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.

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.

scholarly journals Computational Analysis of a Lecture Room Ventilation System

2020 ◽  
Author(s):  
Abayomi Layeni ◽  
Collins Nwaokocha ◽  
Olalekan Olamide ◽  
Solomon Giwa ◽  
Samuel Tongo ◽  
...  
Keyword(s):  
Air Quality ◽  
Indoor Air Quality ◽  
Indoor Air ◽  
Natural Ventilation ◽  
Ventilation System ◽  
Minimum Cost ◽  
Solar Chimney ◽  
Lecture Room ◽  
Room Ventilation System ◽  
Ventilation Systems

The level of Indoor Air Quality (IAQ) has become a big topic of research, and improving it using passive ventilation methods is imperative due to the cost saving potentials. Designing lecture buildings to use less energy or Zero Energy (ZE) has become more important, and analysing buildings before construction can save money in design changes. This research analyses the performance (thermal comfort [TC]) of a lecture room, investigate the use of passive ventilation methods and determine the energy-saving potential of the proposed passive ventilation method using Computational Fluid Dynamics (CFD). Results obtained showed that air change per hour at a wind velocity of 0.05 m/s was 3.10, which was below standards. Therefore, the lecture hall needs external passive ventilation systems (Solar Chimney [SC]) for improved indoor air quality at minimum cost. Also, it was observed that the proposed passive ventilation (SC) system with the size between 1 and 100 m3, made an improvement upon the natural ventilation in the room. There was a 66.69% increase after 10 years in the saving of energy and cost using Solar Chimney as compared to Fans, which depicts that truly energy and cost were saved using passive ventilation systems rather than mechanical ventilation systems.

Performance of Masonry Walls Strengthened with RC Wall Jacket Subjected to Simulated Blast Loads

2017 ◽  
Vol 755 ◽  
pp. 8-17
Author(s):  
Mohamed Abdel-Mooty ◽  
Sayed Alhayawei ◽  
Mohamed Issa
Keyword(s):  
Reinforced Concrete ◽  
Critical Infrastructure ◽  
Blast Loading ◽  
Masonry Wall ◽  
Design Parameters ◽  
Masonry Walls ◽  
Blast Loads ◽  
Concrete Wall ◽  
Blast Effect ◽  
Reinforced Concrete Wall

Mitigation of the blast risk associated with terrorist attacks and accidental explosions threatening critical infrastructure has become a topic of great interest in the civil engineering community, all over the world. One method of mitigating blast risk is to retrofit vulnerable structures to resist the impulsive effects of blast loading. Masonry is one of the most commonly used materials particular in heritage buildings. An effective way to enhance the ability of unreinforced masonry walls to withstand blast loads and consequently to limit the amount of wall damage is strengthening it with reinforced concrete wall. In this research, the assembly of masonry wall with RC wall jacket from one side is simulated using nonlinear finite element method and ANSYS WORKBENCH V14.5 program to study its behavior under blast loading. A parametric study is performed where the influence of variation of some design parameters on the wall performance under blast effect is studied. The design parameters include masonry wall and RC wall thickness, interface between the two wall layers, stand-off distance, boundary condition, and reinforced concrete compressive strength. The performance of the strengthened walls is evaluated in terms of wall damage, maximum lateral deflection, and end rotation at the support.

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.

EXPERIMENTAL STUDIES OF REINFORCED CONCRETE STRUCTURES WITH CROSS-SHAPED SPATIAL CRACK UNDER TORSION WITH BENDING

2020 ◽  
Vol 92 (6) ◽  
pp. 13-25
Author(s):  
Vl.I. KOLCHUNOV ◽  
◽  
A.I. DEMYANOV ◽  
M.M. MIHAILOV ◽  
◽  
...  
Keyword(s):  
Reinforced Concrete ◽  
Experimental Determination ◽  
Calculation Method ◽  
Experimental Studies ◽  
Concrete Structures ◽  
Design Parameters ◽  
Reinforced Concrete Structures ◽  
Experimental Scheme

The article offers a method and program for experimental studies of reinforced concrete structures with cross-shaped spatial crack under torsion with bending, the main purpose of which is to check the design assumptions and experimental determination of the design parameters of the proposed calculation method. The conducted experimental studies provide an opportunity to test the proposed calculation apparatus and clarify the regularities for determining deflections, angles of rotation of extreme sections, and stresses in the compressed zone of concrete. For analysis, the article presents a typical experimental scheme for the formation and development of cracks in the form of a sweep, as well as characteristic graphs of the dependence of the angles of rotation of end sections.

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