Air Extractor Research Articles

Design and manufacture of a prototype dryer for fruits and vegetables using a convection system

The scarcity of funds for acquiring industrial-type equipment and devices for laboratory practices at technological universities is a recurring issue. This financial constraint is particularly evident in the educational program of engineering in Biofood Processes at the Technological University of Tecamachalco, where the absence of drying equipment for water reduction practices in fruits and vegetables is a pressing concern. To address this, we have developed a prototype of a convection dryer. The Mechatronics engineering research group has been at the forefront of developing this innovative prototype. Our team has harnessed the power of a PID control system, integrating a microcontroller, a potentiometer for temperature programming, and an-LED screen for real-time monitoring. This stateof-the-art design is a testament to our commitment to advancing laboratory equipment. If the temperature is reduced, the installed electrical resistances will be activated. If the upper limit of the programmed temperature is exceeded, an air extractor placed in the upper part of the prototype will be activated to reduce it as necessary.After rigorous testing, we conducted three water reduction tests on apples with the guidance of food engineering experts. The apples were subjected to a temperature of 60 °C for approximately two hours, a condition necessary to prevent any deterioration. In all three tests, we successfully reduced the water activity from 70% to 12%, a crucial step for preservation. With the successful completion of the tests, the prototype was transitioned to the Food Engineering laboratory, ready for practical use. This significant advancement in our ability to carry out laboratory practices offers a promising solution to the lack of industrial-type equipment in our educational program. We are optimistic about the potential impact of this prototype and look forward to seeing it in action.

Calidad física y sensorial del café secado en tres prototipos de secadores solares tipo invernadero

Reducing the drying time of coffee without causing negative effects on cup quality has been the subject of several investigations. The objective was to determine the effect of three variants of a greenhouse-type solar dryer prototype on the physical, sensory and microbiological quality of coffee. The solar dryer prototype with three variants, prototype 1 (P1) greenhouse solar dryer, prototype 2 (P2) solar dryer with air extractor and prototype 3 (P3) solar dryer with air extractor and solar powered heaters, was compared to traditional drying (T0) (cement floor). Drying time, physical grain defects, yield, sensory and microbiological quality were evaluated. The best results were obtained in P3 with a drying time of 52 h (2 ¼ days), with dry parchment coffee beans without primary defects, higher yield in exportable gold coffee (83.24 %), sensory profile of 84.25 points qualified as specialty coffee (with Q Premium grade) and better safety than coffee obtained by traditional drying; demonstrating that the greenhouse type solar dryer with air extractor and solar energy heaters is a sustainable alternative to improve the efficiency of coffee drying while preserving its sensory quality, an essential value for producers to achieve better prices.

Modeling for understanding of coronavirus disease-2019 (COVID-19) spread and design of an isolation room in a hospital

We have modeled the transmission of coronavirus 2019 in the isolation room of a patient suffering from severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) at the Royal Brompton Hospital in London. An adaptive mesh computational fluid dynamics model was used for simulation of three-dimensional spatial distribution of SARS-CoV-2 in the room. The modeling set-up is based on data collected in the room during the patient stay. Many numerical experiments have been carried out to provide an optimal design layout of the overall isolation room. Our focus has been on (1) the location of the air extractor and filtration rates, (2) the bed location of the patient, and (3) consideration of the health and safety of the staff working in the area.

Parameter Determination of Coupled and Decoupled Admittance Matrix Methods of the Norton Equivalent Model for an Air Extractor

