scholarly journals On the Ventilation Performance of Low Momentum Confluent Jets Supply Device in a Classroom

Energies ◽  
2020 ◽  
Vol 13 (20) ◽  
pp. 5415
Author(s):  
Harald Andersson ◽  
Alan Kabanshi ◽  
Mathias Cehlin ◽  
Bahram Moshfegh
Keyword(s):  
Energy Efficiency ◽  
Indoor Air ◽  
Classroom Environment ◽  
Heat Removal ◽  
High Momentum ◽  
Ventilation Performance ◽  
Set Up ◽  
Main Effects ◽  
Heat Loads ◽  
Occupied Zone

The performance of three different confluent jets ventilation (CJV) supply devices was evaluated in a classroom environment concerning thermal comfort, indoor air quality (IAQ) and energy efficiency. The CJV supply devices have the acronyms: high-momentum confluent jets (HMCJ), low-momentum confluent jets (LMCJ) and low-momentum confluent jets modified by varying airflow direction (LMCJ-M). A mixing ventilation (MV) slot jet (SJ) supply device was used as a benchmark. Comparisons were made with identical set-up conditions in five cases with different supply temperatures (TS) (16–18 °C), airflow rates (2.2–6.3 ACH) and heat loads (17–47 W/m2). Performances were evaluated based on DR (draft rating), PMV (predicted mean vote), ACE (air change effectiveness) and heat removal effectiveness (HRE). The results show that CJV had higher HRE and IAQ than MV and LMCJ/LMCJ-M had higher ACE than HMCJ. The main effects of lower Ts were higher velocities, DR (HMCJ particularly) and HRE in the occupied zone as well as lower temperatures and PMV-values. HMCJ and LMCJ produce MV conditions at lower airflow rates (<4.2 ACH) and non-uniform conditions at higher airflow rates. LMCJ-M had 7% higher HRE than the other CJV supply devices and produced non-uniform conditions at lower airflow rates (<3.3 ACH). The non-uniform conditions resulted in LMCJ-M having the highest energy efficiency of all devices.

scholarly journals Subzone Control of Air Distribution to Improve Thermal Comfort and Energy Efficiency

2019 ◽  
Vol 111 ◽  
pp. 02008
Author(s):  
Sheng Zhang ◽  
Yong Cheng ◽  
Xiaoliang Shao ◽  
Zhang Lin
Keyword(s):  
Energy Efficiency ◽  
Thermal Comfort ◽  
Conventional Method ◽  
Thermal Condition ◽  
Thermal Environment ◽  
Heat Removal ◽  
Air Distribution ◽  
Overall Performance ◽  
Thermal Preferences ◽  
Occupied Zone

The conventional method for air distribution (e.g., mixing ventilation and stratum ventilation) controls the averaged thermal condition in the occupied zone to satisfy the averaged thermal preference of a group of occupants. However, since the thermal environment cannot be absolutely uniform, the microclimates of occupants can be distinct from the averaged thermal condition of the occupied zone. Moreover, the thermal preferences of occupants are well recognized to be diversified beyond the averaged value. Thus, the conventional method is unable to ensure thermal comfort and risks energy wastage because of overcooling. The method proposed by this study divides the occupied zone into several subzones, and determines the supply air parameters to optimize the overall performance regarding thermal comfort and energy efficiency of the subzones using the multi-criteria decision-making technique. Thermal comfort is indicated by the thermal deviation of the achieved thermal conditions of the subzones from the respective thermal preferences, and energy efficiency is indicated by the heat removal efficiencies of the subzones. Case studies based on experiments of stratum ventilation have demonstrated the effectiveness of the method proposed. Results show that the method proposed achieves thermal comfort for each subzone, and improves the overall performance by 2.1% to 31.0%.

Numerical and Experimental Modeling of Indoor Air Quality Inside a Conditioned Space with Mechanical Ventilation and DX-Air Conditioner

2020 ◽  
Vol 38 (9A) ◽  
pp. 1257-1275
Author(s):  
Wisam M. Mareed ◽  
Hasanen M. Hussen
Keyword(s):  
Air Quality ◽  
Indoor Air Quality ◽  
Indoor Air ◽  
Ventilation System ◽  
Thermal Conditions ◽  
Airflow Rate ◽  
Air Conditioner ◽  
Breathing Zone ◽  
Lecture Room ◽  
Ventilation Performance

 Elevated CO2 rates in a building affect the health of the occupant. This paper deals with an experimental and numerical analysis conducted in a full-scale test room located in the Department of Mechanical Engineering at the University of Technology. The experiments and CFD were conducted for analyzing ventilation performance. It is a study on the effect of the discharge airflow rate of the ceiling type air-conditioner on ventilation performance in the lecture room with the mixing ventilation. Most obtained findings show that database and questionnaires analyzed prefer heights between 0.2 m to 1.2 m in the middle of an occupied zone and breathing zone height of between 0.75 m to 1.8 given in the literature surveyed. It is noticed the mismatch of internal conditions with thermal comfort, and indoor air quality recommended by [ASHRAE Standard 62, ANSI / ASHRAE Standard 55-2010]. CFD simulations have been carried to provide insights on the indoor air quality and comfort conditions throughout the classroom. Particle concentrations, thermal conditions, and modified ventilation system solutions are reported.

