Air System Research Articles

Human thermal comfort in kitchen with different ventilation modes based on a coupled CFD and thermoregulation model

Kitchen ventilation is crucial in effective removal of pollutants and heat in the enclosed kitchens to ensure occupants' thermal comfort and health. However, mechanical ventilation systems, such as range hoods and make-up air systems, often create non-uniform and dynamic thermal conditions, posing challenges for traditional comfort metrics. In response, this study utilizes Computational Fluid Dynamics (CFD) coupled with a human thermoregulation model to evaluate the thermal comfort across various kitchen ventilation modes. Our findings reveal significant non-uniformity in indoor thermal environments surrounding the occupant, with differences in ambient temperature reaching 14.2 °C and air velocity up to 0.64 m/s, directly impacting occupants' comfort. Notably, mechanical ventilation employing air curtains for make-up air surpasses natural methods, enhancing overall thermal sensation by 42 % and reducing mean drought rates by 70 % during winter. Additionally, ceiling supply systems improve upper body comfort in summer, offering personalized thermal comfort solutions, and achieves optimal thermal comfort conditions at a make-up air temperature of 25 °C. This research contributes valuable insights into selecting appropriate ventilation strategies for residential kitchens, thereby promoting occupants' well-being and health.

Pathway to Decarbonization Through Industrial Energy Efficiency: Micro and Macro Perspectives from Compressed Air Usage

Energy audits directly provided the industrial sector with reduced energy costs and avoided emissions. Still, they also lead to far-reaching indirect and induced local, regional, and national benefits. This paper aims to present the techno-economic-environmental analysis to achieve decarbonization through implementing industrial energy efficiency at micro and macro levels. An integrated techno-economic-environmental methodology is developed. Case studies of micro-level carbon reduction efforts through industrial energy efficiency technologies are presented. The broader macroeconomic and environmental effects of technology on society are analyzed using data from 206 energy audits of industrial compressed air systems conducted over 13 years. The impacts show that energy-efficient improvements lead to direct cost savings for manufacturers, boost economic activity across sectors, and affect carbon dioxide emissions both short-term and long-term in the region. Given their extensive benefits, energy audits significantly influence policymaking. We devised a methodology to link micro-level energy audit data with macroeconomic and environmental analyses to quantify these cascading benefits. The economic scenario analysis shows that $228 M has been saved from direct industrial energy savings from implementing all compressed air recommendations in the studied periods and the region. In addition, the investment made through manufacturers would create 2,025 jobs and $383 M annually, cascading regional economic impacts. The environmental analysis shows that the regional manufacturers have directly avoided about 2.8 M metric tons of carbon dioxide emissions.

Optimal evaporation/condensation temperature determination and experimental validation for electric vehicles

This study explores the potential of heat pump air conditioning systems in enhancing the driving range of electric vehicles (EVs) by optimizing evaporator and condenser temperatures to achieve improved system performance and efficiency. A novel methodology is introduced to determine the optimal temperatures for evaporation and condensation within such a system, seamlessly integrated with a primary return system. The validity of this approach is substantiated through rigorous experimental validation. Under New European Driving Cycle (NEDC) conditions, the heat pump air conditioning system demonstrates superior performance and reduced energy consumption, with optimal evaporator temperatures ranging from −2 °C to 2 °C and condenser temperatures between 57.1 °C and 61.8 °C during summer. Winter conditions are optimized with evaporator temperatures from −16 °C to −12 °C and condenser temperatures between 42.4 °C and 48.8 °C. Additional experiments were conducted to validate system performance in both cooling and heating modes. The results highlight a close alignment between the theoretical model for the primary return air system and actual performance, with less than a 10 % discrepancy in calculated outlet temperatures compared to experimental data across various operating conditions. This correlation validates the theoretical model’s capacity to accurately reflect real-world system behavior.

