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  • 1.
    Akbari, Keramatollah
    et al.
    Mälardalen University, School of Sustainable Development of Society and Technology.
    Mahmoudi, Jafar
    Mälardalen University, School of Sustainable Development of Society and Technology.
    Effects of Heat Recovery Ventilation Systems on Indoor Radon2012In: PROCEEDINGS OF ECOS 2012 - THE 25TH INTERNATIONAL CONFERENCE ON EFFICIENCY, COST, OPTIMIZATION, SIMULATION AND ENVIRONMENTAL IMPACT OF ENERGY SYSTEMS / [ed] ECOS, 2012, , p. 10p. 1-10Conference paper (Refereed)
    Abstract [en]

    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 radon

    levels.

    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.

    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 detached house in Stockholm. Results of numerical studies

    indicated that changes of ventilation rate, indoor temperature and moisture by means of ventilation 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.

  • 2.
    Akbari, Keramatollah
    et al.
    Mälardalen University, School of Sustainable Development of Society and Technology.
    Mahmoudi, Jafar
    Mälardalen University, School of Sustainable Development of Society and Technology.
    Numerical Simulation of Radon Transport and Indoor Air Conditions Effects2012In: International journal of scientific and Engineering Research, ISSN 2229-5518, Vol. 3, no 6, p. 1-10Article in journal (Refereed)
    Abstract [en]

    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.

  • 3.
    Akbari, Keramatollah
    et al.
    Mälardalen University, School of Sustainable Development of Society and Technology.
    Mahmoudi, Jafar
    Simulation of Radon Mitigation in Residential Building2008Conference paper (Refereed)
  • 4.
    Akbari, Keramatollah
    et al.
    Mälardalen University, School of Business, Society and Engineering.
    Mahmoudi, Jafar
    Mälardalen University, School of Business, Society and Engineering.
    Ghanbari, M.
    Sharif University of Technology, Tehran, Iran .
    Simulation of ventilation effects on indoor radon2013In: Management of environmental quality, ISSN 1477-7835, E-ISSN 1758-6119, Vol. 24, no 3, p. 394-407Article in journal (Refereed)
    Abstract [en]

    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.

  • 5.
    Akbari, Keramatollah
    et al.
    Mälardalen University, School of Sustainable Development of Society and Technology.
    Mahmoudi, Jafar
    Mälardalen University, School of Sustainable Development of Society and Technology.
    Ghanbari, Mahdi
    Sharif University of Technology, Tehran, Iran.
    Influence of indoor air conditions on radon concentration in a detached house2013In: Journal of Environmental Radioactivity, ISSN 0265-931X, E-ISSN 1879-1700, ISSN ISSN 0265-931X, EISSN 1879-1700, Vol. 116, p. 166-173Article in journal (Refereed)
    Abstract [en]

    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%

  • 6.
    Akbari, Keramatollah
    et al.
    Mälardalen University, School of Business, Society and Engineering.
    Mahmoudi, Jafar
    Mälardalen University, School of Business, Society and Engineering.
    Öman, Robert
    Mälardalen University, School of Business, Society and Engineering.
    Simulation of ventilation effects on indoor radon in a detached house2012In: WSEAS Transactions on Fluid Mechanics, ISSN 1790-5087, Vol. 7, no 4, p. 146-155Article in journal (Refereed)
    Abstract [en]

    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.

  • 7.
    Farrokh, Mohammad
    et al.
    Mälardalen University, School of Business, Society and Engineering.
    Mahmoudi, Jafar
    Mälardalen University, School of Business, Society and Engineering.
    DIASPORIC BAUXITE DIGESTION PROCESS SIMULATION2010Conference paper (Other academic)
    Abstract [en]

    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.

  • 8.
    Farrokh, Mohammad
    et al.
    Mälardalen University, School of Sustainable Development of Society and Technology.
    Mahmoudi, Jafar
    Extracting alumina from bauxite ore in Jajarm process simulation using aspen software2008In: PROCEEDINGS FROM SCIENTIFIC CONFERENCE ON GREEN ENERGY AND IT / [ed] Erik Dahlquist, Malardalen University, 2008, p. 142-157Conference paper (Refereed)
    Abstract [en]

    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.

  • 9.
    Farrokh, Mohammad
    et al.
    Mälardalen University, School of Business, Society and Engineering.
    Mahmoudi, Jafar
    Mälardalen University, School of Business, Society and Engineering.
    THERMODYNAMIC PROCESS SIMULATION OF THE DIGESTION UNIT IN IRAN ALUMINA REFINERY2009In: Proceedings of SIMS 50, Modeling of Energy Technology / [ed] Brian Elmegaard, Christian Veje, Mads Pagh Nielsen, Tommy Mølbak, 2009, p. 173-178Conference paper (Refereed)
    Abstract [en]

    Jajarm bauxite is of the chamosite-diasporic type, one of the hardest types of bauxite for alumina production. The Iran Alumina Refinery uses Jajarm deposits and currently operates at 65-70% of its nameplate capacity. Digestion is one of the most important processes in the refinery and has become the main bottleneck in the production. In this paper we study the effect of selected parameters on the behavior of this important section of the refinery using thermodynamic simulation of the digestion unit. The ASTM tables property method was used for vapor streams and the Elec-NRTL property model was used for the global digestion process. The digestion process was simulated with Aspen plus software. The results show good agreement with experimental data. The relationship between the incoming slurry temperature in the first flash tank and the preheater cold stream (slurry into the furnace) temperature and energy consumption is discussed.

  • 10.
    Farrokh, Mohammad
    et al.
    Mälardalen University, School of Business, Society and Engineering, Future Energy Center.
    Mahmoudi, Jafar
    Mälardalen University, School of Business, Society and Engineering, Future Energy Center.
    Dahlquist, Erik
    Mälardalen University, School of Business, Society and Engineering, Future Energy Center.
    Modeling and Simulation of a DiasporeTubular Digestion Process2013In: International Journal of Simulation and Process Modelling, ISSN 1740-2123, E-ISSN 1740-2131, Vol. 33, no 2, p. 126-133Article in journal (Refereed)
    Abstract [en]

    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.

