scholarly journals The Applicability of Coanda Effect Hysteresis for Designing Unsteady Ventilation Systems

Energies ◽  
2020 ◽  
Vol 14 (1) ◽  
pp. 34
Author(s):  
Aldona Skotnicka-Siepsiak
Keyword(s):  
Mechanical Ventilation ◽  
Energy Efficiency ◽  
Air Quality ◽  
Indoor Air Quality ◽  
Indoor Air ◽  
Residential Buildings ◽  
Coanda Effect ◽  
Air Jet ◽  
Coandǎ Effect ◽  
Ventilation Systems

Energy-saving ventilation systems are designed to improve the energy efficiency of buildings. Low energy efficiency in buildings poses a considerable problem that needs to be addressed. Mechanical ventilation with heat recovery has gained increased popularity in recent years. Mechanical ventilation has numerous advantages, including easy adjustment and control, high indoor air quality and elimination of indoor pollutants. Mixing ventilation is the most popular type of mechanical ventilation, in particular in residential buildings. Unsteady ventilation is a type of mixing ventilation that involves stronger mixing effects and smaller vertical temperature gradients to improve indoor air quality (IAQ) and minimize energy consumption. This study examines the possibility of controlling and modifying Coanda effect hysteresis (CEH) to generate unsteady flow and simulate the conditions of unsteady mixing ventilation. The experiment was performed on a self-designed test bench at the University of Warmia and Mazury in Olsztyn. It demonstrated that an auxiliary nozzle can be applied at the diffuser outlet to control CEH and the angles at which the air jet becomes attached to and separated from the flat plate positioned directly behind the nozzle. The study proposes an innovative mixing ventilation system that relies on CEH. The potential of the discussed concept has not been recognized or deployed in practice to date. This is the first study to confirm that an auxiliary nozzle by the diffuser outlet can be operated in both injection and suction mode to control CEH. In the future, the results can be used to design a new type of nozzles for unsteady ventilation systems that are based on CEH control.

The impact of mechanical ventilation operation strategies on indoor CO2 concentration and air exchange rates in residential buildings

2020 ◽  
pp. 1420326X2096076
Author(s):  
Pedro F. Pereira ◽  
Nuno M. M. Ramos
Keyword(s):  
Mechanical Ventilation ◽  
Air Quality ◽  
Exchange Rates ◽  
Indoor Air Quality ◽  
Indoor Air ◽  
Residential Buildings ◽  
Ventilation Strategy ◽  
The Impact ◽  
Mechanical Extraction ◽  
Air Exchange

In Portugal, residential buildings commonly have their ventilation strategy changed after commissioning. This occurs due to the building managers' willingness to reduce shared costs with the electricity needed for fan operation. However, this option is not technically supported, and the effects of such a strategy on indoor air quality-related to human pollutants are yet to be quantified. CO2 was monitored in 15 bedrooms and air exchange rates were calculated for each room. The air exchange rate values ranged from 0.18 to 0.53 h−1 when mechanical extraction ventilation was off, and from 0.45 to 0.90 h−1 when mechanical extraction ventilation was on, which represents an average increase of 119%. With the current intermittent ventilation strategy, all rooms remain above 1500 ppm for a given percentage of time, and 12 rooms presenting CO2 concentrations above 2000 ppm. Simulations of theoretical CO2 concentrations, for a non-interrupted mechanical ventilation strategy show that no rooms would accumulate CO2 concentrations above 2000 ppm, and only 25% would present CO2 concentrations above 1500 ppm. Pearson correlations between the monitored CO2 and human and spatial factors identified two relevant parameters. Those parameters correspond to ratios between CO2 generation and floor area ([Formula: see text]), and airflow with CO2 generation ([Formula: see text]). The proposed ratios could be used as ways to optimise ventilation costs and indoor air quality.

scholarly journals Evaluation of Effects of the Humidity Level-Based Auto-Controlled Centralized Exhaust Ventilation Systems on Thermal Comfort of Multi-Family Residential Buildings in South Korea

2019 ◽  
Vol 11 (17) ◽  
pp. 4791
Author(s):  
Kwag ◽  
Park ◽  
Kim ◽  
Kim
Keyword(s):  
Air Quality ◽  
South Korea ◽  
Thermal Comfort ◽  
Indoor Air Quality ◽  
Indoor Air ◽  
Residential Buildings ◽  
Humidity Level ◽  
Exhaust Ventilation ◽  
Air Tightness ◽  
Ventilation Systems