Risk of fungal exposure in the homes of patients with hematologic malignancies

BackgroundPatients with hematological malignancies are at a high risk of developing invasive fungal infections (IFI) because they undergo several cycles of treatment leading to episodes of neutropenia. In addition, they alternate between hospital stays and periods spent at home. Thus, when an IFI is diagnosed during their hospital stays, it is highly challenging to identify the origin of the fungal contamination. The objective of this study was to analyze at home fungal exposure of 20 patients with leukemia by taking air and water samples in their living residence. MethodsAir was sampled in 3 rooms of each home with a portable air system impactor. Tap water was collected at 3 water distribution points of each home. For positive samples, fungi were identified by mass spectrometry or on the basis of their morphological features. Results85 % of homes revealed the presence in air of Aspergillus spp. and those belonging to the section Fumigati presented the highest concentrations and the greatest frequency of isolation. Concerning mucorales, Rhizopus spp. and Mucor spp. were isolated in air of 20 % and 5 % of dwellings, respectively. In 4 homes, more than 70 % of the fungal species identified in air were potential opportunists; these were mainly Aspergillus spp. with concentrations greater than 20 cfu/m3. The water samples revealed the presence of Fusarium in 3 dwellings, with concentrations up to 80 cfu/L. Finally, for one patient, fungal species isolated during a period of hospitalization were phenotypically similar to those isolated in samples taken at home. For a second patient, a PCR Mucorale was positive on a sample of bronchoalveolar fluid while air samples taken at his home also revealed also the presence of mucorales. ConclusionThe presence of opportunistic fungal species in the air of all the explored homes suggests the need for strengthened preventive measures in the home of immunocompromised patients. It would be interesting to compare the fungi isolated (from patients and from their environment) by genotyping studies aimed at specifying the correspondence existing between fungal species present in the patients’ homes and those responsible for IFI in the same patients.

IEEE Journal on Miniaturization for Air and Space Systems Special Issue on Network Intelligence for Unmanned Aerial Vehicles

IEEE Journal on Miniaturization for Air and Space Systems Special Issue on Network Intelligence for Unmanned Aerial Vehicles

Sensitivity analysis on transient pressure of entrapped air pocket in deep stormwater tunnel system

In deep stormwater tunnel systems (DSTSs), entrapped air pockets are prone to pressurization and deformation during rapid filling, resulting in pressure surges that threaten system security. This study investigates the effects of structural and inflow parameters on peak pressures. To simulate the pressure surges of entrapped air pockets, a rigid-column model was developed for a simplified DSTS configuration comprising two shafts and one tunnel. The global sensitivities of the air pocket, system structure, and inflow parameters were calculated using the Extended Fourier Amplitude Sensitivity Test (EFAST), which employed indicators of the maximum pressure and relative increment. The results indicate that parameters related to the shape and initial state of the air pocket exert a substantial and direct effect on pressure surges in rapid filling, whereas tunnel system parameters tend to exhibit minimal influence. Notably, compared to the total inflow discharge, the flow difference between two shafts imposes a more significant and direct impact. For the maximum pressure of air pocket, the initial pressure and the maximum water level height of shafts demonstrate more pronounced effects. The proposed sensitivity analysis could be integrated into methodologies for system safety assessment, while the rigid-column model may be extended to accommodate multiple shafts and air pockets.

An optimized time-adaptive aerothermal coupling calculation method for aerothermal analysis of disc cavity system

In order to further achieve the balance between the calculation accuracy and efficiency of the transient analysis of the aero-engine disc cavity system, an Optimized Time-adaptive Aerothermal Coupling calculation (OTAC) method has been proposed. It combines one-dimensional transient calculation of air system, Conventional Sequence Staggered (CSS) method, Time-adaptive Aerothermal Coupling calculation (TAC) method and differential evolution optimization algorithm to obtain an efficient and high-precision aerothermal coupling calculation method of air system. Considering both the heat conduction in the solid domain and the flow in the fluid domain as unsteady states in the OTAC, the interaction of fluid–solid information within a single coupling time step size was implemented based on the CSS method. Furthermore, the coupling time step size was automatically adjusted with the number of iterations by using the Proportional-Integral-Derivative (PID) controller. Results show that when compared with the traditional loosely coupling method with a fixed time step size, the computational accuracy and efficiency of the OTAC method are improved by 8.9% and 30%, respectively. Compared with the tight coupling calculation, the OTAC method can achieve a speedup of 1 to 2 orders of magnitude, while the calculation error is maintained within 6.1%.

