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airflow
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Airflow in buildings with courtyards
, Article Iranian Journal of Science and Technology, Transaction B: Engineering ; Volume 29, Issue 2 , 2005 , Pages 187-206 ; 03601307 (ISSN) ; Bahadori, M. N ; Sharif University of Technology
2005
Abstract
The airflow rate through a two-story building with a courtyard, with and without trees, was estimated and compared with that of a building without a courtyard. The building and the courtyard were of square shapes, each 10 m to the side. The courtyard walls were 3m high and two separate trees of spherical, cylindrical and conical shapes were considered in the yard. The courtyard was directly south of the building and a wind angle of zero degree was considered when the wind was blowing directly from the south. It was found that when the wind angles were between 0 to ±90 degrees, the airflow rate through the building was reduced when compared with the building without a courtyard. The presence...
Development of an integrated model for airflow in building spaces
, Article Renewable Energy ; Volume 31, Issue 4 , 2006 , Pages 401-416 ; 09601481 (ISSN) ; Sattari, S ; Sharif University of Technology
2006
Abstract
In building energy simulation, an integrated modelling of airflow in the building needed. Therefore, in this paper two approaches are used for building energy simulation: zonal network for modelling of the building segments and Computational Fluid Dynamics (CFD) for modelling of the airflow. It is noted that a synchronize solution process is needed for the building and the CFD equation-sets. For this purpose an iterative procedure is used to corresponding solution of these equations. © 2005 Elsevier Ltd. All rights reserved
Rheological Evaluation of Ageing Properties of Modified Bitumens
, M.Sc. Thesis Sharif University of Technology ; Tabatabaee, Nader (Supervisor)
Abstract
Bitumen ageing is one of the principal factors causing the deterioration of asphalt pavements. Ageing is a complex process that is affected by different parameters.With the rapid growth of modified binders in road paving applications over the past twodecades, it is important to study the ageing properties of these binders. A number of laboratory methods are used tosimulatethe bitumenageing at various stages of the production and service of hot mix asphalt.Recent studies have shown that Superpave testing protocol does not fully address the ageing of modified binders. To study the ageing properties of modified binders, three different types of binder modifiers, plastomer, elastomer, and ground...
Numerical Modeling of Surgical Lights Effects on the Operating Room Enviroment
, M.Sc. Thesis Sharif University of Technology ; Saeeidi, Mohammad Hassan (Co-Advisor) ; Kazemzadeh Hannani, Siamak (Co-Advisor) ; Sani, Mahdi (Co-Advisor)
Abstract
Cleanrooms have a broad scope of applications from electronics, pharmacy, biotechnology to hospital industries, and are susceptible to fine and ultra-fine particles. In this work operating room in the category of hospital applications is chosen. Airborne particles in the operating room depends on many factors such as room geometry, inlet and outlet design, air displacement rate, obstacles, etc. Surgical light is one of the most critical obstacles in the operating room as it is upstream to the surgery zone. The study presented in this thesis aimed to numerically investigate the influence of radiation emitted from the medical lamps on the indoor airflow quality in operating room environment....
Automatic Detection of Sleep Arousal from EEG Signal Using Respiratory Information
, M.Sc. Thesis Sharif University of Technology ; Shamsollahi, Mohammad Bagher (Supervisor)
Abstract
Sleep is vital for physical and mental health, affecting neurocognitive, physiological, and psychopathology functions and performance. Arousals are linked with sleep and interrupt the sleep states, forming a sleep/arousal loop. Spontaneous arousals are part of a normal sleep/wake cycle. There are also different clinical conditions causing sleep fragmentation and arousals, including sleep apnea (obstructive, central, and mixed apnea), hypopnea, and non-apnea such as respiratory effort-related arousals (RERA), snoring, teeth grinding, and periodic leg movement.This research introduced a novel approach for automatic arousal detection inspired by extracting respiratory information from EEG...
