scholarly journals NATURAL VENTILATION OF ANIMAL SHEDS DUE TO THERMAL BUOYANCY AND WIND/NATŪRALUS TVARTO VĖDINIMAS VEIKIANT GRAVITACINEI IR VĖJO TRAUKAI/ВОЗДУХООБМЕН ЖИВОТНОВОДЧЕСКОГО ПОМЕЩЕНИЯ ПОД ДЕЙСТВИЕМ ТЕПЛОВЫХ ИЗБЫТКОВ И ВЕТРА

2008 ◽  
Vol 16 (4) ◽  
pp. 188-194 ◽  
Author(s):  
Bronius Kavolėlis ◽  
Rolandas Bleizgys ◽  
Jonas Čėsna
Keyword(s):  
Natural Ventilation ◽  
Ventilation System ◽  
Mathematical Expression ◽  
Natural Conditions ◽  
Mean Values ◽  
Thermal Buoyancy ◽  
The Difference ◽  
Air Speed ◽  
Inlet Opening ◽  
Indoor And Outdoor

In designing a natural ventilation system for animal sheds it is necessary to assess the ventilation induced by thermal buoyancy and wind forces during different seasons and under different animal housing conditions. By applying analytical and experimental investigation a methodology was prepared to establish ventilation intensity caused by thermal buoyancy and wind and data were achieved on thermal buoyancy and wind values and their relationship. The innovation of the methodology can be described by the fact that a simple equation was formed to calculate the air speed in inlet and outlet openings, a mathematical expression of thermal buoyancy and wind ratio was achieved and the required inlet opening area to let in fresh air compared with the outlet opening area to let out polluted air was substantiated to ensure that all polluted air is removed through a rooftop open in winter. It was calculated that the average air speed in the rooftop outlet opening of a typical cold‐type cowshed is 1.3 m/s (when there is no wind, this speed decreases to 0.3 m/s), thermal buoyancy and wind ratio is 0.27 and in order to have all polluted air removed through the rooftop open in winter the inlet opening area in the walls must not exceed 40% of the rooftop opening area. The accuracy of the prepared methodology was tested under natural conditions of barn operation when the distance between air inlet openings and outlet openings was 6.5 m. During the investigation indoor and outdoor temperatures, air speed in the outlet and wind speed were measured. During the experiments the difference of indoor and outdoor temperatures varied from ‐2 to +16°C and air speed in the outlet ‐ from 1.2 to 1.9 m/s. The analytical results reflect the mean values of experimental data under natural conditions of operation rather accurately. The difference between the experimental and calculated air speed values in the outlet opening was insignificant and was within 0–8% range. Santrauka Projektuojant tvarto natūralaus vėdinimo sistemą, reikia įvertinti gravitacinės ir vėjo jėgos skirtingais metų laikais bei skirtingomis gyvulių laikymo sąlygomis sukeltą trauką. Taikant analizinius ir eksperimentinius tyrimus, sudaryta metodika gravitacinės ir vėjo traukos sukeltam vėdinimo intensyvumui nustatyti, gauti duomenys apie gravitacinės ir vėjo traukos reikšmes bei jų santykį. Metodika yra nauja. Sudaryta paprasta lygtis oro greičiui įėjimo ir šalinimo angose skaičiuoti, gauta gravitacinės ir vėjo traukos santykio matematinė išraiška, pagrįstas angų plotas, reikalingas šviežiam orui į patalpą įeiti. Šis plotas lyginamas su angų užterštam orui šalinti plotu, nes visas užterštas oras žiemą turi būti šalinamas per kraigo plyšį. Apskaičiuota, kad tipiškoje neapšiltintoje karvidėje vidutinis oro judėjimo greitis kraigo plyšyje – 1,3 m/s (kai vėjo nėra šis greitis sumažėja iki 0,3 m/s), gravitacinės ir vėjo traukos santykis – 0,27. Tam, kad žiemą visas šalinamas oras išeitų per kraigo plyšį, angų orui įeiti sienose plotas turi neviršyti 40 % kraigo plyšio ploto. Sudarytos metodikos tikslumas patikrintas tvarto natūralios eksploatacijos sąlygomis, kai atstumas tarp oro įėjimo angų ir šachtos viršaus – 6,5 m. Tiriant matuota patalpos ir lauko oro temperatūra, oro greitis šachtoje. Tyrimų metu patalpos ir lauko oro temperatūrų skirtumas kito nuo –2 °C iki +16 °C, o oro judėjimo greitis šachtoje – nuo 1,2 m/s iki 1,9 m/s. Analiziniai rezultatai pakankamai tiksliai atspindi eksperimentinių duomenų vidurkį tvarto natūralios eksploatacijos sąlygomis. Eksperimentinių ir apskaičiuotų oro judėjimo šalinimo angoje greičių reikšmių skirtumas buvo nežymus ir svyravo nuo 0 % iki 8 %. Резюме При проектировании системы воздухообмена здания необходимо учитывать воздухообмен, происходящий под действием тепловых избытков и ветра в разные сезоны года и при разных условиях содержания животных. В результате аналитических и зкспериментальных исследований разработана методика для расчета параметров системы воздухообмена животноводческого помещения, которая обеспечивает стабильную тягу. В методике приведены простые формулы для расчета скорости воздуха в приточных и вытяжных проемах, для определения рационального соотношения площади приточных и вытяжных проемов, для отдельного учета действия тепловых избытков и ветра на производительность системы воздухообмена. Согласно расчетам в типичном неутепленном коровнике шириной 21 м средняя скорость вытяжного воздуха в коньковой щели составляет 1,3 м/с (при отсутствии ветра – 0,3 м/с), соотношение гравитационной и ветровой тяги – 0,27. Для обеспечения стабильной тяги в холодный период года площадь приточных стеновых проемов должна составлять не более 40% площади конькового проема. Точность методики проверена в условиях натуральной эксплуатации животноводческого помещения, в котором расстояние между центрами приточных и вытяжных проемов равно 6,5 м. Во время исследований измерялась наружная и внутренняя температура воздуха, скорость движения воздуха в вытяжном проеме и скорость ветра. Температурный перепад между внутренним и наружным воздухом изменялся от –2 °С до +16 °С, а скорость движения воздуха в вытяжном проеме была 1,2–1,9 м/с. Разница между результатами расчета и экспериментальными данными не превышала 8%. Поэтому можно утверждать, что точность разработанной методики достаточна.

