Data on the natural ventilation performance of windcatcher with anti-short-circuit device (ASCD)

This article presents the datasets which were the results of the study explained in the research paper ‘Anti-short-circuit device: a new solution for short-circuiting in windcatcher and improvement of natural ventilation performance’ [1] which introduces a new technique to reduce or prevent short-circuiting in a two-sided windcatcher and also lowers the indoor CO2 concentration and improve the ventilation distribution. Here, we provide details of the numerical modelling set-up and data collection method to facilitate reproducibility. The datasets includes indoor airflow, ventilation rates and CO2 concentration data at several points in the flow field. The CAD geometry of the windcatcher models are also included

Anti-short-circuit device: A new solution for short-circuiting in windcatcher and improvement of natural ventilation performance

Windcatcher is an effective technique for naturally ventilating a space and improving indoor air quality. A common problem for modern and traditional windcatchers is air short-circuiting. Air-short-circuiting in windcatchers occurs when the air entering through the supply channel immediately exits through the exhaust channel without circulating and mixing inside the enclosed space. Several previous works on windcatchers have observed the “short-circuiting” effect and concluded that it has a negative impact on the ventilation performance however, no work have provided a solution to eliminate this effect. The present study will address this issue by incorporating a component called the anti-short-circuiting device (ASCD) and investigating its potential to eliminate air short-circuiting in windcatchers and improve ventilation performance. Two methods were employed in this research: experimental and Computational Fluid Dynamics (CFD) study. For the experimental work, three scaled models were studied in a wind tunnel. The CFD modelling was validated using the air velocity measurements and good correlation was observed with average error below 10%. The results showed that the ASCD windcatcher with angles between 20° and 80° prevented air-short-circuiting while supplying up to 40–51 l/s per occupant, which is higher than the minimum recommendations of ASHRAE62.2 and BS5925. In addition, the windcatcher without ASCD showed 8% higher CO2 concentration in the room, indicating that the ASCD windcatcher was more effective in removing stale air out of the room. Furthermore, the average air velocity in the room at sitting height with the ASCD windcatcher was 19–28% higher than windcatcher without ASCD

Evaluation of a two-sided windcatcher integrated with wing wall (as a new design) and comparison with a conventional windcatcher

In buildings, 60% of the energy consumption is associated to Heating, Ventilation and Air-conditioning (HVAC) systems. One solution to reduce this share is the application of natural ventilation systems. Windcatcher and wing wall are two well-known techniques for natural ventilation which have been used in different regions. Nevertheless, in areas with low wind speed such as the tropical climate of Malaysia there is hesitation for application of natural ventilation systems. The integration of windcatcher with wing wall can potentially enhance the ventilation performance. However, this configuration was not looked into by pervious investigations thus, this study aims to address this research gap by first evaluating the effect of wing wall with various angles on the ventilation performance and second compare the performance of this new design with a conventional windcatcher. This research used two main investigative steps: experimental scaled wind tunnel testing and Computational Fluid Dynamics (CFD) simulation. Four reduced-scale models of two-sided windcatcher were tested in a low speed wind tunnel. Three models were integrated with wing wall in 30°, 45° and 60° incident angles and another windcatcher was a conventional two-sided windcatcher, which is typical in regions with predominant wind direction. The CFD validation against experiment showed good agreement. The best operation was observed in the windcatcher with 30° wing wall angle which could supply 910 l/s fresh air into the room in 2.5 m/s wind speed. Hence, the new design had 50% more ventilation performance comparing with conventional two-sided windcatcher in the same external wind speed. Finally, it was concluded that the new design satisfied requirements of ASHRAE 62.1

A review on windcatcher for passive cooling and natural ventilation in buildings, Part 1: Indoor air quality and thermal comfort assessment

The most prominent challenge in 21th century is global warming which seriously threats the mankind. Building sector with 40% of global energy consumption and GHG emission play a key role in this threat. In this regard, the impact of cooling systems cannot be ignored where along with ventilation and heating systems totally account for 60% of energy consumed in buildings. Passive cooling systems can be a promising alternative to reduce energy consumption. One of the oldest passive cooling system that is still being used today is windcatcher. By manipulating pressure differences and the buoyancy effect, an adequate level of ventilation in buildings can be provided by windcatchers. Since most of the previous windcatcher studies assessed the design characteristics, the current investigation focused on the indoor air quality (IAQ) and thermal comfort aspects. The review details and compares the different theoretical and experimental methods employed by researchers in different case studies to assess the IAQ and thermal comfort. It was found that most IAQ studies were conducted in the UK using CFD and experimental techniques. Previous studies assessed IAQ based on several parameters such as air flow rate, air change rate, CO2 concentration, air change effectiveness and mean age of air. The findings of the studies revealed that satisfactory IAQ were generally achieved using the windcatcher. On the other hand, thermal comfort studies of windcatchers were mainly conducted in hot climates such as in the Middle East. In addition to night ventilation, the review also looked into the different types of cooling methods incorporated with windcatchers such as evaporative cooling, earth to air heat exchangers (EAHE) and heat transfer devices (HTD). Night ventilation was found to be effective in temperate and cold conditions while additional cooling using evaporative cooling, EAHE and HTD were found to be necessary in hot climates