Context: Studies carried out in low voltage networks have explored the modeling of linear single-phase loads (such as motors) and non-linear ones (such as those based on power electronics). However, induction motors exhibit non-linear characteristics between voltage and current due to the saturation of their magnetic parts. Therefore, it is necessary to study induction motors in the frequency domain with a model that allows reviewing the characteristic nonlinearity of their voltage-current interaction. Methodology: This article presents the frequency domain modeling of a single-phase induction motor used as a silent air extractor (127 V, 60 Hz, 66 W), which presents a capacitive behavior (fp = 0,93 in leading) and harmonic distortion due to a third-order component (7,0%) when fed with a pure sinusoidal voltage of 127 V. Results: This work establishes the parameters of two approaches to the Norton equivalent model (coupled and decoupled admittance matrix) which are used to estimate the distorted current signal and the values ​​of consumed active and non-active power. The results show comparisons errors of P, Q, THDi, and NRMSE indices of less than 7, 4, 14, and 3%, respectively. Conclusions: The parameters of the Norton equivalent model estimated for the single-phase induction motor allow calculating the current signal with a high degree of precision. This signal exhibits nonlinear characteristics and a capacitive behavior due to the permanent presence of a capacitor aiding the start and operation of the engine.

Computational Study of Thermal Comfort and Reduction of CO2 Levels inside a Classroom.

Due to the current COVID-19 pandemic, guaranteeing thermal comfort and low CO2 levels in classrooms through efficient ventilation has become vitally important. This study presents three-dimensional simulations based on computational fluid dynamics of airflow inside an air-conditioned classroom located in Veracruz, Mexico. The analysis included various positions of an air extractor, Reynolds numbers up to 3.5 × 104, four different concentrations of pollutant sources, and three different times of the day. The simulations produced velocity, air temperature, and CO2 concentrations fields, and we calculated average air temperatures, average CO2 concentrations, and overall ventilation effectiveness. Our results revealed an optimal extractor position and Reynolds number conducive to thermal comfort and low CO2 levels due to an adequate ventilation configuration. At high pollutant concentrations, it is necessary to reduce the number of students in the classroom to achieve safe CO2 levels.

REDUCING THERMAL INERTIA TO IMPROVE THERMAL COMFORT BY CONFIGURATION OF A NEW BRICK

Climate change has changed seasons, affecting the indoor temperature of buildings and causing a strong feeling of discomfort, especially in hot weather. This feeling of discomfort is mainly due to thermal inertia. The aim of this work is to reduce the indoor temperature of buildings by using a new brick with a low thermal inertia. As part of this work we have designed a brick with the same characteristics as the ordinary ones but which are perforated so that in the construction of the wall they form a conduit for the transport of air. The latter thus acts as a heat transfer fluid in its upward convective movement, bringing with it the heat stored in the wall. In order to improve thermal exchange, an air-extractor roller system has been installed. This air extractor allows to increase convection in the walls, reducing thermal inertia and implicitly improving thermal comfort.

Experimental Evaluation and Theoretical Optimization of an Indirect Solar Dryer with Forced Ventilation under Tropical Climate by an Inverse Artificial Neural Network

In this theoretical–experimental study is presented a hybridization strategy based on the application of an inverse artificial neural network model (ANNi) coupled with metaheuristic optimization algorithms to optimize the drying velocity (vd) of an active indirect solar dryer for plantain and taro (Colocasia antiquorum). In the experimental stage, both fruits were evaluated in periods from 9:00 a.m. to 5:00 p.m. under a humid tropical climate region, varying the voltage of the air extractor fan (at 6 V, 9 V, and 12 V) to control the fan velocity. The experimental results showed that the maximum drying velocities were reached at 9 V, achieving a drying velocity of 1.5, 0.9, and 0.55 g/min, with a total drying time of 465 min for the taro, and 1.46, 1.46, and 0.36 g/min, with a total drying time of 495 min, for the plantain. As a result of the drying curves, it was observed that the drying velocity is higher in taro than in plantain. Subsequently, an artificial neural network (ANN) architecture was trained using the database generated from the solar dryer’s experimental stage. Six environmental variables and one operational variable were considered as the model’s inputs, feeding the ANN to estimate the drying velocity (vd), obtaining a linear regression coefficient R = 0.9822 between the experimental and simulated data. A sensitivity analysis was performed to determine the impact of all the input variables. A hybrid strategy based on ANNi was developed and evaluated with three metaheuristic optimization algorithms; the best result was obtained by genetic algorithms (ANNi-GA) with an error percentage of 0.83% and an average computational time of 4.3 s. The scope of this optimization strategy was to obtain a theoretical result that allows predicting the behavior of the dryer and improving its performance for its practical application in future work through the implementation in development boards. Lastly, the optimization strategy presented is not limited to indirect solar dryers and opens a research window for evaluating other solar drying technologies.