scholarly journals An OpenFOAM simulation of the natural ventilation system in a university chemical laboratory

2020 ◽  
Vol 167 ◽  
pp. 04003
Author(s):  
M Córdova-Suárez ◽  
O. Tene-Salazar ◽  
F. Tigre-Ortega ◽  
S. Carrillo-Ríos ◽  
D. Córdova-Suárez ◽  
...  
Keyword(s):  
Working Conditions ◽  
Natural Ventilation ◽  
Ventilation System ◽  
Operating Conditions ◽  
Climate Data ◽  
Chemical Laboratory ◽  
Indoor Airflow ◽  
Air Intake ◽  
Air Speed ◽  
Closed Environment

The indoor airflow with a natural ventilation system was numerically calculated using the laminar and turbulent approach. In the chemical laboratory of the Technical University of Ambato, the computational code OpenFoam demonstrated an ability to numerically predict flow patterns. The design contemplated the natural ventilation system considering the laboratories’ working conditions not only in summer, but also in a winter week. These two operating conditions are calculated on a fully open and closed environment. For a room with a capacity of 20 people, the climate data average values were recorded at 14.0 ° C, 81.7%, 1.7 m /s for temperature, relative humidity, and wind speed, respectively. Furthermore, the demonstration has shown that the homogeneous occupancy air speed average is was 0.7 m / s with a facade air intake of 1.0 m / s 0.6 m / s in the room valid for the exchange of air and evacuation of pollutants. The maximum pressures were found in the lower part of the laboratory. This prevents the modification of the thermo-hygrometric conditions.

scholarly journals Study of Four Passive Second Skin Façade Configurations as a Natural Ventilation System During Winter and Summer

2021 ◽  
Vol 28 (1) ◽  
pp. 94-105
Author(s):  
Youssef Hamidi ◽  
Mustapha Malha ◽  
Abdellah Bah
Keyword(s):  
Flow Rate ◽  
Fossil Fuels ◽  
Natural Ventilation ◽  
Climate Models ◽  
Energy Savings ◽  
Volume Flow Rate ◽  
Ventilation System ◽  
Volume Flow ◽  
Design Strategies ◽  
The Difference