Face to face: France, Germany and the future of the European defence industry

ABSTRACT France and Germany agree on the need to further European defence-industrial cooperation, but boast radically different preferences on how to structure such cooperation. Why? To answer this question, we introduce the distinction between the two faces of market size – the first exclusively related to defence, the second including the broader commercial-industrial base. Since Germany is, overall, more competitive than France in the commercial sector but less competitive in the defence one, it will advocate for a full-fledged integration of the European defence market but seek to protect its less competitive defence industry from France by championing autonomy in ad-hoc arms programmes. In turn, France would prefer to leverage its defence-industrial advantage by injecting efficiency on arms programmes but resist pan-EU initiatives to integrate the defence market, which would benefit Germany more over the long-term. To test our argument, we examine French and German preferences towards the European Defence Fund and the Future Combat Air System.

Weather, Air Pollution, Rainfall Monitoring with ZigBee System

based air and rainfall detection system. The design and development of a ZigBee-based monitoring system is a key component of this paper. The proposed monitoring system is in need of the hour in metro cities of dense population countries like India. The carbon emission from industries and a large number of vehicles in metro cities in India demand low-cost, low-power, real-time distributed monitoring systems. We have chosen Pune city in Maharashtra, India for the implementation of the monitoring system due to the frequent changes in weather and rainfall conditions observed in 2019. Our main objective is to provide real-time monitoring of air quality at distributed locations by using ZigBee-based distributed real-time air quality monitoring. The extra efforts that we have done here is to observe and monitor Pollution levels after and before rainfall in Pune City, India. The highlight of this paper is the establishment of the interrelation of air pollution and rainfall and the comparisons of environmental monitoring Keywords: - ZigBee,AQI, rainfall monitoring, , air quality, weather monitoring, Pune India weather, GSM, GPRS, environment monitoring, Wireless sensor networks, MQ135.

Recurrence plot embeddings as short segment nonlinear features for multimodal speaker identification using air, bone and throat microphones

Speech is produced by a nonlinear, dynamical Vocal Tract (VT) system, and is transmitted through multiple (air, bone and skin conduction) modes, as captured by the air, bone and throat microphones respectively. Speaker specific characteristics that capture this nonlinearity are rarely used as stand-alone features for speaker modeling, and at best have been used in tandem with well known linear spectral features to produce tangible results. This paper proposes Recurrent Plot (RP) embeddings as stand-alone, non-linear speaker-discriminating features. Two datasets, the continuous multimodal TIMIT speech corpus and the consonant-vowel unimodal syllable dataset, are used in this study for conducting closed-set speaker identification experiments. Experiments with unimodal speaker recognition systems show that RP embeddings capture the nonlinear dynamics of the VT system which are unique to every speaker, in all the modes of speech. The Air (A), Bone (B) and Throat (T) microphone systems, trained purely on RP embeddings perform with an accuracy of 95.81%, 98.18% and 99.74%, respectively. Experiments using the joint feature space of combined RP embeddings for bimodal (A–T, A–B, B–T) and trimodal (A–B–T) systems show that the best trimodal system (99.84% accuracy) performs on par with trimodal systems using spectrogram (99.45%) and MFCC (99.98%). The 98.84% performance of the B–T bimodal system shows the efficacy of a speaker recognition system based entirely on alternate (bone and throat) speech, in the absence of the standard (air) speech. The results underscore the significance of the RP embedding, as a nonlinear feature representation of the dynamical VT system that can act independently for speaker recognition. It is envisaged that speech recognition too will benefit from this nonlinear feature.

