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Öğe Analysis and optimisation of a cascade active magnetic regenerative refrigeration system(Inderscience Enterprises Ltd, 2016) Ganjehsarabi, Hadi; Dincer, Ibrahim; Gungor, AliIn this paper, comprehensive thermodynamic analysis and optimisation of a cascade active magnetic regenerative refrigeration system are performed. A parametric study is conducted to investigate the effects of various design parameters on the cycle performance through energy and exergy efficiencies. A multi-objective optimisation method based on a fast and elitist non-dominated sorting genetic algorithm is applied to determine the best design parameters for the system. Two objective functions utilised in the optimisation study are the total cost rate of the system and the system exergy efficiency. The total cost rate of the system is minimised while the cycle exergy efficiency is maximised using an evolutionary algorithm. To provide insight, the Pareto frontier is shown for a multi-objective optimisation. The results show that exergy efficiency could be increased by 14.53% using exergy-based optimisation and the cost could be reduced by 12% using the cost-based optimisation.Öğe ANALYSIS OF SOME EXERGOECONOMIC PARAMETERS OF A SMALL WIND TURBINE SYSTEM(Taylor & Francis Inc, 2009) Ozgener, Onder; Ozgener, Leyla; Dincer, IbrahimThis paper investigates some exergoeconomic parameters (energy and exergy loss ratios) for a 1.5 kW wind turbine system, linking capital costs and thermodynamic losses, based on some operating conditions. The results show that while the ratio of energy loss rate to capital cost (R(en)) changes between 0.007 and 0.813 at different wind speeds, the ratio of exergy loss rate to capital cost (R(ex)) changes between 0.006 and 0.411. In addition, the maximum Ren and Rex values are obtained at a wind speed of 12 m/s. Furthermore, a parametric study is undertaken to investigate how varying wind speed will affect the exergoeconomic parameters of the wind turbine system and to develop a correlation between the ratio of thermodynamic loss rate to capital cost and wind speed for practical applications of wind energy systems.Öğe Biomass-based hydrogen production: A review and analysis(Pergamon-Elsevier Science Ltd, 2009) Kalinci, Yildiz; Hepbasli, Arif; Dincer, IbrahimIn this study, various processes for conversion of biomass into hydrogen gas are comprehensively reviewed in terms of two main groups, namely (i) thermo-chemical processes (pyrolysis, conventional gasification, supercritical water gasification (SCWG)), and (ii) biological conversions (fermentative hydrogen production, photosynthesis, biological water gas shift reactions (BWGS)). Biomass-based hydrogen production systems are discussed in terms of their energetic and exergetic aspects. Literature studies and potential methods are then summarized for comparison purposes. in addition, a biomass gasification process via oxygen and steam in a downdraft gasifier is exergetically studied for performance assessment as a case study. The operating conditions and strategies are really important for better performance of the system for hydrogen production. A distinct range of temperatures and pressures is used, such as that the temperatures may vary from 480 to 1400 degrees C, while the pressures are in the range of 0.1-50 MPa in various thermo-chemical processes reviewed. For the operating conditions considered the data for steam biomass ratio (SBR) and equivalence ratio (ER) range from 0.6 to 10 and 0.1 to 0.4, respectively. In the study considered, steam is used as the gasifying agent with a product gas heating value of about 10-1S MJ/Nm(3), compared to an air gasification of biomass process with 3-6 MJ/Nm(3). The exergy efficiency value for the case study system is calculated to be 56.8%, while irreversibility and improvement potential rates are found to be 670.43 and 288.28 kW, respectively. Also, exergetic fuel and product rates of the downdraft gasifier are calculated as 1572.08 and 901.64 kW, while fuel depletion and productivity lack ratios are 43% and 74.3%, respectively. (C) 2009 Professor T. Nejat Veziroglu. Published by Elsevier Ltd. All rights reserved.