Extraction Fans Research Articles

Enhancing water productivity and cost-effectiveness in hemispherical solar stills using sandy beds, reflectors, and a vapor extraction fan

The objective of this study was to enhance the performance of hemispherical solar stills (HSS) through experimental investigations utilizing various types of sand beds as thermal storage materials. The research examined the influence of sand type (yellow and black) and sand bed heights (1, 2, and 3 cm) on the efficacy of HSS. Additionally, the study explored the effects of external reflectors and a vapor extraction fan on the performance of sand-based HSS. The experimental results indicated that HSS using black sand demonstrated superior performance compared to other operating conditions in terms of both productivity and efficiency. Particularly, the most significant improvement in performance for the black sand hemispherical solar still (BSHSS) was observed when employing reflectors and a fan with a sand bed height of 1 cm, resulting in a substantial 154% increase in production, where the production for hemispherical SS and BSHSS + fan and reflectors was 4100 and 10400 mL/m2.day, respectively. Under these optimized conditions, the thermal efficiency of BSHSS + R + F reached 56%. In conclusion, an economic analysis was conducted, revealing that the cost for water treatment was $0.022 per liter for the conventional hemispherical solar still (HSS) and $0.012 per liter for the BSHSS equipped with reflectors and a condenser. These findings represent a significant advancement in enhancing the feasibility and efficiency of solar distillation systems, thereby addressing the global challenges of water scarcity and environmental sustainability.

Feasibility Study of New Geothermal System for Heating Premises and Thermal Complexes: Experimental Investigation of Water-Air Heat Exchanger in the East of Algeria

Abstract This paper constitutes a new technological solution for the exploitation of one of the most important geothermal deposits located in the locality of Biskra (South-east Algeria). This is the Albian aquifer whose hot waters from boreholes, hot springs and spas are poorly exploited while ambient temperatures during winter periods reach very low levels, especially at night. The principle of this geothermal system is to immerse a PVC tubular water-air exchanger in a pool permanently supplied with hot water from a low-energy geothermal borehole with a high flow rate. The choice of PVC material is attributed to the fact that hot geothermal waters are generally of an aggressive composition to steels and metals in general. The geothermal air heater allows the heating of the ambient cold air which is introduced into the exchanger and then extracted hot using an extraction fan. The hot air is then diffused into premises for heating during the winter season. The improvement in the performance of this type of exchanger is highlighted, in particular by acting on the number of pipes of the exchanger and the air flow rate using geothermal energy (low energy) as a source of renewable and clean energy. The experimental results obtained showed that the energy gain is a function of the length of the exchanger and the air flow rate. This gain can be up to 20°C between the inlet and outlet of the miniature exchanger model, which means that the proposed solution could be technically feasible.

Maintenance optimisation of heating, ventilation and air conditioning systems to improve indoor air quality

The purpose of this paper is to develop predictive maintenance optimisation model that allows to identify the critical components in HVAC systems that can compromise the indoor air quality and provide appropriate maintenance actions. The proposed optimisation model is formulated as integer programming problem and provides the optimal solution of when to repair or replace critical components of equipment with the goal to minimise total maintenance costs while maintaining pollutant concentration below an acceptable threshold. In order to evaluate the impact of degradation of equipment and maintenance decisions on the pollution concentration level indoors, pollution reduction factor is modelled as a function of the health of control equipment. To test the model a simple case study of 3d printer generated emissions is considered, where extraction fan is used to control pollution level inside the cabinet.

Performance-Based Design Assessment of Temperature Tenability Condition in a Hotel Atrium