scholarly journals The Dichotomy between Indoor Air Quality and Energy Efficiency in Light of the Onset of the COVID-19 Pandemic

Atmosphere ◽  
2021 ◽  
Vol 12 (6) ◽  
pp. 791
Author(s):  
Gaetano Settimo ◽  
Pasquale Avino
Keyword(s):  
Energy Efficiency ◽  
Air Quality ◽  
Indoor Air Quality ◽  
Indoor Air ◽  
Great Increase

Recently, there has been a great increase in the importance of issues related to energy efficiency [...]

scholarly journals Air Ventilation Performance of School Classrooms with Respect to the Installation Positions of Return Duct

2021 ◽  
Vol 13 (11) ◽  
pp. 6188
Author(s):  
Sungwan Son ◽  
Choon-Man Jang
Keyword(s):  
Air Quality ◽  
Numerical Analysis ◽  
Indoor Air Quality ◽  
Indoor Air ◽  
Three Dimensional ◽  
Cross Infection ◽  
School Students ◽  
Height Range ◽  
Air Ventilation ◽  
Ventilation Performance

For students, who spend most of their time in school classrooms, it is important to maintain indoor air quality (IAQ) to ensure a comfortable and healthy life. Recently, the ventilation performance for indoor air quality in elementary schools has emerged as an important social issue due to the increase in the number of days of continuous high concentrations of particulate matter. Three-dimensional numerical analysis has been introduced to evaluate the indoor airflow according to the installation location of return diffusers. Considering the possibility of the cross-infection of infectious diseases between students due to the direction of airflow in the classroom, the airflow angles of the average respiratory height range of elementary school students, between 1.0 and 1.5 m, are analyzed. Throughout the numerical analysis inside the classroom, it is found that the floor return system reduces the indoor horizontal airflow that causes cross-infection among students by 20% compared to the upper return systems. Air ventilation performance is also analyzed in detail using the results of numerical simulation, including streamlines, temperature and the age of air.

scholarly journals Spatio-temporal expectile regression models

2019 ◽  
Vol 20 (4) ◽  
pp. 386-409
Author(s):  
Elmar Spiegel ◽  
Thomas Kneib ◽  
Fabian Otto-Sobotka
Keyword(s):  
Tensor Product ◽  
Least Squares Regression ◽  
Expectile Regression ◽  
Specific Distribution ◽  
Weighted Means ◽  
Temporal Models ◽  
Error Terms ◽  
Spatio Temporal ◽  
Set Up ◽  
Main Effects

Spatio-temporal models are becoming increasingly popular in recent regression research. However, they usually rely on the assumption of a specific parametric distribution for the response and/or homoscedastic error terms. In this article, we propose to apply semiparametric expectile regression to model spatio-temporal effects beyond the mean. Besides the removal of the assumption of a specific distribution and homoscedasticity, with expectile regression the whole distribution of the response can be estimated. For the use of expectiles, we interpret them as weighted means and estimate them by established tools of (penalized) least squares regression. The spatio-temporal effect is set up as an interaction between time and space either based on trivariate tensor product P-splines or the tensor product of a Gaussian Markov random field and a univariate P-spline. Importantly, the model can easily be split up into main effects and interactions to facilitate interpretation. The method is presented along the analysis of spatio-temporal variation of temperatures in Germany from 1980 to 2014.

The Establishment of Exergy Consumption Evaluation Index in Heated Oil Pipeline Transportation

2013 ◽  
Vol 401-403 ◽  
pp. 2143-2146 ◽  
Author(s):  
Qing Lin Cheng ◽  
Zhe Li ◽  
Shuai Shao ◽  
Wei Sun ◽  
Xu Xu Wang
Keyword(s):  
Energy Efficiency ◽  
Energy Consumption ◽  
Evaluation System ◽  
Index Set ◽  
Oil Pipeline ◽  
Heated Oil ◽  
Consumption Index ◽  
Exergy Consumption ◽  
Exergy Transfer ◽  
Set Up

The exergy consumption during the transportation of heated oil includes four items: valid and invalid pressure exergy consumption, valid and invalid heat exergy consumption. These four parts are taken as the same loss in traditional evaluation systems of pipeline energy consumption, which somewhat hinders the further energy-conservation study. So establishing a scientific exergy consumption evaluation system is an important basis work of energy efficiency management. Based on the index system of energy efficiency for pipeline proposed by predecessors, the meaning of energy quality for exergy and the categories of exergy flow, the energy consumption index set of exergy transfer is set up in this article. Moreover, by computing exergy consumption index of exergy transfer for an oil pipeline in Daqing Oilfield, a part of representative indexes are selected by analyzing the obtained data with correlation coefficient method. Finally, the exergy consumption evaluation system is constructed.

