scholarly journals Impact of Indoor-Outdoor Temperature Difference on Building Ventilation and Pollutant Dispersion within Urban Communities

Atmosphere ◽  
2021 ◽  
Vol 13 (1) ◽  
pp. 28
Author(s):  
Yun Hu ◽  
Yihui Wu ◽  
Qun Wang ◽  
Jian Hang ◽  
Qingman Li ◽  
...  
Keyword(s):  
Temperature Difference ◽  
Natural Ventilation ◽  
Pollutant Dispersion ◽  
Outdoor Temperature ◽  
Ventilation Mode ◽  
Change Rate ◽  
Air Change Rate ◽  
Single Side ◽  
Ventilation Modes ◽  
Building Ventilation

Mechanical ventilation consumes a huge amount of global energy. Natural ventilation is a crucial solution for reducing energy consumption and enhancing the capacity of atmospheric self-purification. This paper evaluates the impacts of indoor-outdoor temperature differences on building ventilation and indoor-outdoor air pollutant dispersion in urban areas. The Computational Fluid Dynamics (CFD) method is employed to simulate the flow fields in the street canyon and indoor environment. Ventilation conditions of single-side ventilation mode and cross-ventilation mode are investigated. Air change rate, normalized concentration of traffic-related air pollutant (CO), intake fraction and exposure concentration are calculated to for ventilation efficiency investigation and exposure assessment. The results show that cross ventilation increases the air change rate for residential buildings under isothermal conditions. With the indoor-outdoor temperature difference, heating could increase the air change rate of the single-side ventilation mode but restrain the capability of the cross-ventilation mode in part of the floors. Heavier polluted areas appear in the upstream areas of single-side ventilation modes, and the pollutant can diffuse to middle-upper floors in cross-ventilation modes. Cross ventilation mitigates the environmental health stress for the indoor environment when indoor-outdoor temperature difference exits and the personal intake fraction is decreased by about 66% compared to the single-side ventilation. Moreover, the existence of indoor-outdoor temperature differences can clearly decrease the risk of indoor personal exposure under both two natural ventilation modes. The study numerically investigates the building ventilation and pollutant dispersion in the urban community with natural ventilation. The method and the results are helpful references for optimizing the building ventilation plan and improving indoor air quality.

scholarly journals Comparison of Downdraught and Up Draft Passive Air Conduction Systems (PACS) in a Winery Building

Buildings ◽  
2021 ◽  
Vol 11 (6) ◽  
pp. 259
Author(s):  
Ádám László Katona ◽  
István Ervin Háber ◽  
István Kistelegdi
Keyword(s):  
Air Conditioning ◽  
Natural Ventilation ◽  
Dynamics Simulation ◽  
Computational Fluid Dynamics Simulation ◽  
General Applicability ◽  
Change Rate ◽  
Air Change Rate ◽  
Simulation Based ◽  
Ventilation Performance ◽  
Air Conduction

A huge portion of energy consumption in buildings comes from heating, ventilation, and air conditioning. Numerous previous works assessed the potential of natural ventilation compared to mechanical ventilation and proved their justification on the field. Nevertheless, it is a major difficulty to collect enough information from the literature to make decisions between different natural ventilation solutions with a given situation and boundary conditions. The current study tests the passive air conduction system (PACS) variations in the design phase of a medium-sized new winery’s cellar and production hall in Villány, Hungary. A computational fluid dynamics simulation based comparative analysis enabled to determine the differences in updraft (UD) and downdraught (DD) PACS, whereby the latter was found to be more efficient. While the DD PACS performed an air change range of 1.02 h−1 to 5.98 h−1, the UD PACS delivered −0.25 h−1 to 12.82 h−1 air change rate. The ventilation performance of the DD version possessed lower amplitudes, but the distribution was more balanced under different wind incident angles, thus this version was chosen for construction. It could be concluded that the DD PACS provides a more general applicability for natural ventilation in moderate climates and in small to medium scale industry hall domains with one in- and one outlet.