  • 11.
    Firouzifar, sohrab
    et al.
    Mälardalen University, School of Sustainable Development of Society and Technology.
    Mahmoudi, Jafar
    Mälardalen University, School of Sustainable Development of Society and Technology.
    Assessment of Power Transformer Cooler with FEMLAB2007In: the 48th Scandinavian Conference on simulation & modelling (SIMS 2007), Göteborg (Särö), Sweden, 2007Conference paper (Refereed)
    Abstract [en]

    The significance of overload in power system has increased substantially due to of consumption and ambient temperature rise. An important consideration when evaluating the impact of overload is their on power system ambient tem-and load. Transformers are major components in power systems. The increase useful lifetime and hence abnormal temperature rise. Existing standards give a procedure to determine the capability of an existing transformers subject to overload problem and ambient temperature rise based on conservative assumptions .in addition, the temperature oil rise of power transformer due to overloading and ambient temperature are estimated based on power and cooling system, and the average daily or monthly temperatures to which a transformer would be subjected while in service. it is the purpose of this research of this effort to quantify the decreased life time due to overloading and the corresponding temperature rise in transformers. This is accomplished using a 2-D FEMLAB Model adapted for cooling simulation in power transformers.

  • 12.
    Firouzifar, Sohrab
    et al.
    Mälardalen University, School of Sustainable Development of Society and Technology.
    Mahmoudi, Jafar
    Mälardalen University, School of Sustainable Development of Society and Technology.
    Evaluation of the Effects of overload & ambient temperature in power transformers in M.R.E.C2007In:  22nd International power system Conference , PSC2007, Tehran, Iran, 2007Conference paper (Refereed)
  • 13.
    Gholinejad, Hassan
    et al.
    Mälardalen University, School of Sustainable Development of Society and Technology.
    Mousavi Takami, Kourosh
    Mahmoudi, Jafar
    Description of techniques for hot spot monitoring and detection in power transformers2008In: Energitinget Scientific Conference 2008, 2008Conference paper (Refereed)
  • 14.
    Mahmoudi, Jafar
    et al.
    Mälardalen University, School of Sustainable Development of Society and Technology. Outokumpu Copper, Sweden.
    Nabati, Hamid
    Mälardalen University, School of Sustainable Development of Society and Technology.
    An Experimental Study on Productivity and Quality Improvement of Horizontal Continuous Casting Process2006In: International Journal of Green Energy, ISSN 1543-5075, E-ISSN 1543-5083, Vol. 3, no 2, p. 185-199Article in journal (Refereed)
    Abstract [en]

    The aim of the current work is to provide information on how to improve the productivity and quality in the Horizontal Continuous Casting process (HCC). After a first numerical 2D/3D survey about the solidification in the HCC, an experimental investigation has been carried out to validate numerical results. Some casting parameters have been measured and collected: inlet and outlet temperatures, flow rate, heat flux and casting temperature. The study results lead to a correlation between these casting parameters and the casting quality. To obtain the best quality for each alloy, a set of operating parameters has been proposed. There is a very good agreement between the current results and earlier numerical results. Also based on the results, one can gain an insight on the productions of each casting machine and the grades of its quality.

  • 15.
    Mousavi Takami, kourosh
    et al.
    Mälardalen University, School of Sustainable Development of Society and Technology.
    Gholinejad, Hasan
    Mahmoudi, Jafar
    Thermal and hot spot evaluations on oil immersed power Transformers by FEMLAB and MATLAB software’s2007In: EuroSime 2007: International Conference on Thermal, Mechanical and Multi-Physics Simulation Experiments in Microelectronics and Micro-Systems, 2007, 2007, p. 529-534Conference paper (Refereed)
    Abstract [en]

    Transformers are important and expensive elements of a power system. Inordinate localized temperature rise, hottest spot temperature (HST), causes rapid thermal degradation of insulation and subsequent thermal breakdown. To prescribe the limits of short-term and long-term loading capability of a transformer, it is necessary to estimate the HST of transformer winding to as high a degree of accuracy as can possibly be made. These papers have now improved the accuracy of estimation of hottest spot temperature. Inordinate temperature rise in a power transformer due to load current is known to be the most important factor in causing rapid degradation of its insulation and decides the optimum load catering ability or the load ability of a transformer. The Top Oil Temperature (TOT) and Hottest Spot Temperature (HST) being natural outcome of this process, an accurate estimation of these parameters is of particular importance. IEEE / IEC among others have proposed procedure to estimate the temperatures, however, the accuracy of the predictions are not always as good as are desired. Unacceptable temperature rise may occur due to several fault conditions other than overloading, and hence warrant an online monitoring of the transformer.

  • 16.
    Mousavi Takami, Kourosh
    et al.
    Mälardalen University, School of Sustainable Development of Society and Technology.
    Jafar, Mahmoudi
    A novel device (oil spraying system) for local cooling of hot spot and high temperature areas in power transformer2007Conference paper (Refereed)
    Abstract [en]

    Power transformer is a vital device in substations. Load and no load losses create a hot spot point in transformer, so it is obviously necessary to limit the core temperature to values that cause no damage to the core itself, adjacent materials, or the oil. Core temperatures as low as 110 C–120 may degrade oil. This has led experts in the field to suggest that 130 C would be a reasonable limit for the core temperature. For this reason, need to a device for local cooling is necessary. Authors in this paper find a novel method for oil cooling in hot spot point or area. Oil spraying device is simulated and then path of pressured oil after shooting in hot spot point, is evaluated. With using of 230/63/20kv Punel substation in Iran data, and after simulation and calculation, authors find that with using of this device utilities could remove their problem for over loading of transformers in the load peak time.

