scholarly journals Numerical Study on Natural Ventilation Characteristics of a Partial-Cylinder Opening for One-Sided-Windcatcher of Variable Air-Feeding Orientations in Taif, Saudi Arabia

2021 ◽  
Vol 13 (20) ◽  
pp. 11310
Author(s):  
Ashraf Balabel ◽  
Mamdooh Alwetaishi ◽  
Wageeh A. El-Askary ◽  
Hamza Fawzy
Keyword(s):  
Saudi Arabia ◽  
Natural Ventilation ◽  
Numerical Study ◽  
Pressure Coefficient ◽  
Opening Angle ◽  
Arid Zones ◽  
Wind Speeds ◽  
Flow Features ◽  
Ventilation Rates ◽  
Inlet Opening

To provide a clean and cheap source of natural ventilation in windy and arid zones, a windcatcher facility is the best option. This paper aims to study the effect of the inlet opening angle of a new windcatcher model with different values ranging from 60° to 90° for three different feeding orientations at leading-down, central-up, and trailing-down locations. The ventilation performance of the new one-sided windcatcher is numerically examined using CFD simulations, where the 3D RANS and k-epsilon equations are applied at different wind speeds. The flow features of the new models are analyzed and compared with a basic traditional model based on the induced air distribution, aerodynamic losses, and ventilation rates. Results revealed that the sharp edge of the inlet opening leads to an increase in the flow separation and recirculation zone, especially when the opening angle is increased. The highest pressure coefficient is achieved by the trailing-down model compared with the other windcatcher models at an opening angle of 90°. The total pressure drop and ventilation rates increase in all the new windcatcher models due to the increase in the opening angle from 60° to 90°. At identical conditions, with an opening angle of 90° and wind speed of 5 m/s, the trailing-down model achieved a higher pressure coefficient than the leading-down and central-up models by 20.55% and 37.37%, respectively. Furthermore, the trailing-down model could provide higher ventilation rates than the central-up and leading-down models by 31% and 42%, respectively. Finally, the trailing-down windcatcher model can be recommended as the best choice to provide natural ventilation at Taif City in Saudi Arabia.

CFD Modeling of Pressure Coefficients for a Natural Ventilation Study in an Experimental Low Rise Building

2013 ◽  
Author(s):  
Robel Kiflemariam ◽  
Cheng-Xian Lin
Keyword(s):  
Natural Ventilation ◽  
Pressure Coefficient ◽  
Wind Pressure ◽  
Analytical Models ◽  
Cfd Modeling ◽  
Engineering Practice ◽  
Pressure Coefficients ◽  
Wind Pressure Coefficient ◽  
Detailed Assessment ◽  
Ventilation Rates

Mean wind pressure coefficient (Cp) is one of the major input data for natural ventilation study using building energy simulation approach. Due to their importance, they need to be accurately determined. In current engineering practice, tables and analytical Cp models only give mostly averaged results for simpler models and configurations. Considering the limitation of tables and analytical models, Computational Fluid Dynamics (CFD) could provide a means for an accurate and detailed assessment of Cp. In this paper, we make use of a relatively high resolution, detailed experiments done at Florida Intentional University to validate a CFD modeling of the pressure coefficients Cp. The results show that existing CFD model has a good agreement with experimental results and gives important information of distribution of Cp values over the surface. The local values of the Cp are investigated. In addition, the CFD derived Cp and discharge coefficient (Cd) values are utilized in semi-analytical ventilation models in order to get a more accurate value of ventilation rates.

scholarly journals A natural ventilation "calculator": The challenge of defining a representative 'performance sketch' in practice and research

2021 ◽  
Author(s):  
Michael Donn ◽  
Nilesh Bakshi
Keyword(s):  
High Performance ◽  
Natural Ventilation ◽  
Sound Design ◽  
Wind Speeds ◽  
Building Shape ◽  
Net Zero ◽  
Complementary Role ◽  
Window Opening ◽  
Ventilation Rates

Too often in architecture and engineering, the simplicity in early design of the apparent guarantees of HVAC equipment manufacturers wins out over the complexity of estimating the effectiveness of natural ventilation even in Net Zero Buildings. The reality is many people in offices and schools find themselves sitting at a fixed desk, in full direct sun, with the cold draft from the HVAC equipment guaranteeing that on average they are comfortable. The drawing of blinds 'solves' the immediate sun problem, but not the quality of the air. Experience with 200+ students designing low energy, high performance naturally ventilated spaces each year over the past decade has demonstrated that the formulae that exist in the literature for early estimation of window opening size have potential if presented in an appropriate format to facilitate sound design decisions. This paper reports the evolution of that format to a calculation dashboard that facilitates accounting for: outdoor and indoor CO2 levels; wind speeds and frequencies of occurrence; coincidence of periods of calm with high outdoor temperatures; window effectiveness coefficients; single-sided vs cross-ventilation options; building shape and orientation; code minimum ventilation rates; and even infiltration. The paper focuses on the limitations of the approach and its potential complementary role in the future as a Quality Assurance tool for critiquing the output of CFD studies of natural ventilation.

