Ventilation Airflow Rate Research Articles

S0503-3-5 列車風を活用した地下鉄省エネ安心システム(トンネルの空気力学、換気、火災(3))

We present a new subway operation support system for energy saving of air conditioning and ventilation and fire risk reduction, by taking into account of the train-driven wind in the control model. Our system consists of a) high reliable parameter estimation and accurate model prediction of wind, pollutant and smoke, especially considering the train-driven wind, b) optimal selection of air conditioning, ventilation air flow rate, in-air return rate and shutter operation for smoke.

Influences of Air Exchange Effectiveness and its Rate on Thermal Comfort: Naturally Ventilated Office

This article presents the effects of air exchange rate (ACH) and air exchange effectiveness (AEE) on thermal comfort level of a naturally ventilated office room. The study was conducted in an office at UPM, Malaysia. Influence of ACH and AEE on thermal comfort has not been investigated and is, therefore, not well understood. The main objective of this research is to investigate and assess these influences through the variable windows-door opening arrangements. To determine the windows-door opening performance in terms of ventilation air flow rate, 14 opening configurations have been considered. Thermal comfort variables were measured at the same time when ACH and AEE were evaluated. Through these data, the thermal comfort Fanger's indices (Predicted Mean Vote (PMV) and Predicted Percentage Dissatisfied (PPD)), ACH and AEE were calculated. These results showed that for a naturally ventilated office room three linear regression equations of PMV versus ACH and three linear regression equations of PMV versus AEE can be derived.

Control of Outdoor Ventilation Airflow Rate - Evaluation of Setting Methods

Ventilation is essential for the health and comfort of building occupants. It is particularly required to dilute and/or remove pollutants emitted by occupants' metabolism and activities. The concentration of metabolic CO2 is well correlated to metabolic odour intensity. Therefore CO2 concentration can be efficiently chosen as an indoor air quality index when occupants are the main source of pollution inside the buildings.This paper presents details of the research conducted in order to adjust and compare five advanced techniques based on CO2 level measurement in order to adapt ventilation extractor fan speed to the intermittent occupation of an office. An experimental device (HybCell one-zone test cell) was chosen to compare these five control technologies (i.e. on/off, proportional integrative regulator, fuzzy logic control, analytical control function and radio frequency identification) under the same experimental conditions. A method was developed to define the setting parameters of a proportional integrative and a fuzzy logic control regulator of an extract fan. Criteria based on control precision, command stability and global air exchanged were then established for the final evaluation.The results revealed fine control accuracy. They showed a good stability with a reduced and simplified setting period for the developed methods compared to current controllers.

Passive air exchanges between building and urban canyon via openings in a single façade

The results of an experimental study examining the steady exchange of air and heat between a building and an urban canyon are presented. The focus is on the effect of the canyon aspect ratio on the airflow through openings made exclusively in one side of the building. The interaction of the external wind flow and the internal thermally-driven flow was shown to depend upon the ratio of the building height H b to the canyon width W (distance between buildings forming the canyons). The trends observed as this aspect ratio ( H b/ W) was varied allow for identification of canyon geometries that yield reduced or enhanced building ventilation airflow rates.

Exergy Analysis as an Assessment Tool of Heat Recovery of Dwelling Ventilation Systems

This paper presents steady-state energy and exergy analyses for dwelling ventilation with and without air-to-air heat recovery, and discusses the relative influence of heat and electricity on the exergy demand by ventilation airflows. Energy and exergy analysis results for De Bilt, NL, are presented in terms of heat and electricity use, on an instantaneous and a daily basis. The amount of electricity input to fans and the heat recovery unit (HRU) is much more significant in terms of exergy than of energy, due to the higher exergy value of electricity. From an exergy viewpoint, it could make sense to use the HRU only when environmental air temperature is low enough to compensate the additional need for electricity. When the air temperature is not too low, electricity input could be decreased by letting ventilation air bypass the HRU or by operating the HRU at low ventilation airflow rate, depending on outdoor temperatures and indoor occupancy conditions.