ESDA2010-24400 A THEORETICAL APPROACH FOR FREE VIBRATION ANALYSIS OF THE NANO- PLATES CONSIDERING THE SMALL SCALE EFFECT

ABSTRACT The free vibration analysis of a nano-plate is investigated based on the first order shear deformation theory considering the small scale effect. The governing equations of motion are obtained using Hamilton's principle by considering the nonlocal constitutive equations of Eringen. These coupled partial differential equations are reformulated into two new equations called the edge-zone and interior equations. Analytical solutions are obtained for a nano-plate with Levy boundary conditions. In order to find the natural frequencies of the nano-plate, the various boundary conditions at one direction of the plate should be imposed. Applying these conditions and setting the determinant of the six order coefficient matrix equal to zero, the natural frequencies of the nano-plate are evaluated. Nondimensional frequency parameters are presented for over a wide range of nonlocal parameters and different boundary conditions. In addition, the effects of nonlocal parameter on the natural frequency of a nano-plate are discussed in details. INTRODUCTION Due to the vast computational expenses of nanostructures analyses when using atomic lattice dynamics and molecular dynamic simulations, there is a great interest in applying continuum mechanics for analysis of nano-structures. Eringen The nonlocal theory of elasticity has been extensively used to study buckling and vibration analyses of carbon nano-tubes with the help of beam and shell theories

A review of numerical modelling of multi-scale wind turbines and their environment

Global demand for energy continues to increase rapidly, due to economic and population growth, especially for increasing market economies. These lead to challenges and worries about energy security that can increase as more users need more energy resources. Also, higher consumption of fossil fuels leads to more greenhouse gas emissions, which contribute to global warming. Moreover, there are still more people without access to electricity. Several studies have reported that one of the rapidly developing source of power is wind energy and with declining costs due to technology and manufacturing advancements and concerns over energy security and environmental issues, the trend is predicted to continue. As a result, tools and methods to simulate and optimize wind energy technologies must also continue to advance. This paper reviews the most recently published works in Computational Fluid Dynamic (CFD) simulations of micro to small wind turbines, building integrated with wind turbines, and wind turbines installed in wind farms. In addition, the existing limitations and complications included with the wind energy system modelling were examined and issues that needs further work are highlighted. This study investigated the current development of CFD modelling of wind energy systems. Studies on aerodynamic interaction among the atmospheric boundary layer or wind farm terrain and the turbine rotor and their wakes were investigated. Furthermore, CFD combined with other tools such as blade element momentum were examined

Distribution of genes encoding resistance to macrolides, lincosamides, and streptogramins among methicillin-resistant Staphylococcus aureus strains isolated from burn patients

The increasing resistance to macrolide, lincosamide, and streptogramin B agents among methicillin-resistant Staphylococcus aureus (MRSA) is a worldwide problem for the health community. This study aimed to investigate the prevalence of ermA, ermB, ermC, and msrA in MRSA strains isolated from burn patients in Ahvaz, southwest of Iran. A total of 76 isolates of S. aureus were collected from January to May 2017 from Taleghani Burn Hospital in Ahvaz. Among 76 S. aureus strains collected, 60 (78.9%) isolates were MRSA. The antimicrobial susceptibility testing for MRSA showed extreme high resistance rate to clarithromycin (100%) and azithromycin (100%), followed by erythromycin (98.3%). The PCR assay revealed that the frequency rates of msrA, ermA, and ermC genes were 23 (38.3%), 28 (46.7%), and 22 (36.7%), respectively. In addition, none of the MRSA isolates had the ermB gene. Because of the high prevalence of macrolide and lincosamide resistance found in MRSA isolates from infections of burn patients in Ahvaz, southwest of Iran, it is recommended that local periodic survey be performed for controlling the dissemination of antimicrobial resistance