Fire safety risk assessment to prevent loss of human life and property is necessary for complex structures where the traditional prescriptive designs are inapplicable. Maintaining tenable temperature conditions is essential for the safe evacuation of building occupants. This study considered British Standards (BS) 7974 and the Code of Practice for Fire Precautions in Buildings to analyze the temperature tenability conditions in the hotel atrium through a performance-based design approach. Further, the Computational Fluid Dynamics (CFD) code, Pyrosim, a Graphical User Interface (GUI) of the Fire Dynamics Simulator (FDS), was utilized to simulate a constant Heat Release Rate (HRR) steady state design fire of 5 Megawatts (MW) igniting from the hotel brasserie (ground floor) within the atrium. The researcher used the big design fire of 5MW to generalize the results to similar fires in similar structures. The objective was to conduct a fire safety risk assessment to prevent loss of property and fatalities by activating a smoke management control system with a ‘what if’ condition when the fire suppression system failed to start. Temperature data was collected through the statistical steady state profile, smoke layer temperatures, thermocouples, and 2-dimensional slice temperature recordings. The ground floor, the fire source, was found to have untenable conditions for human survival with temperatures above 2250C, as confirmed by thermocouple and steady-state temperature profile readings. Other floors demonstrated tenable conditions for human survival with temperatures below 400C due to the effect of natural vents and mechanical extractors, which extracted the hot smoke at a rate of 15m/s. The temperature recordings from this study compared well with those from Chew and Liew’s (2000) Computational Fluid Dynamics results, which had fire igniting within the atrium, without sprinklers, and had mechanical extraction fans and a constant Heat Release Rate of 5 Megawatts (MW). The results indicated that the smoke control management system maintained tenable temperature conditions within the hotel atrium, even without the fire suppression system through sprinklers. Considering the design fire size was 5 MW, which was significantly big, the results could be generalized for other hotels or structures with similar designs.

Improving terminal fire safety with minor impact on operational continuity using performancebased design

Bologna Airport is dealing with a significant increase in passenger flows. Even after the COVID-19 pandemic, traffic volume is rapidly growing and will soon exceed previous traffic records. Against this background, the airport has supported new infrastructure investments in order to both optimise existing terminal functional use and to comply with stringent fire safety requirements on terminal buildings, in line with new Italian airport safety legislation. In particular, Bologna Airport has planned a short-term investment specifically regarding the Terminal Smoke Management System, consisting of smoke vents and smoke extraction fans that work in coordination with fire detection systems and other fire suppression systems already installed into the building, and with the Terminal Fire Emergency Plan. For this kind of system, the Italian laws and standards set a basic prescriptive approach that simplifies the design phase with conservative solutions, with invasive, costly and time-consuming installations that are generally not compatible with operational continuity needs for terminal areas. As an alternative, a performance-based design approach is allowed for more customised solutions, focusing more closely on the design phase and terminal functional strategy. This case study shows how Bologna Airport implemented a performance-based design approach in order to minimise the impact of the new system installation throughout the terminal, optimising the engineering solutions with no constraints from the terminal functional flexibility point of view as well as saving over 75 per cent costs and construction time, compared to a traditional prescriptive approach.

Influence of air inlet distance on coal dust pollution characteristics in working environment during tunneling based on CFD method

Coal dust is one of the pollutants generated during the coal tunneling process. However, the air inlet distance will increase with the advancement of the working face, resulting in the redistribution of the air flow field, further affecting the pollution characteristics of coal dust. This effect weakens the effectiveness of dust removal equipment. Therefore, transient CFD modeling was used to study the influence of air inlet distance on air flow, dust migration distance, and dust concentration distribution in the breathing zone and achieve the highest dust reduction efficiency. Results showed that the air flow formed two reflows in the tunnel under forced ventilation. When the air inlet distance increased from 6.0 m to 8.4 m, wind flow diffusion distance (along the return side coal wall) Lp and air inlet distance d can be described as Lp = 34.272–7.108d + 0.570d2 . Furthermore, the dust diffusion time to the outlet increased from 35 s to 40 s, and the dust migration distance increased as a power function of air inlet distance. Meanwhile, the dust migration distance in the first 10 s accounted for 45–50% of that for the entire time period. In addition, the dust migration distance decreased only after 25 s, and the dust concentration in the return side breathing zone gradually increased. Finally, air curtains and dust removal fans were recommended for dust control, and the dust in the daily tunneling process can be effectively controlled when da = 15.0 m and de = 8.0 m. The dust reduction efficiency was 85.29–99.90%. The research results provide technical support for the dust outlet installation of dust extraction fans during tunneling and guidance for dust control in the similar working environment.

Development of a Coal Dust Concentration Sensor Based on the Electrostatic Induction Method.