Building air-tightness has been increased to make energy efficient buildings. However, various indoor air quality issues can be caused by high building air-tightness because it allows low air and moisture transmission through building envelop. In order to solve and prevent these issues, mechanical ventilation systems can be used to control the indoor humidity level. The purpose of this paper is to evaluate the performances of the Relative Humidity (RH)-sensor based auto-controlled centralized exhaust ventilation systems to manage indoor air quality and thermal comfort of multi-family residential buildings in South Korea. A series of field tests were performed for different target zones and for various moisture source scenarios. As a result, it was found that the auto-controlled centralized exhaust ventilation systems were able to control indoor air quality and to maintain the zones thermal comfort faster than the baseline cases that did not operate exhaust vents. The results presented in this paper can show the potential and the feasibility of the auto-controlled centralized exhaust ventilation systems for multi-family residential buildings in South Korea. It is expected that the results presented in this paper would be useful for building owners, engineers, and architects when designing building systems.

scholarly journals Energy Efficiency – Indoor Air Quality Dilemma in Educational Buildings

2020 ◽  
Author(s):  
◽  
Līva Asere
Keyword(s):  
Energy Efficiency ◽  
Energy Consumption ◽  
Air Quality ◽  
Greenhouse Gas Emissions ◽  
Greenhouse Gas ◽  
Indoor Air Quality ◽  
Indoor Air ◽  
Gas Emissions ◽  
Educational Buildings ◽  
Ventilation Systems

The largest energy consumer in Europe is the building sector, which uses about 40 % of total energy consumption and generates around 36 % of total CO2 emissions in the EU [1], [2]. Rising trends in energy consumption can be observed globally due to the demand of citizens for increased comfort, wider use of electrical equipment as well as other reasons. As energy consumption increases, climate change is promoted. In a number of areas energy could be used more efficiently, minimizing its consumption and, thus, resulting in a reduction of greenhouse gas emissions. To achieve carbon neutrality in 2050 in Europe Union, ambitious targets have been set, such as improving energy efficiency by 41 %, using 100 % of renewable energy sources and reducing greenhouse gas emissions of 80 % to 100 % [1], [3], [4]. Energy efficient buildings help to reduce heat consumption. State and local authorities need to set an example by improving the energy efficiency of their own buildings in order to encourage changes in other buildings as well. Moreover, the introduction of energy efficiency measures in buildings owned by the public sector contributes to the objectives of national climate policy. However, increasing energy efficiency has resulted in buildings becoming more airtight and natural ventilation systems need to be replaced by mechanical ventilation. However, this, in turn, leads to additional energy consumption costs. To avoid cost increases, building managers do not operate or operate unsatisfactory ventilation systems creating unfavourable indoor air quality. This creates a dilemma of energy efficiency and indoor air quality, which reduces performance of building occupants. This dilemma reduces pupils’ performance in educational buildings, reducing their chances of obtaining a good education and in the future working with higher added value which in turn reduces the country’s gross domestic product. The objective of the Thesis is to perform an assessment on energy efficiency – indoor air quality dilemma in educational buildings, its impact analyses on national prosperity, and to propose a solution to the prevention of the dilemma. The Thesis is based on six thematic joint scientific publications. The thesis consists of an introduction and three chapters. Four hypotheses have been formulated in the work that are further studied by various research methods, including system dynamic modelling, measurements in real sites and cost-benefit analysis. The thesis begins with an introduction continuing with a literature review of the topics. Chapter 2 presents the study methods. Chapter 3 examines the results obtained during the study and at the end of the Thesis, the findings are summarised according to the hypotheses.

scholarly journals Numerical Assessment of Seven Ventilation Systems for Social Residential Buildings based on Indoor Air Quality and Energy Consumption

2021 ◽  
Vol 2069 (1) ◽  
pp. 012181
Author(s):  
Guillaume Sérafin ◽  
Marc O. Abadie ◽  
Patrice Joubert
Keyword(s):  
Air Quality ◽  
Indoor Air Quality ◽  
Indoor Air ◽  
Natural Ventilation ◽  
Residential Buildings ◽  
Living Room ◽  
Internal Sources ◽  
Controlled Mechanical Systems ◽  
Ventilation Systems

Abstract This work presents a modelling approach for evaluating ventilation systems for their ability to provide good indoor air quality in dwellings. Infiltration and ventilation rates are defined by the conventional French 3CL-DPE standard. The case study is a two-bedroom apartment with a shared or separate kitchen and living room. Three natural ventilation options and four mechanical ventilation systems are compared with respect to exposure to PM2.5, NO2 and formaldehyde. Pollutant concentration levels are assessed in each room based on a scenario of daily occupancy, average annual outdoor concentrations and internal sources. The daily exposure of the occupants to the targeted substances allows the comparison of ventilation systems on the basis of the ULR-QAI index developed at LaSIE laboratory from La Rochelle University. For this case study, it results that controlled mechanical systems are much more efficient than natural ventilation systems, especially in the case of an open-plan kitchen.