Solar integrated energy system for a green building

Shanghai is characteristic of subtropical monsoonal climate with the mean annual temperature of 17.6 °C, and receives annual total radiation above 4470 MJ/m 2 with approximately 2000 h of sunshine. A solar energy system capable of heating, cooling, natural ventilation and hot water supply has been built in Shanghai Research Institute of Building Science. The system mainly contains 150 m 2 solar collector arrays, two adsorption chillers, floor radiation heating pipes, finned tube heat exchangers and a hot water storage tank of 2.5 m 3 in volume. It is used for heating in winter, cooling in summer, natural ventilation in spring and autumn, hot water supply in all the year for 460 m 2 building area. The whole system is controlled by an industrial control computer and operates automatically. Under typical weather condition of Shanghai, it is found that the average heating capacity is up to 25.04 kW in winter, the average refrigerating output reaches 15.31 kW in summer and the solar-enhanced natural ventilation air flow rate doubles in transitional seasons. The experimental investigation validated the practical effective operation of the adsorption cooling-based air-conditioning system. After 1-year operation, it is confirmed that the solar system contributes 70% total energy of the involved space for the weather conditions of Shanghai.

Energy consumption analysis on a dedicated outdoor air system with rotary desiccant wheel.

A dedicated outdoor air system (DOAS) with rotary desiccant wheel is the combination of a desiccant dehumidification system and a vapor compression refrigeration system. An energy consumption model of this hybrid DOAS is established for its analysis. Coefficient of performance, COP, is appropriately defined for evaluation on performance of the hybrid DOAS. The results indicate that, compared with a conventional DOAS, energy savings are possible for the suggested DOAS, when solar energy or natural gas is used for regeneration. Ventilation air flow rate, temperature or humidity of outdoor air, as well as regeneration-to-process air ratio, influence the energy consumption and the COP of the hybrid DOAS, greatly.

Thermal analysis of an off-road machine with a conjoint 3-D CFD and 1-D network simulation package

To gain insight into the ventilation needs of an enclosed engine compartment of an off-road machine, we performed analyses to predict underhood ventilation air flow and component temperatures in the test rig. The analytical work involved development, validation, and application of these methods to optimise ventilation air flow rate. A 1-D thermal-fluid network model was developed to account for overall energy balance and to simulate ventilation and hydraulic system response. This model was con-jointed with a 3-D computational fluid dynamics (CFD) model for the ventilation air circulation to determine the flow patterns and the distributed surface heat transfer. The tests provide an opportunity to understand the isolated effect of ventilation air cooling on underhood thermal control.

Application of Building Science Principles to Reduction of Indoor Air Pathogens

RATIONALE: In hot, humid climates, if building science principles of pressurization, humidity control, and ASHRAE Ventilation Standard 62.2-2003 with HEPA filtration are implemented in high aerosol and VOC exposure residences without non-mechanical ventilation the concentration of indoor mold spores, pollen, dust mite debris and other pathogenic aerosols as well as VOCs will be significantly reduced. Products of microbiological activity within exterior wall cavities will be blocked from entry into the breathing zone by resulting air pressure differentials. METHODS: In a hot, humid climate, the interiors of test dwellings without mechanical ventilation were pressurized to + 0.8 to + 2.0 pascals most of the time by a new, variable rate mechanical ventilation system . Humidity was controlled to less than 50% most of the time by modulating ventilation airflow rates according to indoor humidity and ASHRAE Standard 62.2-2003. All ventilation air was HEPA filtered and delivered into the breathing zone of the home at an average rate in conformity with ASHRAE Standard 62.2-2003. RESULTS: Pathogenic aerosols and VOCs were significantly reduced. CONCLUSIONS: In hot, huimid climates, implementation of building science principles of pressurization, humidity control and controlled ventilation with HEPA filtered outdoor air in average conformity with ASHRAE Standard 62.2-2003 significantly reduced the presence of airborne pathogens and VOCs in initially high aerosol and VOC exposure residences which did not earlier have mechanical ventilation even when outdoor aerosols were very high.