Indoor hygrothermal loads for the deterministic and stochastic design of the building envelope for dwellings in cold climates

2017 ◽  
Vol 41 (6) ◽  
pp. 547-577 ◽  
Author(s):  
Simo Ilomets ◽  
Targo Kalamees ◽  
Juha Vinha
Keyword(s):  
Field Measurements ◽  
Heating System ◽  
Building Envelope ◽  
Cold Climates ◽  
Outdoor Temperature ◽  
Change Rate ◽  
Levels Of Detail ◽  
Air Change Rate ◽  
Excess Value ◽  
Occupancy Rates

In this study, several years of field measurements of indoor hygrothermal loads in 237 dwelling units are analysed. Moisture excess is calculated from hourly values of temperature, and relative humidity measured both indoors and outdoors. Air change rate and moisture production in bedrooms are calculated on the basis of carbon dioxide measurements. It is found that indoor temperature profiles differ depending on whether a building has central heating, a stove or combined heating system. The determined average moisture excess value, 2.8 g/m3 with a standard deviation of 1.6 g/m3 for cold periods, can be used in stochastic calculations. Critical values for moisture excess at the 90th percentile, ranging from 3–8 g/m3, depending upon occupancy rates, can be used in the deterministic analysis. Averages and weekly maxima of moisture excess in the study are reported at different percentiles. Considerable deviations from the EN ISO 13788 standard are discovered, concerning the breaking point depending on outdoor temperature and moisture excess during the summer. The average and critical moisture production in bedroom is presented and insufficient ventilation determined based on measurements. During the heating period, the air change rate is relatively stable while moisture production levels increase along with the dropping outdoor temperature. Two indoor temperatures and three humidity models with different levels of detail and influencing factors are proposed. Temperature and humidity loads derived using the proposed models can be used to determine the indoor hygrothermal boundary conditions for the building envelope of dwellings in cold climates.

scholarly journals Application of the Chimney Cap as a Method of Improving the Effectiveness of Natural Ventilation in Buildings

2020 ◽  
Vol 27 (3) ◽  
pp. 168-175
Author(s):  
Romana Antczak-Jarząbska ◽  
Maciej Niedostatkiewicz
Keyword(s):  
Natural Ventilation ◽  
Transition Period ◽  
Physical Phenomenon ◽  
Ventilation System ◽  
Cost Savings ◽  
Change Rate ◽  
Indoor Pollutants ◽  
Air Change Rate ◽  
Chimney Effect

AbstractAdequately designed natural ventilation is the cheapest and easiest way to effectively remove indoor pollutants and keep the air inside a building fresh. A prediction of the performance and effectiveness of ventilation in order to determine the design of a ventilation system can provide real and long-term cost savings. The worst time in terms of the efficiency of natural ventilation is the spring-autumn transition period [7]. In order to improve the efficiency of natural ventilation, chimney caps are used, among others. They are designed to improve the chimney effect described in colloquial language as a chimney draft. The chimney effect is a physical phenomenon of the formation of a spontaneous flow of a warmer gas, e.g. air, from the bottom up in stem channels [12]. The article analyses the influence of the chimney cowl on the improvement of the chimney effect in an apartment of a multi-family building with natural ventilation. Long-term tests of the chimney draft were carried out for the case without and with a chimney cap. The paper presents the results of the performance (air change rate, ACH) of natural ventilation for a building with an inlet gap measured for the transitional season (between the heating and the summer season). The measurements were performed during a windy period.

scholarly journals A Discussion Regarding the Measurement of Ventilation Rates Using Tracer Gas and Decay Technique

2020 ◽  
Vol 5 (10) ◽  
pp. 85
Author(s):  
Ricardo M. S. F. Almeida ◽  
Eva Barreira ◽  
Pedro Moreira
Keyword(s):  
Cross Contamination ◽  
Single Family ◽  
Outdoor Temperature ◽  
Time Dependency ◽  
Tracer Gas ◽  
Large Variability ◽  
Change Rate ◽  
Air Change Rate ◽  
Ventilation Rates