In order to solve the problems of easy blockage and difficult maintenance of the current coal dust concentration sensor, a coal dust concentration sensor based on the electrostatic induction method was designed. Based on the analysis of the principle of electrostatic induction dust concentration detection, an electrostatic induction dust concentration sensor composed of a electrostatic detection electrode, a dust extraction fan, an induction signal processing circuit, an insulator, a shield, and other parts was designed. The influence of the length and width of the electrostatic detection electrode and the particle flow rate on the standard deviation of the induction signal was analyzed through experiments to optimize them. The induction signals on the electrostatic detection electrode at different dust concentrations were determined in tests, and the mathematical relationship between the standard deviation of the induction signal and the dust concentration was obtained. According to segment multiple-curve height fitting, the maximum deviation between the detected value and actual dust concentration does not exceed 10%.

Numerical modeling of a sneeze, a cough and a continuum speech inside a hospital lift

The global COVID-19 and its variants put us on notice of the importance of studying the spread of respiratory diseases. The most common means of propagation was the emission of droplets due to different respiration activities. This study modeled by computational fluid dynamics (CFD) techniques a high risk scenario like a hospital elevator. The cabin was provided with an extraction fan and a rack for air renewal. Inside, a sneeze, a cough and a continuum speech were simulated. Inside the lift, two occupants were introduced to observe the risk of propagation of emitted droplets and the impact in diseases spreading risk. The fan effectivity over the droplets ejection was analyzed, as well as environmental condition of a clinical setting. For this purpose the amount of droplets inside were counted during whole time of simulations. The effect of the fan was concluded as able to eject the 60% of small droplets, but also a high performance in spreading particles inside. Among the three cases, the riskiest scenario was the continuum speech due to the saturation of droplets in airborne.

Study on air curtain cooperative spray dust removal in heading face based on swirl theory

With the improvement of mechanization, fully mechanized excavators are widely used in roadway excavation, which produces a large number of fine dust particles in the process of tunneling. The smaller the dust particle size, the greater the impact of the environment, and the more difficult it is to be captured. Experiments and numerical simulations have been used to study the cooperative spray dust removal of the wall-mounted air duct based on the swirl theory, which is to prevent the escape of dust particles in the long-pressure and short extraction ventilation. Under the condition that the power of the push-in and extraction fans remain unchanged, it is determined that when the aspect ratio of air outlet is 6:1, the airflow can form an annular vortex area on the left side of the roadway, and the airflow velocity in 30 % of the area is greater than 1 m/s. When the opening angle is between 120° and 150°, the wall effect of airflow movement is weak, and the airflow velocity of 70 % of the cross-sectional area of the roadway is larger than 2 m/s, which enables the air curtain to block about 70 % of the dust. Under the action of the swirl air curtain, when the spray pressure is 6 MPa, 80 % of the droplets have a particle size of less than 2.5e-5 m, and the spray effect is better. The droplets move to the tunnel section under the swirling flow, and actively control the dust, establishing an air curtain-droplet flow field, thereby blocking and capturing the excavation dust.

Numerical Simulation of Smoke Control in Underground Space

As the underground space is relatively closed compared to other buildings, the space is hardly connected to the outside world through entrances and exits, which makes it difficult to ventilate and exchange heat with the outside. In this case, it is easy to cause a large number of casualties when a fire breaks out. When the fire happens smoke will be discharged merely by the mechanical exhaust, and air system should work simultaneously to replenish the oxygen inside. By setting four-group models, the paper analyzes the strategies for smoke extraction and air makeup in the underground construction. The paper points out that when the fire happens in a smoke bay, the neighborhood smoke extraction fan should be opened and the air makeup system should not be located at the top to disturb the smoke layer. By comparing and analyzing the performance of the smoke extraction and air conditioning system, the casualties caused by the high temperature toxic smoke from the fire can be reduced as far as possible.