A Novel Window Type Air-Conditioner with Energy Recovering

2011 ◽  
Vol 250-253 ◽  
pp. 3021-3024
Author(s):  
Qing Hai Luo ◽  
Peng Fei Zhang ◽  
Xiu Fei Yang ◽  
Jun Zou
Keyword(s):  
Energy Efficiency ◽  
Heat Exchanger ◽  
Indoor Air Quality ◽  
Indoor Air ◽  
The Other ◽  
The Novel ◽  
Air Conditioner ◽  
Efficiency Ratio ◽  
Additional Heat ◽  
Experimental Prototype

A novel window type air-conditioner with energy recovering was experimented. The experimental prototype can make fresh air exchange heat with exhaust air in an additional heat exchanger, which consist no additional moving parts. The EER (energy efficiency ratio) of the experimental air-conditioner (EAC) is increased by 17.4~37.3% than that of the original ordinary window type air-conditioner (OAC). On the other hand, the fresh air proportion of the EAC is increased by 20% or so than that of the OAC, so indoor air quality can be greatly improved via the EAC; however the indoor noise of the EAC is increased by 3.2 dB or so. The novel experimental prototype is of great significance for energy efficiency.

Research of the energy efficiency of a combined air and water heating of a public building

2021 ◽  
Vol 14 (2) ◽  
pp. 124-131
Author(s):  
K. A. Ignatiev ◽  
E. R. Giniyatullin ◽  
M. G. Ziganshin
Keyword(s):  
Energy Efficiency ◽  
Indoor Air ◽  
Energy Efficient ◽  
Heating System ◽  
Temperate Climate ◽  
Water Heating ◽  
Efficient Control ◽  
Temperature And Humidity ◽  
Academic Building ◽  
Continental Climate

Combined air and water heating schemes have been actively used recently for heating public and residential premises. They have certain advantages in countries with a warm climate, whereas in a temperate climate, their use may be unfeasible. The most effective regulation of the heating system in the building can be expected, if all the technology specifics are taken into account, in terms of both the purpose of the room and the methods of regulation. A system focused only on weather-based regulation falls short of meeting to energy-efficient control classes: a heat carrier with the same temperature is distributed among rooms with different requirements for temperature and humidity characteristics. The issues of ensuring the energy efficiency of the combined air and water heating system in public buildings for the temperate continental climate of Russia — the academic building (AB) and laboratory building (LB) of the Kazan State Energy University (KSEU) have been considered. Heating devices of the KSEU heating system have manual control valves installed in the premises, or radiator valves with thermostatic heads, but without room controllers, which does not meet the energy-efficient control classes. An experimental survey of the functioning of the heating system of the KSEU buildings during the 2019 – 2020 and 2020 – 2021 heating seasons was conducted. The optical pyrometry method was used to measure the temperature of the surfaces of windows, walls and elements of the heating system, as well as the temperature and humidity of the air in lecture rooms and corridors of the AB and LB of the KSEU. The parameters of heating devices and indoor air in rooms of various purposes were found compliant with the current sanitary and hygienic requirements. At the same time, the need to switch to a higher class of regulation has been revealed, since, under the current situation, the parameters of the indoor air depend on the outdoor temperature: in the abnormally warm winter of 2020, the indoor air temperature was at the edge of the maximum permissible value, while in the normal climate of winter of 2021, it was at the edge of the minimum permissible value.

The Potential of Natural Ventilation in Single-Sided Ventilated Apartment to Improve Indoor Thermal Comfort and Air Quality

2011 ◽  
Author(s):  
M. F. Mohamed ◽  
M. Behnia ◽  
S. King ◽  
D. Prasad
Keyword(s):  
Air Quality ◽  
Thermal Comfort ◽  
Indoor Air Quality ◽  
Indoor Air ◽  
Natural Ventilation ◽  
Architectural Element ◽  
Flat Design ◽  
Effective Ventilation ◽  
Computational Fluid Dynamics Cfd ◽  
Ventilation Performance

Cross ventilation is a more effective ventilation strategy in comparison to single-sided ventilation. In the NSW Residential Flat Design Code1 (RFDC) the majority of apartments are required to adopt cross ventilation. However, in the case of studio and one-bedroom apartments, it is acknowledged that single-sided ventilation may prevail. Deep plan studio and one-bedroom apartments may achieve lower amenity of summer thermal comfort and indoor air quality where mechanical ventilation is not provided by air conditioning. Since compliance with the code may allow up to 40% of apartments in a development in Sydney to be single sided, it is important to understand the natural ventilation performance of such apartments. The objective of this paper is to investigate the natural ventilation potential in single-sided ventilated apartments to improve indoor air quality and thermal comfort. This investigation includes simulating various facade treatments involving multiple opening and balcony configurations. Balcony configurations are included in this study because, in Sydney, a balcony is a compulsory architectural element in any apartment building. The study uses computational fluid dynamics (CFD) software to simulate and predict the ventilation performance of each apartment configuration. This study suggests that properly configured balconies and openings can significantly improve indoor ventilation performance for enhanced indoor air quality and thermal comfort, by optimizing the available prevailing wind. However, it is important to note that inappropriately designed fac¸ade treatments also could diminish natural ventilation performance.

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