scholarly journals A natural ventilation "calculator": The challenge of defining a representative 'performance sketch' in practice and research

2021 ◽  
Author(s):  
Michael Donn ◽  
Nilesh Bakshi
Keyword(s):  
High Performance ◽  
Natural Ventilation ◽  
Sound Design ◽  
Wind Speeds ◽  
Building Shape ◽  
Net Zero ◽  
Complementary Role ◽  
Window Opening ◽  
Ventilation Rates

Too often in architecture and engineering, the simplicity in early design of the apparent guarantees of HVAC equipment manufacturers wins out over the complexity of estimating the effectiveness of natural ventilation even in Net Zero Buildings. The reality is many people in offices and schools find themselves sitting at a fixed desk, in full direct sun, with the cold draft from the HVAC equipment guaranteeing that on average they are comfortable. The drawing of blinds 'solves' the immediate sun problem, but not the quality of the air. Experience with 200+ students designing low energy, high performance naturally ventilated spaces each year over the past decade has demonstrated that the formulae that exist in the literature for early estimation of window opening size have potential if presented in an appropriate format to facilitate sound design decisions. This paper reports the evolution of that format to a calculation dashboard that facilitates accounting for: outdoor and indoor CO2 levels; wind speeds and frequencies of occurrence; coincidence of periods of calm with high outdoor temperatures; window effectiveness coefficients; single-sided vs cross-ventilation options; building shape and orientation; code minimum ventilation rates; and even infiltration. The paper focuses on the limitations of the approach and its potential complementary role in the future as a Quality Assurance tool for critiquing the output of CFD studies of natural ventilation.

Numerical investigations on the effect of volute casing treatment for performance augmentation in a centrifugal fan

2021 ◽  
pp. 095440622110341
Author(s):  
Manjunath L Nilugal ◽  
K Vasudeva Karanth ◽  
Madhwesh N
Keyword(s):  
Total Pressure ◽  
Static Pressure ◽  
Numerical Study ◽  
Pressure Coefficient ◽  
Three Dimensional ◽  
Pressure Rise ◽  
Centrifugal Fan ◽  
Casing Treatment ◽  
Sliding Mesh ◽  
Optimum Configuration

This article presents the effect of volute chamfering on the performance of a forward swept centrifugal fan. The numerical analysis is performed to obtain the performance parameters such as static pressure rise coefficient and total pressure coefficient for various flow coefficients. The chamfer ratio for the volute is optimized parametrically by providing a chamfer on either side of the volute. The influence of the chamfer ratio on the three dimensional flow domain was investigated numerically. The simulation is carried out using Re-Normalisation Group (RNG) k-[Formula: see text] turbulence model. The transient simulation of the fan system is done using standard sliding mesh method available in Fluent. It is found from the analysis that, configuration with chamfer ratio of 4.4 is found be the optimum configuration in terms of better performance characteristics. On an average, this optimum configuration provides improvement of about 6.3% in static pressure rise coefficient when compared to the base model. This optimized chamfer configuration also gives a higher total pressure coefficient of about 3% validating the augmentation in static pressure rise coefficient with respect to the base model. Hence, this numerical study establishes the effectiveness of optimally providing volute chamfer on the overall performance improvement of forward bladed centrifugal fan.

scholarly journals Proposing Alternative Solutions to Enhance Natural Ventilation Rates in Residential Buildings in the Cfa Climate Zone of Rasht

2021 ◽  
Vol 13 (2) ◽  
pp. 679
Author(s):  
Roya Aeinehvand ◽  
Amiraslan Darvish ◽  
Abdollah Baghaei Daemei ◽  
Shima Barati ◽  
Asma Jamali ◽  
...  
Keyword(s):  
Natural Ventilation ◽  
Residential Buildings ◽  
Residential Building ◽  
Ventilation Rate ◽  
Humid Climate ◽  
The Sustainable Development ◽  
Passive Strategies ◽  
Development Goals ◽  
Ventilation Rates ◽  
Ventilation Systems