  • 17.
    Mousavi Takami, Kourosh
    et al.
    Mälardalen University, School of Sustainable Development of Society and Technology.
    Jafar, Mahmoudi
    danielson, Örja
    High temprature power reflector simulation using of COMSOL software's2007Conference paper (Refereed)
    Abstract [en]

    Super heater elements concentrated in very high and clean power at temperature up to 1800 ºc is needed for aluminium melting, oil drying equipment using for power transformers and same that material. There fore, always it is need to minimize power consumption and increase effectiveness at power reflector customers. This means to minimize heat losses in the High Power Reflector, and to optimize heat performance with respect to output power and temperature distribution. This can be done by altering the size and form of the insulating ceramic fiber to have as much power as possible 'reflected' out from the module. It can also be done by altering the size and form of the element.It has been done and the task solved mainly by heat transfer simulations, using COMSOL and MTLAB software’s. To minimize the number of different designs (and thus the number of calculations) were studied; it is also done that statistical methods for experimental design used to determine which designs should be used in the calculations.When an optimal solution has been found, it has been tested at Kanthal's facilities, with two reference designs.

  • 18.
    Mousavi Takami, Kourosh
    et al.
    Mälardalen University, School of Sustainable Development of Society and Technology.
    Mahmoudi, Jafar
    Mälardalen University, School of Sustainable Development of Society and Technology.
    A new apparatus for mitigating the hot spot problem in large power transformers using Ants algorithm2007In: IEEE PES PowerAfrica 2007 Conference and Exposition, PowerAfrica, 2007, p. 587-594Conference paper (Refereed)
    Abstract [en]

    Hot spot temperature (HST) is the most important parameter in the operation of power transformers. The HST has to be held under a prescribed limit. HST has a considerable effect on the insulation aging. Therefore detecting, monitoring and removing the HST could be a very important and necessary action for Utilities. A new design of oil spraying and its effect, along with a thermal management in a transformer cooling system has been studied in this paper. The effect of oil fluid flow on the HST problem has been considered in this paper; and the calculations and simulation have been performed by Ants algorithm. The simulation results have been validated based on a 230/63/20 kV, 250MVA transformer at the Sari substation in Iran, and the results indicate that the new design could mitigate the limitations of transformer loading due to the HST problem. The Ants algorithm have been proposed and applied for accomplishing this task and to give an improved level of accuracy.

  • 19.
    Mousavi Takami, Kourosh
    et al.
    Mälardalen University, School of Sustainable Development of Society and Technology.
    Mahmoudi, Jafar
    Design of a new oil spraying device for hot spot cooling in large scale electric power transformers2008In: International Journal of Emerging Electric Power Systems, ISSN 2194-5756, E-ISSN 1553-779X, Vol. 9, no 2Article in journal (Refereed)
    Abstract [en]

    Hot spot temperature (HST) is the most important parameter in the operation of power transformers. The HST has to be held under a prescribed limit. HST has a considerable effect on the insulation aging. Therefore detecting, monitoring and removing the HST could be a very important and necessary action for utilities. A new design of oil spraying and its effect, along with a thermal management in a transformer cooling system has been studied in this paper. The effect of oil fluid flow on the HST problem has been considered in this paper; and the calculations and simulation have been performed by Ants algorithm. The simulation results have been validated based on a 230/63/20 kV, 250MVA transformer at the Sari substation in Iran, and the results indicate that the new design could mitigate the limitations of transformer loading due to the HST problem. The Ants algorithm have been proposed and applied for accomplishing this task and to give an improved level of accuracy.

  • 20.
    Mousavi Takami, Kourosh
    et al.
    Mälardalen University, School of Sustainable Development of Society and Technology.
    Mahmoudi, Jafar
    Identification of a best thermal formula and model for oil and winding2007Conference paper (Refereed)
    Abstract [en]

    System identification is about building models from data. A data set is characterized by several pieces of information: The input and output signals, the sampling interval, the variable names and units, etc.Similarly, the estimated models contain information of different kinds, estimated parameters, their covariance matrices, and model structure and so on. In this paper we collected Temperature of oil and winding in 230/63kv transformer of SARI Substation and considered the winding temperature for input in the model and oil temperature for out put. After that calculated their data by MATLAB software and get a new model with the good best fit for the heat transfer from core and winding to oil. For verification of were calculated results, has been simulated the process in COMSOL Software.

  • 21.
    Mousavi Takami, Kourosh
    et al.
    Mälardalen University, School of Sustainable Development of Society and Technology.
    Mahmoudi, Jafar
    Numerical Modelling of Heat Generation and Distribution in the Core and Winding of Power Transformers2008In: International Journal of Emerging Electric Power Systems, ISSN 1553-779X, Vol. 9, no 2, p. 1-20Article in journal (Refereed)
    Abstract [en]

    The power transformer is a complex and critical component of the power transmission and distribution system. System abnormalities, loading, switching and ambient condition normally contribute to accelerated aging and sudden failure. In the absence of critical components monitoring, the failure risk is always high. For early fault detection and real time condition assessment, an online monitoring system in accordance with the age and conditions of the asset would be an important tool. Power loss, heat generation and heat distribution evaluations in a large-scale oil immersed power transformer are presented here, along with the details of computer implementation and experimental verification. Core power losses are approximately constant with temperature variation or may decrease with that. Over the temperature range of 20 to 100°C the change in hysteresis loss Ph with temperature was negligible. Since the total core loss PT decreased with increasing temperature over this range, almost all the loss reduction was due to a reduction in the eddy current loss component Pe that was inversely proportional to the resistivity. Winding and oil temperature will increase with the load increasing and may create a hot spot. This is caused by degradation insulation and the loss of life in the power transformer. Hottest spot temperature and temperature profiles in radial and height coordinates were found using three different methods in this paper. The finite element method (FEM), finite difference method (FDM) and discrete furrier transform methods (DFT) are used to analyze algorithms in this paper. Computational results based on theoretical considerations and using the DFT method are shown to be in good agreement with FDM and FEM. Two mathematical formulae are proposed for temperature distribution in both radial and horizontal axes of core and windings. COMSOL for FEM, GEMINI for FDM and MATLAB for DFT are used.

