improved to make it useful for a wider application.

Cooling effect analysis on para-ortho hydrogen conversion coupled in vapor-cooled shield

The conversion process from parahydrogen to orthohydrogen accompanies an endothermic effect. Embedment of a para-ortho hydrogen converter into the thermal insulation could enhance the thermal protection of a liquid hydrogen storage tank. A physical model was proposed to simulate the heat transfer behavior of the insulation structure that integrates a polyurethane foam, a blanket of multilayer insulation, a vapor-cooled shield, and a para-ortho hydrogen converter. The effect of the para-ortho conversion process was considered. The model was validated by experimental data and then used to investigate how the para-ortho hydrogen conversion influences the temperature distribution inside the composite insulation. It was found that a single converter improves the cooling performance most effectively if it is placed at the middle length of the venting pipe mounted on the vapor-cooled shield. Either incorporating more converters or extending the length of the vapor-cooled shield pipes brings limited further improvement. The optimum position of the vapor-cooled shield inside the multilayer insulation moves towards the cold boundary in the presence of para-ortho conversion, compared to conventional vapor-cooled shield and multilayer insulation structures. A net heat flux reduction of over 10% could be achieved when the para-ortho conversion is located at the optimal position inside the vapor-cooled shield.

PERANCANGAN SISTEM PLAMBING PADA BANGUNAN WISMA MESS SEPOLWAN CIPUTAT

The construction of high-rise buildings in big cities is currently increasing rapidly, before the building is built, it is necessary to plan a plumbing system to meet the needs of water supply for daily needs in buildings and waste water disposal. In planning the plumbing of Wisma Mess Sepolwan 3 floors, the need for clean water is 28.92 m3/day, the GWT (Ground Water Tank) bottom tank capacity is 6.5 m3/day, the top tank capacity (Roof Tank) is 5.4 m3/day and the sewer tank 25 m3/day.The transfer of clean water from the ground water tank to the top water tank (roof tank) uses a transfer pump with a capacity of 5.4 m3/minute, pump head of 39.64 m. Fordistribution of clean water on 3 floors using a pressure booster pump with a capacity of 0.16 m3/minute and a pump head of 10.3 m.Transfer of clean water from the bottom water tank (Ground Water Tank) to the top water tank (Roof Tank) using a pipe size of 40 mm. The design of the diameter of the clean water distribution pipe for each floor gets a size of 150 mm diameter of the main pipe / water main pipe and 50 mm per floor.The design of the diameter of the sewerage pipe from (closet and toilet) size to the standpipe for each floor is 100 mm and the diameter of the riser standpipe is 150 mm. The design of the diameter of the waste water pipe from (hand sinks and traps) to the size of the standpipe for each floor is 80 mm and the diameter of the riser standpipe is 100 mm. The design of the vent pipe diameter for the size of the standpipe for each floor is 50 mm and the diameter of the riser standpipe is 80 mm

Wind Speed Thresholds for Adjusting Conventional Design Criteria for the Ventilated Improved Pit Latrine without Compromising Odour Control

Aims: The objective of this paper is to re-evaluate the wind speed threshold at which the 100 mm polyvinyl chloride (PVC) vent pipe may be used without compromising the ventilation rate required for effective odor control in a ventilated improved pit (VIP) latrine. The paper also sought to investigate the chances of leveraging upon high wind speeds to grant user preferences for multiple windows and installation of insect screens, which are conventionally forbidden.
 Study Design: A comparative experimental design was carried out in a VIP latrine with internal cubicle dimensions of 1.2 m x 1.5 m built over a pit of cross-section 1.2 m x 2.5 m and depth of 3.0 m which was fitted with a 100 mm PVC vent pipe.
 Place and Duration of Study: The experimental setup was located on the compound of a public basic school in Prampram, a peri-urban coastal community in Southern Ghana. The setup was monitored for twelve hours a day (5 am to 5 pm) for twelve days.
 Methodology: The experimental setups comprised of four designs of the VIP latrine: single-window and multi-window designs each with and without insect screen in the window. The ventilation rate in each modified design was monitored simultaneously with the external wind speed.
 Results: The results of the study indicate that the 100 mm PVC vent pipe could attain the recommended ventilation rate of 20 m3/h at an average wind speed as slow as 1.5 m/s as compared to the 3 m/s previously suggested. The influence of wind speed on the ventilation rate is insignificant at wind speed variations not exceeding 0.5 m/s when the 100 mm PVC vent pipe is used.
 Conclusion: At an average wind speed of 1.5 m/s, either the multiple-window design or insect screen used in combination with the 100 mm PVC vent pipe could attain the recommended ventilation rate and should not be outrightly forbidden. However, a wind speed threshold of 2.5 m/s is required for the adoption of the multi-window design with insect screens when the 100 mm PVC vent pipe is used.

