Air Distribution Pattern Research Articles

In-situ measurement of potassium and sodium concentrations in a 16 MW MSW incinerator employing the FES system

To comprehensively understand the release characteristics of alkali metals which can cause corrosion and slagging problems in municipal solid waste (MSW) incinerators, the temporal concentrations of sodium (Na) and potassium (K) in a 16 MW MSW incinerator were measured employing a calibrated flame emission spectroscopy (FES) system. The experimental results revealed that the concentrations of alkali metals increased first and then decreased from the left side to the right side of the MSW incinerator. The maximum concentrations of Na and K were 111 ppm and 184 ppm, respectively. The peak and average concentrations of K near the left wall were 27 % and 58 % higher than those near the right wall at the same height of the MSW incinerator, owing to the different combustion stages of the MSW. The differences of the peak and average concentrations of K at the different heights of the MSW incinerator were 33.7 % and 23.5 %, respectively. Moreover, a positive correlation between the concentration of alkali metals and flame temperature was confirmed during the char phase combustion stage. Since the primary air distribution pattern of MSW incinerator decreased form the left side to the right side, the concentration of alkali metals near the left wall was positively correlated with the primary air flow, and that near the right wall exhibited a positive correlation with the garbage caloric value. This research provided an effectual solution for in-situ measurement of alkali metal concentration and flame temperature in MSW incinerators.

Numerical Simulation of Hydrogen–Coal Blending Combustion in a 660 MW Tangential Boiler

With the adjustment of energy structure, the utilization of hydrogen energy has been widely attended. China’s carbon neutrality targets make it urgent to change traditional coal-fired power generation. The paper investigates the combustion of pulverized coal blended with hydrogen to reduce carbon emissions. In terms of calorific value, the pulverized coal combustion with hydrogen at 1%, 5%, and 10% blending ratios is investigated. The results show that there is a significant reduction in CO2 concentration after hydrogen blending. The CO2 concentration (mole fraction) decreased from 15.6% to 13.6% for the 10% hydrogen blending condition compared to the non-hydrogen blending condition. The rapid combustion of hydrogen produces large amounts of heat in a short period, which helps the ignition of pulverized coal. However, as the proportion of hydrogen blending increases, the production of large amounts of H2O gives an overall lower temperature. On the other hand, the temperature distribution is more uniform. The concentrations of O2 and CO in the upper part of the furnace increased. The current air distribution pattern cannot satisfy the adequate combustion of the fuel after hydrogen blending.

Reversible decentralized ventilation: Experimental determination of efficiency by carbon dioxide level

We studied decentralized ventilation devices based on a regenerative heat exchanger with a reverse mode of operation. These devices are capable of recovering up to 90% of the heat used for ventilation of premises. They are a cheaper alternative to central units, and can solve the problem of high heat consumption for ventilation of buildings. Such devices are of little use in practice, since their efficiency concerning providing the required air exchange is poorly studied. The reverse mode of operation is not typical for room ventilation, since the same device constantly changes its purpose between supply and exhaust, which constantly changes the air distribution pattern in the room and can affect the efficiency of dilution and removal of harmful substances. Taking this fact into account makes the study original. The aim of the study is to experimentally determine the efficiency of ventilation in the premises of civil buildings when using such devices. The efficiency criterion was the level of carbon dioxide concentration in the room with a specified limit value of 1000 ppm. People were the source of carbon dioxide. Ventilation was represented by two decentralized devices. The experiment consisted in determining the level of carbon dioxide concentration in natural conditions with a different number of people in the room and different ventilation performance. The results of the experiment were verified by analytical determination of the level of carbon dioxide in the room. As a result of the experiment, dependences of changes in CO2 concentration over time were obtained when one, two and five people were in a room with and without ventilation. To ensure the level of carbon dioxide concentration below the limit (1000 ppm), the required ventilation capacity for one person was 40 m3/h, for two people – 80 m3/h, for five people – more than 160 m3/h. The results allow us to make conclusions about the efficiency of decentralized ventilation devices with reversible mode for premises with a small number of people.