Numerical Investigation of Flow and Dust Concentration Distributions in the Work Area of a Mountain Tunnel Currently under Construction

Flow patterns, dust concentration profile, and particle motion in a mountain tunnel under construction were calculated numerically for a full-scale tunnel to evaluate the effectiveness of the planned ventilation system. The influence of ventilation air flow rate, the configuration of air tubes, and an obstacle near the working face were investigated. The trajectories of different size particles were calculated at different wall conditions for deposition. A vortex flow was found to form between the air inlet and the working face for all ventilation types examined. The average dust concentration at a height of 1.5 m, corresponding to the average breathing height of a worker, did not consistently decrease with an increased air flow rate in an injection-suction type system. An optimal air flow rate for minimizing the dust concentration may exist. A vortex flow developed around an obstacle near the working face, leading to an increase in dust concentration between the obstacle and the working face. The concentration of dust near the working face was extremely high and was too spatially variable to be accurately described by the average dust concentration in the area between the working face and the air inlet. The fraction of particles removed through the air outlet was dependent on the ventilation pattern, and also decreased with increasing particle size due to immediate deposition of coarse particles on the tunnel floor.

石炭資源の開発・利用に係わる環境技術と安全のアジアネットワーク 坑内リスク管理情報システム

Communication in underground is essential for mine safety and the importance is increasing rapidly. JCOAL and CSIRO in Australia are cooperating a research project about underground communication and risk management information system. The aim of the research is to make a revolutionary new mine safety monitoring system that involves a total risk management information system called Nexsys in the center. The new monitoring system intends to include a real time risk profile that indicates safety conditions in underground and decision support system that offer appropriate counter measures to mine operators in case of an accident. To realize these functions a knowledge base about various accidents is very important. Historical various accidents data on gas explosions and spontaneous combustions in Japan have been reviewed and a new accident knowledge base has been developed which includes newly-made three dimensional views of mine structure where the accidents occurred.Ventilation is a key factor for underground mine safety. An abnormal condition in a ventilation network such as a mine fire or roadway collapse is reflected on ventilation airflow rates rapidly. A computer program to locate the abnormal condition in the network using the airflow data from underground through the mine monitoring system was also developed and tested to add a useful tool to the new monitoring system. The details about the method for locating of abnormal condition in the network are described in the paper.

Measurement of indoor air quality for ventilation with the existence of occupants in schools

This paper evaluates the performance of ventilation for the removal of indoor pollutants as a function of ventilation rate and the number of occupants in a test room and school classroom. An experimental apparatus consists of a test room, a tracer gas supply system, a gas detector, and a fan for ventilation air supply with a controller. The ventilation performance is evaluated in a step-down method based on ASTM Standard E741-83 using CO2 gas as a tracer gas in the test room of 35 m3. For the ventilation air flow rate of 1.0 ACH, a recommended ventilation flow rate of Korea school standard for acceptable indoor air quality in the case of one person, CO2 gas concentration decreases up to 55% within 50 minutes without occupancy and increases up to 75% in the case of one occupant. Also indoor air quality at the school classroom is investigated experimentally.

2階機械給排気方式及び床下給気方式についての実験と数値計算 : 住宅用ハイブリッド換気システムの性能評価に関する研究 その2

For the purpose of complementing the lack of ventilation airflow rate on the 2nd floor, the mechanical supply for the 2nd floor with passive exhaust system and the crawl space supply with hybrid exhaust system were suggested. Experiments and long-term numerical analysis were carried out for evaluating the system performance. As the results, the followings are reported; About the forth system, airflow rate of mechanical supply showed close connection to the balance of ventilation airflow rate. High building air-tightness and large amount of fan airflow rate for the 2nd floor are desirable for cold climate area especially. In the case of crawl space supply with hybrid exhaust system, good balance of ventilation airflow rate was obtained by adjusting the air inlet opening area on the 1st floor and the crawl space temperature. According to the calculation result for hybrid ventilation system, no correlation was shown with regional climate differences. It was found that airtight building needed larger air inlet opening area on the 1st floor for the balance of ventilation airflow rate.

