scholarly journals Design of a Passive Downdraught Evaporative Cooling Windcatcher (PDEC-WC) System for Greenhouses in Hot Climates

Energies ◽  
2020 ◽  
Vol 13 (11) ◽  
pp. 2934 ◽  
Author(s):  
Marouen Ghoulem ◽  
Khaled El Moueddeb ◽  
Ezzedine Nehdi ◽  
Fangliang Zhong ◽  
John Calautit
Keyword(s):  
Relative Humidity ◽  
Natural Ventilation ◽  
Ventilation System ◽  
Evaporative Cooling ◽  
Cross Flow ◽  
Flow Distribution ◽  
Average Error ◽  
Ambient Conditions ◽  
Mass Flow Rates ◽  
Computational Fluid Dynamics Cfd

A windcatcher is a wind-driven natural ventilation system that catches the prevailing wind to bring fresh airflow into the building and remove existing stale air. This technology recently regained attention and is increasingly being employed in buildings for passive ventilation and cooling. The combination of windcatchers and evaporative cooling has the potential to reduce the amount of energy required to ventilate and cool a greenhouse in warm and hot climates. This study examined a greenhouse incorporated with a passive downdraught evaporative cooling windcatcher (PDEC-WC) system using Computational Fluid Dynamics (CFD), validated with experimental data. Different hot ambient conditions of temperature (30–45 °C) and relative humidity (15–45%) were considered. The study explored the influence of different spray heights, layouts, cone angles and mass flow rates on indoor temperature and humidity. The average error between measurements and simulated results was 5.4% for the greenhouse model and 4.6% for the evaporative spray model. Based on the results and set conditions, the system was able to reduce the air temperature by up to 13.3 °C and to increase relative humidity by 54%. The study also assessed the influence of neighbouring structures or other greenhouses that influence the flow distribution at the ventilation openings. The study showed that the windcatcher ventilation system provided higher airflow rates as compared to cross-flow ventilation when other structures surrounded the greenhouse.

IMPROVEMENT OF THERMAL COMFORT INSIDE A MOSQUE BUILDING

2016 ◽  
Vol 78 (8-4) ◽  
Author(s):  
Fawaz Ghaleb Noman ◽  
Nazri Kamsah ◽  
Haslinda Mohamed Kamar
Keyword(s):  
Thermal Comfort ◽  
Natural Ventilation ◽  
Ventilation System ◽  
Side Wall ◽  
The West ◽  
Cfd Simulations ◽  
Interior Space ◽  
Flow Simulations ◽  
Computational Fluid Dynamics Cfd ◽  
Cfd Method

A combined natural ventilation and mechanical fans are commonly used to cool the interior space inside the mosques in Malaysia. This article presents a study on thermal comfort in the Al-Jawahir Mosque, located in Johor Bahru, Malaysia. The objective is to assess the thermal comfort inside the mosque under the present ventilation system by determining the Predicted Mean Vote (PMV) and the Predicted Percentage of Dissatisfied (PPD). These values were then compared to the limits stated in the ASHRAE Standard-55. It was found that the PMV varies from 1.68 to 2.26 while the PPD varies from 61% to 87%. These show that the condition inside the mosque is quite warm. Computational fluid dynamics (CFD) method was used to carry out flow simulations, to identify a suitable strategy to improve the thermal comfort inside the mosque. Results of CFD simulations show that installing four exhaust fans above the windows on the west-side wall of the mosque is the most effective strategy to improve the thermal comfort inside the mosque. Both the PMV and PPD values can potentially be reduced by more than 60%.

Numerical analysis of local thermal comfort in a plan office under natural ventilation

2019 ◽  
Vol 29 (7) ◽  
pp. 972-986 ◽  
Author(s):  
Xiang Deng ◽  
Zijing Tan
Keyword(s):  
Thermal Comfort ◽  
Natural Ventilation ◽  
Meteorological Data ◽  
Ventilation System ◽  
Comfort Level ◽  
Open Plan ◽  
Computational Fluid Dynamics Cfd ◽  
Internal Volume ◽  
Local Thermal Comfort ◽  
Primary Focus

The utilisation of automatic controlled natural wind in office buildings to maintain indoor thermal comfort has gained wide attention in recent years. Generally, it is not necessary to ensure that the whole internal volume of a building with large open spaces meets thermal comfort requirements. Primary focus should be on occupied areas. Accordingly, the local thermal comfort in an open-plan office with automatic controlled natural ventilation system was investigated numerically and experimentally. A computational fluid dynamics (CFD)-based method was presented for indoor environment and thermal comfort prediction. Long-term in situ measurement was conducted during summer and transition seasons. The meteorological data were collected by a mini weather station located on the roof of the target building. Meanwhile, indoor air velocity, temperature, turbulence intensity and wall temperatures were recorded locally. Three thermal comfort indices, i.e. thermal stratification represented by percentage dissatisfied (PD), the extended predicted mean vote (PMVe) and draught rate were employed to evaluate the thermal comfort level of the interested areas during natural ventilation period. The numerical results revealed a risk of local thermal dissatisfaction under low outdoor temperature and strong windy conditions.