Numerical simulation of unsteady airflow in a nasal cavity for various sizes of maxillary sinus opening in a virtual endoscopic surgery
, Article Respiratory Physiology and Neurobiology ; Volume 291 , 2021 ; 15699048 (ISSN) ; Amjadimanesh, H ; Faramarzi, M ; Sadrizadeh, S ; Abouali, O ; Sharif University of Technology
Elsevier B.V
2021
Abstract
Functional endoscopic sinus surgery (FESS) is performed to treat sinusitis when treatment with medication fails. In the present study, three different virtual maxillary sinus endoscopic surgeries were performed on a realistic 3-D computational model of the nasal cavity of an adult male under the supervision of a specialist. They included only uncinectomy, uncinectomy + 8mm Middle Meatal Antrostomy (MMA) and uncinectomy + 18 mm MMA. Simulations were performed for two human activity respiratory rates, including rest and moderate activities, and effects of different surgeries and respiratory rates on maxillary sinus were investigated. It was found that after endoscopic sinus surgery, the volume...
Effects of anti-vortex plates on air entrainment by free vortex
, Article Scientia Iranica ; Volume 20, Issue 2 , 2013 , Pages 251-258 ; 10263098 (ISSN) ; Borghei, S. M ; Sharif University of Technology
2013
Abstract
Free surface vortex and air entrainment are not favorable experiences in hydropower and pumping projects. While complete omission of vortex and air entrainment is not always cost effective, partially weakened free-surface vortex flow is more economical and practical. Hence, in this study, a comprehensive set of experiments were conducted to partially reduce vortex strength and air entrainment at vertical pipe intakes, using rectangular anti-vortex plates. This phenomenon results in increasing water discharge compared with a corresponding free-surface vortex for the same water depth, i.e. in cases of shaft spillway. The plates were used as singles and in pairs and placed symmetrically and...
Simulation approach to investigate the effect of the jet structure and air pressure on the performance of siro-jet spinning
, Article Fibres and Textiles in Eastern Europe ; Volume 92, Issue 3 , 2012 , Pages 46-50 ; 12303666 (ISSN) ; Hasani, M ; Sharif University of Technology
2012
Abstract
In this paper, the effects of different parameters on the hairiness of siro-jet spun yarns, such as the nozzle pressure, the distance between the front roller nip and inlet of the nozzle, and jet structure were investigated. Using the Taguchi method, it was concluded that the factor air pressure has the strongest effect and the factor distance between the front roller nip and inlet of the nozzle does not have a significant effect on the performance of the siro-jet spinning system in reducing yarn hairiness. A computational fluid dynamics model was developed to simulate the airflow pattern inside the jets. The effect of air pressure and the jet structure was simulated using Fluent 6.3...
On dynamic instability of a pressurized functionally graded carbon nanotube reinforced truncated conical shell subjected to yawed supersonic airflow
, Article Composite Structures ; Volume 153 , 2016 , Pages 938-951 ; 02638223 (ISSN) ; Asadi, H ; Wang, Q ; Sharif University of Technology
Elsevier Ltd
Abstract
The aeroelastic flutter characteristics of a functionally graded carbon nanotube reinforced composite (FG-CNTRC) truncated conical shell under simultaneous actions of a hydrostatic pressure and yawed supersonic airflow are scrutinized. The nonlinearity in geometry of the conical shell is considered in Green–Lagrange sense and the model is derived according to the Novozhilov nonlinear shell theory. The aerodynamic pressure is modeled based on the quasi-steady Krumhaar's modified supersonic piston theory by considering the effect of the panel curvature and flow yaw angle. Parametric studies are conducted to investigate the effects of boundary conditions, semi-vertex angle, distribution and...
Experimental investigation of a modular wind tower in hot and dry regions
, Article Energy for Sustainable Development ; Volume 39 , 2017 , Pages 21-28 ; 09730826 (ISSN) ; Bahadori, M. N ; Dehghani Sanij, A. R ; Sharif University of Technology
Elsevier B.V
2017
Abstract
Passive cooling systems such as wind towers or wind catchers can create thermal comfort for building residents in hot and dry regions. This paper introduces an experimental study of a modular design of wind tower called the modular wind tower with wetted surfaces. Air temperature, relative humidity (RH) and airflow velocity parameters were measured at different times and at points when the velocity of the ambient air was zero. The results show that the modular wind tower can decrease the air temperature by an average of 10 °C and increase the relative humidity of airflow in a building by approximately 36% on average. Additionally, the wind tower can create the airflow velocity entering the...
