The Experts below are selected from a list of 60612 Experts worldwide ranked by ideXlab platform
I. Horuz - One of the best experts on this subject based on the ideXlab platform.
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A comparison between Ammonia-Water and Water-lithium bromide solutions in absorption heat transformers
International Communications in Heat and Mass Transfer, 2001Co-Authors: E. Kurem, I. HoruzAbstract:Abstract The study included an investigation to analyze the Absorption Heat Pump (AHP) and Absorption Heat Transformers (AHT) using Ammonia-Water and Water-lithium bromide solutions. A fundamental AHP and AHT systems are described and the operating sequence is explained. Since the AHT system widely use Ammonia-Water solution with Ammonia as the refrigerant and Water-lithium bromide solution with Water as the refrigerant, the comparison of the two is presented in respect of the coefficient of performance (COP), the flow ratio (FR) and the maximum system pressure. It is concluded that the AHT system using Water-lithium bromide solution provided better performance than the system using Ammonia-Water solution.
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A comparison between Ammonia-Water and Water-lithium bromide solutions in vapor absorption refrigeration systems
International Communications in Heat and Mass Transfer, 1998Co-Authors: I. HoruzAbstract:The study included an investigation to analyze the Vapor Absorption Refrigeration (VAR) systems using Ammonia-Water and Water-lithium bromide solutions. A fundamental VAR system is described and the operating sequence is explained. Since the most common VAR systems use Ammonia-Water solution with Ammonia as the refrigerant and Water-lithium bromide solution with Water as the refrigerant, the comparison of the two is presented in respect of the coefficient of performance (COP), the cooling capacity and the maximum and minimum system pressures. It is concluded that the VAR system using Water-lithium bromide solution provided better performance than the system using Ammonia-Water solution. However, there are some points to be considered such as; the danger of crystallization and impossibility of operating in very low temperatures because of the use of Water as the refrigerant.
Ibrahim Dincer - One of the best experts on this subject based on the ideXlab platform.
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thermodynamic performance assessment of an Ammonia Water rankine cycle for power and heat production
Energy Conversion and Management, 2010Co-Authors: W. R. Wagar, Calin Zamfirescu, Ibrahim DincerAbstract:Abstract In this paper, an Ammonia–Water based Rankine cycle is thermodynamically analyzed for renewable-based power production, e.g. solar, geothermal, biomass, oceanic-thermal, and nuclear as well as industrial waste heat. Due to the nature of the Ammonia–Water mixture, changes in its concentration allow thermodynamic cycles to adapt to fluctuations in renewable energy sources, which is an important advantage with respect to other working fluids. The non-linearity of the working fluid’s behaviour imposes that each cycle must be optimized based upon several parameters. A model has been developed to optimize the thermodynamic cycle for maximum power output and carry out a parametric study. The lowest temperature state of the system is fixed, and three other parameters are variables of study, namely, maximum system temperature, Ammonia concentration and energy ratio, which is a newly introduced parameter. Energy ratio indicates the relative position of the expansion state and is defined in terms of enthalpies. The study is conducted over a concentration range of 0–0.5, the maximum temperature studied varies between 75 °C and 350 °C for extreme cases, and the energy ratio from saturated liquid to superheated vapour. As a result, the optimal expansion energy ratio is predicted. The cycle efficiencies are drastically affected by the concentrations and temperatures. Depending on the source temperature, the cycle energy efficiency varies between 5% and 35% representing up to 65% of the Carnot limit. The optimal energy ratio has been determined for several concentrations and reported graphically.
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Thermodynamic performance assessment of an Ammonia–Water Rankine cycle for power and heat production
Energy Conversion and Management, 2010Co-Authors: W. R. Wagar, Calin Zamfirescu, Ibrahim DincerAbstract:Abstract In this paper, an Ammonia–Water based Rankine cycle is thermodynamically analyzed for renewable-based power production, e.g. solar, geothermal, biomass, oceanic-thermal, and nuclear as well as industrial waste heat. Due to the nature of the Ammonia–Water mixture, changes in its concentration allow thermodynamic cycles to adapt to fluctuations in renewable energy sources, which is an important advantage with respect to other working fluids. The non-linearity of the working fluid’s behaviour imposes that each cycle must be optimized based upon several parameters. A model has been developed to optimize the thermodynamic cycle for maximum power output and carry out a parametric study. The lowest temperature state of the system is fixed, and three other parameters are variables of study, namely, maximum system temperature, Ammonia concentration and energy ratio, which is a newly introduced parameter. Energy ratio indicates the relative position of the expansion state and is defined in terms of enthalpies. The study is conducted over a concentration range of 0–0.5, the maximum temperature studied varies between 75 °C and 350 °C for extreme cases, and the energy ratio from saturated liquid to superheated vapour. As a result, the optimal expansion energy ratio is predicted. The cycle efficiencies are drastically affected by the concentrations and temperatures. Depending on the source temperature, the cycle energy efficiency varies between 5% and 35% representing up to 65% of the Carnot limit. The optimal energy ratio has been determined for several concentrations and reported graphically.