Öğe Biomass-based hydrogen production: A review and analysis(Pergamon-Elsevier Science Ltd, 2009) Kalinci, Yildiz; Hepbasli, Arif; Dincer, IbrahimIn this study, various processes for conversion of biomass into hydrogen gas are comprehensively reviewed in terms of two main groups, namely (i) thermo-chemical processes (pyrolysis, conventional gasification, supercritical water gasification (SCWG)), and (ii) biological conversions (fermentative hydrogen production, photosynthesis, biological water gas shift reactions (BWGS)). Biomass-based hydrogen production systems are discussed in terms of their energetic and exergetic aspects. Literature studies and potential methods are then summarized for comparison purposes. in addition, a biomass gasification process via oxygen and steam in a downdraft gasifier is exergetically studied for performance assessment as a case study. The operating conditions and strategies are really important for better performance of the system for hydrogen production. A distinct range of temperatures and pressures is used, such as that the temperatures may vary from 480 to 1400 degrees C, while the pressures are in the range of 0.1-50 MPa in various thermo-chemical processes reviewed. For the operating conditions considered the data for steam biomass ratio (SBR) and equivalence ratio (ER) range from 0.6 to 10 and 0.1 to 0.4, respectively. In the study considered, steam is used as the gasifying agent with a product gas heating value of about 10-1S MJ/Nm(3), compared to an air gasification of biomass process with 3-6 MJ/Nm(3). The exergy efficiency value for the case study system is calculated to be 56.8%, while irreversibility and improvement potential rates are found to be 670.43 and 288.28 kW, respectively. Also, exergetic fuel and product rates of the downdraft gasifier are calculated as 1572.08 and 901.64 kW, while fuel depletion and productivity lack ratios are 43% and 74.3%, respectively. (C) 2009 Professor T. Nejat Veziroglu. Published by Elsevier Ltd. All rights reserved.Öğe Comparative assessment and optimization of fuel cells(Pergamon-Elsevier Science Ltd, 2015) Mert, Suha Orcun; Ozcelik, Zehra; Dincer, IbrahimIn this study, a comprehensive exergoeconomic analysis and a multi-objective optimization study are performed for four different types of fuel cell systems, in order to determine their maximum power production capacities, exergy efficiencies, and minimum production costs, by use of a genetic algorithm method. The investigated fuel cell types are Polymer Electrolyte Membrane (PEMFC) and Direct Methanol (DMFC) for low temperature fuel cells, and Solid Oxide (SOFC) and Molten Carbonate (MCFC) for high temperature fuel cells. The selected fuel cell systems are modeled exergetically and exergoeconomically. After modeling, the cases are studied parametrically with various available operating conditions, such as temperature, pressure, surrounding temperature and pressure, current density, and relative humidity, using the developed computer program MULOP (Multi-Objective Optimizer). For the low temperature fuel cells it is observed that the efficiencies are in the range of 10-30% and the costs are around $3-4/kW. On the other hand, for the high temperature fuel cell systems, efficiencies are in the range of 15-45% and the costs seems to be $0.003-0.01/kW. The results show that high temperature fuel cells operate more effectively for large scale applications. Copyright (C) 2014, Hydrogen Energy Publications, LLC. Published by Elsevier Ltd. All rights reserved.Öğe Comparative assessment and optimization of fuel cells(Pergamon-Elsevier Science Ltd, 2015) Mert, Suha Orcun; Ozcelik, Zehra; Dincer, IbrahimIn this study, a comprehensive exergoeconomic analysis and a multi-objective optimization study are performed for four different types of fuel cell systems, in order to determine their maximum power production capacities, exergy efficiencies, and minimum production costs, by use of a genetic algorithm method. The investigated fuel cell types are Polymer Electrolyte Membrane (PEMFC) and Direct Methanol (DMFC) for low temperature fuel cells, and Solid Oxide (SOFC) and Molten Carbonate (MCFC) for high temperature fuel cells. The selected fuel cell systems are modeled exergetically and exergoeconomically. After modeling, the cases are studied parametrically with various available operating conditions, such as temperature, pressure, surrounding temperature and pressure, current density, and relative humidity, using the developed computer program MULOP (Multi-Objective Optimizer). For the low temperature fuel cells it is observed that the efficiencies are in the range of 10-30% and the costs are around $3-4/kW. On the other hand, for the high temperature fuel cell systems, efficiencies are in the range of 15-45% and the costs seems to be $0.003-0.01/kW. The results show that high temperature fuel cells operate more effectively for large scale applications. Copyright (C) 2014, Hydrogen Energy Publications, LLC. Published by Elsevier Ltd. All rights reserved.