Search for: ventilation
Total 73 records
Numerical–analytical assessment of fire and ventilation interaction in longitudinally ventilated tunnels using jet fans, Article Heat Transfer Engineering ; Volume 38, Issue 5 , 2017 , Pages 523-537 ; 01457632 (ISSN) ; Afshin, H ; Farhanieh, B ; Sharif University of Technology
Taylor and Francis Ltd 2017
Longitudinal ventilation system is a frequent method of tunnel ventilation which is commonly implemented by use of jet fans. In most studies on longitudinal ventilation application, the effect of fire on its upstream is neglected and a constant-velocity flow is considered in the tunnel entrance. In this paper, fire consequences on ventilation system performance are investigated. It is noticed that airflow induced in tunnel declines as the fire intensifies. High reductions up to about 50% are observed and are attributed to two main phenomena; elevated downstream resistance and fire plume blockage. These effects are combined to form a parameter named fire pressure loss (FPL). An analytical...
Article Scientia Iranica ; Volume 11, Issue 4 , 2004 , Pages 398-404 ; 10263098 (ISSN) ; Sharif University of Technology
Sharif University of Technology 2004
The present study is undertaken to calculate the rate of change of pressure and residual air mass in die casting for vacuum venting under choked flow conditions. In these calculations, the influence of friction factor, due to roughness and vent air velocity change through the Mach number, has been taken into account. The results show that there is a critical area ratio below which the pressure and vent inlet Mach number increase with time and above which decrease with time. In addition, for an area ratio less than the critical area, the rate of change of residual air mass seems to be more changed at the late stages than at the early stages of the filling time. The picture is reversed for a...
Article International Journal of Ventilation ; Volume 14, Issue 3 , Mar , 2015 , Pages 303-320 ; 14733315 (ISSN) ; Afshin, H ; Farhanieh, B ; Sharif University of Technology
VEETECH Ltd 2015
Longitudinal ventilation is a common technique for smoke management during a fire accident within tunnels. In this paper, fire and smoke movement behaviour in longitudinally ventilated tunnels is investigated focusing on critical ventilation velocity. Firstly, critical velocity (VC) is evaluated for different heat release rates and results are compared and verified with model scale experimental data. Secondly, two fire scenarios inside tunnels with different cross sections are arranged and the reliability of some existing correlations for VC is explored. Results illustrate that using a combined geometric scale rather than the traditional single length-scale ones results in better estimation...
Experimental study of the ventilation arrangement’s effect on particle concentration in a surgery room, Article 7th International Conference on Fluid Flow, Heat and Mass Transfer, FFHMT 2020, 15 November 2020 through 17 November 2020 ; 2020 , Pages 151-1-151-4 ; Mousemi, A ; Alotaibi, S. A ; Khademi, A ; Sharif University of Technology
Avestia Publishing 2020
Hospital ventilation is defined as the providing of fresh and clean air stream in hospital wards or patients’ room to provide and establish a healthy environment for personnel’s and patient’s breath, reducing concentration of produced contaminations in hospital and removing them from clean spaces. Thus, it can prevent spread of airborne infections among patients, people who works around and more importantly, outside the hospital. Hospital infections have a huge influence on mortality of the patients in which respiratory tract infections and surgical wound infections plays a major role. Depending on the quality and the mass flow rate of the exploited air, cleanness of a surgery room can be...
M.Sc. Thesis Sharif University of Technology ; Farhanieh, Bijan
One of the methods of drilling coal mines is mine blasting (drilling with explosives). In this method, explosives such as dynamite are used to excavate the mine and destroy the coal seams. During this type of drilling, in addition to dust, dangerous toxic gases are also produced, so quick and proper ventilation of mine tunnels is necessary in this type of drilling.Depending on the type of mining, the required ventilation system may be different. For example, if the drilling method is long-term method, the mine ventilation is of the U type, but if the mine drilling is the sub-level caving type, auxiliary ventilation is used.In this study, the method of mining is sub-level caving, so that one...
Article Applied Mechanics and Materials ; Vol. 527 , 2014 , Pages 146-151 ; ISSN: 16609336 ; Kazemipour, A ; Afshin, H ; Farhanieh, B ; Sharif University of Technology
In this study, the influence of volumetric flow rate and inclination angle of air jet is evaluated on the performance of a Saccardo ventilation system in a straight rectangular tunnel in case of fire. Simultaneous effects of volumetric flow rate and inclination angle of jet exiting the Saccardo nozzle on the behavior of smoke plume is considered by studying the structure of velocity profile before the fire source. It is found that this factor has a remarkable influence on the behavior of smoke plume and therefore, on the temperatures experienced near the fire. Besides, the influence of tunnel slope on the performance of the Saccardo system to sweep the plume is investigated. It is shown that...