The fight against climate change is a significant challenge, resulting mainly from the linear and extensive exploitation of natural resources, particularly fossil fuels. Its impacts are now recognized. The current climate models are neither sustainable nor ecological in economic and social terms, especially as we live in a century marked by galloping demography and urbanization. Researchers worldwide have paid great attention to passive solar design strategies such as double skin or Second Skin Façade.  From this point, the present work aims to contribute to a better understanding of the feasibility of using a passive façade as a useful technology for natural ventilation to achieve potential energy savings and improve thermal comfort and indoor air quality. For this purpose, a parametric study was conducted for a room with four different southern facade configurations in six Moroccan climatic zones; the difference between each lies in the vent's position in the entrance and exit. This process was done by using COMSOL Multiphysics software. Velocity and volume flow rate fields were analyzed. The proposed configurations provided an average volume flow rate between 200 m3/h and 400 m3/h for a surface of 1 m2 of southern façade with an air vent area of 0.1mx0.2m.

scholarly journals Kecukupan Udara Mempengaruhi Kenyamanan Pada Ruang Kamar

2021 ◽  
Vol 18 (1) ◽  
pp. 19
Author(s):  
Syaidatul Maulianti ◽  
Zulfikar Ali As ◽  
Junaidi Junaidi
Keyword(s):  
Natural Ventilation ◽  
Ventilation System ◽  
Turnover Time ◽  
Future Research ◽  
Cross Sectional ◽  
Clean Air ◽  
The Difference ◽  
Relationship Of ◽  
Air Circulation ◽  
The Relationship

Ventilation is the process of exchanging clean air from outside into the room. Good ventilation is able to ensure smooth air circulation. This study aims to determine the relationship of air adequacy with comfort in room space. This research is an analytic study with cross sectional approach. The sample of this study was 30 rooms that used natural ventilation systems. The air change time is calculated from the volume of the room, the height and area of the ventilator, as well as the difference in the temperature of the outside and indoor air. Adequacy of air available with the air needed by its inhabitants. Objective comfort is based on the difference between outside and inside room temperature, and subjectively based on the room occupant's perspective. The results showed as many as 87% of the rooms had no air turnover time and as many as 20% of the rooms had insufficient air. Objectively stated rooms are uncomfortable as much as 57%, but subjectively reaching 77%. Statistically there is a significant relationship between air adequacy with comfort in the room objectively (p = 0.024). It can be concluded that the adequacy of the air represented by the ventilation system is related to the comfort of the air in the room space, to create a comfortable and healthy room space. Future research is expected to consider and include other factors that affect the ventilation system such as the layout of the furniture, the position of the ventilation, and the characteristics of the building so that research on comfort is more objective.

scholarly journals Thermal Diagnostics of Natural Ventilation in Buildings: An Integrated Approach

Energies ◽  
2019 ◽  
Vol 12 (23) ◽  
pp. 4556 ◽  
Author(s):  
Joanna Ferdyn-Grygierek ◽  
Andrzej Baranowski ◽  
Monika Blaszczok ◽  
Jan Kaczmarczyk
Keyword(s):  
Energy Demand ◽  
Natural Ventilation ◽  
Ventilation System ◽  
Residential Building ◽  
Integrated Approach ◽  
Airflow Rate ◽  
The Real ◽  
Heat Demand ◽  
Design Values ◽  
The Difference

Diagnostics of natural ventilation in buildings is problematic, as the airflow rate changes considerably over time. One constant average airflow is usually assumed when calculating energy demand for a building, however, such a simplification could be fraught with considerable error. The paper describes a comprehensive methodology for the diagnostics of a natural ventilation system in a building and its practical application. Based on in situ measurements and simulations in two existing buildings (dwelling house and school) in Poland, the real values of the ventilating airflows were analyzed and resulting heat demand was compared with the design values. The pros and cons of various methods for evaluation of natural ventilation are discussed. The real airflow was determined by measurements in a ventilation grille or by a tracer gas concentration decay method. The airtightness of the buildings’ envelope was evaluated based on the fan pressurization test. The last stage entailed computer simulations of air exchange in buildings using CONTAM software. The multizone models of the buildings were calibrated and verified with existing measured data. Measured airflow in a multifamily house was small and substantially deviated from the Polish standard. In case of a school, the air flow rate amounted to an average of 10% of the required value. Calculation of the heat demand for ventilation based on the standard value of the airflow led to a considerable overestimation of this value in relation to the real consumption. In the analyzed cases, the difference was 40% for the school and 30% for the residential building.