  • 22.
    Mousavi Takami, Kourosh
    et al.
    Mälardalen University, School of Sustainable Development of Society and Technology.
    Mahmoudi, Jafar
    Numerical modelling of heat generation and distribution in the core and winding of power transformers2008In: International Journal of Emerging Electric Power Systems, ISSN 2194-5756, E-ISSN 1553-779X, Vol. 9, no 2, p. article number: 7-Article in journal (Refereed)
    Abstract [en]

    The power transformer is a complex and critical component of the power transmission and distribution system. System abnormalities, loading, switching and ambient condition normally contribute to accelerated aging and sudden failure. In the absence of critical components monitoring, the failure risk is always high. For early fault detection and real time condition assessment, an online monitoring system in accordance with the age and conditions of the asset would be an important tool. Power loss, heat generation and heat distribution evaluations in a large-scale oil immersed power transformer are presented here, along with the details of computer implementation and experimental verification. Core power losses are approximately constant with temperature variation or may decrease with that. Over the temperature range of 20 to 100°C the change in hysteresis loss Ph with temperature was negligible. Since the total core loss PT decreased with increasing temperature over this range, almost all the loss reduction was due to a reduction in the eddy current loss component Pe that was inversely proportional to the resistivity. Winding and oil temperature will increase with the load increasing and may create a hot spot. This is caused by degradation insulation and the loss of life in the power transformer. Hottest spot temperature and temperature profiles in radial and height coordinates were found using three different methods in this paper. The finite element method (FEM), finite difference method (FDM) and discrete furrier transform methods (DFT) are used to analyze algorithms in this paper. Computational results based on theoretical considerations and using the DFT method are shown to be in good agreement with FDM and FEM. Two mathematical formulae are proposed for temperature distribution in both radial and horizontal axes of core and windings. COMSOL for FEM, GEMINI for FDM and MATLAB for DFT are used. 

  • 23.
    Mousavi Takami, Kourosh
    et al.
    Mälardalen University, School of Sustainable Development of Society and Technology.
    Mahmoudi, Jafar
    Simulation and optimization of high power super heater reflectors2007Conference paper (Refereed)
    Abstract [en]

    Super heater elements concentrated in very high and clean power at temperature up to 1800 ºc is needed for aluminium melting, oil drying equipment using for power transformers and same that material. There fore, always it is need to minimize power consumption and increase effectiveness at power reflector customers. This means to minimize heat losses in the High Power Reflector, and to optimize heat performance with respect to output power and temperature distribution. This can be done by altering the size and form of the insulating ceramic fiber to have as much power as possible 'reflected' out from the module. It can also be done by altering the size and form of the element .It has been done and the task solved mainly by heat transfer simulations, using COMSOL and MTLAB software’s. To minimize the number of different designs (and thus the number of calculations) were studied; it is also done that statistical methods for experimental design used to determine which designs should be used in the calculations. When an optimal solution has been found, it has been tested at factory’s facilities, with two reference designs.

  • 24.
    Mousavi Takami, Kourosh
    et al.
    Mälardalen University, School of Sustainable Development of Society and Technology.
    Mahmoudi, Jafar
    Simulation of a novel copper heat Sink using copper pipe and AM method for CPU group heat removing in power transformer’s cabinet2007In: Proceedings of the Electronic Packaging Technology Conference, EPTC, IEEE , 2007, p. Article number 4441469-Conference paper (Refereed)
    Abstract [en]

    Heat sinks operate by conducting heat from the processor to the heat sink and then radiating it to the air. The better the transfer of heat between the two surfaces (the CPU and the heat sink metal) the better the cooling. Some processors come with heat sinks glued to them directly, ensuring a good transfer of heat between the processor and the heat sink. In this paper author have simulated a new copper heat sink and heat pipe (is a simple device that can quickly transfer heat from one point to another) that has a best heat transferring. A three Dimensional finite element is used for simulations of temperature behaviour on around of heat sink. Analytically approach is applied to determine of heat transfer coefficients. The method has a good convergence and is adaptive with other best designed heat sinks. And so we examine the use of activity migration which reduces peak junction temperature by moving computation between multiple replicated units.

  • 25.
    Mousavi Takami, Kourosh
    et al.
    Mälardalen University, School of Sustainable Development of Society and Technology.
    Mahmoudi, Jafar
    Thermal evaluation and energy saving with loss reduction in core and winding of power transformers2007Conference paper (Refereed)
    Abstract [en]

    A power loss, heat generation and heat distribution evaluations in a large-scale oil cooled power transformer are presented here, along with the details of computer implementation and experimental verification. In this paper, we consider that core power losses are approximately constant with temperature various or might decreased with that. Winding temperature and oil will increase with the load increasing and might create a hot spot and that is caused by degradation insulation and the loss of life in the power transformer. Therefore the authors tried to Asses these phenomena with use of electrical and thermal soft wares. On the results (with Iranian network data) of simulation showed that in case of oil spraying on the hotspot point or area, very low temperature with the best conditions would be obtained. Then it is best to provide a cooling system with the best insulation and with the minimum side effect on the magnetic and electrical field distribution. Finally by reduction in transformer losses, could savings potential of 22 TWh / year for EU.

  • 26.
    Mousavi Takami, Kourosh
    et al.
    Mälardalen University, Department of Public Technology.
    Mahmoudi, Jafar
    Mälardalen University, Department of Public Technology.
    Dahlquist, Erik
    Mälardalen University, Department of Public Technology.
    Process control in steel core production to reduce of power losses in electrical machines and transformers: Process Control2009In: Proceedings MATHMOD 09 Vienna, Vienna- Austria: Mathematical Modelling (MATHMOD) 2009 , 2009Conference paper (Refereed)
    Abstract [en]

    The main aim of cold rolling is reduction of strips to the desired final thickness. As the cold rolled strip is being manufactured from hot rolled strip, the uniformity of width, thickness, hardness, etc. are all now intended for improvement.  To reach to this target, need to abound control system to reach the higher quality of slabs.  It should satisfy the several factors, as regards geometrical, mechanical, chemical and surface properties.

    Process control has taken advantage of new measurement equipments, new control actuators and algorithms. Automation and automatic process control can advance the quality further than what is achievable by manual control. This is an important desideration in rolling industry that rolling of slabs needs advanced and optimized process control to increase the productivity and reduction of the variations in the final properties.