Article Scientia Iranica ; Volume 23, Issue 2 , 2016 , Pages 678-684 ; 10263098 (ISSN) ; Forughi, A. F ; Vesali, F ; Mahmoodabadi, M. S ; Sharif University of Technology
Sharif University of Technology 2016
Proper orientation of walkways, based on regional winds and local shade, provides good control over walkway ventilation. The architecture of the old town of Sirjan had experimentally orientated the city's walkways in such a manner that the shadows in the walkways produced the maximum possible natural ventilation in this hot and dry town. This study has focused on the optimum design of Sirjan city considering a natural ventilation mechanism. At first, a typical walkway with certain geometric parameters is considered. Then, considering the symmetry of the shadows cast in the walkway, the natural ventilation rate is investigated at 7 different angles and at 15° intervals. The problem is modeled...
Article 12th International Conference on Indoor Air Quality and Climate 2011 ; Volume 4 , 2011 , Pages 3194-3199 ; 9781627482721 (ISBN) ; Ahmadi, G ; Saidi, M. H ; Sharif University of Technology
Surgical site infection (SSI) is one of the important infectious problems in hospitals. It is well known that appropriate ventilation strategy is most effective way to control bacteria-carrying airborne particles responsible for SSI. With considerable improvement in the computational capacity of computers, computational fluid dynamics (CFD) technique has been widely used to study the indoor airflow and contaminant dispersion over the enclosures. In this research, the effect of inlet air velocity on the ultra-clean ventilation system performance is investigated Eulerian-Lagrangian numerical approach. The results show that surgical wound contamination may be highly affected by inlet velocity....
M.Sc. Thesis Sharif University of Technology ; Kazemzadeh Hannani, Siamak
The purpose of present work is to study the effect of different parameters on the solar chimney used in ventilation. Experimental model and numerical model were used to achieve this goal. First, the model was numerically analyzed by Fluent software using Boussinesq approximation. The results of numerical modeling were validated by the empirical model. Finally, the numerical model can be used to investigate the effects of parameters which modeling is not possible by the empirical model for any reason. Experimental modeling was performed on a chimney with height and width of 180 and 62 cm, respectively. The thickness and angle of chimney in both experimental and numerical methods varied from 5...
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
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...
M.Sc. Thesis Sharif University of Technology ; Farhanieh, Bijan
Suitable design of ventilation systems is one of the strategies to deal with phenomenon like fire in tunnels. For design a ventilation system first should recognize fire and effective parameters on it. So we need a good modeling of fire. Whereas the aim of this research is investigate the critical ventilation velocity, we only studying the effects of fire. Two effective parameter of fire is the rate of heat release and rate of smoke release, therefore with studying physics and nature of fire, obtain these parameters. After calculation of fire effects, we should investigate the effective parameters on critical ventilation velocity. The critical velocity is the air flow that helps prevent...
M.Sc. Thesis Sharif University of Technology ; Farhanieh, bijan
Due to growth of the number of passengers in subway transportation systemsthe capacity of the metro stations are on the rise.The generated heat loads in subway line shall be increased by thegrowth of the its capacity. As a result, current subway ventilation systems cannot provide comfort conditions for passengers. Nowadays, modern ventilation systems are designedto improve ventilation performance and to create suitable thermal conditions. Among of these, the under platform andover track exhaust systems and use of platform screen doors can be Cited. The aim of this study is three-dimensional simulation of air flow in modern ventilation systems of subway stations. Numerical simulations are in...
Evaluation and Simulation of Tunnel Mid-shaft Effects on the Natural and Normal Ventilation Performance in a Subway Tunnel, M.Sc. Thesis Sharif University of Technology ; Farhanieh, Bijan
Necessity of a public transport network, environmental protection and a highly land cost in urban areas have increased the desire for underground transportation systems. On the other hand, ventilation system design should be done precisely specially for longer tunnels, large undergrounds spaces and crowded places. Rate of energy reduction for vent systems operation is dependent on their proper implementation. Tunnel design efficiently is influenced by ventilation system. The tunnel mid shaft is complementary part of the underground railway systems that is required for exchange air between the tunnel and the railway station with ambient fresh air. An important application of the tunnel mid...
Article ASME 2012 Gas Turbine India Conference, GTINDIA 2012, 1 December 2012 through 1 December 2012 ; December , 2012 , Pages 265-270 ; 9780791845165 (ISBN) ; Parizi, P. N ; Taheri, R ; Sharif University of Technology
Because of their high performance and unique abilities like producing none-rotating wake, Counter Rotating Propellers (C.R.P.) are being used in many advanced propulsion or ventilation systems. But due to complicated design procedure of C.R.P. fans up to now it was not possible to apply the concept in reversible systems. For the first time in this research, a new method presented to design a reversible counter rotating propeller system. This method is based on designing a basic C.R.P. by a reliable edition of blade element theory to achieve maximum performance in main rotating course and then to optimize it in order to have almost same performance in reverse rotating course. After expressing...