Safety and Security-Specific Application of Multiple Drone Sensors at Movement Areas of an Aerodrome

Nowadays, the public service practice applicability of drones and remote sensing sensors is being explored in almost all industrial and military areas. In the present research, in collaboration with different universities, we investigate the applicability of drones in airport procedures, assessing the various potential applications. By exploiting the data from remote sensing sensors, we aim to develop methodologies that can assist airport operations, including managing the risk of wildlife threats to runway safety, infrastructure maintenance, and foreign object debris (FOD) detection. Drones equipped with remote sensing sensors provide valuable insight into surface diagnostics, helping to assess aprons, taxiways, and runways. In addition, drones can enhance airport security with effective surveillance and threat detection capabilities, as well as provide data to support existing air traffic control models and systems. In this paper, we aim to present our experience with the potential airport applications of UAV high-resolution RGB, thermal, and LiDAR sensors. Through interdisciplinary collaboration and innovative methodologies, our research aims to revolutionize airport operations, safety, and security protocols, outlining a path toward a safer, more efficient airport ecosystem.

Exploring the Use of Cold Atmospheric Plasma for Sound and Vibration Generation.

In this study, we investigate the potential of cold atmospheric plasma (CAP) as a non-contact excitation device, comparing its performance with an ultrasound transmitter. Utilizing a scanning Laser Doppler Vibrometer (LDV), we visualize the acoustic wavefront generated by a CAP probe and an ultrasound sensor within a designated 50 mm × 50 mm area in front of each probe. Our focus lies in assessing the applicability of a CAP probe for exciting a small polymethyl methacrylate (PMMA) sample. By adjusting the dimensions of the sample to resonate at the excitation frequency of the probe, we can achieve high vibrational velocities, enabling further mechanical analysis. In contrast with traditional vibration excitation techniques such as electrodynamical shakers and hammer impact excitation, a plasma probe can offer distinct advantages without altering the structure's dynamics since it is contactless. Furthermore, in comparison with laser excitation, plasma excitation provides a higher power level. Additionally, while pressurized air systems are applicable for limited low frequencies, plasma probes can perform at higher frequencies. Our findings in this study suggest that CAP is comparable with acoustic excitation, indicating its potential as an effective mechanical excitation method.

Sustainability of Alternative Energy Sources: Thermo-Gravimetric Analysis of Energy Crops in Ekiti State, Nigeria

Ekiti State is a farming region with the ability to produce biomass reserves, which include yet refined crop cultivation product leftovers like sugar cane, corn cobs, palm husk shells, and okanagan wood, for use as fuel. The vast energy-generating potential of crops for use in industry and household applications is examined in this article. Biomass crops were subjected to a thermogravimetric examination to determine their unique thermal activity in an airtight and benign atmosphere with a temperature increase of 10°C per minute up to 800°C. The decrease in weight pattern was shown to be similar across all four waste specimens. Three reactive regions were identified during the nitrogen-rich environment assessment, which correlate to water loss, flammable generation, and char breakdown. Three response domains in an air system corresponded to the degradation, burning, and drying of char. The proximate and ultimate evaluation outcomes demonstrated that each of the bioenergy crop leftovers under investigation is fit for gas extraction and fuel combustion to meet power and thermal needs. The computational and experimental analysis revealed that Okanagan wood has the highest calorific value which indicates the highest heat values and considered the best for biomass energy production in Ekiti State for entrepreneurial venture.