Numerical Investigation of the Initial Charging Process of the Liquid Hydrogen Tank for Vehicles

Liquid hydrogen has been studied for use in vehicles. However, during the charging process, liquid hydrogen is lost as gas. Therefore, it is necessary to estimate and reduce this loss and simulate the charging process. In this study, the initial charging process of a vehicle liquid hydrogen tank under room temperature and atmospheric pressure conditions was numerically investigated. A transient thermal-fluid simulation with a phase-change model was performed to analyze variations in the volume, pressure, mass flow rate, and temperature. The results showed that the process could be divided into three stages. In the first stage, liquid hydrogen was actively vaporized at the inner wall surface of the storage tank. The pressure increased rapidly, and liquid droplets were discharged into the vent pipe during the second stage. In the third stage, the mass flow rates of liquid and hydrogen gas at the outlet showed significant fluctuations, owing to complex momentum generated by the evaporation and charging flow. The temperatures of the inner and outer walls, and insulation layer, decreased significantly slower than that of the gas region because of its high heat capacity and insulation effect. The optimal structure should be further studied because the vortex, stagnation, and non-uniform cooling of the wall occurred near the inlet and outlet pipes.

Throttle and expansion characteristics of supercritical carbon dioxide during its venting

Supercritical CO2 has important applications in the fields of power cycle generation systems and carbon capture, utilization and storage (CCUS). The venting equipment represents a fundamental pressure-relief method for the purpose of depressurizing sections of those systems for inspection, maintenance or repair. The extremely low temperatures, dry ice blockage and overpressurization will appear in the system due to the throttling and expansion effect during venting. Meanwhile, the released CO2 may cause the exposure for the high density gaseous CO2, solid CO2 particles and cryogenics to the people in the venting area. The study of flow characteristics during CO2 venting is absolutely essential for assessing the hazard probability of dry ice formation and the blockage of relief valves during emergency or routine operational venting. In this paper, the theoretical analysis and experimental tests were conducted to study the throttle and expansion characteristics through the elbow, valve and orifice during straight vertical venting of supercritical CO2 with a 258 m long, 233 mm inner diameter pipeline system. The pressures and temperatures inside the main pipe and vent pipe, and the temperatures near field region were recorded during venting. After the valve was opened, the pressure in the vent pipe rose rapidly, and the rising range decreased with the decrease of the distance from the orifice. The temperature drops of CO2 were obvious after supercritical CO2 passed through the bend, the valve and the orifice. The supercritical CO2 in the main pipe changed into gas-liquid two-phase, and the liquid CO2 were produced in the vent pipe due to the throttling expansion effect. The CO2 temperature near the orifice were in quasi steady state after reaching the lowest value due to the continuous vaporization of liquid-phase CO2 and sublimation of dry ice particles, accompanied by the air entrainment process.

Influence of Vent Pipe Bottom Connection Position on the Discharge Capacity of Two Building Drainage Pipe Systems

Influence of Vent Pipe Bottom Connection Position on the Discharge Capacity of Two Building Drainage Pipe Systems

Improving the performance of the compound labyrinth weirs using an artificial ventilation approach

Abstract Compound labyrinth weirs are a new shape that is used to increase discharge. The air pockets behind the nappe flow are a big problem for the hydraulic performance of the labyrinth weirs. The study aims to use the artificial ventilation approach to improve the performance of the compound labyrinth weirs. The current study proposes artificial ventilation techniques to mitigate the pressure behind nappe flow and to improve the coefficient of discharge. The data have been collected for three cases (without vented (WV), with vented (V), and with suction (S)). The results indicated that the pressure distribution behind nappe flow was not similar for all tested points. Also, a slight negative pressure was observed when H′t/P′ was measured between 0.1 and 0.2. Artificial ventilation with a suction pump was the best technique to reduce pressure behind the nappe flow when compared with a vent pipe device. Furthermore, the compound coefficient of discharge (Cdc) using the suction and vent devices was greater than the compound coefficient of discharge (Cdc) without the vent devices by 10% and 4.5%, respectively. The empirical equations were provided to predict the compound coefficient of discharge when pressure data behind nappe flow is available.

Air pollutant dispersion around high-rise buildings due to roof emissions

Air quality in the built environment has a significant impact on public health, particularly in densely populated cities where residents live in closely-packed high-rise buildings. In this case, communicable respiratory diseases are apt to spread through vent pipe emissions on the building roof and facilitate community transmission. This study applied computational fluid dynamics to simulate the dispersion of the pollutants discharged from the roof vent pipes around high-rise buildings. The results show that the dispersion process is dominated by wind-structure interaction, wind incidence angle, air pollutant discharge location, and vent pipe height, and the dispersion is more complex around crucifix-form buildings than cubic ones. When the wind incidence angle reaches around 90°, the air pollutants are entrained in the re-entry of the building, thus impeding the dispersion process. The building areas most adversely affected by air pollutants are located on high floors near the vent pipe. Changing air pollutant discharge location and increasing the height of the vent pipe can significantly reduce the affected area. Where the height of the vent pipe is restricted, parapets at the roof edges are suggested to further reduce the adverse effects of air pollutants. These research findings can help to reduce the risk of airborne contaminants/diseases spreading in current and future built environments.