Sensors and energy harvesters based on (1–x)PMN-xPT piezoelectric ceramics

With recent advancements in energy conversion mechanisms, piezoelectric ceramics (1–x)PbMg1/3 Nb2/3Ο3-xPbTiΟ3 (1–x)PMN-xPT have demonstrated their abilities for converting mechanical vibrations into electricity. Three (1–x)PMN-xPT compositions were used in the present work with (x = 0.25, 0.31 and 0.33). The purpose of this paper is to investigate their piezoelectric performance as generators for energy harvesting applications. The energy harvester is numerically analyzed in this work. It consists of a piezoelectric bimorph clamped at one end to vibrating machinery, and a proof mass mounted on its other end. The energy harvester is also analyzed and experimental measurements of the harvested power are compared to the simulation results. A good agreement was observed between the experimental and the simulations results. According the application to exploit the vibrations of a hot air extractor, the results show that the harvested energy density of solid ceramics (1–x)PMN-xPT is 0.043 W/m2.

<b>Evaluation of CFD simulations with wind tunnel experiments: pressure coefficients at openings in sawtooth building

Wind tunnel experiments and Computational Fluid Dynamics (CFD) simulations are used to analyze natural ventilation in a sawtooth roof building. A 1:10 scale model is tested in an atmospheric boundary layer wind tunnel. The CFD simulations are performed with Ansys CFX software. The aim of this study is to evaluate the reliability of CFD simulation in predicting pressure data at opening height in a sawtooth roof building with wind tunnel data. The model is evaluated for prevailing wind in five directions: 0 and 45° (air extractor sheds), 90° (neutral situation) and 135 and 180° (air collector sheds). The computational grid resolution shows that the inclusion of prisms and the increase of the grid refinement in the building’s surface cause insignificant differences in Cp (wind pressure coefficient). In general, the error values below 10% indicate a good agreement between CFD simulations and wind tunnel data.

Recovering water from brine: Assessments of feasibility and applicability to irrigation processes

This study investigated the recovery of moisture from brine drying processes and evaluated the applicability of recovered water for irrigation purposes, while taking into consideration applicable Chilean regulations. For moisture recovery, a heat exchanger was installed on the outside of the solar dryer and connected to an air extractor that ejected the vapor produced during the process; the objective of this setup was to condense vapor produced while drying brine inside the solar dryer. Using refrigerated circulation (0.136 L/s flow), 312 g of freshwater was recovered. Overall condensation performance was 17.2%, with each kg of condensed water requiring 40,480 J/s of transferred condensation heat, a logarithmic mean temperature difference of 12.9 °C, and 7.9 kWh of specific energy consumption. The condensed water was subsequently assessed according to Chilean regulations for irrigation-water quality, as well as through phytotoxicity analyses using lettuce (Lactuca sativa) seeds. All evaluated quality parameters met legal requirements, and the condensed water was nontoxic for L. sativa seeds. The return-on-investment for the process was 5.4 years, and the produced freshwater costed 0.35 US$/L.

Numerical Simulations and Analysis of a Low Consumption Hybrid Air Extractor

Hybrid low pressure air extractors are an economic way to enhance indoor air quality. The evaluation of their energetic performances needs the analysis of flow parameters that is typically done with wind tunnel data and numerical simulations. The purpose of this study is to analyze, numerically and experimentally, the flow and the energetic performances of a hybrid rooftop extractor. This innovative extractor has two main features: it works at low difference of pressure, below 50 Pa, and its fan is placed far above the duct outlet, out of the fluid flow. The hybrid extractor works following three modes of operation: stack effect, Venturi effect, and fan rotation. The two first modes of operation allow large energy saving. To analyze the three modes of operation, three sets of corresponding Reynolds-averaged Navier–Stokes (RANS) simulations are developed. The first one allows us to estimate the pressure drop due to the geometry of the air extractor. The second one is used to check the ability of the extractor to generate a suction into the duct in the presence of wind. The final one involves multiple reference frame (MRF) modeling in order to study the flow when the electric motor drives the fan. The numerical simulation configurations are validated with experimental data. A good behavior of the extractor is found for simulations of stack effect mode and Venturi effect mode. The stack effect and the Venturi effect allows the hybrid extractor to work most of the time without electric power. Finally, energetic comparisons are given.