Numerical Simulation of the Flow Field for Rotor Ventilation System of Large-Scale Nuclear Power Turbo-Generator

2012 ◽  
Vol 152-154 ◽  
pp. 1498-1504 ◽  
Author(s):  
Xiao Hu Zhang ◽  
Lei Hu ◽  
Jian Hua Yuan ◽  
Yi Chao Yuan
Keyword(s):  
Flow Field ◽  
Nuclear Power ◽  
Large Scale ◽  
Ventilation System ◽  
Flow Distribution ◽  
Basic Unit ◽  
Turbo Generator ◽  
Key Issues ◽  
Computational Fluid Dynamics Cfd ◽  
And Performance

The nuclear power turbo-generator with large capacity is a basic unit of nuclear power plant, while the cooling technology becomes one of the key issues which affect its design and operation deeply. Axial-radial ventilation structure for rotor is commonly used in large nuclear power generator. In this article, according to the basic principles of computational fluid dynamics (CFD), ventilation’s structure and performance is analyzed, 3D flow model is also established. After the boundary conditions are determined, the numerical calculation and analysis is finished. And then, the rules of flow distribution is obtained, the flow field and the static pressure character of the gap is also computed, which could be very important to the ventilation system of the whole generator.

scholarly journals ANALYSIS OF AIR FLOW DISTRIBUTION IN RESIDENTIAL ROOMS WITH SUPPLY WINDOW VALVES BY MATHEMATICAL MODELING IN ANSYS FLUENT

2019 ◽  
Vol 4 (10) ◽  
pp. 67-73
Author(s):  
О. Симбирев ◽  
O. Simbirev
Keyword(s):  
Mathematical Modeling ◽  
Mathematical Model ◽  
Natural Ventilation ◽  
Residential Buildings ◽  
Ventilation System ◽  
Flow Distribution ◽  
Ansys Fluent ◽  
Airflow Distribution ◽  
Standard Values ◽  
Technical Solutions

The main problem highlighted in the article is the deviation of the microclimate parameters from the standard values due to the improper organization of airflow in the residential rooms of apartment buildings. The objective is to obtain a working mathematical model of the natural ventilation system, its study for optimization or modernization. The analysis of the normative literature, scientific works of domestic and foreign scientists, developments in the field of natural ventilation and ventilation of residential buildings is carried out. A mathematical model of air exchange of a residential room with convection is presented and analyzed. The flow rate and air temperature, the temperature on the surface of the heater are set as boundary conditions when creating a mathematical model. The features and regularities of airflow distribution in the room obtained as a result of mathematical modeling are revealed. The distributions of air velocity in the room are given. Difficulties of the organization of effective natural inflow of air and the problems with design of valves of infiltration are designated. Technical solutions aimed at improving the quality of indoor microclimate and energy saving are proposed.

scholarly journals Investigation of a Ventilation System for Energy Efficiency and Indoor Environmental Quality in a Renovated Historical Building: A Case Study

2019 ◽  
Vol 16 (21) ◽  
pp. 4133 ◽  
Author(s):  
Richard Nagy ◽  
Ľudmila Mečiarová ◽  
Silvia Vilčeková ◽  
Eva Krídlová Burdová ◽  
Danica Košičanová
Keyword(s):  
Energy Consumption ◽  
Relative Humidity ◽  
Environmental Quality ◽  
Natural Ventilation ◽  
Ventilation System ◽  
Sick Building Syndrome ◽  
Co2 Concentration ◽  
Indoor Environmental Quality ◽  
Historical Building ◽  
The Mean

This paper emphasizes the importance of environmental protection regarding the reduction of energy consumption while maintaining living standards. The aim of the research is to observe the effects of mechanical and natural ventilation on energy consumption and building operation as well as indoor environmental quality (IEQ). The results of indoor environmental quality testing show that the mean relative humidity (31%) is in the permissible range (30%–70%); the mean CO2 concentration (1050.5 ppm) is above the recommended value of 1000 ppm according to Pettenkofer; and the mean PM10 concentration (43.5 µg/m3) is under the limit value of 50 µg/m3. A very large positive correlation is found between relative humidity and concentration of CO2 as well as between the concentration of PM5 and the concentration of CO2. The most commonly occurring sick building syndrome (SBS) symptoms are found to be fatigue and the feeling of a heavy head.