Today, renewable resources and the crucial role of passive strategies in energy efficiency in the building sector toward the sustainable development goals are more indispensable than ever. Natural ventilation has traditionally been considered as one of the most fundamental techniques to decrease energy usage by building dwellers and designers. The main purpose of the present study is to enhance the natural ventilation rates in an existing six-story residential building situated in the humid climate of Rasht during the summertime. On this basis, two types of ventilation systems, the Double-Skin Facade Twin Face System (DSF-TFS) and Single-Sided Wind Tower (SSWT), were simulated through DesignBuilder version 4.5. Then, two types of additional ventilation systems were proposed in order to accelerate the airflow, including four-sided as well as multi-opening wind towers. The wind foldable directions were at about 45 degrees (northwest to southeast). The simulation results show that SSWT could have a better performance than the aforementioned systems by about 38%. Therefore, the multi-opening system was able to enhance the ventilation rate by approximately 10% during the summertime.

scholarly journals Numerical Study on Damage Zones Induced by Excavation and Ventilation in a High-Temperature Tunnel at Depth

Energies ◽  
2021 ◽  
Vol 14 (16) ◽  
pp. 4773
Author(s):  
Jianyu Li ◽  
Hong Li ◽  
Zheming Zhu ◽  
Ye Tao ◽  
Chun’an Tang
Keyword(s):  
High Temperature ◽  
Lateral Pressure ◽  
Numerical Study ◽  
Pressure Coefficient ◽  
Fracture Morphology ◽  
In Situ Stress ◽  
Surrounding Rock ◽  
Geothermal System ◽  
Mechanical Coupling ◽  
Lateral Pressure Coefficient

Geothermal power is being regarded as depending on techniques derived from hydrocarbon production in worldwide current strategy. However, it has artificially been developed far less than its natural potentials due to technical restrictions. This paper introduces the Enhanced Geothermal System based on Excavation (EGS-E), which is an innovative scheme of geothermal energy extraction. Then, based on cohesion-weakening-friction-strengthening model (CWFS) and literature investigation of granite test at high temperature, the initiation, propagation of excavation damaged zones (EDZs) under unloading and the EDZs scale in EGS-E closed to hydrostatic pressure state is studied. Finally, we have a discussion about the further evolution of surrounding rock stress and EDZs during ventilation is studied by thermal-mechanical coupling. The results show that the influence of high temperature damage on the mechanical parameters of granite should be considered; Lateral pressure coefficient affects the fracture morphology and scale of tunnel surrounding rock, and EDZs area is larger when the lateral pressure coefficient is 1.0 or 1.2; Ventilation of high temperature and high in-situ stress tunnel have a significant effect on the EDZs scale; Additional tensile stress is generated in the shallow of tunnel surrounding rock, and the compressive stress concentration transfers to the deep. EDZs experiences three expansion stages of slow, rapid and deceleration with cooling time, and the thermal insulation layer prolongs the slow growth stage.

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.

Numerical Study of the Natural Ventilation in House: Cases of Three Rectangular Scale Models

2011 ◽  
Vol 4 (2) ◽  
pp. 137-154 ◽  
Author(s):  
Augustin Memeledje ◽  
Maurice Djoman ◽  
Alhassane Fofana ◽  
Aboudramane Gbane ◽  
Aboubakar Sako
Keyword(s):  
Natural Ventilation ◽  
Numerical Study ◽  
Scale Models

scholarly journals Performance Characteristics of Solid-Desiccant Evaporative Cooling Systems

Energies ◽  
2018 ◽  
Vol 11 (10) ◽  
pp. 2574 ◽  
Author(s):  
Ramadas Narayanan ◽  
Edward Halawa ◽  
Sanjeev Jain
Keyword(s):  
Air Conditioning ◽  
Natural Ventilation ◽  
Waste Heat ◽  
Numerical Study ◽  
Evaporative Cooling ◽  
Peak Load ◽  
Dew Point ◽  
Low Grade ◽  
Subtropical Climate ◽  
Cooling Systems

Air conditioning accounts for up to 50% of energy use in buildings. Increased air-conditioning-system installations not only increase total energy consumption but also raise peak load demand. Desiccant evaporative cooling systems use low-grade thermal energy, such as solar energy and waste heat, instead of electricity to provide thermal comfort. This system can potentially lead to significant energy saving, reduction in carbon emissions, and it has a low dew-point operation and large capacity range. Their light weight, simplicity of design, and close-to-atmospheric operation make them easy to maintain. This paper evaluates the applicability of this technology to the climatic conditions of Brisbane, Queensland, Australia, specifically for the residential sector. Given the subtropical climate of Brisbane, where humidity levels are not excessively high during cooling periods, the numerical study shows that such a system can be a potential alternative to conventional compression-based air-conditioning systems. Nevertheless, the installation of such a system in Brisbane’s climate zone requires careful design, proper selection of components, and a cheap heat source for regeneration. The paper also discusses the economy-cycle options for this system in such a climate and compares its effectiveness to natural ventilation.

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