Investigation of the factors influencing the efficiency of a solar still combined with a solar collector

A solar still was designed for the evaporation of desalination brine. The influence of several factors, such as the basin heating, the material of the cover (glass or polycarbonate), the existence of a mirror, the activation of an air extractor, and the existence of a black painted floor in the solar still, was evaluated in terms of their contribution to brine evaporation. The experiments were conducted with a factorial design approach. The combination of the factors that produced the best results was used in a subsequent daily monitoring study for brine evaporation. The monitoring parameters were the hourly average incident radiation, the changes in the temperature, the brine mass, and the brine volume. The accumulated amounts of the solar energy were calculated, and the correlation relationship was assessed.

Catalytic removal of a mixture of volatile organic compounds present in indoor air at various work sites over Pt, MnOx and Pt/MnOx supported monoliths

The elimination of volatile organic compounds (VOCs) was investigated placing a novel catalytic system in the chimney venting of a commercial air extractor, using Pt, Mn and Pt/Mn catalysts supported on ceramic monoliths. The VOCs oxidized were chloroform (CHCl3), methyl ethyl ketone (MEK), toluene and xylene, alone, in a binary mixture and in a mixture of all of them. The conversion of VOCs is in general similar, regardless of whether they are in a mixture or alone. Pt/Mn monoliths exhibited the highest destruction activity for the abatement of VOCs alone and in mixtures, due to a synergetic effect between platinum and manganese. The results show that these catalytic systems can be coupled satisfactorily in the venting of the air extraction equipment still working at high flow rates.

Microbiological and radioactive contamination from radioaerosol ventilation scanning: is there a problem?

Radioaerosol lung imaging may result in (a) microbiological contamination of nebulizer circuits (a potential hazard to patients if the circuit is re-used), and (b) radioaerosol contamination of the atmosphere (a hazard to staff, particularly if inhaled, ingested or both). Altogether, 138 circuits were assessed for bacteriological contamination, 93 of which had been used for ventilation perfusion studies and 45 for lung permeability studies in human immunodeficiency virus (HIV) positive patients. The circuits used for ventilation/perfusion (V/Q) studies were re-used over a period of 1-5 days. The mouthpiece and Y-piece were changed between patients. The circuits used for permeability studies were changed in toto for each patient. Organisms belonging to normal respiratory flora were isolated from the Y-piece, mouthpiece or both in 9 of 138 cases. An additional case (from one of the HIV-positive patients) demonstrated a growth of methicillin-resistant Staphylococcus. We also demonstrated bacteriological growth, most likely of patient origin, in circuit tubing in 11 cases at the end of the first day's use and 9 cases by day 5. None of the circuits used for HIV-positive cases were culture-positive. Airborne radioactive contamination was assessed during radioaerosol inhalation with and without an air extractor device (Nederman) during 40 ventilation studies. The 20 studies with air extraction showed a large decrease in room air contamination. Nebulizer circuits can, and occasionally do, become contaminated with patients' organisms; this represents a potential infection control hazard and therefore re-use is contraindicated. The use of an air extractor will significantly reduce airborne radioaerosol contamination.