Design, Construction, and Performance Evaluation of an Evaporative Cooling System for Tomatoes Storage

2020 ◽  
Vol 24 (4) ◽  
pp. 1-12
Author(s):  
Edward A. Awafo ◽  
Samuel Nketsiah ◽  
Mumin Alhassan ◽  
Ebenezer Appiah-Kubi
Keyword(s):  
Relative Humidity ◽  
Cooling System ◽  
Storage System ◽  
Evaporative Cooling ◽  
Ambient Conditions ◽  
Data Logger ◽  
Significant Difference ◽  
Jute Sack ◽  
Tomato Processing ◽  
Evaporative Cooling System

AbstractAn evaporative cooling system was designed and constructed to increase the shelf life of stored vegetables. The evaporative cooler was tested and evaluated using freshly harvested roma tomatoes. The equipment operates on the principle of evaporative cooling which increased the relative humidity and decreased temperature in the preservation chamber. The storage system was made up of wood of 25.4 mm thickness. A side of the system is made of jute sack, which was moistened with water flowing through a series of perforated pipes from a reservoir located at the top of the storage system. The water flowed under gravity. The relative humidity and temperature of the tomatoes were analyzed using tinytag humidity, temperature data logger. The weight loss of the tomatoes was also analyzed using a dial gauge scale. The results revealed that there was significant difference in using the evaporative cooling system for storing tomatoes as compared to ambient conditions. The average cooling efficiency was found to be 81%. The average temperature achieved in the cooling system dropped to an average of 23℃ when compared to the average ambient temperature of 33℃, and the relative humidity also increased up to 99% when compared to the average ambient of 59%. The analysis of the evaporative cooling system showed that tomatoes can be stored for more than 6 days with negligible changes in weight, colour and firmness as compared to those under ambient condition, which deteriorated after day 3. The evaporative cooling system was found to be effective and hence can be used by farmers, households, and tomato processing factories for short term storage of fresh tomatoes.

scholarly journals Sustainable Smoke Extraction System for Atrium: A Numerical Study

2021 ◽  
Vol 13 (13) ◽  
pp. 7406
Author(s):  
Martin Lyubomirov Ivanov ◽  
Wei Peng ◽  
Qi Wang ◽  
Wan Ki Chow
Keyword(s):  
Mechanical Ventilation ◽  
Natural Ventilation ◽  
Numerical Study ◽  
Ventilation System ◽  
High Heat ◽  
Fire Dynamics ◽  
Sustainable Environment ◽  
Design Fire ◽  
Smoke Layer ◽  
Computational Fluid Dynamics Cfd

Smoke extraction systems, either static with natural ventilation, or dynamic with mechanical ventilation are required to keep smoke layer at high levels in many tall atria. It is observed that a design fire with high heat release rate (HRR) is commonly used for designing natural vents, but a low HRR is used for mechanical ventilation system. This will not produce a sustainable environment. There are no internationally agreed on design guides to determine the HRR in the design fire for different extraction systems and scenarios. This issue will be studied using a Computational Fluid Dynamics (CFD)-based software, the Fire Dynamics Simulator (FDS) version 6.7.1. Simulations on natural smoke filling, static and dynamic smoke extractions were carried out in a big example atrium. CFD-FDS predictions were compared with previous full-scale burning tests. Results confirmed that static smoke extraction is a good option for big fires, and a dynamic system is best for small fires. A sustainable new hybrid design combining the advantages of static and dynamic systems is proposed, which could result in a lower smoke temperature and higher smoke layer interface height, indicating a better extraction design.

Thermal Performance of a Natural Ventilation System

2010 ◽  
Author(s):  
M. J. Jime´nez ◽  
J. D. Guzma´n ◽  
M. R. Heras ◽  
J. Arce ◽  
J. P. Xama´n ◽  
...  
Keyword(s):  
Thermal Effects ◽  
Natural Ventilation ◽  
Ventilation System ◽  
Experimental Studies ◽  
Design Parameters ◽  
Ambient Conditions ◽  
Solar Chimney ◽  
Concrete Wall ◽  
Reinforced Concrete Wall ◽  
One Year

Natural ventilation in buildings using solar passive systems, such as solar chimneys, has emerged in the last years. Several theoretical and experimental studies in the literature show that their design parameters strongly depend on the ambient conditions, in which they are installed. In order to increase the knowledge of this kind of systems, this work presents the thermal behavior of a stand alone experimental solar chimney during one year. The dimensions of the solar chimney are 5.60 m high, 1.0 m width, and 0.52 m depth. The absorber plate is made of a common reinforced concrete wall of 4.5 m high, 1.0 m wide and 0.15 m depth. This system was designed by Marti´ J., and Heras M.R. in 2003 [1,2] and it is located in the Laboratorio de Ensayos Energe´ticos para Componentes de la Edificacio´n (LECE) in the Plataforma Solar of Almeri´a (PSA) in Spain. The entrance of this solar chimney was redesigned in 2007 by Arce et al. [3] and also the instrumentation of the system was increased and improved. During one year, the solar chimney was monitored and several experimental variables were measured. The results present the temperature profiles of the different measured elements of the solar chimney as well as the air mass flow rate through the solar chimney channel. It was observed that the effect of the outdoor wind added to the thermal effects plays an important role affecting the performance of the solar chimney studied.