Low-Frequency Magnetic Fields in Diagnostics of Low-Speed Electrical and Mechanical Systems

The magnetic field created by technical devices is a source of information. This information could be used in contactless diagnostics and predictive maintenance or for resolving problems along with standard NDT (nondestructive testing) methods, especially if we consider large, slow-speed devices, such as electromotors, transmissions, or generators. Identification of causalities of device failure processes with near magnetic field is one of the suitable NDT methods improving sustainability of systems. The measurements presented in the article were performed with the VEMA 04 fluxgate vector magnetometer with the DC-250 Hz bandwidth and 2 nT sensitivity. Postprocessing of the results was performed in the means of standard methods of discrete Fourier Transform, spectrogram creation and Wavelet Transform. The article presents data gathered during the measurement of a pair of extraction fans with power of 140 kW each and maximum revolutions up to 740 rev/min controlled by frequency converters and a single semi-Kaplan water power plant with 400 kW peak power at 1005 rev/min maximum generator speed. The measurements were performed before and after repairs of one of the ventilators in the ventilation system at 60% and 100% of maximal output power. The rotating magnetic fields of the fan electromotor stator, fan rotor revolutions, rotor slip frequency and ball-bearing frequencies were identified in frequency spectrums in the distance of 700 mm from fan electromotor axis in both cases. During the measurements on the semi-Kaplan turbine, the changes in states of mechanical and electrical components of the machine were monitored in the magnetic fields with increase of the power in the range of 0–95%, before and after phasing to the electrical grid. Standard processing methods, Discrete Fourier Transform, spectrograms and Discrete Wavelet Transform were used. In the spectrograms of the measured magnetic fields, the 1st–4th harmonics of the turbine shaft, generator shaft and also their side frequencies were identified. Significant changes of magnetic fields in time were identified in the area of 60–95% power. With the help of the Wavelet, transform intervals were identified where it is desirable to operate the turbine. The analyses of magnetic fields measurements performed on the power plant were compared with vibro-diagnostic principles.

Experiments of combinational fans affecting smoke ceiling in an undersea metro interval tunnel VSES

Based on a case study of the undersea metro interval tunnel, this study proposes a model to evaluate the Ventilation and Smoke Exhaust System (VSES). In the VSES experiments, data of fan frequencies, powers, velocities, and static pressures in carriageways are collected, under the TPTE (Two Pressing-in fans + Two Extracted-out fans), the TPOEL (Two Pressing-in fans + One Extraction fan on the Left side of a smoke ceiling vent) and the TPOER (Two Pressing-in fans + One Extraction fan on the Right side of a smoke ceiling vent) combinations. The results show that the static pressures in both carriageways have fluctuation phenomena and symmetrical distributions, whose axis of symmetry is the smoke ceiling, regardless of combination type. These fluctuations have almost constant static pressures, which are associated with the increase in consumed powers while hardly compensate for the increase in volume flow rates. These rare compensations are essential to evaluate the effects of combinations on the relative shock loss. In order to quantify the differences, this study proposes a VSES performance and a deviation percentage model, and the results show that the TPTE resistance has the smallest shock losses of airflow going through the smoke ceiling vent.

Current ventilation strategies in Greenlandic dwellings

The Arctic winters are long and cold. When temperatures drop deep below freezing point, the occupants of Arctic dwellings become hesitant to opening windows in order to avoid cold draught. Natural vents are typically sealed. Mechanical ventilation is either not existing or comprises of bathroom fan and range hood. Air tightening of the building envelope to prevent draught results in a lack of makeup air for the extraction fans. This leads to further reduction of air change in majority of the dwellings. One consequence is poor indoor air quality. The other may be moisture levels high enough to damage the construction. The current Greenlandic building code does not require use of complex ventilation systems. Lack of experience and requirements together with higher construction costs will typically cause ruling the complex mechanical ventilation systems out of the projects and replacing them by bare minimum. In this project we mapped, three ventilation solutions. Two renovations and one new home. The measurements have shown that the IAQ (evaluated based on CO2 and humidity measurements and occupant interviews) had improved significantly with use of balanced mechanical ventilation with heat recovery. The occupants have reported increase in their comfort. The systems were capable of continuous operation throughout the Arctic winter. Installation of the mechanical ventilation had proved to be an efficient solution to IAQ problem in Greenland.