    A typical cold rolling stand performs one step in a chain of processes in the cold rolling mill, which can include pickling, rolling, annealing, temper rolling and downstream processes. All these processes contribute to the final properties of the strips. When the main process or the main objective is well controlled, it is important to continue with the other processes. In continuous annealing furnaces, the temperature controls the mechanical properties, but temperature differences and bending around rollers change the flatness. Temper rolling needs the same flatness control as other cold rolling processes. Cooling and lubrication can affect several properties of the strips.

    Precise general control of the strip in a cold steel rolling mill will be discussed in this article.

    Typically, the rolling process is modelled with numerical techniques. But these are not appropriate for a controller design, because they are too difficult. Thus, a linear mathematical model for the rolling process is presented here, which describes the interaction of the required influencing parameters. The attempt leads to numerically professional algorithms, which are essential to run in a real-time situation. With the help of these linear descriptions, the vital elements for the control are investigated. Modern rolling mills are equipped with a servo-hydraulic gap adjustment system, eccentricity control of the rolls, thickness, speed, force and tension controls.

    A model to optimize of the control design process and increasing of accuracy is presented. In this way using the process transfer function in system at different control mode like to thickness, flatness, shape and etc designed a PID and PI optimized controller with using of the best optimization method, final properties increased. The measurements are used to verify the model approach and to detect the most significant sources of disturbances.

    A new linearised numerical model for the rolling process which is suitable for closed loop control has been developed. The model is based on the calculation of the operating point using an available numerical method, followed by determining the partial derivatives at the operating point with respect to all input parameters. Finally, the partial derivatives are combined using superposition to describe the behaviour of the complete system. In this manner, the changes in the output parameters can be determined for small changes in the input parameters. This calculation is numerically efficient and suitable for use in closed loop control.

    Moreover, the roll eccentricity problem and the possibilities to perform compensation will be explained here. Due to the great variety of solutions, a classification of the methods will be sketched. The basic properties of these classes are discussed. Then, a special solution is presented, which has proved its worth already in a practical application. The investigation of its properties is proposed to be typical for the every class, to which the method belongs.

    Finally measurement data which can be used to verify the new model will be performed. The model has been incorporated as a simulation system developed by the authors who enable the simulation of a multi-pass single stand rolling process. To get practical information about the rolling process, a data logging system was developed and installed in Sura AB for data collection.

  • 27.
    Mousavi Takami, Kourosh
    et al.
    Mälardalen University, Department of Public Technology.
    Mahmoudi, Jafar
    Mälardalen University, Department of Public Technology.
    Dahlquist, Erik
    Mälardalen University, Department of Public Technology.
    Lindenmo, Magnus
    Surahammars Bruks AB, R&D.
    Evaluation of magnetic aging in transformers and electrical machines cores during operation: Modelling2009In: Proceedings of the Scientific Conference on Energy and IT at Älvsjö fair, Stockholm March 11-12, 2009 in connection with the “Energitinget 2009, 2009, p. 218-232Conference paper (Refereed)
    Abstract [en]

    Electric steels are processed to avoid the phenomenon known as magnetic aging. Non-oriented electrical steels are mostly used in rotating electrical machines and oriented steels used in transformers, which during operation generates heat. This could cause carbide precipitation/coalescence in the metallic matrix, impairing the magnetic properties of the steel, called magnetic aging. The steel has to contain very little carbon to avoid aging. This is achieved during the making of the steel or by a decarburising annealing of the final thickness strip or of the stamped laminations.

    The magnetic material for cores of a transformer and electrical machines should be characterised by high permeability and low energy losses in changing magnetic flux.

    In order to test that the magnetic properties do not become worse during these working conditions, the steel can be tested for magnetic ageing. The European standard defines the test cycle as 225°C for 24 hours. The American ASTM standard suggests two different cycles: 100 hours at 150°C or 600 hours at 100 °C.

     

    A test the losses after a heat treatment of 150°C f or 10 days for coils with higher carbon content than 26 ppm of the final product has performed here. This longer cycle has proved to give larger increases in the loss than the shorter one according to the European standard.

    The ageing process was much faster for a higher carbon content slab with 90 ppm C than for a lower one with 30 ppm C.

    ANN method using LMS has performed to aging real time identification. Results showed a 97% best fit. It showed that using ANN can predict the aging and a modern advanced relay can control the loading and temperature of electrical equipments to prevent of harmful damages.

  • 28.
    Mousavi Takami, Kourosh
    et al.
    Mälardalen University, School of Sustainable Development of Society and Technology.
    Mahmoudi, Jafar
    Gholinejad, Hasan
    Evaluation of Large Power Transformer Losses for green house gas and final cost reductions2007Conference paper (Refereed)
    Abstract [en]

    Transformers are more complex devices, consisting of an iron core around which are wrapped various coils of insulated wires, inside a tank filled with insulating oil, along with connectors, bushings and various other small components. Overloading causes excess heat in a transformer, the negative effects of which are degradation of the kraft paper insulation around the wires (leading to internal failures of the coils), excessive tank pressure or degradation of the insulating oil (either of which can cause catastrophic failures, even explosions), and leaking gaskets and seals. (Since the copper used in the windings is already soft (annealed) and is not under tension, overheating of the conductors is generally not a concern.) Thermal cycling contributes to mechanical damage by loosening connections. Because of hysteresis in the transformer core, overloading generates harmonics and these can cause mechanical vibration of the transformer, contributing to physical damage. Overloading also assumes that faults near the transformer, when they occur, will be greater than normal, so there is the increased likelihood of damage to the transformer from fault currents; such damage can be manifested by coil failures, bushing flashovers, blown gaskets and seals, connector failures, oil explosions and fires, and physical displacement of internal components due to electromechanical torques. In the world consume millions barrels oils for cover of electrical losses then produced green house gas. With introduce of new method for loss reduction authors find a new method that presented in this paper. In this paper we Asses the impact of losses on final cost of transformer and so green house gas. And would proved that losses cost is equal of capital investment for buying a transformer. Emissions of in electrical network is 0.4 kg / kWh, that for the world only for transformer losses are (11,500 billion kilowatts hours are produced electricity) closed to 46 billion tons and can reduce it to 23 billion ton by a good looses management.

