Positive Pressure Control Research Articles

Simulation Research on Ventilation Control of Gaseous Pollutants in Urban Sentry Boxes

The tiny spaces of sentry boxes in cities, such as mobile security guards, highway toll booths, etc., are mostly located beside roads with harsh outdoor environments. Due to office demands, work windows often need to be kept or frequently opened. The intrusion of outdoor pollutants through the windows leads to the deterioration of the indoor air quality, and threatens the health of employees. This paper takes the gaseous pollutant NO2 as the representative and discusses the effective ventilation design scheme for improving the air quality in the sentry box with openings using two attached ventilation modes as the carrier. Taking the vertical wall-attached ventilation as an example, the formation of the air curtain at the window hole and its barrier performance to outdoor pollutants were studied. The conclusion is that when the air supply velocity is sufficient to form a complete air curtain at the window hole, it can effectively block the pollutants. The horizontal wall-attached ventilation shows that clean air is delivered to the space with openings, and the indoor air quality can also be well improved due to the dilution effect, but the effect of positive pressure control is not obvious due to the large opening. The conclusions can provide guidance for the ventilation design of sentry boxes with openings.

Research on Calculation and Control of Positive Pressure Air Supply System for Offshore Booster Station

Introduction The paper aims to maintain a good and safe operating environment for offshore booster station， reduce the corrosion effect of high-salt and high-humidity gas on the equipment， and increase the service life of process equipment， the calculation method and control method of ensuring the indoor positive pressure are analyzed. Method Through the comparative analysis of the calculation results of the gap method and the number of air changes method， the calculation principle of the positive pressure air supply was determined. Through variable air volume adjustment and residual pressure valve control analysis， the indoor positive pressure control method was determined. Result The results show that the indoor positive pressure air supply volume of offshore booster station should be calculated according to the gap method， and the conventional number of air change method is not suitable for the scenario. At the end of the variable air volume， a smaller air volume is suggested to be used to achieve precise positive pressure control and reduce energy consumption significantly. Conclusion The research results can quickly and accurately calculate the positive pressure air supply volume， and at the same time can realize the precise control of the positive pressure air supply system， which provides theoretical guidance for the design of the anti-salt and anti-fog positive pressure air supply system for offshore booster station.

Purifier or fresh air unit? A study on indoor particulate matter purification strategies for buildings with split air-conditioners

Buildings with split air-conditioners (referred to as SAC buildings) are not equipped with mechanical ventilation systems. The fresh air supply in these buildings primarily relies on natural ventilation and air infiltration, both of which can introduce outdoor particulate matter (PM) pollutants into the indoor environment. To simultaneously satisfy fresh air and indoor PM concentration requirements, two indoor air purification strategies can be employed, including air purifiers (APs) combined with open-window ventilation (AP-Mode) and fresh air units (FAUs) combined with positive pressure control (FAU-Mode). Accordingly, an investigation is required in order to determine which of the two strategies is more suitable for various types of SAC buildings. In this study, firstly, a new method for calculating the mechanical fresh air supply rate needed to maintain a positive room pressure is proposed for SAC buildings. It is concluded that positive room pressure can be maintained if the mechanical fresh air supply rate is more than 3.2 times the natural air infiltration rate (i.e., air infiltration rate when a room is not supplied with mechanical fresh air). Then, based on the mass balance principle of indoor particulate matter, the clean air delivery rates (CADRs) are calculated for APs used in the AP-Mode and FAUs used in the FAU-Mode under different PM2.5 I/O ratios and fresh air supply rates, and the annual energy consumptions of the two strategies are compared. Consequently, it is determined that in most cases, the FAU-Mode has a lower annual energy consumption when used in SAC buildings in Beijing, Shanghai, and Guangzhou. Finally, considering the room airtightness requirement for positive pressure control and the indoor PM2.5 concentration upper limit of 35 μg/m3, the AP-Mode should be used in rooms with fresh air requirements lower than 1 h−1, whereas the FAU-Mode should be used in other cases.

A-29 通気弁排水システムの排水能力評価に関する研究 : (第1報) 排水横枝管通気における正圧発生防止手法の検討

A-29 通気弁排水システムの排水能力評価に関する研究 : (第1報) 排水横枝管通気における正圧発生防止手法の検討

Design of Control Scheme for Variable Air Volume Air-Conditioning System

The air quantity of variable air volume system for the rooms and the total air quantity of the system changes with the change of room load. Combined with the system composition in the laboratory, the paper determines the control scheme of the variable air volume system, that is, indoor temperature-control, indoor positive pressure control, air distribution static pressure control, air-supply temperature control and new air volume control. The dotted lines with arrows mean the output signals from the control unit to actuator, and the solid lines with arrows represent the input signals from the actuator to the control unit.