Heat Transfer and Natural Ventilation Airflow Rates from Single-sided Heated Solar Chimney for Buildings

Heat transfer process and natural ventilation driven by a solar chimney attached to a sidewall of building are investigated with CFD technique (MITFLOW) in detail. In this paper, conditions and parameters studied in the modelling study are the cavity width of the solar chimney, the wall temperature, the height and breadth of the solar chimney, the ratio of outlet area to inlet area as well as the outlet location of the solar chimney. The ranges of calculation parameters focused on a solar chimney with single-sided solar collector (single-sided heated wall) cover following conditions: solar chimney length L = 0.5m~5.0m, breadth B=0.1m~0.5m, height H=2.0m~5.0m, and B/H=0.05~0.25. Heated wall surface temperature Tw is changed in the range of 30°C~70°C; the ratio of the outlet area to inlet area Ar is changed in the range of 0.6~1.0. It is found that for given building geometry and inlet areas, there is an optimum cavity width at which a maximum airflow rate can be achieved. Based on the prediction, the airflow rate reaches maximum when B/H is approximately 1/10. It is also found that for given chimney geometry, solar chimney ventilation flow rate can be increased with the enhancement of chimney height only the cross sectional area no more than the critical area, because cross section area has a strong effect on the transitional and/or turbulent convective heat transfer in an enclosure. From the view of economy technology, the optimized height of a solar chimney can be determined according to the optimized section ratio of breadth to height and available breadth in practice. On the analysis of CFD prediction, it is noted that optimized ventilation flow rate can be obtained when the outlet area takes the same area as the inlet area. Generally, there is good agreement among the numerical results, available experimental data from literature and theoretical analysis of natural ventilation from the solar chimney.

Safety benefits of using a sub-atmospheric pressure hydride gas source for MOCVD

The reduced risks associated with storing toxic and flammable hydride gases on a high surface area substrate within a cylinder at sub-atmospheric pressures have been assessed. Tests have been performed on 2.2 and 49 L sub-atmospheric pressure cylinders filled to various pressures with arsine and phosphine to quantify the gas release rates that occur under conditions of simulated valve failure. Gas releases from sub-atmospheric pressure cylinders are diffusion rather than pressure-controlled and are found to be discrete rather than continuous. Average release concentrations measured at a ventilation air flow rate of 1.42 m 3/min are well below the permissible exposure limit for both hydride gases over the test period. The results are compared to calculated release rates from high-pressure arsine and phosphine cylinders fitted with a restrictive flow orifice under otherwise similar conditions. The findings show that gas release rates from high-pressure cylinders are approximately four orders of magnitude higher than those from sub-atmospheric pressure cylinders. In addition to lowering the safety risks, benefits of adsorbed phase gas storage include the possibility of having increased volumes of hydride gas on site, improved process repeatability and reduced installation and operating costs.

Optimal and robust control of outdoor ventilation airflow rate for improving energy efficiency and IAQ

Combining demand-controlled ventilation (DCV) and economizer control can achieve adequate and even better indoor air quality with minimum cooling/heating energy consumption in buildings. The control instability during the transition processes between different control modes is among the major difficulties faced when combining DCV control with economizer control in applications. The practical energy benefit is another concern when using free cooling in the subtropical climate like Hong Kong. A robust control strategy, using “freezing”, gain scheduling, I-term reset and feedback transition control for different transition processes, is developed addressing the instability problems. The energy benefit of using economizer control is evaluated by over one year's comparison tests on two air-handling units in a building.

A-31 ダクト式全般換気システムの風量設計に関する研究 : 第3種換気システムの設計風量と実測風量に関する評価実験

A-31 ダクト式全般換気システムの風量設計に関する研究 : 第3種換気システムの設計風量と実測風量に関する評価実験

Fault-tolerant control for outdoor ventilation air flow rate in buildings based on neural network

This paper describes a supervisory control scheme that adapts to the presence of the measurement faults in outdoor air flow rate control using sensor-based demand-controlled ventilation, maintains an adequate indoor air quality and minimizes the resulting increase in energy consumption. A strategy, which is based on neural network models, is employed to diagnose the measurement faults of outdoor and supply flow sensor, and accomplishes the fault-tolerant control of outdoor air flow when faults occur. The neural network models are trained using the data collected under various normal conditions. The residuals between the measurements of flow sensors and the outputs of the neural network models are used to diagnose the faults. When the fault of outdoor or supply air flow sensor occurs, the recovered estimate of outdoor or supply air flow rate obtained on the basis of the neural network models is used in the feedback control loop to regain the control of outdoor air flow. Tests using dynamic system simulation are conducted to validate the strategy. The control, IAQ and energy performances of the system under fault-tolerant control strategy in the presence of the faults in air flow sensor are also presented.