scholarly journals Identifying mechanical ventilation issues in classrooms

2018 ◽  
Vol 44 ◽  
pp. 00055
Author(s):  
Julia Janiga ◽  
Joanna Krzempka ◽  
Aleksandra Szczerbińska
Keyword(s):  
Mechanical Ventilation ◽  
Air Quality ◽  
Indoor Air Quality ◽  
Indoor Air ◽  
Ventilation System ◽  
Operating Time ◽  
Mechanically Ventilated ◽  
Ventilation Systems

This article focuses on the issues of indoor air quality in mechanically ventilated classrooms. The aim of the study was to determine the reasons for inadequate air quality reported by occupants. Two different ventilation systems were assessed by measuring CO2 and VOC concentrations in classrooms during operating time. Results showed that in both cases, CO2 levels in the air, even though mostly acceptable, were exceeded throughout the measuring periods on occasion. Based on obtained data, in both cases probable causes for reported ventilation system malfunctions were proposed.

scholarly journals Indoor air quality and control methods for mechanical ventilation systems inside large passive objects

2020 ◽  
pp. 1-8
Author(s):  
Nina Szczepanik-Ścisło
Keyword(s):  
Mechanical Ventilation ◽  
Air Quality ◽  
Indoor Air Quality ◽  
Indoor Air ◽  
Test Object ◽  
Control Methods ◽  
And Control ◽  
Sanitary Conditions ◽  
Ventilation Systems

This paper summarises the indoor air quality of a sports hall built in the passive standard. The sanitary conditions within the object were measured and analysed to identify whether the standards were met and if the test object was safe for occupants. This paper summarises the indoor air quality of a sports hall built in the passive standard. The sanitary conditions within the object were measured and analysed to identify whether the standards were met and if the test object was safe for occupants. This paper summarises the indoor air quality of a sports hall built in the passive standard. The sanitary conditions within the object were measured and analysed to identify whether the standards were met and if the test object was safe for occupants. This paper summarises the indoor air quality of a sports hall built in the passive standard. The sanitary conditions within the object were measured and analysed to identify whether the standards were met and if the test object was safe for occupants. This paper summarises the indoor air quality of a sports hall built in the passive standard. The sanitary conditions within the object were measured and analysed to identify whether the standards were met and if the test object was safe for occupants. This paper summarises the indoor air quality of a sports hall built in the passive standard. The sanitary conditions within the object were measured and analysed to identify whether the standards were met and if the test object was safe for occupants. This paper summarises the indoor air quality of a sports hall built in the passive standard. The sanitary conditions within the object were measured and analysed to identify whether the standards were met and if the test object was safe for occupants.

scholarly journals Analysis of Indoor Air Pollutants and Guidelines for Space and Physical Activities in Multi-Purpose Activity Space of Elementary Schools

Energies ◽  
2021 ◽  
Vol 15 (1) ◽  
pp. 220
Author(s):  
Yeo-Kyung Lee ◽  
Young Il Kim
Keyword(s):  
Mechanical Ventilation ◽  
Elementary Schools ◽  
Air Quality ◽  
Indoor Air Quality ◽  
Indoor Air ◽  
Natural Ventilation ◽  
Co2 Concentration ◽  
Activity Space ◽  
Optimum Number ◽  
Ventilation Systems

Owing to the recent increase in the number of warning reports and alerts on the dangers of fine dusts, there has been an increasing concern over fine dusts among citizens. In spaces with poor ventilation, the occupants are forced to open the window to initiate natural ventilation via the direct introduction of the outside air; however, this may pose a serious challenge if the external fine-dust concentration is high. The lack of natural ventilation increases the indoor carbon dioxide (CO2) concentration, thus necessitating the installation of mechanical ventilation systems. This study analyzed the frequency of the application of mechanical ventilation systems in the Multi-purpose activity space of elementary schools, which are spaces where children require a higher indoor air quality than adults owing to the rapid increase in the CO2 concentration of the Multi-purpose activity space during activities. In addition, the architectural and equipment factors of the Multi-purpose activity spaces of nine elementary schools were characterized. The results revealed that five out of the nine elementary schools installed mechanical ventilation systems, whereas the remaining four schools installed jet air turnover systems. The indoor air quality of the Multi-purpose activity space of D elementary school, which had the minimum facility volume among the schools investigated in this study (564.2 m3), with up to 32 participants for each activity, was investigated. The results revealed that the ultrafine-dust (PM2.5) concentration of the facility was as high as 4.75 µg/m3 at a height of 1.2 m, and the CO2 concentration was as high as 3183 ppm. The results of the analysis of three elementary schools with different volumes were compared and analyzed using CONTAM simulation. This study determined the required volume per occupant and the optimum number of occupants for a given volume and presented guidelines for the optimum number of occupants, activities, and volume to reduce the high concentration of pollutants in the analyzed Multi-purpose activity space. The guideline proposed in this study is aimed at maintaining the CO2 concentration of the Multi-purpose activity space below 1000 ppm, as prescribed by the Indoor Air Quality Control in Public-Use Facilities, Etc. Act in South Korea.

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