Öğe Comparative assessment and optimization of fuel cells(Pergamon-Elsevier Science Ltd, 2015) Mert, Suha Orcun; Ozcelik, Zehra; Dincer, IbrahimIn this study, a comprehensive exergoeconomic analysis and a multi-objective optimization study are performed for four different types of fuel cell systems, in order to determine their maximum power production capacities, exergy efficiencies, and minimum production costs, by use of a genetic algorithm method. The investigated fuel cell types are Polymer Electrolyte Membrane (PEMFC) and Direct Methanol (DMFC) for low temperature fuel cells, and Solid Oxide (SOFC) and Molten Carbonate (MCFC) for high temperature fuel cells. The selected fuel cell systems are modeled exergetically and exergoeconomically. After modeling, the cases are studied parametrically with various available operating conditions, such as temperature, pressure, surrounding temperature and pressure, current density, and relative humidity, using the developed computer program MULOP (Multi-Objective Optimizer). For the low temperature fuel cells it is observed that the efficiencies are in the range of 10-30% and the costs are around $3-4/kW. On the other hand, for the high temperature fuel cell systems, efficiencies are in the range of 15-45% and the costs seems to be $0.003-0.01/kW. The results show that high temperature fuel cells operate more effectively for large scale applications. Copyright (C) 2014, Hydrogen Energy Publications, LLC. Published by Elsevier Ltd. All rights reserved.Öğe A comparative study on energetic, exergetic and environmental performance assessments of novel M-Cycle based air coolers for buildings(Pergamon-Elsevier Science Ltd, 2012) Caliskan, Hakan; Dincer, Ibrahim; Hepbasli, ArifIn this study, three various novel air coolers based on M-Cycle are evaluated using energy and exergy analyses based efficiency assessments along with environmental impact and sustainability parameters. The M-Cycle systems are considered to cool a building room air while their inlet air parameters are same, but outlet cooled air parameters are different. Systems I and III draw electricity directly taken from an electric grid in the building while System II, which is stand alone system, produces and draws electricity from its solar PV panels. In the energy analysis, wet bulb effectiveness, cooling capacity. Coefficient of Performance (energetic COP) and Primary Energy Ratio (PER) are found. In the exergy analysis, exergy input and output rates, exergy loss rate, exergy destruction rate, Exergetic Coefficient of Performance (COPex), Primary Exergy Ratio (PExR) and exergy efficiency are obtained for six different dead state temperatures changing between 10 degrees C and 35 degrees C. Also, sustainability assessments of the systems are obtained using sustainability index (SI) tool for these various dead state temperatures. Finally, environmental assessments of the systems are calculated from their greenhouse gas (GHG) emissions (gCO(2)/kW h) due to their electricity consumptions. Maximum exergy efficiencies and sustainability assessments are found to be 35.13% and 1.5415 for System III and 34.94% and 1.5372 for System II, respectively. GHG emissions of the systems are calculated to be 2119.68 gCO(2)/day, 153.6 gCO(2)/day and 3840 gCO(2)/day for Systems I, II and III respectively. So, System II becomes a good choose to prevent the global warming and to attain sustainable future. (C) 2011 Elsevier Ltd. All rights reserved.Öğe Efficiency assessment of an integrated gasifier/boiler system for hydrogen production with different biomass types(Pergamon-Elsevier Science Ltd, 2010) Kalinci, Yildiz; Hepbasli, Arif; Dincer, IbrahimIn this study, we utilize some experimental data taken from the literature, especially on the air-blown gasification characteristics of six different biomass fuels, namely almond shell (ASF), walnut pruning (WPF), rice straw (RSF), whole tree wood chips (WWF), sludge (SLF) and non-recyclable waste paper (NPF) in order to study the thermodynamic performance of an integrated gasifier-boiler power system for its hydrogen production. In this regard, both energy and exergy efficiencies of the system are investigated. The exergy contents of different biomass fuels are calculated to be ranging from 15.89 to 22.07 MJ/kg, respectively. The hydrogen concentrations based on the stack gases at the cyclone exit are determined to be between 7 and 18 (%v/v) for NPF and ASF. Also, percentages of combustible vary from 30% to 46%. The stack gas has physical and chemical exergies. The total specific exergy rates are calculated and illustrated. These values change from 3.54 to 6.41 MJ/kg. Then, two types of exergy efficiencies are calculated, such as that exergy efficiency 1 is examined via all system powers, exergy