Synergistic Impact on Indoor Air Quality: The Combined Use of Air Conditioners, Air Purifiers, and Fresh Air Systems

As concerns about indoor air quality increase, air purifiers and fresh air systems are increasingly being used in conjunction with air conditioners in office buildings. To study the synergistic effects of multisystem joint operation on indoor air quality, this study used a combination of experimental and simulation methods to study the indoor particulate matter with a diameter of less than 2.5 µm (PM2.5) and carbon dioxide (CO2) concentrations under different operation conditions. The purification time and the PM2.5 concentration distribution under different conditions were compared with the condition in which the purifier was used alone. The results showed that the purification time required for the condition that the air conditioner runs together with the purifier was shortened by 15.2%. When the fresh air system is running together with the purifier, the purification time can be reduced by 30.4%. It was reduced by 32.6% when the three systems were operating at the same time. The PM2.5 concentration distribution under the joint operating condition was much more even than that under the condition in which the purifier was running alone. To analyze the impact on the CO2 distribution, the CO2 distributions under different joint operations were compared. The results show that the fresh air system can effectively dilute CO2 below 1000 ppm in 30 min. The air conditioner and purifier could help to mix the indoor air to provide a much more uniform indoor CO2 distribution.

Influence of the natural makeup air system on the kitchen environment in low-energy buildings in severely cold regions

As an essential part of residential buildings, kitchens may exhibit the release of large amounts of pollutants during cooking. However, it is challenging to extract heat and pollutants from kitchens in low-energy buildings (LEB) due to their high airtightness and low air permeability. Therefore, the natural makeup air system in kitchens of low-energy buildings is critical for improving the range hood performance. In this study, an environmental laboratory was established in Harbin to quantitatively investigate the exhaust of pollutants and analyze the impact of the natural makeup air system on the indoor environment in severely cold regions. Multiple measuring points were arranged to indicate the pollutant concentration in the breathing area and the indoor air temperature. The experimental results showed that natural makeup air could help control the diffusion of waste heat and cooking pollutants. The average concentrations of the total volatile organic compounds (TVOCs) and fine particulate matter (PM2.5) in the breathing area decreased by 45.0 % and 34.7 %, respectively, compared with those without the natural makeup air system. The natural makeup air system with a higher exhaust rate of the range hood (700 m3/h) could effectively reduce the TVOC and PM2.5 concentrations by 26.2 % and 83 %, respectively, compared with the system with an exhaust rate of 400 m3/h. Moreover, the trapping efficiency of the system for pollutants and waste heat highly depended on the temperature of the natural makeup air. Cold natural makeup air in winter could lead to thermal discomfort and higher pollutant concentrations than those in summer.

Experimental Testing of Filter Materials for Two-Stage Inlet Air Systems of Internal Combustion Engines

This paper presents an experimental study of the effect of the mass of dust retained on a fibrous filter bed operating singly and in a “cyclone-filter-bed” system on changes in filtration efficiency and accuracy, as well as the increase in flow resistance. The research was carried out using a novel and unprecedented method, determining the dust absorption coefficient km of the filter baffle under laboratory conditions. A filtration system built of a single cyclone and a cylindrical filter cartridge with an appropriately sized surface set behind it was studied. Conditions corresponding to the actual operating conditions of the air filter were maintained: dust concentration, filtration speed and dust extraction from the cyclone settling tank. The purpose of the research was to evaluate filter materials with different structures in terms of filtration efficiency and accuracy, as well as flow resistance. The study showed that the parameters of the structure of filter materials—permeability, grammage and thickness—affect the process of retaining dust particles. It was shown that the increase in the flow resistance of the filter bed has a higher intensity when dust grains of small sizes are directed at it, which is the case when the bed is operated behind a cyclone, which separates larger dust grains from the air. There is a reduction in the operating time of the filtration system due to the limitation of the permissible resistance ∆pfdop, and the corresponding dust absorption km has a lower value. For a fixed value of the flow resistance, the dust absorption coefficient km2 of three different filtration baffles AC, B2, and B, working with a cyclone, take values 50–100% smaller than when working in a single-stage system. It has been shown that the “cyclone-filter baffle” unit, due to its greater dust separation capability, allows the filter cartridge to operate for a longer time until a certain flow resistance is reached. This allows the unit to operate longer at lower flow resistance without changing the filter cartridge, thus saving energy. The km values obtained during the tests, using the proposed original method, allow the selection of the filter bed for specific vehicle operating conditions by modelling its course.