A full-scale experimental study of sub-slab pressure fields induced by underground perforated pipes as a soil depressurisation technique in radon mitigation

Sub-slab depressurisation systems have proven to effectively mitigate radon entry. A poor understanding of the fluid physics underlying the technique has been shown to lower the success rate substantially. This article describes a study of pressure fields in a sub-slab gravel bed induced by a soil depressurisation system consisting of perforated pipes run under the slab at a depth of 75 cm. The advantage of the approach is that pipes can be laid from outside the building to be protected. The study was conducted on a large-scale experimental facility where the variations in morphology and scope of pressure fields with different pipe combinations could be monitored and characterised. The findings showed that pressure was uniform across the entire area in the gravel bed, whereas the sensors buried in natural soil showed pressure to depend on distance from the source. Pressure transfer to the sub-slab plane was also observed to vary depending on the active pipe. Air-flow resistance studies in the layers of soil lying between the pipes and the gravel delivered different results for each pipe. That finding would appear to be related to the presence of preferential pathways in some parts of the soil. Total pressure when several pipes were activated was observed to be practically the same as the sum of the pressures transferred by each when working separately. The correlation between extraction fan power and pressure generated was also analysed. These and other factors are discussed and analysed from a perspective of the understanding of such highly effective techniques.

Assessment of evaporative cooling system potential for short-term storage management of vegetables during transportation

A system based on direct evaporative cooling principle for short-term storage management of vegetables during transportation was designed, developed and assessed its performance. The evaporative cooling applies the principle of water evaporation to achieve temperature reduction and relative humidity increment. The system comprises evaporative cooler, power supply (battery, battery charger and power inverter), control panel, storage unit and real-time data monitoring (of temperature, T and relative humidity, RH). The evaporative cooler consists water reservoir, pump, cooling pad, extraction fan, connecting pipe and control panel. The system (that applies alternating current (AC)) can be powered by two-12 V serial truck batteries (direct current, DC) via power inverter. In this research, the effect of water type towards cooling process inside storage unit was studied too. The use of icy water as an evaporation media exhibited higher temperature reduction, T (6.11 ± 2.30 C) as compared to ambient water (4.06 ± 1.91 C). RH for both cases achieved 99 %. The quality of selected leafy vegetables (green amaranth, water spinach and choysum) for fresh market that underwent evaporative cooling storage treatment (T1) was assessed. Post four-hour storage, leafy vegetables stored under T1 exhibited the least weight loss as compared to ambient storage treatment (T2) and cold storage treatment (T3). However, post two-week storage, the vegetables quality that underwent T1 was comparable to T2, but slightly lower than T3. The system exhibited potential to maintain vegetables quality during the short-term storage in transportation.

A novel method for pre-ventilation of shipping containers.

Numerous shipping containers arrive with high levels of hazardous volatile chemicals in the interior air. This may constitute a health risk during inspection and unstuffing. The problem remains largely unaddressed due to ignorance, lack of suitable field instruments for chemical identification, and lack of easy to use, effective ventilation methods. Here, we present a novel ventilation approach based on extraction of air from the closed container via the existing top corner ventilators. A suction plate was developed to fit tightly over the corner ventilator and connected with a flexible hose to an extraction fan. Air flow rates and vacuum under the plate were measured in the lab with five different types of extraction fans. The vacuum produced under the suction plate held it securely in place. Washout of air contaminants under different configurations and ventilation scenarios was studied in an experimental 20-ft container stuffed with acetone emitting cardboard boxes and in the field with containers stuffed with commercial goods. Volatiles in container air were continuously recorded with logging photoionization detectors in various positions before, during and after ventilation. A maximum air flow through the ventilator of 186m3/h was achieved. At 100m3/h, the initial acetone levels were reduced to 11% and 4.9% in the tightly stuffed and to 6.0% and 3.1% in the loosely stuffed (pallets) experimental container after 1h and 4h, respectively, as measured inside the closed door (mean values). As expected, the washout was somewhat slower in nine 40-ft field containers and reached 22% and 11%, respectively. In both experimental and field containers the concentration rose quickly when ventilation ceased. In conclusion, the new ventilation method allows for convenient, safe and efficient ventilation of risk containers. The container should be continuously ventilated until it is opened, or rapid re-accumulation of volatiles will occur.