Comparison of two air sampling methods to monitor operating room air quality and assessment of air quality in two operating rooms with different ventilation systems in the national hospital of Sri Lanka

2016 ◽  
Vol 12 (3) ◽  
Author(s):  
Tshokey Tshokey ◽  
Pranitha Somaratne ◽  
Suneth Agampodi
Keyword(s):  
Air Quality ◽  
Sri Lanka ◽  
Operating Room ◽  
Ventilation System ◽  
Surgical Site Infections ◽  
National Hospital ◽  
Air Contamination ◽  
Acceptable Method ◽  
The Difference ◽  
Laminar Air Flow

Air contamination in the operating room (OR) is an important contributor for surgical site infections. Air quality should be assessed during microbiological commissioning of new ORs and as required thereafter. Despite many modern methods of sampling air, developing countries mostly depended on conventional methods. This was studied in two ORs of the National Hospital of Sri Lanka (NHSL) with different ventilation system; a conventional ventilation (CV) and a laminar air flow (LAF). Both ORs were sampled simultaneously by two different methods, the settle plate and sampler when empty and during use for a defined time period. Laboratory work was done in the Medical Research Institute. The two methods of sampling showed moderate but highly significant correlation. The OR with CV was significantly more contaminated than LAF when empty as well as during use by both methods. Overall, the difference in contamination was more significant when sampled by the sampler. Differences in contamination in empty and in-use ORs were significant in both ORs, but significance is less in LAF rooms. The consistent and significant correlation between settle plate and sampler showed that the settle plate is an acceptable method. The LAF theatre showed less contamination while empty and during use as expected. Air contamination differences were more significant when sampled with sampler indicating that it is a more sensitive method. Both CV and LAF ORs of the NHSL did not meet the contamination standards for empty theatres but met the standards for in-use indicating that the theatre etiquette was acceptable.

Seasonal trends in the stable isotopic composition of snow and meltwater runoff in a subarctic catchment at Okstindan, Norway

2004 ◽  
Vol 35 (2) ◽  
pp. 119-137 ◽  
Author(s):  
S.D. Gurney ◽  
D.S.L. Lawrence
Keyword(s):  
Isotopic Composition ◽  
Mean Value ◽  
Mean Values ◽  
Stable Isotopic Composition ◽  
Meltwater Runoff ◽  
Stable Isotopic ◽  
The Mean ◽  
The Difference ◽  
Δ18o And Δd

Seasonal variations in the stable isotopic composition of snow and meltwater were investigated in a sub-arctic, mountainous, but non-glacial, catchment at Okstindan in northern Norway based on analyses of δ18O and δD. Samples were collected during four field periods (August 1998; April 1999; June 1999 and August 1999) at three sites lying on an altitudinal transect (740–970 m a.s.l.). Snowpack data display an increase in the mean values of δ18O (increasing from a mean value of −13.51 to −11.49‰ between April and August), as well as a decrease in variability through the melt period. Comparison with a regional meteoric water line indicates that the slope of the δ18O–δD line for the snowpacks decreases over the same period, dropping from 7.49 to approximately 6.2.This change points to the role of evaporation in snowpack ablation and is confirmed by the vertical profile of deuterium excess. Snowpack seepage data, although limited, also suggest reduced values of δD, as might be associated with local evaporation during meltwater generation. In general, meltwaters were depleted in δ18O relative to the source snowpack at the peak of the melt (June), but later in the year (August) the difference between the two was not statistically significant. The diurnal pattern of isotopic composition indicates that the most depleted meltwaters coincide with the peak in temperature and, hence, meltwater production.