  • 29.
    Nabati, Hamid
    et al.
    Mälardalen University, School of Sustainable Development of Society and Technology.
    Mahmoudi, Jafar
    Mälardalen University, School of Sustainable Development of Society and Technology.
    Evaluation of CFD Method for Efficiency Improvement in CO2Capturing with Application of Pin Fin TechnologyIn: Chemical Product and Process Modeling, ISSN 1934-2659Article in journal (Refereed)
  • 30.
    Nabati, Hamid
    et al.
    Mälardalen University, School of Sustainable Development of Society and Technology.
    Mahmoudi, Jafar
    Mälardalen University, School of Sustainable Development of Society and Technology.
    Flue Gas Condenser Modelling for Improving the CO2 Capturing Efficiency2009In: Proceedings of 6th MathMod Conference, 2009Conference paper (Other academic)
  • 31.
    Nabati, Hamid
    et al.
    Mälardalen University, School of Sustainable Development of Society and Technology.
    Mahmoudi, Jafar
    Fluid flow and heat transfer simulation in a barrel type CVD reactor2008Conference paper (Refereed)
    Abstract [en]

    Thin-film coating plays an important role in the manufacturing of many cutting and drilling tools. One of the most common types of thin-film coating methods is chemical vapor deposition that is known as CVD in industry. The CVD involves deposition of a thin film from gas phase precursors onto a solid substrate. The uniformity of film thickness is a critical in tools production. To achieve this uniformity, it is necessary to understand the governing transport processes, flow behavior and heat transfer inside the CVD reactor. In the coming paper the aim is numerical modeling of CVD processes using an existing simulation software, Fluent©. The objective of the work focuses on understanding and predicting the flow regime and heat transfer characteristics in a CVD reactor. At the current stage the work involves studying a single-species flow and heat transfer without chemical reaction. The simulation results will be verified using the real data collected from manufacturing company. These results will show the possibilities in improving the coating efficiency and uniformity in an effective way.

  • 32.
    Nabati, Hamid
    et al.
    Mälardalen University, School of Sustainable Development of Society and Technology.
    Mahmoudi, Jafar
    Mälardalen University, School of Sustainable Development of Society and Technology.
    Heat transfer and fluid flow analysis of power transformer's cooling system using CFD approach2009In: Chemical Product and Process Modeling, ISSN 1934-2659, Vol. 4, no 1, p. art. no. 43-Article in journal (Refereed)
    Abstract [en]

    This paper presents the results of numerical modeling of temperature distribution and flow pattern in a block radiator used in power transformer cooling system. Each block radiator consists of eighteen plane radiators which are parallel together and a typical power transformer (like a 30MVA) has 6 radiator blocks in each side which means it has 12 blocks totally. The numerical study using fluent software has been conducted to find the explanation of low cooling efficiency in this especial power transformer currently used in industry. Our main desire is the study of relation between radiator block characteristics and cooling behavior of system which can be used for its optimization in the future studies. The results indicate that recirculation occurs whenever pressure increase at the end of a radiator block that consequently prevents the enough oil flow through the last radiator of block. Experimental data taken from company and technical data extracted from transformer documents have been used for model calibration and results verification.

  • 33.
    Nabati, Hamid
    et al.
    Mälardalen University, School of Sustainable Development of Society and Technology.
    Mahmoudi, Jafar
    Mälardalen University, School of Sustainable Development of Society and Technology.
    Numerical Study of Thermal Performance of Different Pin-Fin  Morphologies2005In: 46th Conference on Simulation and Modeling (SIMS 2005), Trondheim, Norway, 2005Conference paper (Refereed)
  • 34.
    Nabati, Hamid
    et al.
    Mälardalen University, School of Sustainable Development of Society and Technology.
    Mahmoudi, Jafar
    Mälardalen University, School of Sustainable Development of Society and Technology.
    Optimal Pin Fin Heat Exchanger Surface for Pulp and Paper Industry2006Conference paper (Refereed)
    Abstract [en]

    A large number of different heat exchangers are used in a pulp and paper mills, specially in the recovery boiler which is the heart of the pulp and paper mill. The pulp and paper industry consumes a noticeable portion of all the primary energy consumed in the industrial countries manufacturing. This paper is trying to introduce a new concept in heat exchanger design which is originated from new e-cooling technology to improve energy efficiency. The efficiency of the air-side heat transfer is a primary consideration when determining the best heat exchanger for a particular application. Surface enhancement using pin fins could be a promising method to overcome the described problem as well as maintenance efforts. Study's results have shown the drop-shaped pin-fins have a better heat transfer performance comparing to the two other cylindrical and triangular morphologies.

  • 35.
    Nabati, Hamid
    et al.
    Mälardalen University, School of Sustainable Development of Society and Technology.
    Mahmoudi, Jafar
    Mälardalen University, School of Sustainable Development of Society and Technology.
    Time, R.W.
    PREDICTION OF CONDENSING FLOW WITH RELEVANCE TO FLUE GAS CONDENSER AND CO2 CAPTURING2009In: Proceedings of SIMS 50, 2009Conference paper (Other academic)
  • 36.
    pourian, bijan
    et al.
    Mälardalen University, Department of Public Technology.
    mahmoudi, jafar
    irwin, mark
    3-Dimensional numerical and analytical study of flow and thermal behavior of proposed mechanical fabrication copper heat sinkIn: Journal of green energyArticle in journal (Refereed)
  • 37.
    pourian, bijan
    et al.
    Mälardalen University, Department of Public Technology.
    mahmoudi, jafar
    irwin, mark
    Experimental determination of the thermal performance of a free standing fin2008In: The 49th Scandinavian Conference on Simulation and Modeling (SIMS 2008), 2008Conference paper (Refereed)
  • 38.
    pourian, Bijan
    et al.
    Mälardalen University, Department of Public Technology.
    mahmoudi, jafar
    irwin, mark
    Numerical and experimental study of the inclined free fins applied for thermal managementIn: International journal of numerical methods for heat & fluid flow, ISSN 0961-5539, E-ISSN 1758-6585Article in journal (Refereed)
  • 39.
    Sadeghi, Mohammad
    et al.
    Mälardalen University, School of Business, Society and Engineering, Future Energy Center.
    Mahmoudi, Jafar
    Mälardalen University, School of Sustainable Development of Society and Technology.
    Experimental and Theoretical Studies on the Effect of Die Temperature on the Quality of the Products in High-Pressure Die-Casting Process2012In: Advances in Materials Science and Engineering, ISSN 1687-6822, no 434605Article in journal (Refereed)
    Abstract [en]

    Die temperature in high-pressure die casting of A380 alloy is optimized by experimental observation and numerical simulation. Ladder frame (one part of the new motor EF7) with a very complicated geometry was chosen as an experimental sample. Die temperature and melt temperature were examined to produce a sound part. Die temperatures at the initial step and the final filling positions were measured and the difference between these values was calculated. ProCAST software was used to simulate the fluid flow and solidification step of the part, and the results were verified by experimental measurements. It is shown that the proper die temperature for this alloy is above 200 degrees C.

