| 1. |
- Akbari, Keramatollah, 1961-, et al.
(author)
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Effects of Heat Recovery Ventilation Systems on Indoor Radon
- 2012
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In: PROCEEDINGS OF ECOS 2012 - THE 25TH INTERNATIONAL CONFERENCE ON EFFICIENCY, COST, OPTIMIZATION, SIMULATION AND ENVIRONMENTAL IMPACT OF ENERGY SYSTEMS. ; , s. 1-10
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Conference paper (peer-reviewed)abstract
- A heat recovery ventilation system enables us to control indoor conditions such as ventilation rate,temperature, relative humidity and pressure difference. These environmental conditions affect indoor radonlevels.Computational fluid dynamics (CFD) is a powerful tool for predicting and visualizing radon content and indoorair quality and is cost effective in comparison with other methods such as full scale laboratory and gas tracetechniques.In this study a mechanically balanced ventilation system and a continuous radon monitor (CRM) were usedto measure the indoor ventilation rate and radon levels. In a numerical approach the FLUENT CFD packagewas used to simulate radon entry into the building and effects on indoor air conditions.The effects of different ventilation rates, indoor temperature and relative humidity on indoor radonconcentrations were investigated in a one family detached house in Stockholm. Results of numerical studiesindicated that changes of ventilation rate, indoor temperature and moisture by means of ventilation systemshave significant effects on indoor radon content. Ventilation rate was inversely proportional to indoor radonconcentration. Minimum radon levels were estimated in the range of thermal comfort, i.e. at 21 andrelative humidity between 50-70%.The analytical solution was used to validate numeric results at 3 distinct air change rates. Comparisonsbetween numerical and analytical results showed good agreement but there was poor agreement betweensimulations and measurement results due to the short measuring period.
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| 2. |
- Akbari, Keramatollah, 1961-
(author)
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Impact of Radon Ventilation on Indoor Air Quality and Building Energy saving
- 2009
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Licentiate thesis (other academic/artistic)abstract
- Industrial living is caused much people do live and work in closed and confined places; offices and residential buildings. This is why in this new world more fresh air which is generally provided by forced ventilation plays a vital role in living of human being. Furthermore because of many different indoor pollutants, like radon and artificial pollutants, the amount of fresh air and in turn the energy consumption has increased. This energy consumption related to ventilation has reached up to about 30 percent of energy used of building section. So making interaction between indoor air quality (IAQ) and optimization of energy saving is a necessary work. Radon as a natural pollutant is occurred in environment and in many countries threatens people health whereas is called the second causes of cancer. For reducing radon concentration in residential building at the acceptable level forced ventilation is used usually. Ventilation can improve IAQ but in the other side would increase the energy consumption in building sector and just now the contribution of ventilation exceeds up 50 percent of building sector's share. The aim of this thesis is to study the impact of ventilation on indoor radon by using Computational Fluid Dynamics (CFD) to achieve indoor air quality and energy efficiency. Application of CFD as a new technology, because of its cost and time savings, and on the other side, of its flexibility and precision is increasingly grown and can be used as a very important and valuable tool for the prediction and measurement of radon distribution in a ventilated building . Currently, measurement techniques and proposed standards and regulations of indoor pollutants and ventilation, particularly related to indoor radon cannot be able to provide a secure, safe and energy efficient indoor climate. This is why the indoor airflow distribution is very complex and with changing building geometry and operation condition, the treatment of air flow pattern, substantially would be changed, whereas the rules are usually independent of the buildings features. Furthermore, the indoor standards and regulations are based on average amount of pollutants in a room, whereas the pollutant distributions aren't identical and are varied throughout the room. Then the current techniques aren't so exactly valuable and acceptable. From different methods which is privilege to control pollutants, ventilation method is applicable in existing buildings. Designing effective ventilation can reduce radon concentration to very level low with regarding energy conservation remarks. This thesis presents results from simulation studies on ventilation and radon mitigation in residential buildings, in view points of indoor air quality and energy savings. The CFD technique is applied to predict, visualize and calculate of mixture radon-air flow. The distribution of indoor radon concentration, air velocity and room temperature also have considered together for achieving indoor air quality and energy saving. The results are also compared with the experimental data and related previous works. It was found that with increasing ventilation rate, the radon concentration is decreased, but the location of ventilation system is also important. From the simulation results, it is observed that within the ventilated room, there are some zones, which are good for living and somewhere is more polluted. The traditional radon detectors basically show the average value of radon content in 1m3 of air. That is why detector measuring is not exact and safe. Simulation results proved that floor heat can be supported ventilation effect and speed up the mixture movement. Floor heating reinforces the buoyancy effect, which is useful to reduce radon content in the floor (seating area) and then lower ventilation rate can be applied.
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| 3. |
- Akbari, Keramatollah, 1961-, et al.