DIE AUSSCHEIDUNG VON TESTOSTERON UND EPITESTOSTERON BEI FRAUEN AM ENDE DER SCHWANGERSCHAFT

1969 ◽  
Vol 60 (4) ◽  
pp. 579-585
Author(s):  
K. Schollberg ◽  
E. Seiler ◽  
J. Holtorff
Keyword(s):  
Urinary Excretion ◽  
Late Pregnancy ◽  
Mean Values ◽  
Pregnant Females ◽  
Female Foetus ◽  
The Mean ◽  
The Difference ◽  
Normal Women ◽  
In Pregnancy

ABSTRACT The urinary excretion of testosterone and epitestosterone by women in late pregnancy has been studied. The mean values of 22 normal women in pregnancy mens X are 12.9 ± 9.2 μg/24 h in the case of testosterone and 16.1 ± 16.2 μg/24 h in the case of epitestosterone. Both values do not differ significantly from those of non-pregnant females. The excretion values of mothers bearing a male foetus (17.3 ± 8.9 μg/24 h) are higher than those of mothers with a female foetus (6.4 ± 4.8 μg/24 h). The difference is statistically significant with P = 0.01.

Natural-Ventilation Flow in a 3-D Room Fitted With Solar Chimney

2012 ◽  
Author(s):  
B. P. Huynh
Keyword(s):  
Heat Flux ◽  
Flow Pattern ◽  
Natural Ventilation ◽  
Air Flow ◽  
Ventilation Rate ◽  
High Heat Flux ◽  
Solar Chimney ◽  
Solar Heat ◽  
Solar Heat Flux ◽  
Inlet Opening

Natural-ventilation flow induced in a real-sized rectangular-box room fitted with a solar chimney on its roof is investigated numerically, using a commercial CFD (Computational Fluid Dynamics) software package. The chimney in turn is in the form of a parallel channel with one plate being subjected to uniform solar heat flux. Ventilation rate and air-flow pattern through the room are considered in terms of the heat flux for two different locations of the room’s inlet opening. Chien’s turbulence model of low-Reynolds-number K-ε is used in a Reynolds-Averaged Navier-Stokes (RANS) formulation. It is found that ventilation flow rate increases quickly with solar heat flux when this flux is low, but more gradually at higher flux. At low heat flux, ventilation rate is not significantly affected by location of the inlet opening to the room. On the other hand, at high heat flux, ventilation rate varies substantially with the opening’s location. Location of the inlet opening to the room also affects strongly the air-flow pattern. In any case, ample ventilation rate is readily induced by the chimney.

scholarly journals Influence of Apical Patency and Cleaning of the Apical Foramen on Periapical Extrusion in Retreatment

2013 ◽  
Vol 24 (5) ◽  
pp. 482-486 ◽  
Author(s):  
Marili Doro Andrade Deonizio ◽  
Gilson Blitzkow Sydney ◽  
Antonio Batista ◽  
Roberto Pontarolo ◽  
Paulo Ricardo Bittencourt Guimarães ◽  
...  
Keyword(s):  
Material Removal ◽  
Filling Material ◽  
Mean Values ◽  
Filtration System ◽  
Root Canal Retreatment ◽  
Significant Difference ◽  
Before And After ◽  
The Mean ◽  
The Difference ◽  
Removal Technique

This study evaluated the influence of apical patency, root filling removal technique and cleaning of the apical foramen, concerning the amount of debris extruded during root canal retreatment. Forty mandibular incisors were randomly assigned to 4 groups - GIM (n=10), GIIM (n=10), GIPT (n=10) and GIIPT (n=10), which were named according to leaving (I) or not (II) apical patency during canal preparation and filling removal technique (manual - M or ProTaper system - PT). After filling material removal, each specimen of each group had the apical foramen cleaned by sizes 15, 20 and 25 instruments, generating 12 subgroups: GIM15, GIM20, GIM25, GIIM15, GIIM20, GIIM25, GIPT15, GIPT20, GIPT25, GIIPT15, GIIPT20 and GIIPT25. Extruded filling debris was collected by a Milipore filtration system, an HV-durapore, 0.45 µm pore filter with a 25 mm diameter. The filters were weighed before and after the collection on an analytical scale (10–5 g), and the difference was calculated. The mean weight of extruded filling debris was analyzed statistically by Kruskal-Wallis and Friedman ANOVA tests (α=0.05). The mean values found in the groups (in mg) were: GIM (0.95±0.94), GIIM (0.47±0.62), GIPT (0.30±0.31) and GIIPT (0.32±0.44). There was no statistically significant difference among any of the groups or subgroups (p>0.05). ProTaper provided the smallest amount of extruded filling material, regardless of presence or absence of apical patency, followed by manual technique, without and with apical patency. Additional amounts of debris were collected during cleaning of the apical foramen, regardless of the instrument, presence/absence of patency or root filling removal technique.

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