  • 40.
    Sadeghi, Mohammad
    et al.
    Mälardalen University, School of Business, Society and Engineering, Future Energy Center.
    Mahmoudi, Jafar
    Mälardalen University, School of Business, Society and Engineering.
    Numerical determination of process parameters for fabrication of automotive component2010In: solidification simulation, 2010Conference paper (Other academic)
    Abstract [en]

    The casting defects that are caused by molten metal are cold shut formation, entrapment of air, gas, and inclusion. But the control of casting defects has been based on the experience of the foundry engineers. One of the most parameters that can influence the casting defects is cooling rate. In this paper, computer simulations have been carried out to analyze the flow of molten metal and effect of die temperature on the cooling rate and subsequently the casting defects. Flow patterns of molten metal in one of the Iranian automotive component were examined to find the optimal temperature for the die-casting die temperature. The finite element ProCast software was used for simulation and results of simulation was compared with the experiment. The calculated results for automobile Ladder frame body to control the die-casting process have achieved good agreements with the experimental data. Results show that temperatures between 20°C to 25°C are good for the die casting.

  • 41.
    Tabatabaee Ghomi, Mohammad
    et al.
    Mälardalen University, School of Business, Society and Engineering. Technology Development Institute (TDI) and ACECR Researcher, Tehran, Iran .
    Mahmoudi, Jafar
    Mälardalen University, School of Business, Society and Engineering.
    Darabi, M
    Technology Development Institute (TDI) and ACECR Researcher, Tehran, Iran.
    Concrete Plate Thickness Measurement Using the Indirect Impact-Echo Method2013In: NDT & E international, ISSN 0963-8695, E-ISSN 1879-1174, Vol. 28, no 2, p. 119-144Article in journal (Refereed)
    Abstract [en]

    A new method for measuring the thickness of concrete plates indirectly is proposed. In this approach, a steel ball impacts on a steel bar and the generated stress waves transfer to the concrete plate. Numerical simulations of the process were carried out using different plate thicknesses. The results indicate that the impact response of the concrete plate for a dominant thickness frequency in the indirect method agrees with the results obtained in the classic direct method in which the impactor collides directly on the specimen being tested. The results also show that the proposed method can be used to measure the thickness of concrete plates with reasonable accuracy. The behaviour of stress waves in the steel bar was investigated and revealed to be consistent with previous research.

  • 42.
    Tabatabaee Ghomi, Mohammad
    et al.
    Mälardalen University, School of Sustainable Development of Society and Technology.
    Mahmoudi, Jafar
    Mälardalen University, School of Sustainable Development of Society and Technology.
    Darabi, Mehdi
    echnology Development Institute (TDI), ACECR, Iran .
    Steel Plate Thickness Measurement using Impact-Echo Method2011In: Proceedings of the IASTED International Conference on Applied Simulation and Modelling, ASM 2011, 2011, p. 168-173Conference paper (Refereed)
    Abstract [en]

    In this study we use impact echo method for measuring the thickness of steel plates. Numerical simulation of steel plates by the purpose of thickness measurement was performed on the different plate thicknesses. The impact echo method is usually using for concrete structures. In this study we applied this method for steel plates and the results indicated that this method also could be report truly the thickness of the steel plates.

  • 43.
    Tabatabaee Ghomi, Mohammad
    et al.
    Mälardalen University, School of Sustainable Development of Society and Technology.
    Mahmoudi, Jafar
    Mälardalen University, School of Sustainable Development of Society and Technology.
    Khalkhali, A
    Iran Univ Sci & Technol, Sch Automot Engn, Tehran, Iran.
    Liaghat,, G
    Tarbiat Modares Univ, Tehran, Iran.
    Explosive Welding of Unequal Surface using Groove Method2012In: Transactions of the Canadian Society for Mechanical Engineering, ISSN 0315-8977, Vol. 36, no 2, p. 113-125Article in journal (Refereed)
    Abstract [en]

     Bond strength of welded joints is an important factor in the explosive welding process. In such welding process, stress waves produced by explosive energy propagate at the, free surface and produce tension stresses. These waves result in spalling and scabbing at the edges of metals and reduce the tensile bond strength of explosive welding. The most common method for solving this problem is cutting and sizing the edges. However, this is not possible when the two metal parts to be joined are of unequal surfaces (a small plate to a large plate). This paper focuses on applying a new technique (Groove Method) for solving the strength problem at the edges for obtaining uniform welding. In this way, experimental and numerical analyses are performed to evaluate the Groove Method. The obtained results show the success and effectiveness of the groove method suggested in this paper.

  • 44.
    Tabatabaee Ghomi, Mohammad
    et al.
    Mälardalen University, School of Sustainable Development of Society and Technology.
    Mahmoudi, Jafar
    Liaghat, Gholamhossein
    Removing leakage from oil and gas low pressure pipes by explosive welding method2011In: Journal of Petroleum and Gas Exploration Research, ISSN 2276-6510, Vol. 1, no 1, p. 34-42Article in journal (Refereed)
    Abstract [en]

    Explosive welding occurs under high velocity oblique impact, and it is possible to use explosiveenergy to form a conventional cold pressure weld. One of the advantages of this method is that itcan be used to weld different materials with different shapes. Explosive welding can be used for themaintenance of pipes and vessels, in repairing leaks especially in under water pipes in the oil andgas industries. We describe a new explosive welding method for repairing leaks in metal pipes thatis very economical and easy to apply.