and efficiency 2 is calculated according to specific exergy rates of biomass fuels and product gases. While the exergy efficiencies 1 change between 4.33% and 11.89%, exergy efficiencies 2 vary from 18.33% to 39.64%. Also, irreversibilities range from 9.76 to 18.02 mJ/kg. Finally, we investigate how nitrogen contents of biomass fuels affect on energy and exergy efficiencies. The SLF has the highest amount of nitrogen content as 5.64% db while the NPF has the lowest one as 0.14% db. The minimum and maximum exergetic efficiencies belong to the same fuels. Obviously, the higher the nitrogen content the lower the efficiency based on an inverse ratio between exergy efficiency and nitrogen content. (C) 2009 Professor T. Nejat Veziroglu. Published by Elsevier Ltd. All rights reserved.Öğe Energy and exergy analyses of a new four-step copper-chlorine cycle for geothermal-based hydrogen production(Pergamon-Elsevier Science Ltd, 2010) Balta, M. Tolga; Dincer, Ibrahim; Hepbasli, ArifIn this paper, energy and exergy analyses of the geothermal-based hydrogen production via thermochemical water decomposition using a new, four-step copper chlorine (Cu-Cl) cycle are conducted, and the respective cycle energy and exergy efficiencies are examined. Also, a parametric study is performed to investigate how each step of the cycle and its overall cycle performance are affected by reference environment temperatures, reaction temperatures, as well as energy efficiency of the geothermal power plant itself. As a result, overall energy and exergy efficiencies of the cycle are found to be 21.67% and 19.35%, respectively, for a reference case. (C) 2010 Elsevier Ltd. All rights reserved.Öğe Exergetic and sustainability performance comparison of novel and conventional air cooling systems for building applications(Elsevier Science Sa, 2011) Caliskan, Hakan; Dincer, Ibrahim; Hepbasli, ArifThis study presents energy and exergy analyses and sustainability assessment of one novel and three conventional types of air cooling systems for building applications. First, effectivenesses of the systems are determined using energy analysis method. Second, exergy aspects of the systems are investigated for twelve different dead state temperatures varying from -5 degrees C to 50 degrees C with a temperature interval of 5 degrees C. The specific exergy flows of humid air, dry air and water, exergy efficiency, and specific exergy destruction are then calculated. Sustainability index is also used to define and discuss the systems' sustainability aspects. Finally, the results obtained here show that at the dead state temperatures of higher than 23 degrees C (comfort temperature), exergy efficiency and sustainability of the novel system, which is based on the novel Maisotsenko cycle (M-Cycle), is higher than those of the conventional systems. At a dead state temperature of 50 degrees C, novel cooling system's exergy efficiency can reach 60.329% as the maximum, while the minimum exergy efficiency of other conventional cooling systems becomes as low as 35.866%, respectively. (C) 2011 Elsevier B.V. All rights reserved.Öğe Exergetic performance analysis of Dora II geothermal power plant in Turkey(Pergamon-Elsevier Science Ltd, 2012) Ganjehsarabi, Hadi; Gungor, Ali; Dincer, IbrahimAn exergy analysis of the Dora II geothermal power plant (DGPP) with 9.5 MW net power output is carried out by using actual plant data to evaluate plant performance and pinpoint the locations of exergy destructions/losses. It aims to determine exergy efficiencies, and exergy destructions in each component of the plant. Exergy destructions in each of the components of the whole plant are determined and illustrated based on the actual data. The exergy destructions/losses take place through losses in the vaporizer, preheater, turbines, pumps and cooling tower, and the re-injection of the geothermal fluid. The exergy destruction ratios for these units and processes accounts for 7.97%, 1.25%, 11.93%, 1.3%, 14.92% and 32.18% of the total exergy input to the plant, respectively. Among the observed components in the plant, the most efficient equipment is found to be the preheater with an exergy efficiency value of 98%. The overall energetic and exergetic efficiencies of the plant are calculated to be 10.7% and 29.6%, respectively. The results show that geothermal energy can make a significant contribution toward reducing the emissions of greenhouse gases. Crown Copyright (C) 2012 Published by Elsevier Ltd. All rights reserved.