Ambient Air Quality, Pollutant Behavior, and Distribution Pattern in Rabigh City Using an Air Dispersion Model

The rise in industrial development and modern technology is one of the major causes of atmospheric pollution, which negatively affects human health. In this study, meteorological conditions and atmospheric pollution dispersion in Rabigh city and its catchments were analyzed using measured data and an air quality dispersion model. The Hybrid Single-Particle Lagrangian Integrated Trajectory model was used to simulate the dispersion of atmospheric pollutants. A dataset from 2018 was analyzed to clarify the seasonal distributions of atmospheric pollutant concentrations in Rabigh and other areas (Thuwal and Khulais). A significant variation in atmospheric pollutants was recorded across the seasons, which may be caused by changes in meteorological conditions. Variations in other anthropogenic sources related to high population density or heavy traffic in the nearby road may also be involved in these fluctuations. Predictions indicated that pollutants would impact the Thuwal area (>50 μg m−3) and Khulais (>35 μg m−3) during the winter season and affect Thuwal (>20 μg m−3) and Rabigh (>20 μg m−3) during the fall season. The concentrations of pollutants were mostly negatively correlated with wind speed, except for carbon monoxide. We established variations in the seasonal concentration of pollutants and the effect of meteorological conditions on atmospheric pollutants for the year 2018 in the study area. Policymakers and stakeholders must provide solutions to mitigate the environmental effect of atmospheric pollution in Rabigh city, Thuwal, and Khulais for the health of inhabitants.

A method to identify coal spontaneous combustion-prone regions based on goaf flow field under dynamic porosity

Once the residual coal occurs spontaneous combustion in mine, it will cause a fire accident resulting in heavy personal injury and property damage. So it is of great significance for mine safety to quickly determine the location of dangerous areas of residual coal spontaneous combustion. A fracture-pore evolution model of goaf is constructing, the pore evolution and porosity distribution in a goaf overburden are simulated by the distinct-element modeling software Particle Flow Code (PFC). By compiling the extracted porosity distribution data into Fluent using a User Defined Function (UDF), a dynamic porosity model of goaf is being proposed. With this model, the air flow field in a goaf is simulated, and the regular air distribution pattern in that area is obtained. Using oxygen concentration as the indicator, the residual coal spontaneous combustion-prone region in the goaf is identified, and the results are basically the same as those determined from real mine measurements. The consistency in results validates that the residual coal spontaneous combustion-prone region can be accurately and reliably identified by investigating the goaf flow field distribution under consideration of porosity dynamics. Our approach offers a new concept and method with a higher precision of results for identifying residual coal spontaneous combustion prone-regions in goafs, and it provides the basis for preventing and extinguishing goaf fires and guarantees the mine safety.

Thermal performance analysis of a naturally ventilated system using PMV models for different roof inclinations in composite climatic conditions

Computational analysis has become a very useful tool for a detailed understanding of building physics before actual building constructions and for predicting such system behaviors where massive urbanizations are envisaged. The present study attempts to describe the efficacies of CFD as an “analysis led design” tool, where a computationally modeled cross-ventilation system with asymmetric positions of openings is analyzed to estimate the comfort zones according to the PMV (predicted mean vote) model for evaluating the influence due to roof inclinations, thereby providing opportunities in rectifying any anomalies pertaining to it, prior to the actual construction. A numerical analysis has been carried out to examine the effects of natural ventilation in a wind-driven system using the established extended PMV model (PMVe). The study focuses on thermal comfort and the effect of roof inclination angle over the three different weather conditions in Delhi—winter season (high humidity and low temperature), summer season (low humidity and high temperature) and monsoon season (high humidity and mild temperature). Appropriate roof inclination angles provide a better ventilation rate and air distribution pattern, which significantly affects comfort condition. Study shows that for winter season, the PMV values decrease as the roof inclination angle is increased and the ventilation rate for 30° inclined roof increases about 16% as compared to the flat roof case, while PMV values increase with roof inclination for summer season, signifying zone of discomfort. It also concludes that a moderate roof inclination is beneficial for monsoon season.

Performance Evaluation of An Innovative Column Attachment Ventilation

An innovative column attachment ventilation (CAV) was proposed for heating, ventilating and air-conditioning (HVAC) systems and its performance was evaluated through experimental investigation and numerical modeling. Airflow pattern, air temperature distribution, air diffusion performance index (ADPI), predicted mean vote (PMV), and draught rate (DR), were used as the performance indicators to investigate the air distribution performance. The ventilation effectiveness for heat removal in the CAV mode was compared with a conventional mixing ventilation (MV). The results showed that the discharged air from the linear slot diffuser can attach to the column and enter into the occupied zone creating air lake phenomenon. The airflow spread over the floor in a radial pattern behaved as a stratified air distribution like displacement ventilation (DV), providing good air quality and comfort level for occupants. Moreover, the heat removal effectiveness in the CAV was found to be higher than in the MV, i.e. 1.32 in the C-CAV and 1.29 in the S-CAV modes. The column attachment ventilation can achieve thermal comfort in the occupied zone without local discomfort caused by high vertical temperature difference and draught, and this ventilation strategy could be expected as a new and efficient air distribution pattern for different HVAC applications.