The measurement of ventilation rates is crucial in understanding buildings’ performances, but can be a rather complex task due to the time-dependency of wind and buoyancy forces, which are responsible for the pressure differences that induce air movement across the envelope. Thus, assessing air change rate through one-time measurements during brief periods of time may not be a reliable indicator. In this paper, the variability in the measurement of ventilation rates using the decay technique was evaluated. To that end, two compartments of a typical single-family detached dwelling were selected as a case study and 132 tests were performed, considering two different boundary conditions (door closed and door open). This work allowed the large variability of the results to be highlighted, as the coefficient of variation ranged from 20% to 64%. Wind speed had a key effect on the results, especially because during the measurements indoor–outdoor temperature differences were not so significant. The possibility of using occupant-generated carbon dioxide as tracer gas was also analyzed, but problems of cross-contamination were identified.

Courtyard Space and Natural Ventilation of National Fitness Center in Hot and Humid Areas

2013 ◽  
Vol 361-363 ◽  
pp. 988-994
Author(s):  
Wei Zhang ◽  
Jin Li
Keyword(s):  
Natural Ventilation ◽  
Comfort Level ◽  
Analog Computation ◽  
Fitness Centers ◽  
Change Rate ◽  
Fitness Center ◽  
Air Change Rate ◽  
External Conditions

To improve the air change rate under natural ventilation and the comfort level of sport field of national fitness centers in hot and humid areas, an analog computation was conducted for courtyard models with different sizes and shapes via the softwares such as Fluent and Weather Tool, taking Guangzhou area as an example. It is discovered that under the same external conditions and in a certain building boundary size, enlarging the width of courtyard is beneficial for improving indoor ventilation of sport spaces with the same depth, and semi-open courtyard can lead to better ventilation compared with completely open courtyard with the same width.

Night Ventilation Research of Office Buildings Part 1: Sensitivity Analysis of Ventilation Parameters

2011 ◽  
Vol 250-253 ◽  
pp. 3002-3007
Author(s):  
Xin Rong Zhu ◽  
Wei Liu ◽  
Liu Yang ◽  
Jia Ping Liu
Keyword(s):  
Temperature Difference ◽  
Field Investigation ◽  
Simulation Software ◽  
Office Buildings ◽  
Large Temperature ◽  
Change Rate ◽  
Main Work ◽  
Air Change Rate ◽  
Night Ventilation ◽  
The City

Night ventilation has been proved to be an effective cooling method, especially in regions with a large temperature difference between day and night. The main work of this paper is to analyze the parameters associated with ventilation effects in office buildings with night ventilation in the city of Xi'an. For this purpose, field investigation about different kinds of office buildings has been carried out, based on which, a typical office building simulation model has been built. Three parameters, including temperature difference between day and night, thermal storage performance and air change rate are studied by the energy simulation software DeST and the optimum values have been proposed for each parameter. The conclusions can be useful in night ventilation design process.

Influence of Natural Ventilation on Indoor PM2.5 Concentration in Residential Building

2014 ◽  
Vol 675-677 ◽  
pp. 194-198
Author(s):  
Li Zhao ◽  
Chao Chen ◽  
Guo Qing Cao
Keyword(s):  
Pollution Control ◽  
Natural Ventilation ◽  
Residential Building ◽  
Ventilation Rate ◽  
Outdoor Air ◽  
Change Rate ◽  
Air Change Rate ◽  
Indoor Pm2.5 ◽  
Life Behavior ◽  
Pm2.5 Concentration

According to PM2.5 contamination in residential building, a mathematical model is established about the effect of natural ventilation on PM2.5 pollution control based on calculus method. On the basis of some actual cases, such as indoor smoking and cleaning, indoor PM2.5 concentration is calculated for different air change rate and outdoor air quality. The concept of critical ventilation rate is provided. The conclusion of the paper provides some advice on natural ventilation and indoor life behavior.

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