The rolling simulation for cold work metal hardening

This article describes the results of a calculation and experimental analysis of destructive physical phenomena that appear in critical sections of industrial and power-related equipment, and lead to occurrence of various operational damages. It was shown that pipeline welded connections are the sections most prone to crack development, therefore the traditional strength calculations need to be combined with fracture mechanics criteria and thorough materials analysis of flawing and structural imperfection. The cold work hardening technique was proposed as a solution for the problem of critical sections performance property restoration. The technique uses surface plastic deformation phenomenon to change the material’s throughthickness stress distribution. In order to optimise surface hardening for welded connections prone to defect formation, we proposed a simulation for analysing an actual pipeline sections load. To assess the applicability of the simulation results, the cold work hardening technique was developed and introduced using a full-scale test sample for damaged areas of welded connections in ø426×40 vent pipes at Novovoronezh NPP Unit No.5.

Ventilation of roadways using kinetic energy of air flows

The article presents the studies into effectiveness of ventilation by local sources of draught installed in the brattice-free roadways. The relevance of this topic is defined by the need to improve mine ventilation, prevent leaks in the conditions of insufficient fresh air, as well as to remove harmful impurities from faces. The efficiency of ejector units is analyzed versus the aerodynamic drag of a ventilation section and a cross section area of a mixing chamber. On this basis, the optimal parameters for the ejector unit to reach the maximum performance are determined. The numerical simulation of the ejection effect in large crosssection roadways has found that a part of the kinetic energy of the jet is spent for the formation of an air vortex which plays the role of a mixing chamber. The problem connected with insufficient airing is eliminated by means of series arrangement of fans, which reduces air circulation and leakage in minedout voids, and ensures air feed to work spaces. The variants of application of air curtains to reduce air leaks via roadways which cannot be shut by brattices are discussed. It is shown that this method is costeffective when pressure drops are under 2 daPa and is ineffective in prevention of leaks via installations above ground. In ventilation of dead-end roadways, the increase in the distance between the end of the vent pipe and the face surface prevents the damage of the vent pipe by blasted rock chips and reduces the labor input of installation and dismantling. The analytical estimation of the permissible spacing for the face surface–vent pipe is carried out as function of excess flow rate as against the required air flow. The ventilation simulation was carried out using the theory of turbulent jets and elements of numerical simulation in specialized software products for the verification of analytical dependences.The study was supported by the Russian Foundation for Basic Research and by the Perm Krai Government within the framework of R&D Project No. 20-45-596021 r_NOTS_Permskii krai.

BTEX and Nitrogen Oxides fume Assessments in Fuel Dispense Stations and Residential Areas

Fuel vapors are released from storage tanks through vent pipes and from filling pump fuel dispensary stations. These petroleum-based by-products are introduced into ambient atmospheres and neighboring areas and may become a potential health risk. To investigate the quantity of benzene, toluene, ethylbenzene, and xylene (BTEX) and nitrogen oxides (NOx) concentrations as they are considered air pollutants and proven that they have negative health impacts on human. A selected fuel dispensing stations within Kuwaiti residential areas, passive samplers were deployed within selected fuel stations and also several residential areas for one week. Findings reveal that the concentration of BTEX at the fuel dispensing stations was significantly elevated than it was for the breathing pipe in residential areas. The concentration of benzene of 5.5 μg/m3 is slightly higher than the mean ambient concentrations in the rural and urban areas that 1 μg/m3 and 5–20 μg/m3, respectively. The levels are higher near such sources of benzene emission as fuel dispensing stations. As a result, the benzene close to the fuel stations is higher up to 70 μg/m3. Emissions escalate during weather change because of meteorological variables like temperature and wind direction influence dispersion of noxious compounds in the ambient air. With significant additions of harmful petroleum products into Kuwaiti air, a weary for respiratory and digestive implications may be paving the way to cause an ecological uproar. Hence, the government should use this baseline data and provide guidance to fuel dispensary stations for an improved method of fuel dispense, improvising fuel storing to minimise temperature change for fuel state preservation and, use of nozzles that increase dispensary speeds while minimising vapour production.

Assessment of sludge formation in diesel storage tanks and eradication measures

The sludge formation and its accumulation in fuel tanks cause several problems such as clogging of vent and suction pipes, reduction in fuel quality and tank capacity, and deterioration of tank material. Sludge is a complex composition of water, fuel, sand, waste oil, metals, bacteria, minerals, and other organic matter. It grows with time because of bacterial growth (that feeds on fuel and water), impurities, and the aerobic polymerization of hydrocarbons in the fuel. The main objective of the present work is to delay the sludge from forming in the diesel storage tanks. It aims at breaking down information collected from various sources on how sludge formation occurs with time and produce research results on the chemical analysis performed on a diesel sludge sample collected from a fuel depot. Two experimental cases have been set up to show how stirring affects sludge growth over a period of time. It is observed that the sludge growth is less in the sample that is agitated when compared with the sample without agitation. By taking this into account, a stirring design isproposed and developed. Also, an idea is provided for reducing the metal ions in the sludge, thus maintaining a high-quality fuel ready for dispensing at the fuel stations.