(author)
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Influence of indoor air conditions on radon concentration in a detached house
- 2013
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In: Journal of Environmental Radioactivity. - Elsevier : Elsevier BV. - 0265-931X .- 1879-1700. ; 116, s. 166-173
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Journal article (peer-reviewed)abstract
- Radon is released from soil and building materials and can accumulate in residential buildings. Breathing radon and radon progeny for extended periods hazardous to health and can lead to lung cancer. Indoor air conditions and ventilation systems strongly influence indoor radon concentrations. This paper focuses on effects of air change rate, indoor temperature and relative humidity on indoor radon concentrations in a one family detached house in Stockholm, Sweden.In this study a heat recovery ventilation system unit was used to control the ventilation rate and a continuous radon monitor (CRM) was used to measure radon levels. FLUENT, a computational fluid dynamics (CFD) software package was used to simulate radon entry into the building and air change rate, indoor temperature and relative humidity effects using a numerical approach.The results from analytical solution, measurements and numerical simulations showed that air change rate, indoor temperature and moisture had significant effects on indoor radon concentration. Increasing air change rate reduces radon level and for a specific air change rate (in this work Ach = 0.5) there was a range of temperature and relative humidity that minimized radon levels. In this case study minimum radon levels were obtained at temperatures between 20 and 22 °C and a relative humidity of 50-60%
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| 4. |
- Akbari, Keramatollah, 1961-, et al.
(author)
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Numerical Simulation of Radon Transport and Indoor Air Conditions Effects
- 2012
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In: International journal of scientific and Engineering Research. - 2229-5518. ; 3:6, s. 1-10
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Journal article (peer-reviewed)abstract
- Computational fluid dynamics (CFD) is a powerful tool for predicting and visualizing radon content and indoor air quality and is cost effective in comparison with other methods such as full scale laboratory and gas trace techniques. The intention of this article is to use CFD to simulate indoor radon distribution and ventilation effects. 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 effects on indoor air conditions. The effects of different ventilation rates, indoor temperature and relative humidity on indoor radon concentrations were investigated in a one family de-tached house in Stockholm. Results of numerical studies indicated that changes of ventilation rate, indoor temperature and moisture by means of ventila-tion systems have significant effects on indoor radon content. Ventilation rate was inversely proportional to indoor radon concentration. Minimum radon levels were estimated in the range of thermal comfort, i.e. at 21 and relative humidity between 50-70%. The analytical solution was used to validate numeric results at 3 distinct air change rates. Comparisons between numerical and analytical results showed good agreement but there was poor agreement between simulations and measurement results due to the short measuring period.
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| 5. |
- Akbari, Keramatollah, et al.
(author)
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Simulation of Radon Mitigation in Residential Building
- 2008
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In: Proceedings of SIMS 2008. - 9788257946326 ; , s. 177-183
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Conference paper (peer-reviewed)abstract
- There are many indoor pollutants in the residentia lbuildings. Of those radon is a major and harmful indoor pollutant in most countries. Radon sometimes entries to the house through building materials. High insulation and tightness in order to increase energy efficiency and to lower energy costs is led to the indoor air quality problems. Ventilation is a good method to dilute radon contaminant and maintain indoor air quality. The more fresh air is brought into the indoor environment, the better the indoor air quality can be achieved, if the fresh air comes from non polluted ambient source. However ventilation can consume a lot of energy (currently 29-59% of energy building use), especially in cold climate same as Sweden, energy consumption could be much more. Though for coping with high energy consumption the building tightness is acted very well, but for ventilation plays against. This contradiction makes a poor indoor air quality. The aim of this paper is to simulate and visualize radon treatment and mechanical ventilation rates for achieving to indoor air quality. The Fluent (CFD) program software is employed for simulation.
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| 6. |
- Akbari, Keramatollah, et al.
(author)
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Simulation of ventilation effects on indoor radon
- 2013
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In: Management of environmental quality. - : Emerald. - 1477-7835 .- 1758-6119. ; 24:3, s. 394-407
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Journal article (peer-reviewed)abstract
- 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. Findings: Results of the numerical study indicated that indoor pressure created by ventilation systems and infiltration through doors or windows have significant effects on indoor radon content. The location of vents was found to affect the indoor radon level and distribution. Research limitations/implications: It may be possible to improve any discrepancies found in this article by using a more refined representation of grids and certain boundary conditions, such as pressure and temperature differences between inside and outside and by considering some real situations in residential buildings and external situations. Originality/value: From the viewpoints of indoor air quality (IAQ) and energy savings, ventilation has two opposing functions; on the positive side it enhances IAQ and the establishment of thermal comfort, and on the negative side it increases energy consumption. This paper describes the search for a solution to cope with this contradiction.
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| 7. |
- Akbari, Keramatollah, et al.