Numeric Analysis of Air Distribution in Air-Conditioned Room to Obtain Optimum Energy Effeciency Level

The demand for household energy in Indonesia is dominated by air conditioning sector. One of the efforts to optimize air conditioner (AC) is to figure out the best air distribution pattern. Nowadays, there are three air distribution types of marketed AC; (1) perfect mixing, (2) displacement, and (3) radiant cooling. This research examines the influence of those types toward energy consuption to ensure indoor thermal comfort. It was conducted by conducting literature review, mathematical calculation, and numerical simulation. Based on SNI 03-6572-2001, the research applied comfort criteria of indoor air temperature of 24oC as setpoint with 28.1oC initial temperature. Energy consumption is estimated based on time required to achieve the setpoint. The fastest cooling time is obtained by displacement in 80 seconds, then perfect mixing in 112 seconds, and the longest is radiant cooling in 460 seconds. Energy calculation establishes three scenarios of heat load represented by air con’s idle time; (a) high load, 30 seconds, (b) moderate load, 60 seconds, and (c) low load, 90 seconds. For 300 hours of operational time per month, displacement consumes (a) 148.4, (b) 116.6, and (c) 96 kWh/month, whilst perfect mixing needs (a) 160.9, (b) 132.8, and (c) 113.1 kWh/month. Lastly, radiant cooling spends (a) 191.5, (b) 180.5, and (c) 170.6 kWh/month.

Studi Distribusi Udara Pada Ruang Ber-AC Untuk Mencapai Tingkat Efisiensi Energi yang Optimal

Penggunaan energi listrik bangunan di Indonesia didominasi oleh pemenuhan kebutuhan AC. Salah satu upaya untuk mengoptimalkan kinerja AC adalah dengan memperhatikan pola distribusi aliran udaranya. Saat ini, di pasaran terdapat 3 tipe pola distribusi udara AC, yaitu (1) perfect mixing, (2) displacement, dan (3) radiant cooling. Penelitian ini menguji pengaruh tipe-tipe distribusi AC tersebut terhadap konsumsi energi pendinginan dengan metode studi literatur, perhitungan matematis, dan simulasi komputer. Adapun kriteria kenyamanan yang digunakan bersumber dari SNI 03-6572-2001 dengan besaran suhu udara 24oC sebagai titik tuju (setpoint) AC dari kondisi awalnya 28,1oC. Sedangkan perhitungan tingkat konsumsi energi didapatkan dari lamanya waktu mencapai setpoint. Perhitungan menggunakan skema tiga skenario beban kalor diasumsikan menjadi lamanya waktu mesin AC saat jeda (idle), yaitu; (a) beban kalor besar, waktu jeda 30 detik, (b) beban kalor sedang, 60 detik, dan (c) beban kalor kecil, 90 detik. Dengan waktu operasional 300 jam per bulan, hasil perhitungan konsumsi energi pola displacement sesuai skenario adalah; (a) 148,4 kWh/bulan, (b) 116,6 kWh/bulan, dan (c) 96 kWh/bulan. Sedangkan perfect mixing; (a) 160,9 kWh/bulan, (b) 132,8 kWh/bulan, dan (c) 113,1 kWh/bulan, serta radiant cooling; (a) 191,5 kWh/bulan, (b) 180,5 kWh/bulan, dan (c) 170,6 kWh/bulan.Kata kunci: efisiensi energi, pengkondisian udara, pola distribusi udara

Experimental study of dense gas contaminant transport characteristics in a large space chamber

Flammable gases and vapours are widely used in industrial field, which brings up the explosion risk in the large premises. In this paper, several transient experiments have been conducted in a newly built large space chamber. Sulfur hexafluoride (SF6) was released in a specific place in each experiment while the space was ventilated throughout each experiment. The concentrations were measured and recorded at several points. Several parameters have been changed, namely air distribution pattern, air change rate, contaminant gas emission rate and contaminant source releasing method. The approximate accessibility of contaminant source (ACS) in different experiment conditions have been yielded with experimental data and compared. The dimensionless number (g'qV/D)1/3/Uinlet has been proposed on the basis of the passive gas criterion of (g'qV/D)1/3/U to represent the magnitude of the gas gravity effect. The experiment results show obvious correlations between ACS and (g'qV/D)1/3/Uinlet at different locations.