Öğe Exergoeconomic Analysis of a Heat Pump Tumbler Dryer(Taylor & Francis Inc, 2014) Ganjehsarabi, Hadi; Dincer, Ibrahim; Gungor, AliIn this study, exergy and exergoeconomic analyses of a heat pump tumbler dryer are carried out by using actual thermodynamic and cost data. The wet cotton fabric is used as the test drying material. The results show that the specific moisture extraction rate (SMER) and evaporation rate of dryer are equal to 1.08kg/kWh and 0.018kg/s, respectively. Also, the respective exergetic efficiencies of the heat pump and overall system are equal to 0.07 and 0.11. A parametric study is then conducted in order to investigate the system performance and costs of the components, depending on the operating temperature and mass flow rate of air.Öğe Exergoeconomic analysis of geothermal district heating systems: A case study(Pergamon-Elsevier Science Ltd, 2007) Ozgener, Leyla; Hepbasli, Arif; Dincer, Ibrahim; Rosen, Marc A.An exergoeconomic study of geothermal district heating systems through mass, energy, exergy and cost accounting analyses is reported and a case study is presented for the Salihli geothermal district heating system (SGDHS) in Turkey to illustrate the present method. The relations between capital costs and thermodynamic losses for the system components are also investigated. Thermodynamic loss rate-to-capital cost ratios are used to show that, for the devices and the overall system, a systematic correlation appears to exist between capital cost and exergy loss (total or internal), but not between capital cost and energy loss or external exergy loss. Furthermore, a parametric study is conducted to determine how the ratio of thermodynamic loss rate to capital cost changes with reference temperature and to develop a correlation that can be used for practical analyses. The correlations may imply that devices in successful district heating systems such as the SGDHS are configured so as to achieve an overall optimal design, by appropriately balancing the thermodynamic (exergy-based) and economic (cost) characteristics of the overall systems and their devices. (c) 2006 Elsevier Ltd. All rights reserved.Öğe Exergoeconomic based multi-objective optimisation of a solid oxide fuel cell system(Inderscience Enterprises Ltd, 2014) Mert, Suha Orcun; Ozcelik, Zehra; Dincer, IbrahimIn this study, the multi-objective optimisation of a solid oxide fuel cell (SOFC) system by defining the objective functions to maximise the power output, energy efficiency and exergy efficiency, and minimise the cost under various constraints is conducted. In this regard, energy, exergy and exergoeconomic analyses are performed. Some specific cases are considered and studied parametrically by varying practical operating conditions, namely temperature, pressure, current density and stack assembly thickness. An exergoeconomic model is developed for the system and incorporated into the developed computer program MULOP (multi-objective optimiser) which is based on a genetic algorithm to investigate the system parametrically, depending on the multi-objective optimisation of the objective function ratios. The best result obtained for each objective function is 1.65 W for the power produced, 0.242 and 0.269 for both exergy and energy efficiencies, respectively, and 0.0017 $/W for the cost generated.Öğe Exergoeconomic evaluation of a geothermal power plant(Inderscience Enterprises Ltd, 2014) Ganjehsarabi, Hadi; Gungor, Ali; Dincer, IbrahimIn this study, exergy and exergoeconomic analyses of the Dora II geothermal power plant (DGPP) with 9.5 MW net power output are carried out by using real thermodynamic and cost data. The exergetic efficiency of this plant is calculated to be 29.6%. The highest exergy destruction rate among the DGPP components occurs in the cooling towers followed by the turbines, vaporisers, preheaters and pumps. For exergoeconomic analysis, the cost balance equation for each component is written based on certain parameters and auxiliary equations to determine the cost values of exergy destruction. The costs of exergy destruction and electricity produced are determined based on the analysis and data used. The cooling tower I exhibits the greatest exergy destruction cost, followed by the turbines. The present results show that the unit cost of electricity produced and the exergy cost of geothermal fluid are 5.3 cents/kWh and 1.67 cents/kWh for DGPP, respectively.