Odour and colour information in the foraging choice behaviour of the honeybee

1. Honeybees Apis mellifera ligustica were trained to work on a patch with artificial rewarding and non-rewarding flowers, coupled to an air extractor. The perceptual colour distance between the rewarding and the non-rewarding flowers was varied and the flower choice and the repellent scent-marking behaviour of the bees were recorded. 2. The discrimination between rewarding and non-rewarding flowers depended on their colour distance, improving with a greater colour difference. This task was guided thus visually and was not affected by activating the air extractor. 3. The scent-marking activity was only observable when the colour information of both groups of flowers was the same or very similar. This thus represents the first reported case of a modulation of an olfactory activity through the visual input provided by colour distances. When the air extractor was activated, rejections associated with the scent-marking behaviour disappeared, thus confirming the olfactory nature of this behaviour. 4. Honeybees are thus capable of using one or more sensory cues to enhance their foraging efficiency, according to the environmental situation. This great plasticity allows them to attain an enhanced efficiency while foraging. 5. We successfully applied the model of colour choice behaviour of the honeybee. Since the original theory was developed for Apis mellifera carnica, this work also constitutes the first attempt to describe the behaviour of the honeybee race, Apis mellifera ligustica, using the postulated model, and reaffirms thus its generality.

The repellent scent-mark of the honeybeeApis mellifera tigustica and its role as communication cue during foraging

Experimental evidence for flower-marking in honeybees (Apis mellifera ligustica), using pairs of workers from the same colony foraging on an artificial patch of flowers, is reported. Workers marked artificial flowers with scent and strongly rejected all flowers they had recently visited. The same rejection behavior, in a lower although significant proportion, was observed when bees visited flowers just abandoned by the other individual of the pair. The repellent nature of this scent-mark was demonstrated with the use of an air extractor connected to the patch of artificial flowers. When the apparatus was turned on, the rejection behavior disappeared and bees accepted both flowers just abandoned by themselves and flowers just abandoned by the other bee. Differences in the response level of bees to their own marks or to the partner's marks suggest that the repellent scent-mark applied by a bee during foraging would basically be a self-use signal, although it certainly has value in communicating with other workers.

Honeybees mark with scent and reject recently visited flowers.

Experimental evidence is reported for flower-marking by honeybees (Apis mellifera ligustica) while they were foraging on an artificial patch of flowers yielding a continuous and equal flow of sucrose solution. Honeybees marked with scent and rejected all recently visited and nectar-depleted flowers. The short fade-out time of this scent allowed discrimination of flowers that temporarily provided no food. The repellent nature of this scent mark was demonstrated by the use of an air extractor connected to the patch; when the apparatus was turned on, the rejection behaviour disappeared. The movement pattern of foraging bees also contributed to foraging efficiency, as the probability of an immediate return to the flower just abandoned was very low. However, when a quick repeat visit took place, the presence of the repellent scent-mark promoted rapid rejection.

Smallest room.

A mini bathroom unit, especially adapted for use by disabled people has been produced by Stannah Lifts. The unit, made of glass reinforced plastic, measures 1.1 metres and contains a shower, wash basin, toilet and air extractor.

Minimum ignition temperature of a self-raising flour on a standard hot-plate

A hot-plate to the draft specification of the International Electrotechnical Commission (Committee 31H) was constructed and located in a chamber with an air extractor and a transparent door. A commercial self-raising flour was tested to assess the relationship between minimum ignition temperature (MIT) and layer depth (5–40 mm in steps of 5 mm). MIT varied from 311°C for 5 mm to 265°C for 20 mm and to 238°C for 40 mm layers. The results fitted the relationship ln ( δ cT 2 r 2 )= M − ( N T ) , with a correlation coefficient of 0·994 for 4 points above the recommended minimum ratio of sample diameter-to-depth of 5:1 and 0·995 for 8 points above the ratio of 2·5:1. The latter relationship had a slightly flatter slope than the former. The variation in results from the two lines was examined. It is recommended for self-raising flour that more reliable results are obtained from 15 mm layer depth than 5 mm because of the tendency of the latter layers to buckle and crack under test. Relationships between hot plate temperature and (a) time taken for layer to reach plate temperature, (b) maximum temperature generated in sample and (c) percent residue after each test, were obtained for the 15 mm layer at plate temperatures up to 410°C.