  • 45.
    Tabatabaee, Mohammad
    et al.
    Mälardalen University, School of Sustainable Development of Society and Technology.
    Mahmoudi, Jafar
    Mälardalen University, School of Sustainable Development of Society and Technology.
    An advanced method for Aluminium - iron - copper bonding using explosive welding method2008In: PROCEEDINGS FROM SCIENTIFIC CONFERENCE ON GREEN ENERGY AND IT, 2008Conference paper (Refereed)
  • 46.
    Tabatabaee, Mohammad
    et al.
    Mälardalen University, School of Sustainable Development of Society and Technology.
    Mahmoudi, Jafar
    Mälardalen University, School of Sustainable Development of Society and Technology.
    FEM method simulation of Aluminium - iron - copper bonding using explosive welding method2008Conference paper (Refereed)
  • 47.
    Tabatabaee, Mohammad
    et al.
    Mälardalen University, School of Sustainable Development of Society and Technology.
    Mahmoudi, Jafar
    Mälardalen University, School of Sustainable Development of Society and Technology.
    Finite element simulation of explosive welding2008Conference paper (Refereed)
  • 48.
    Takami, Kourosh Mousavi
    et al.
    Mälardalen University, School of Sustainable Development of Society and Technology.
    Danielsson, Orjan
    Kanthal AB, SE-73427 Hallstahammar, Sweden.
    Mahmoudi, Jafar
    Mälardalen University, School of Sustainable Development of Society and Technology.
    High power reflector simulation to optimise electrical energy consumption and temperature profile2011In: Applied Thermal Engineering, ISSN 1359-4311, E-ISSN 1873-5606, Vol. 31, no 4, p. 477-486Article in journal (Refereed)
    Abstract [en]

    The high power reflector is a new heating solution for use in high power heating systems. It consists of a vacuum formed ceramic fibre hood with an integrated Kanthal (R) Super ceramic heating element. This paper describes simulations that have been performed to optimise characteristics of the high power reflector with respect to output heat power and temperature distribution. The main motivation for this task is to use this system in the annealing furnaces of Surahammar Bruks AB. Simulations of heat transfer were performed with different reflector configurations in the COMSOL (R) software environment. We examined six different types of proposed reflector using a two dimensional model approach. The temperature variations with distance above the reflectors and the temperature profiles in surfaces 20 cm above the elements were simulated. Optimum shapes and dimensions were found that produced the highest peak temperature, mean temperature, and uniform temperature distribution in the surface above the element. 3D simulations were performed to verify the accuracy of the 20 simulations. The maximum difference between the 2D and 3D results was about 5%. The results showed a satisfactory fit with average furnace temperatures. (C) 2010 Elsevier Ltd. All rights reserved.

  • 49.
    Takami, Kourosh Mousavi
    et al.
    Mälardalen University, School of Sustainable Development of Society and Technology.
    Mahmoudi, Jafar
    Mälardalen University, School of Sustainable Development of Society and Technology.
    Dahlquist, Erik
    Mälardalen University, School of Sustainable Development of Society and Technology.
    Adaptive control of cold rolling system in electrical strips production system with online-offline predictors2010In: The International Journal of Advanced Manufacturing Technology, ISSN 0268-3768, E-ISSN 1433-3015, Vol. 50, no 9-12, p. 917-930Article in journal (Refereed)
    Abstract [en]

    One of the main concerns of strips producers is to measure strip thickness accurately as it is produced. Correct modelling of the sensitivity of output variables to input variables in a rolling mill model is one of the keys to obtaining more accurate data. An adaptive control system that uses an artificial neural network (ANN) creates a model of the process directly from measurement data. Using the model, the control system can predict how the process will react to control actions. The creation of the model and the computation of the control strategy are carried out automatically by the control system. The proportional-integral-derivative controller is used in this method to increase accuracy of final estimated variables and to increase accuracy of control of the system. To determine the correct tuning for thickness control, three control parameters are considered: the roll gap, and front and back tensions. A predictive model is used, based on the sensitivity equations of the process, where the sensitivity factors are computed by differentiating a previously trained neural network. Results of a case study in a real plant show that this online-offline model is effective in reducing thickness variations in produced strips.

  • 50.
    Takami, Kourosh Mousavi
    et al.
    Mälardalen University, School of Sustainable Development of Society and Technology.
    Mahmoudi, Jafar
    Mälardalen University, School of Sustainable Development of Society and Technology.
    Dahlquist, Erik
    Mälardalen University, School of Sustainable Development of Society and Technology.
    Lindenmo, Magnus
    Cogent Power Ltd, Surahammars Bruk.
    Multivariable data analysis of a cold rolling control system to minimise defects2011In: The International Journal of Advanced Manufacturing Technology, ISSN 0268-3768, E-ISSN 1433-3015, Vol. 54, no 5-8, p. 553-565Article in journal (Refereed)
    Abstract [en]

    This paper focuses on the application of principal component analysis (PCA) to thoroughly analyse and interpret multidimensional data from a cold rolling process. The analysis includes the effects of variables on the final properties of strips in a cold rolling mill. Unscrambler software was used to analyse and identify hidden variables. Variable correlations were also used to derive correlations between the control parameters. The results of this research will be used to improve the selection of material in order to reduce the occurrence of defects in the cold rolling process and to improve the adjustment of the set points that are performed in every pass or section of the cold rolling process. The hot rolled strips that enter the cold rolling mill are made of different materials and are produced by different strip manufacturers. Some strips break during the thickness reduction process in the cold rolling mill. This paper focuses on two possible causes of breakage: non-uniform strip material properties and failures in the rolling mill process. Two types of rolled strips (those that break and those that do not break) were compared to identify causes of breakage. The results indicate that breakages are caused by material or process failures. PCA was applied to the dataset in order to identify and analyse the relationships between the variables in the process. This information was used to interpret and diagnose the process behaviour. Swarm analysis and relating observations to process behaviour were able to distinguish between different start-up conditions, and between desirable and undesirable process conditions.

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