Öğe Exergoeconomic, enviroeconomic and sustainability analyses of a novel air cooler(Elsevier Science Sa, 2012) Caiskan, Hakan; Dincer, Ibrahim; Hepbasli, ArifThis study presents the energy, exergy, environmental, exergoeconomic, enviroeconomic and sustainability analyses of the Maisotsenko cycle based novel air cooler considering the nine different dead state temperatures, while the environment temperature is kept constant. In the energy analysis, the wet bulb and dew point effectivenesses, cooling capacity, energetic coefficient of performance and primary energy ratio rates are calculated. Also, in the exergy analysis, exergy input, output, loss and destruction rates as well as exergetic coefficient of performance and primary exergy ratio and exergy efficiency values are determined. Furthermore, sustainability analysis of the system is conducted through a sustainability index method. The electrical energy consumption cost of this novel air cooler shows that, it consumes only 59.85 $/year, when it is operated 8 h a day and 125 days in a year. The maximum exergetic cost rate is found to be 0.0228 kWh/$-year at a dead state temperature of 37.77 degrees C. Also, according to the enviroeconomic (environmental cost) analysis, this novel air cooler has very CO2 emissions cost as 6.96 $/year. Consequently, these results show the originality of the Maisotsenko cycle based novel air cooler. (C) 2012 Elsevier B.V. All rights reserved.Öğe Exergy analysis and environmental impact assessment of a photovoltaic-hydrogen production system(Inderscience Enterprises Ltd, 2011) Yilanci, Ahmet; Ozturk, Harun Kemal; Dincer, Ibrahim; Ulu, Eylem Yilmaz; Cetin, Engin; Ekren, OrhanIn this study, exergy analysis and environmental impact assessment of a Photovoltaic (PV)-hydrogen production system and its components are carried out. Actual data measured in the system are employed for analysis purposes. Daily hydrogen production amount from solar energy through water electrolysis is 4.43 kg. The average system exergy efficiency is determined to be 3.18%. It is found that the highest exergy destruction occurs in the PVs. In the PVs, 93.3% of the total exergy input (incoming solar exergy) is destroyed. The second highest exergy destruction is from the electrolyser as 4.76% of the total exergy destruction. The average percent exergy destructions are 1.29% and 1.94% for charge controllers-inverter and batteries, respectively.Öğe Exergy Analysis and Sustainability Assessment of a Solar-Ground Based Heat Pump With Thermal Energy Storage(Asme, 2011) Caliskan, Hakan; Hepbasli, Arif; Dincer, IbrahimIn this study, both energy and exergy analyses and sustainability assessment of a thermal energy storage system with a solar-ground coupled heat pump installed in a 120 m(2) house are performed. The actual operating data taken from the literature are utilized for model validation. The system considered here mainly consists of a solar collection system, an underground thermal storage system, an indoor air conditioning system, and a data collection system. First, energy analysis is employed to the system and its components, and the rates of energy input (solar radiation), energy storage, collector heat loss, and other heat loss are found to be 4.083 kW, 1.753 kW, 1.29 kW, and 1.04 kW for a 5 h working time, respectively, while the energy efficiency of the system is calculated to be 42.94%. Exergy analysis of the entire system is then conducted for various reference temperatures varying from 0 degrees C to 25 degrees C with a temperature interval of 5 degrees C. As a result of this analysis, the rates of the maximum exergy input, exergy storage, and exergy losses are determined for a reference temperature of 0 degrees C to be 0.585 kW, 0.24 kW, and 0.345 kW, respectively. Finally, the maximum exergy efficiency of the system is obtained to be 40.99% and the maximum sustainable development using sustainability index, which is a function of exergy efficiency, is calculated to be 1.6946 for a reference temperature of 0 degrees C. Furthermore, the energy and exergy results are illustrated through Sankey (energy flow) and Grassmann (exergy loss and flow) diagrams. [DOI: 10.1115/1.4003040]Öğe Exergy analysis of two geothermal district heating systems for building applications(Pergamon-Elsevier Science Ltd, 2007) Ozgener, Leyla; Hepbasli, Arif; Dincer, IbrahimThis study evaluates the exergetic performance of two local Turkish geothermal district heating systems through exergy analysis. The exergy destructions in these geothermal district heating systems are quantified and illustrated using exergy flow diagrams for a reference temperature of 1 degrees C using the 2003 and 2004 actual seasonal heating data. The results indicate that the exergy destructions in these systems particularly occur due to losses in pump, heat exchangers, pipelines, and the reinjection of thermal water. Exergy efficiencies of the two systems are investigated for the system performance analysis and improvement and are determined to be 42.89% and 59.58%, respectively. (c) 2006 Elsevier Ltd. All rights reserved.