Environmental indicators for assessing the welfare of dairy cattle housed indoors

2017 ◽  
Vol 13 (1) ◽  
pp. 71-82
Author(s):  
Anna Wójcik ◽  
Tomasz Mituniewicz ◽  
Sara Dzik ◽  
Łukasz Kostrubiec ◽  
Anna Wolska ◽  
...  
Keyword(s):  
Relative Humidity ◽  
Dairy Cattle ◽  
Natural Ventilation ◽  
Ventilation System ◽  
Environmental Indicators ◽  
Physical Parameters ◽  
Average Relative Humidity ◽  
Autumn And Winter ◽  
Microclimate Conditions ◽  
Good Heat

The objective of the research was to evaluate the microclimate and environmental indicators used to assess the welfare of dairy cattle housed indoors in a tie-stall barn located in the Kuyavian-Pomeranian Voivodeship. Microclimate conditions were analysed using the physical parameters of the microclimate and selected environmental indicators characterizing the level of livestock welfare. The study showed that the temperature in the barn during autumn and winter corresponded to recommendations, whereas in the spring, when the outdoor temperature was high, the indoor temperature exceeded the optimum temperature by about 7°C. In the autumn and winter, when high levels of outdoor humidity were noted, the relative humidity inside the barn was also very high, which is an undesirable effect. The average relative humidity in the spring did not exceed recommendations. The excessive relative humidity inside the barn was indicative of poorly functioning natural ventilation. To improve the temperature and humidity conditions, the door was opened to ventilate the building, thus affecting other parameters of the microclimate. It was concluded from the microclimate indicators that the building had good heat insulation and ensured the welfare of the animals during low temperatures. However, the research showed that the natural gravity ventilation system did not work properly, which during some periods may have a detrimental effect on the welfare of dairy cattle.

scholarly journals Analysis of Ventilation Efficiency in the Earth Covered Magazine for Ammunition Storage Using Numerical Simulation

2021 ◽  
Vol 1203 (2) ◽  
pp. 022069
Author(s):  
Nurin Zecevic ◽  
Jasmin Terzic ◽  
Berko Zecevic ◽  
Adis Ajanovic
Keyword(s):  
Numerical Simulation ◽  
Relative Humidity ◽  
Natural Ventilation ◽  
Ventilation System ◽  
Experimental Studies ◽  
Environmental Parameters ◽  
Airflow Velocity ◽  
Ansys Fluent ◽  
Rapid Decomposition ◽  
Negative Effect

Abstract Internal environment parameters such as temperature, relative humidity and airflow velocity in ammunition storage facilities have a significant impact on the condition and overall life of ammunition, especially on the process of ammunition degradation in situations when their values deviate from required standards for safe storage. High temperatures inside the magazine, as well as in the ammunition packaging, can have a very negative effect on the structure of ammunition and explosives, and high values of relative humidity can result in corrosion and rapid decomposition of chemical compounds. Therefore, a properly designed ventilation system should ensure that the values of internal temperature and relative humidity are within the permitted limits, which is a very important aspect of the storage process itself, so that ammunition and explosives can be completely safe and ready for transport, use and handling. Experimental studies conducted in several magazines of ammunition and explosives in Bosnia and Herzegovina (BiH), had aim to monitor changes of environmental parameters such as temperature, relative humidity and airflow velocity. During these experimental measurements, high values of relative humidity were in these magazines observed, as well as uneven airflow in some ventilation ducks. The main cause of such measured values can be related to the inadequate performance of the natural ventilation system of the analysed magazines. Using numerical simulations (finite volume method) in the ANSYS – Fluent program, the analysis of the existing ventilation system of earth covered magazine in BiH from the aspect of airflow velocity was performed, as well as analysis of modifications that can improve airflow within the analysed magazine. The results of numerical simulation for the existing state of analysed magazine corresponded to the results of airflow measurements at certain places in the magazine. It was confirmed that the existing ventilation system does not provide proper ventilation, which further causes higher relative humidity values. The results of numerical simulation for the proposed modifications of the ventilation system have shown significantly better air circulation in the magazine, i.e. that a more efficient natural ventilation was achieved.

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