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thermodynamic analysis of a novel Ammonia Water trilateral rankine cycle
Thermochimica Acta, 2008Co-Authors: Calin Zamfirescu, Ibrahim DincerAbstract:Abstract In this paper we thermodynamically assess the performance of an Ammonia–Water Rankine cycle that uses no boiler, but rather the saturated liquid is flashed by a positive displacement expander (e.g., reciprocating, centrifugal, rotating vane, screw or scroll type expander) for power generation. This cycle has no pinch point and thus the exergy of the heat source can be better used by matching the temperature profiles of the hot and the working fluids in the benefit of performance improvement. The second feature comes from the use of the Ammonia–Water mixture that offers further opportunity to better match the temperature profiles at the sink level. The influence of the expander efficiency, Ammonia concentration and the coolant flow rate is investigated and reported for a case study. The optimized cycle is then compared to four organic Rankine cycles and a Kalina-type cycle and shows the best performance. It is also shown that, in order to determine the best cycle configuration and parameters, energy efficiency must be used only in conjunction with the amount of the heat recovered from the source. The efficiency of the cycle running with Ammonia–Water is 0.30 in contrast to steam-only case showing 0.23 exergy efficiency, which means an increment of 7.0% is obtained for the same operating conditions. If cogeneration is used the cycle effectiveness may even be over 70%. The cycle can be applied for low power/low temperature heat recovery from geothermal sources, ocean thermal energy conversion, solar energy or process waste heat, etc.
Kyoungjin Kim - One of the best experts on this subject based on the ideXlab platform.
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assessment of pinch point characteristics in heat exchangers and condensers of Ammonia Water based power cycles
Applied Energy, 2014Co-Authors: Kyoung Hoon Kim, Kyoungjin KimAbstract:In heat exchanging devices of Ammonia–Water based power generation cycles for the recovery of waste heat in the form of sensible energy, assessment of pinch point (PP) is far more complicated compared to the case of working fluid of pure substance. In this study, efficient and novel method is suggested for PP assessments in source heat exchanger and condenser in Ammonia–Water based power generation cycles. The concept of imaginary source and coolant outlet temperatures is proposed in the present method and PP characteristics can be efficiently evaluated by using the proposed approach. The present method is especially useful when PP occurs in the middle between bubble and dew points during variable temperature phase transition due to the nature of binary mixture. The effects of system parameters are investigated on the PP characteristics including PP location and the corresponding mass flow ratios of working fluid to source and coolant fluids. The analysis shows that the PP characteristics are affected quite complicatedly and sensitively with changing Ammonia concentration or working fluid pressure. Depending on the working conditions, the PP location within heat exchanging devices exhibit abrupt changes between a middle point between bubble and dew points and usual PP locations such as device inlet/exit or bubble point of working fluid.
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effects of Ammonia concentration on the thermodynamic performances of Ammonia Water based power cycles
Thermochimica Acta, 2012Co-Authors: Kyoung Hoon Kim, Chul Ho Han, Kyoungjin KimAbstract:Abstract The power generation systems using a binary working fluid such as Ammonia–Water mixture are proven to be the feasible method for utilizing a low-temperature waste heat source. In this work, Ammonia–Water based Rankine (AWR) regenerative Rankine (AWRR) power generation cycles are comparatively analyzed by investigating the effects of Ammonia mass concentration in the working fluid on the thermodynamic performances of systems. Temperature distributions of fluid streams in the heat exchanging devices are closely examined at different levels of Ammonia concentration and they might be the most important design consideration in optimizing the power systems using a binary working fluid. The analysis shows that the lower limit of workable Ammonia concentration decreases with increasing turbine inlet pressure. Results also show that both the thermal and exergy efficiencies of AWRR system are generally better than those of AWR system, and can have peaks at the minimum allowable Ammonia concentrations in the working range of system operation.
Srinivas Garimella - One of the best experts on this subject based on the ideXlab platform.
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development of a micro scale heat exchanger based residential capacity Ammonia Water absorption chiller
International Journal of Refrigeration-revue Internationale Du Froid, 2018Co-Authors: Marcel A Staedter, Srinivas GarimellaAbstract:Abstract A standalone absorption chiller based on microchannel heat exchanger technology was developed with a cooling capacity of 7 kW. A review of recent advances in microscale heat and mass exchangers and vapor absorption technology guided this development. Thermodynamic and heat and mass transfer design procedures are discussed. A control system for standalone operation was developed. Experimental evaluation demonstrated the achievement of target cooling capacities. An overall system COP of 0.44, and an Ammonia–Water cycle COP of 0.51 were achieved. Reasons for differences between model predictions and actual performance are discussed. This development validates scalability and application of microscale heat exchanger technology for absorption heat pumps at residential-scale capacities. In contrast to conventional absorption systems, core heat and mass exchangers require only small portion of overall system volume and weight, which significantly improves the prospects of this technology for small capacity applications.