Article Management of Environmental Quality ; Volume 24, Issue 3 , 2013 , Pages 394-407 ; 14777835 (ISSN) ; Mahmoudi, J ; Ghanbari, M ; Sharif University of Technology
Purpose: The purpose of this paper is to describe the use of computational fluid dynamics (CFD) to simulate indoor radon distribution and ventilation effects. This technique was used to predict and visualize radon content and indoor air quality in a one-family detached house in Stockholm. The effects of intake fans, exhaust fans and doors on radon concentration were investigated. Design/methodology/approach: In this study a mechanically balanced ventilation system and a continuous radon monitor (CRM) were used to measure the indoor ventilation rate and radon levels. In a numerical approach, the FLUENT CFD package was used to simulate radon entry into the building and ventilation effects....
Article Advanced Materials Research, 16 September 2011 through 18 September 2011 ; Volume 433-440 , Septembe , 2012 , Pages 983-991 ; 10226680 (ISSN) ; 9783037853191 (ISBN) ; Maddahin, R ; Afshin, H ; Farhanie, B ; Sharif University of Technology
Development of cities as well as population growth causes to development of public transportation especially subway lines. The high capacity besides the high speed in transportation makes them the popular transportation system. Fire is the one of the most important issues that may occur in subways. The difference in flame size, emissionheat, smoke and pollutants generation of subway fires attracts an especial attention of fire investigators. The emergency ventilation of subways in the case of fire should have the ability of discharging heat, smoke and pollutants from passenger escape route and preparing a safe place for a specific duration. The optimal performance of emergency ventilation...
Article Journal of Applied Fluid Mechanics ; Volume 9, Issue 1 , 2016 , Pages 279-292 ; 17353572 (ISSN) ; Pourghasemi, M ; Afshin, H ; Farhanieh, B ; Sharif University of Technology
Isfahan University of Technology
Fire is a potential hazard in public transportation facilities such as subways or road tunnels due to its contribution to high number of deaths. To provide an insight into fire development behavior in tunnels which can serve as the basis for emergency ventilation design, model-scale railcar fire is explored numerically in this research. Fire growth and its spread are investigated by analyzing the HRR curve as the representative of fire behavior in different stages. Fire development has been predicted through a new approach using an Arrhenius-based pyrolysis model, established to predict the decomposition behavior of solid flammable materials exposed to heat flux. Using this approach,...
Computer modeling of the operating room ventilation performance in connection with surgical site infection, Article Scientia Iranica ; Volume 27, Issue 2 , 2020 , Pages 704-714 ; Saidi, M. H ; Ahmadi, G ; Sharif University of Technology
Sharif University of Technology 2020
The primary source of surgical site infection is the deposition of flakes released from the exposed skin of surgical staff or the patient on the exposed surgical wound. In this study, a computational model for simulating air ow and thermal conditions in an operating room is developed, and transport and deposition of particulate contaminants near the wound are analyzed. The results show the formation of a thermal plume over the wound tissue, which is typically at a higher temperature than the surrounding. The thermal plume protects the wound from the deposition of contaminants. In addition, the computational model predicts an optimum value for the inlet air velocity that is mainly maintaining...
Article 2005 ASME Fluids Engineering Division Summer Conference, Houston, TX, 19 June 2005 through 23 June 2005 ; Volume 1 PART A , 2005 , Pages 741-749 ; 0791841987 (ISBN); 9780791841983 (ISBN) ; Yazdani, M ; Sharif University of Technology
In this work, numerical simulation is used to study the stability enhancement of high speed supercavitating Shkval missile. Although supercavitation is known as one of the most effective methods for drag reduction, producing the cavity, either by ventilation or by cavitator at front of the body, may cause some instabilities on cavity surface and thus on the projectile's motion. Therefore removing these instabilities comes as an important point of discussion. First of all, we calculate the sources of instabilities and measure respective forces and then present some approaches that significantly reduce these instabilities. One of these methods that could produce more stable supercavities is...
M.Sc. Thesis Sharif University of Technology ; Roshandel, Ramin ; Shafiei, Mohammad Behshad
In the last three decades, the world has experienced enormous increases in energy consumption as a consequence of the economic and population growth. This causes renewable energy and energy recovery to become a requirement in building designs rather than option. A direct expansion (DX) air conditioning system is an efficient way to supply fresh and dehumidified air to a built environment a long side it plays a key role in preventing the spread of respiratory diseases. To improve the efficiency of a conventional DX system in hot and humid regions, fresh air dehumidification and conditioning systems with energy recovery measures are the key equipment to reach such a goal. To achieve this goal...