Experimental study on airflow characteristics of a square column attached ventilation mode

A new air distribution pattern, the square column attached ventilation mode, which can be applied to ventilation and air-conditioning systems in large space buildings, is presented in this work. An experimental method was employed to visualize and investigate the airflow characteristics of this novel ventilation mode under isothermal conditions. Our results show the behavior of square column attached ventilation in the form of maximum jet velocity decay, non-dimensional velocity profiles and jet spreading rate at different supply air velocities. The empirical equations governing these characteristic parameters were derived and compared with other types of air jets. The results show that the square column attached ventilation mode is a particular air distribution pattern which combines the advantages of mixing and displacement ventilation. When using the slot outlet with an aspect ratio of 20, the air flow can be treated as a conventional plane wall jet, however the velocity decay and jet diffusion in the occupied zone can be much faster. The obtained results can be helpful in understanding a new air distribution—square column attached ventilation used for ventilation and air-conditioning systems design.

Recent changes in the features of hypertrophic pyloric stenosis.

Hypertrophic pyloric stenosis (HPS) is a rare cause of non-bilious vomiting in young infants; the condition requires surgical management. Diagnosis is based on clinical, laboratory, and radiological findings. In the present study, we evaluate recent changes in the features of HPS. We retrospectively reviewed the demographic, clinical, and laboratory data on 56 HPS patients who underwent pyloromyotomy between 1996 and 2015. Patients were divided into two groups according to date of operation (group 1, 1996-2006; group 2, 2007-2015). Group 1 consisted of 30 patients and group 2, 26. The age at diagnosis was longer in group 2 (43.3 ± 13.1 days) than group 1 (37.4 ± 17.7 days). All diagnoses were confirmed on ultrasonography. Pyloromyotomy was performed on all 56 patients (48 boys, 8 girls). Significant between-group differences were evident in terms of age at onset of vomiting; rate of dehydration; development of palpable olive-shaped abdominal mass; serum urea and creatinine; acid-base status; and air distribution pattern on abdominal radiography (all P < 0.05). The frequency of olive-shaped abdominal mass evident on physical examination decreased significantly over time, and was lower than published values. Early diagnosis triggers timely support and surgical intervention, and may thus prevent development of the classical clinical and laboratory findings of late-stage HPS. The remarkable recent advances in ultrasonography and techniques allow HPS to be diagnosed earlier than formerly.

Capture and Containment Efficiency of the Exhaust Hood in a Typical Chinese Commercial Kitchen with Air Curtain Ventilation

In typical Chinese commercial kitchens, the large amount of heat and moisture that is generated must be removed. The ventilation and energy consumption rates can be huge. Middle and small scale commercial kitchens in China produce an exhaust airflow rate so large that without a reasonably effective ventilation system, the temperature and contaminant concentrations are far more than acceptable levels. To fulfil all the requirements of indoor air conditioning in an economical manner, a new air distribution pattern called air curtain ventilation (ACV) is presented in this study. To fully optimize the entire plan, a model to record efficiency values has been derived to estimate the influence of the ACV on the total efficiency of the commercial kitchen case-study. In this paper, a simple equation is demonstrated for the average contaminant level in the occupied zone. This could be a suitable platform for capture and containment (C&C) efficiency analysis. With air curtain ventilation system, the C&C efficiency can be as high as 81–86%.

Combustion Characteristics of Coal–Water Slurry in a Slag-Tap Vertical Cyclone Furnace through Digital Imaging

This study presented a novel diagnosis for the combustion of coal–water slurry (CWS) in a pilot-scale slag-tap vertical cyclone furnace using flame images and three-dimensional temperature distributions reconstructed from these flame images through a two-step inverse radiation analysis. The accuracy of the reconstructed temperature was evaluated by infrared thermometer measurements, with a discrepancy of less than 50 K. The effects of the air/fuel equivalence ratio, the air distribution pattern, and the furnace load on combustion performance were analyzed based on the reconstructed temperature profiles. Experimental and analytical results showed that flame stability was clearly represented by the variance of the image pixel values. The three-dimensional temperature profiles also effectively illustrated the combustion characteristics in the cyclone furnace under different air/fuel settings. By appropriately supplying air, the combustion efficiency of CWS can be maintained at >99% in the proposed cyclone fu...