Preventing the entry of outdoor particles with the indoor positive pressure control method: Analysis of influencing factors and cost

Maintaining positive pressure indoors with a mechanical ventilation system is a popular control method for preventing the entry of outdoor airborne particles. This paper analyzes the factors which affect the satisfied superfluous airflow rates of positive pressure control. Through modeling a large amount of cases with a validated model, the factors, e.g. temperature difference, outdoor wind velocity, effective air leakage gaps in the envelopes, the area of the air leakage and the room, were analyzed. Based on the theoretical model, a correlating equation to calculate the satisfied superfluous airflow rate was established by multiple full quadratic regressions. The correlating equation is simple for engineers or designers to use to determine the satisfied superfluous airflow rate. This paper also aims to find which method, pressure control or indoor air cleaning, costs less to prevent the same amount of outdoor-originated particles from entering indoor environments. Generally speaking, indoor air cleaning control method requires less supply airflow rate than positive pressure control method for reducing the concentration of indoor particles with outdoor origin. An exception for this is a situation with a very low indoor/outdoor particle concentration ( I/O ratio) requirement.

Impact of two-way air flow due to temperature difference on preventing the entry of outdoor particles using indoor positive pressure control method

Maintaining positive pressure indoors using mechanical ventilation system is a popular control method for preventing the entry of outdoor airborne particles. The idea is, as long as the supply air flow rate is larger than return air flow rate, the pressure inside the ventilated room should be positive since the superfluous air flow must exfiltrate from air leakages or other openings of the room to the outdoors. Based on experimental and theoretical analyses this paper aims to show the impact of two-way air flow due to indoor/outdoor temperature difference on preventing the entry of outdoor particles using positive pressure control method. The indoor positive pressure control method is effective only when the size of the opening area is restricted to a certain level, opening degree less than 30° in this study, due to the two-way air flow effect induced by differential temperature. The theoretical model was validated using the experimental data. The impacts of two-way air flow due to temperature difference and the supply air flow rate were also analyzed using the theoretical model as well as experimental data. For real houses, it seems that the idea about the positive pressure control method for preventing the entry of outdoor particles has a blind side.

Tollbooth Workers and Mobile Source-Related Hazardous Air Pollutants: How Protective Is the Indoor Environment?

Tollbooth workers are potentially exposed to high levels of mobile source-related air pollutants due to the proximity and intensity of the source. To evaluate this worker hazard, we measured the concentration of air toxins including volatile organic compounds (VOCs) and particle-bound polycyclic aromatic hydrocarbons (PAHs) inside and outside a Baltimore Harbor Tunnel tollbooth during the summer of 2001. Mean outdoor benzene and 1,3-butadiene concentrations varied by shift with the morning (10.7 and 19.8 microg/m3) exceeding afternoon (7.2 and 14.9 microg/m3) and the lowest levels observed during the night (3.7 and 4.9 microg/m3, respectively) when traffic volume was the lowest. In comparison, considerable protection was provided to workers bythe indoor environment where lower concentrations of 1,3-butadiene and benzene were observed for all three shifts (2.9 and 6.7, 0.9 and 3.2, and 0.9 and 2.4 microg/m3, respectively). The greatest protection offered by the tollbooth was observed during the afternoon shift (5-8-fold reduction in indoor concentration), whereas the morning and night shifts experienced similar protection (2-4-fold reduction). Chlorinated hydrocarbons were observed at higher concentrations within the tollbooth, indicating the presence of indoor sources and the opportunity for exposure mitigation. Levels of PAHs were similarly reduced from outdoors (50 ng/m3) to indoors (15.4 ng/m3). The protective nature of the tollbooth highlighted in this study is likely due to the positive pressure control ventilation system that was present at this specific facility, which represents 55% of tollbooths in Maryland. This study provides an estimate of tollbooth workers potential exposures to various mobile source-related pollutants and highlights the protective nature of tollbooths equipped with positive pressure control ventilation systems.

Dynamic Simulation of Pressure Control System for the Closed Ecology Experiment Facility.

It is necessary to develop a small positive pressure control system for the closed ecology experiment facilities because of the needs to prevent contamination from the atmosphere and to protect against over differential pressure loading. In the present study, a numerical analysis method was developed to calculate the quantity of state of the closed module which is fitted with rubber buffers for the small positive pressure control system. Experiments to examine the pressure change of the closed module caused by rapid temperature control of an air conditioner were carried out at Biosphere-J. Comparison of calculated and experimental results showed that the present dynamic simulation is suited to estimating the quantity of state of the closed module.