AIR QUALITY AND EMISSION MEASUREMENT METHODOLOGY AT SWINE FINISHING BUILDINGS

Reliable measurements of air quality and emissions at large livestock buildings with inherently large spatial andtemporal variations of pollutant concentrations are relatively difficult and expensive. Appropriate methodologies for suchmeasurements are not readily apparent and techniques and strategies vary widely. Several important technical issues needto be addressed by an air pollutant emission measurement plan. This article describes comprehensive field measurements ofindoor air quality and air pollutant emissions at eight commercial swine finishing buildings.<br><br>The objective of the field test was to evaluate the effect of a manure additive on concentration and emission of ammonia,hydrogen sulfide, and odor. Continuous measurements of gases, ventilation rate, building static pressure, inside and outsidetemperature and humidity, and wind speed and direction were conducted at four naturallyventilated buildings and fourmechanicallyventilated buildings. Air was pumped continuously from inside each building into airsampling manifolds. Oneair stream was drawn from beneath the floor to assess pit headspace air concentrations. Another air stream was drawn fromventilation exhaust points to assess inside gas concentrations and building emission rates. Gas analyzers were switchedbetween sampling manifolds on 10 to 15min sampling intervals. Ammonia was measured with chemiluminescence NOxanalyzers after conversion to nitric oxide. Hydrogen sulfide was converted to sulfur dioxide and measured withpulsedfluorescence, sulfur dioxide analyzers. Odor samples were collected in bags and evaluated using olfactometry. Gasand odor emission rates were determined by multiplying mean gas concentrations in the exhaust air by ventilation airflowrates. Ventilation rates of naturallyventilated buildings were estimated using sensible heat and carbon dioxide balances.Ventilation rates of mechanicallyventilated buildings were determined by monitoring wall fan operation and directlymeasuring airflow of some variablespeed pit fans with fullsize impeller anemometers. Labor and equipment requirements,pitfalls, problems, and solutions to problems of field studies are discussed. Several recommendations for future studies of thistype were developed based on experience gained during this measurement campaign.

Enclosed Pool Fires In Low Ventilation Enclosures: Flame Temperatures And Global Heat Loss Using Gas Analysis

Enclosed kerosene pool fues were investigated with ventilation equivalent to normal leakage into a room with the doors and windows closed and air in leakage due to gaps around doors and windows. A 1.9 m3 enclosed fire test facility with separate air inlet at floor level and fue product outlet at ceiling level was used. A fully heated gas sample system was used, including unburnt fuel analysis, as total hydrocarbons are required as well as CO to determine the combustion efficiency and the airlfuel ratio by carbon balance. This air /fuel was used to determine the adiabatic mean flame temperature of the fue as a function of time as well as the entrained air mass flow rate. The adiabatic temperature was compared with the measured flame temperature and it was shown that the time to peak temperature was the same. The temperature difference was used to determine the global heat loss to the enclosure walls as a function of time. The peak heat transfer per unit wall surface area was 6 kW/ m' for the highest ventilation rate. The global heat transfer to the enclosure was 70-80% of the heat release at the peak fue intensity for three ventilation air flow rates. NOx concentrations were also determined and the rate of formation of NOx was used to compute the temperature of the hot zone that formed the NOx. This temperature was shown to increase very rapidly after the start of the fue to a maximum of approximately 1500K for all three ventilation rates. The size of this hot zone was taken as a cylinder of vertical height equal to a free pool f r e flame height and diameter. The surface area of this at 1500K was shown to account for the measured global heat transfer.