Experimental Investigation of Operating Room Air Distribution in a Full-Scale Laboratory Chamber Using Particle Image Velocimetry and Flow Visualization

Room air distribution in hospital operating rooms (OR) is critical to the effective functioning of surgical procedures, but the air distribution patterns are governed by complex physics that are currently not well understood. Both qualitative and quantitative flow visualization techniques were used to evaluate the room air distribution in a full-scale chamber designed to simulate a hospital operating room. A laser sheet illumination technique was used to identify key features of the room air distribution, and particle image velocimetry (PIV) was used to measure the velocity field in a plane crossing the surgical site. Hospital operating rooms require the use of ASHRAE Group E diffusers in an array above the surgical table, providing downward, unidirectional, non-aspirating air flow across the sterile region of the room. The supply air jet is characterized by complex physics, including annular shape, impingement, buoyancy, a large jet to room aspect ratio, and recirculation. The large diameter of the jet relative to the room size makes the overall room air distribution highly sensitive to the parameters of the supply air. The air distribution pattern in the room was found to have relatively low velocity and turbulence near the supply air diffuser, but increasing velocity and turbulence in the shear region at the edge of the supply air jet. Flow visualization and PIV methods both demonstrated an angle of the shear layer inwards towards the center of the jet. This flow feature reduces the overall coverage area for the sterile air flow and may pose a risk to the protection of the surgical patient.

Critical review on hospital surgical room and mechanical system designs

The design of HVAC systems for surgical operating rooms requires specific guidance for the design engineer in order to insure that thermal comfort and sepsis control are maintained at all times in order to protect the occupants of the room. Operating room ventilation has been through significant design improvements from the beginning of the 20th century until now. Researchers have found that the room air distribution pattern is a critical parameter for airborne sepsis control, as most contaminants are introduced into the operating room by occupants and object within the room. Computational models have been used by many researchers to determine the room air distribution patterns for a variety of ventilation system and room configurations, but few of these models have been validated with experimental data. Further research is needed to both validate the models that are used for understanding the role of air distribution patterns in surgical sepsis control, as well as studying the impact of increasing heat loads in the next generation of surgical procedures.

Airflow characteristics by air curtain jets in full-scale room

A new air distribution pattern, air curtain jet ventilation was presented. The ventilation or airflow patterns and the air velocity produced by air curtain jet were investigated in detail. To identify the airflow characteristics of this novel air curtain jet ventilation system, a full-scale room was used to measure the jet velocity with a slot-ventilated supply device, with regards to the airflow fields along the vertical wall as well as on the horizontal floor zones. The airflow fields under three supply air velocities, 1.0, 1.5 and 2.0 m/s, were carried out in the full-scale room. The experimental results show the velocity profiles of air distribution, the airflow fields along the attached vertical wall and the air lake zones on the floor, respectively. The current experimental research is helpful for heating, ventilation and air conditioning (HVAC) engineers to design better air distribution in rooms.

Investigation on the Electronic Components High Temperature Alarm in High Computer Density Internet Data Centers

This paper analyzes the phenomenal essence of the electronic components high temperature alarm in high computer density internet data center and the effect of controllable variables of microthermal environment around the computer racks, presents the risk index of electronic components high temperature alarm, i.e., unmatch ratio; carries out the onsite investigation on the situation of air distribution of two internet data centers in Xi’an city, and evaluates the probability of emerging the high temperature alarm, finally puts forward the suggestions of improving air distribution pattern.

A membrane reformer with permeate side combustion for CO2 capture: Modeling and design

The design of a pre-combustion natural gas fired power plant is presented, which makes use of a membrane assisted reformer with permeate side combustion. A detailed reactor model has been made with which the impact of the air distribution pattern is assessed. The results demonstrate that a flat air distribution pattern is sufficient for avoiding hot spots in the reactor. A system assessment shows that the concept is competitive with conventional membrane reformers in terms of system efficiency, and offers a more compact design.

Control of airborne infectious diseases in ventilated spaces

We protect ourselves from airborne cross-infection in the indoor environment by supplying fresh air to a room by natural or mechanical ventilation. The air is distributed in the room according to different principles: mixing ventilation, displacement ventilation, etc. A large amount of air is supplied to the room to ensure a dilution of airborne infection. Analyses of the flow in the room show that there are a number of parameters that play an important role in minimizing airborne cross-infection. The air flow rate to the room must be high, and the air distribution pattern can be designed to have high ventilation effectiveness. Furthermore, personalized ventilation may reduce the risk of cross-infection, and in some cases, it can also reduce the source of infection. Personalized ventilation can especially be used in hospital wards, aircraft cabins and, in general, where people are in fixed positions.