Offset-Free Koopman Model Predictive Control of Thermal Comfort Regulation for a Variable Refrigerant Flow-Dedicated Outdoor Air System-Combined System

Abstract Variable refrigerant flow (VRF) system has been an appealing solution of air conditioning for residential and commercial buildings, due to its flexibility and cost effectiveness, while lack of ventilation capability is a major drawback. Incorporation of dedicated outdoor air system (DOAS) is a typical practice. However, good coordination between DOAS and VRF is critical for achieving desired thermal comfort is challenging due to the possible complexity of mixed sensible and latent heat exchanges. In this paper, to handle the nonlinear dynamic characteristics of VRF-DOAS system, we propose an offset-free Koopman model predictive control (MPC) strategy for thermal comfort regulation, in which the MPC design is computationally more efficient due to the convex problem formulation and the use of reduced-order Koopman models, and the offset-free MPC structure enhances the robustness to model uncertainties and unmeasured disturbances. A control-oriented model is obtained by hybridizing the first-principle and data-driven modeling approach. The proposed controls strategy is evaluated with a Modelica simulation model of a VRF-DOAS system. A Dymola-Python cosimulation platform is developed via the functional mockup interface (FMI), for which the MPC algorithms are implemented in Python. Simulation results show significantly better performance of the offset-free Koopman MPC in thermal comfort regulation.

Analysis and Optimization of the Performances of the Tandem Blade Radial Compressor Using the CFD

Centrifugal compressors are frequently used in both military and commercial areas because they can be easily manufactured and reach high-pressure compression ratios. The factor that limits the performance and operating range of compressors is flow instability. Many ideas have been put forward for performance improvement, but tandem blade radial compressors, which do not require an extra air system, have attracted the most interest. In this study, computational fluid dynamics (CFD) analyses were carried out on various parameters of the tandem blade (TB) radial compressor, and an optimization study was carried out to find the best design using a genetic algorithm on a whole operating curve. It was investigated how these parameters affected the efficiency and total pressure ratio between the determined lower and upper limits. The numerical analyses of the optimum design obtained as a result of the iterations were carried out. As a result of the iterations, three optimum designs were obtained and numerical analysis was carried out according to one of them, and then they were compared with the results in the literature. The general agreement of computational fluid dynamics and the literature data served as a validation for the computational approach. The error rates between the numerical analysis results and the experimental results in the literature were calculated for different flow rates and were found to be 1.98% as the highest and 0.35 as the lowest. The work carried out in this article will provide a valuable reference for future advanced tandem blade compressor designs.

Experimental Investigation of Effect of Orifice Diameter on Volumetric Efficiency of Two-Stage Reciprocating Air Compressor

The volumetric efficiency is an important parameter commonly adopted to quantify the performance of air compressors. The present work is concerned with the design of an optimum air intake system for a single acting two stage reciprocating air compressor. The intake air system comprised of different diameter of orifice which affect the quantity, pressure of air to the compressor. The study approaches the effect of change in the intake orifice opening, affects the volumetric efficiency of air compressor. In this we used the standard procedure to find the efficiency, and it shows us the as orifice diameter increases the volumetric efficiency changes with increasing order to some extent

Преимущества интеграции автоматизированных систем управления технологическим процессом угольных шахт с системами определения местоположения

Coal mining companies, especially those involved in underground operations, are currently at different stages on their way to digitalization and face a number of challenges, which are described in the article. One group of such problems is the difficulties concerned with the coal mine dispatching control. The paper shows how a properly selected approach, i.e. the integration of various automated process control systems with positioning systems, provides a solution to these problems and offers significant advantages both regarding the industrial safety and maximizing the economic effect. Examples of such integration are given for the conveyor transport control system, for the air and mine gas control systems as well as a CCTV systems with positioning systems within the Smart Mine® complex. An assessment of the current technical basis for the implementation of this approach is given, and the advantages of using a single platform for subsystems of the multi-functional safety system and production management systems are shown.