(author)
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Simulation of ventilation effects on indoor radon in a detached house
- 2012
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In: WSEAS Transactions on Fluid Mechanics. - 1790-5087. ; 7:4, s. 146-155
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Journal article (peer-reviewed)abstract
- CFD is widely used in indoor air quality, air flow pattern, indoor pollutant distribution and thermal comfort as a cost effective and powerful tool and it can be used to predict, estimate and visualize the indoor radon level. The intention of this article is to use computational fluid dynamics (CFD), as a standalone tool to simulate indoor radon distribution and ventilation effects. This technique can be used to predict and visualize radon content and indoor air quality throughout a one family detached house in Stockholm. In this study a mechanical balanced ventilation system and a continuous radon monitor (CRM) were also used to measure the indoor ventilation rate and radon levels. In numerical approach the FLUENT, CFD package was used to simulate radon entry into the building and ventilation effects. Results of numerical study indicated that indoor pressure made by means of ventilation systems and infiltration through door or window has significant effects on indoor radon content. It is observed that the location of vents can affect the indoor radon level, particularly in breathing (seating) zone. The analytic solution is used to validate numeric results at 3 distinct air change rates. The comparison amongst analytical, numerical and measurement results shows close agreement.
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| 8. |
- Farrokh, Mohammad, 1964-, et al.
(author)
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DIASPORIC BAUXITE DIGESTION PROCESS SIMULATION
- 2010
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Conference paper (other academic/artistic)abstract
- The alumina digestion process in the Bayer overall process like the other hydrometallurgical processes is under the effect of various factors and the control and optimization of quality and efficiency of the process and also reducing the energy consumption are of prime importance. Process simulation provides the possibility to investigate the impact of various factors and study the optimum conditions for obtaining the desired quality and reducing the energy consumption and environmental impact. In the digestion unit, the high pressure diasporic bauxite slurry, a mixture of ground bauxite, lime and caustic liquor, is decomposed. The bauxite slurry is preheated in the high pressure tube pre-heater and then is heated up to the decomposition temperature in the furnace. The dissolution takes place in the tubular digesters and resulting product, aluminate slurry, passes through the expanding stage, including 11 flash tanks to recover the thermal energy. In this paper the thermodynamic simulation consecutive stages of the digestion unit process including the property methods and the evaluation and verifying the simulation results against their accordance with the real conditions are studied. The obtained results showed that the outputs of the simulation have good and acceptable accordance with the empirical data. Using the simulation program; the results of some case studies showed that in the current situation, less than 70% of the energy generated in the dissolution process is directed to the pre-heaters. Also more than 30% of vapor generated in the dissolution process is dissipated and wasted. By using the vapor generated in the last two flash tanks, the efficiency of energy recycling will be increased and thus the water waste and environmental pollution will be decreased considerably.
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| 9. |
- Farrokh, Mohammad, et al.
(author)
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Extracting alumina from bauxite ore in Jajarm process simulation using aspen software
- 2008
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In: PROCEEDINGS FROM SCIENTIFIC CONFERENCE ON GREEN ENERGY AND IT. - 9789197749329 ; , s. 142-157
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Conference paper (peer-reviewed)abstract
- Installed DCS system in Jajarm alumina production factory in Iran, help to us for transferred the signals from equipments to simulators. The simulators can help to operator for control, monitoring and training. Authors have tried to find a new simulator using ASPEN plusTM software and write a new protocol for discussed tasks.Aspen PlusTM by Aspen Technology is one of the major process simulators that arewidely used in alumina process industries today. It specialises on steady-state analysis.For implementation, simulation and interpretive of the alumina process flowsheet in jajarm factory was used from the Aspen Plus simulator. We have tried to be able to provide a list key operating and design parameters and equipment selection criteria for a limited set of unit operations and processes. And so for determinanation the economic potential of a process and to identify the operational variables that affect the economics we have studied the process and flowsheets.Using the general information of factory, process informations same as temperature, measuredpressure and so PFD, cinitic informations and finallay clin, bauxite and sodium sulphateinforamations we have design a new simulation method for digestion and control process in Jajarmfactory. The process has implemented on LCR1,PU08, PU10 and PU11 units.
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| 10. |
- Farrokh, Mohammad, et al.
(author)
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Modeling and Simulation of a DiasporeTubular Digestion Process
- 2013
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In: International Journal of Simulation and Process Modelling. - 1740-2123 .- 1740-2131. ; 33:2, s. 126-133
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Journal article (peer-reviewed)abstract
- A simulation model is developed to predict the performance of a tubular digestion process of a low alumina/silica ratio diaspore bauxite type. The electrolyte - NRTL property method is used to calculate the equilibrium and thermodynamic properties of the slurry. The Aspen Plus simulator has been employed to solve the reaction and thermodynamic submodels. The model was validated with several sets of the industrial experimental data in terms of the flash tanks temperatures and close agreement was found. The simulation model has been utilized by the R&D department to predict the digestion process behaviour at various operation conditions. One practical output of this work is suggestion for a new design to increase the vapour and thermal energy recovery in the digestion process unit. As a result, the exhaust vapour from the last flash tank was directed to a new pre-heater section. The industrial output has been confirmed by the energy department that has decreased 8% in the furnace fuel consumption and leads to an increase of water recovery in the digestion unit.
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