Numerical simulation of the effect of visitor's movement on bacteria-carrying particles distribution in hospital isolation room
, Article Scientia Iranica ; Volume 24, Issue 3 , 2017 , Pages 1160-1170 ; 10263098 (ISSN) ; Abbassi, A ; Saidi, M. H ; Sharif University of Technology
Abstract
The aim of this paper is to simulate numerically the airflow induced by a walking visitor and its effects on the contaminant transport and ventilation system effectiveness. To this end, the following models will be used in this study: the Lagrangian Discrete Random Walk (DRW) model to trace the motion of BCPs, the dynamic mesh method to simulate the visitor movement, and the Reynolds Averaged Navier-Stokes (RANS) model to solve the airflow. The validation results of the numerical method are in full agreement with the available experimental data in the literature. The findings of the present study indicate that the visitor's movement has remarkable effect on the basic airflow, and the...
Bubble-particle collision efficiency in rotating dissolved air flotation in paper-recycling wastewater treatment: experiments and modeling
, Article Desalination and Water Treatment ; Volume 260 , 2022 , Pages 52-62 ; 19443994 (ISSN) ; Amini Rad, H ; Borghei, S. M ; Vossoughi, M ; Rouhollahi, R ; Sharif University of Technology
Desalination Publications
2022
Abstract
Paper-recycling mills are serious environmental threats due to their high water consumption and highly polluted wastewater. Particles are the most common issue of paper-recycling wastewater, and their removal is of particular interest for recycling. Rotating dissolved air flotation (RDAF) is a system for separating particles, and the mixing zone of this system, where particles collide with air bubbles, is the most important part. As a widely used system in various industries, RDAF has rarely been investigated in the literature in terms of its optimization and efficiency improve-ment. In general, RDAF processes are basically the same as those of conventional dissolved air flotation (DAF)...
Prediction of particle deposition in the respiratory track using 3D-1D modeling
, Article Scientia Iranica ; Volume 19, Issue 6 , December , 2012 , Pages 1479-1486 ; 10263098 (ISSN) ; Dastanpour, R ; Saidi, M. S ; Pishevar, A. R ; Sharif University of Technology
2012
Abstract
Airflow simulation of the whole respiratory system is still unfeasible due to the geometrical complexity of the lung airways and the diversity of the length scales involved in the problem. Even the new CT imaging system is not capable of providing accurate 3D geometries for smaller tubes, and a complete 3D simulation is impeded by the limited computational resources available. The aim of this study is to develop a fully coupled 3D-1D model to make accurate prediction of airflow and particle deposition in the whole respiratory track, with reasonable computational cost and efficiency. In the new proposed method, the respiratory tree is divided into three parts to be dealt with using different...
Numerical investigation on the solid flow pattern in bubbling gas-solid fluidized beds: Effects of particle size and time averaging
, Article Powder Technology ; Vol. 264, issue , September , 2014 , p. 466-476 ; Salehi, M. S ; Molaei Dehkordi, A ; Sharif University of Technology
Abstract
The effects of particle size on the solid flow pattern in gas-solid bubbling fluidized beds were investigated numerically using two-fluid model based on the kinetic theory of granular flow. In this regard, the set of governing equations was solved using finite volume method in two-dimensional Cartesian coordinate system. Glass bead particles with mean sizes of 880. μm, 500. μm, and 351. μm were fluidized by air flow at excess gas velocities of 0.2. m/s and 0.4. m/s. For particle diameters of 880 and 351. μm, the predicted characteristic times for solid dispersion were 0.14. s and 0.15. s, respectively, while characteristic times for solid diffusivity were 1.68. ms and 0.75. ms in the same...
Effect of leading-edge roughness on boundary layer transition of an oscillating airfoil
, Article Scientia Iranica ; Volume 20, Issue 3 , 2013 , Pages 508-515 ; 10263098 (ISSN) ; Soltani, M. R ; Sharif University of Technology
2013
Abstract
A series of experiments were conducted to study the effect of leading-edge roughness on the state of the boundary layer of a wind turbine blade section using multiple hot-film sensors. The experiments involved static and dynamic tests, where airfoil motion was of plunging type oscillation. The application of surface grit roughness simulates surface irregularities that occur on the wind turbine blades. The measurements showed that increasing the angle of attack results in movement of transition locations toward the leading edge. Surface roughness moved the transition point toward the leading edge and caused early trailing edge turbulent separation, which resulted in reducing the effectiveness...