Impact of cavity extraction fans on thermal and energy performance of existing UK hotel

The advantages of double-skin facade (DSF) systems, ranging between their aesthetic architectural benefits, acoustic benefits and ability to decrease the heating demand of the internal environment, have increased their popularity in Europe since the mid-1980s. However, appropriate consideration must be accorded to their design to ensure that their possible advantages are not negated. This work evaluates how the effect of extraction fans installed in the cavity of the DSF adjoining a central atrium impacts the thermal condition of the atrium and, consequently, the overall energy consumption of an existing UK hotel building. The results of the investigation demonstrated that the DSF extraction fans improve the internal temperature and condition of the adjacent central atrium, particularly in the summer. The fans result in a marginal increase in the overall energy consumption when operated throughout the year; hence, the optimum schedule for the operation of the extraction fans is during the cooling-dominant period.

Removal of dust produced in the roadway of coal mine using a mining dust filtration system

Dust particles, which are produced both on the ground and in underground workspaces, significantly affect the human body and the atmosphere. In fact, underground dust hazards are more serious, especially in the heading face of coal mines. People who work in the heading face are exposed to a high concentration of fine particulate matter. Traditional methods such as water sprays, dust removal by ventilation and foam technology, cannot completely solve the problem of dust pollution. Therefore, a mining dust filtration system was designed for removing dust produced in the roadway of coal mines. The study on eight frequently used air duct arrangements indicates that the mining dust filter achieved the best dust collection efficiency when the inlet of the extraction air duct and the outlet of the forced air duct were 3 m and 13 m away from the heading face, respectively. Under the optimum condition, the dust concentration can be significantly reduced in the rear of the dust exhaust hood and gradually decreased along the direction of the roadway. The system proposed in the study reduced the dust concentration to below 3 mg/m3 in the rear of the extraction fan and greatly improved the environment in the roadway of coal mines.

Theoretical prediction model and full-scale experimental study of central smoke extraction with a uniform smoke rate in a tunnel fire

A large amount of smoke may be discharged from a smoke extraction damper located close to extraction fans in central smoke extraction systems, which greatly reduces the efficiency and increases the energy consumption. Therefore, we propose the concept of smoke extraction with a uniform smoke rate. Adjusting the damper angle can make the extraction rate uniform for each damper, so the higher temperature smoke can be discharged furthest through the damper nearest the fire. We established theoretical models according to the relationships between the smoke velocities, extraction rate, damper angle, and wind pressure for fans in traditional and uniform systems. Based on the Hong Kong-Zhuhai-Macao immersed tunnel in China, an experimental tunnel with the largest cross section size in the world is constructed. The results showed that in the traditional system, 40–60% of smoke was discharged through the damper nearest to the fan, whereas the extraction rate for each damper could be equalized by controlling the angle in the uniform system and 8–23% of the energy could also be conserved. The results suggested that the damper nearby the fire should be open and the number of dampers can be adjusted to control the smoke spread range and achieve effective energy savings.

Numerical Analysis for Smoke Spread in an Aircraft Hangar

Smoke is one of the most dangerous factors in aircraft hangar in case of fire. As it causes reduce in visibility and deaths due to high temperature or toxicity also prevents applying evacuation plan for workers. This study present numerical analysis for improving traditional system of ventilation system to manage smoke produced due to push-back vehicle on fire at hangar. By studying effect of changing extraction and supply rates, the number of extraction and supply fans, and the arrangement of extraction and supply fans on the visibility, temperature and air velocity at human level to insure not to exceed limits stated by NFPA 130[1] to apply evacuation plan for workers. The study is performed using Fire dynamic simulator to simulate 16 case studies in the hangar of airports in Brandenburg. The hangar has the outer dimensions of 83.40 m width and 77.60 m depth and thus an inner area of approx. 6,472 m2. The hangar has a medium interior height of approximately 18.20 m. The results show that using extraction fans with rate (ACH) double the supply rate for the traditional ventilation system gives very good results in controlling the smoke. As well as, decreasing the number of supply fans will make the smoke spread rate inside the hangar lower, which helps to control the smoke spread of fire in less time.