On the induced airflow and particle resuspension due to a falling disk
, Article Particulate Science and Technology ; Volume 31, Issue 2 , Jun , 2013 , Pages 190-198 ; 02726351 (ISSN) ; Saidi, M. H ; Ahmadi, G ; Kenney, S. M ; Taylor, J ; Sharif University of Technology
2013
Abstract
In this article, the induced airflow and the resultant particles resuspension due to a disk falling freely under the effect of gravity is studied using numerical and experimental approaches. The results showed that an axisymmetric vortex is generated on the disk tip as the disk falls and sheds after impacting the floor. While the effect of this ring vortex on the particles detachment from the floor is small, it has considerable influence on the dispersion of resuspended particles. The simulation results indicated that particles are mainly resuspended from an annular area beneath the disk tip where the generated wall shear is sufficiently high. As particles detachment is mainly controlled by...
Experimental investigation of air flow over domed roofs
, Article Iranian Journal of Science and Technology, Transaction B: Engineering ; Volume 33, Issue 3 , 2009 , Pages 207-216 ; 10286284 (ISSN) ; Bahador, M.N ; Sharif University of Technology
2009
Abstract
Domed roofs have been used in Iran and many other countries to cover large buildings such as mosques, shrines, churches, schools, etc. However their favorable thermal performance has allowed them to be employed in other buildings like bazaars, or market places in Iran. In this investigation, wind pressure coefficients were determined experimentally for a domed roof model in a boundary layer wind tunnel. The model was a 1/10 scale model of the dome of an old school in the city of Yazd, in the central desert region of Iran. The model included a number of windows at the collar of the dome, and a hole on its apex. A total of 48 pressure tabs were employed to measure the air pressure at various...
Experimental and numerical investigation of using pulsating heat pipes instead of fins in air-cooled heat exchangers
, Article Energy Conversion and Management ; Volume 181 , 2019 , Pages 653-662 ; 01968904 (ISSN) ; Bijarchi, M. A ; Shafii, M. B ; Sharif University of Technology
Elsevier Ltd
2019
Abstract
The goal of this study is the experimental and numerical investigation of using pulsating heat pipes (PHPs) as substitutes for fins in a typical air-cooled heat exchanger. Due to the small temperature difference between the cooling air and internal airflow in the case study, it was necessary that appropriate PHPs with the capability to work in small temperature difference conditions be investigated and an appropriate working fluid be selected. After reviewing various studies, R134a was selected as the best working fluid from the heat transfer standpoint. Afterward, a testing device was designed and fabricated. Additionally, in order to predict the behaviors of the main tubes with pulsating...
Thermal performance assessment of an evaporative condenser-based combined heat pump and humidification-dehumidification desalination system
, Article Desalination ; Volume 496 , 2020 ; Shafii, M. B ; Sharif University of Technology
Elsevier B.V
2020
Abstract
A new design for heat pump integrated humidification-dehumidification (HDH-HP) desalination cycles was proposed in the current experimental study. An evaporative condenser was designed and fabricated instead of a separate humidifier, heater, and air/water-cooled condensers find in previous HDH-HP systems. Meanwhile, the air dehumidification process in this work directly occurred inside the heat pump evaporator. The effect of several operating parameters such as ambient wet-bulb temperature, spraying saline water and airflow rates, compressor speed, superheat, and evaporator saturation temperature control modes of the electronic expansion valve (EEV) on freshwater production and GOR were...
Numerical simulation of buoyancy affected turbulent air flow in a room
, Article Scientia Iranica ; Volume 15, Issue 3 , 2008 , Pages 398-404 ; 10263098 (ISSN) ; Fathi Gishnegani, A ; Sharif University of Technology
Sharif University of Technology
2008
Abstract
In this paper, a three-dimensional steady state incompressible turbulent air flow is considered in a large single room. The buoyancy affected turbulent air flow is numerically simulated by solving governing equations. The turbulence modeling includes both κ - ε and zero-equation models and their results are compared to the experimental data. The paper reviews several aspects, such as displacement of radiator system performance, temperature and flow field distribution and comfort conditions. The results show that the best temperature distribution and comfort condition are obtained when the radiator is installed under the window and its height is equal to or greater than that of the window. ©...