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experimental evaluation of a small capacity waste heat driven Ammonia Water absorption chiller
International Journal of Refrigeration-revue Internationale Du Froid, 2017Co-Authors: Anurag Goyal, Marcel A Staedter, Dhruv C Hoysall, Mikko J Ponkala, Srinivas GarimellaAbstract:Abstract This paper presents the results from an experimental evaluation of a small-scale, waste-heat driven Ammonia-Water absorption chiller. The cycle is thermally driven, using the waste heat from diesel generator exhaust to desorb the refrigerant solution. The absorber and condenser are directly-coupled to the ambient air. The remaining heat exchangers are packaged in a compact microchannel monolithic structure for enhancing heat transfer. The system is designed to deliver 2.71-kW of cooling at extreme ambient temperature of 51.7 °C at a coefficient of performance of 0.55. Experiments on a heat pump breadboard system are conducted at ambient conditions of 29.7–44.2 °C, with delivered cooling duties of 2.54–1.91 kW. System and individual component performance is analyzed and compared with cycle model predictions, and deviations are explained. The absorber and desorber were identified to be the limiting components in the system. Effects of variation in ambient temperature are studied to characterize the performance at off-design conditions.
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model based feedback control of an Ammonia Water absorption chiller
Science and Technology for the Built Environment, 2015Co-Authors: Anurag Goyal, Alexander S Rattner, Srinivas GarimellaAbstract:In this study, potential control strategies for a small-scale, 3.5-kW Ammonia–Water absorption chiller are developed and investigated numerically using a dynamic simulation model. The dynamic model is employed to study the response of the system under varying ambient temperatures and cooling load demands. Two strategies are investigated for feedback control of the system. The first control loop maintains the evaporator temperature glide set-point (Tevap,out – Tevap,in), while the second control loop regulates desorption temperature to provide the desired cooling duty and maintain the delivered coolant temperature at a set-point. At design operating conditions, the proposed control for evaporator temperature glide requires ∼250 s to reach the set-point of 3°C, starting from ambient conditions. With the proposed implementation of desorption temperature control, the system can respond to changes in ambient temperature and cooling load demand, and maintain the delivered coolant temperature within ±0.75°C of t...
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Ammonia Water desorption heat and mass transfer in microchannel devices
International Journal of Refrigeration-revue Internationale Du Froid, 2011Co-Authors: Matthew D Determan, Srinivas GarimellaAbstract:Abstract This paper presents the results of an experimentally validated model for the prediction of local heat and mass transfer rates in a microchannel Ammonia–Water desorber. The desorber is an extremely compact 178 mm × 178 mm × 0.508 m tall component capable of transferring the required heat load (∼17.5 kW) for a residential heat pump system. The model predicts temperature, concentration and mass flow rate profiles through the desorber, as well as the effective wetted area of the heat transfer surface. Previous experimental and analytical research by the authors demonstrated the performance of this same microchannel geometry as an absorber. Together, these studies show that this compact geometry is suitable for all components in an absorption heat pump, which would enable the increased use of absorption technology in the small-capacity heat pump market.
Jocelyn Millette - One of the best experts on this subject based on the ideXlab platform.
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Simulation of an Ammonia–Water absorption chiller
Renewable Energy, 2013Co-Authors: Brice Le Lostec, Nicolas Galanis, Jocelyn MilletteAbstract:An increased interest in absorption chillers has been observed [1] because these systems can utilize solar, geothermal and biomass energy sources, but also because they are quiet, vibration-free, require little maintenance and are ecological [2]. Instead of a compressor system, which uses electricity, an absorption cooling system, using renewable energy and kinds of waste heat energy, may be used for cooling. This paper presents the simulation of a single stage solar absorption chiller operating with an Ammonia–Water mixture under steady state conditions. This simulation is based on heat and mass balances for each component. The heat and mass transfers in the absorber, the condensation of binary vapor of Ammonia–Water in the condenser and a thermosyphon desorber placed under the purification column were modeled. The numerical model was compared and validated with experimental data obtained with a solar absorption chiller. The calculated results agree well with experimental data. Simulations based on experimental data were used to predict the temperature and concentration profiles in each heat exchanger. A parametric study was conducted to investigate the effect of evaporator and desorber temperature on the absorption chiller's performance. The COP decreases by 25% with a decrease of 10 °C in evaporator temperature and the COP increases by 4% with an increase of 10 °C in desorber temperature.
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simulation of an Ammonia Water absorption chiller
Renewable Energy, 2013Co-Authors: Brice Le Lostec, Nicolas Galanis, Jocelyn MilletteAbstract:An increased interest in absorption chillers has been observed [1] because these systems can utilize solar, geothermal and biomass energy sources, but also because they are quiet, vibration-free, require little maintenance and are ecological [2]. Instead of a compressor system, which uses electricity, an absorption cooling system, using renewable energy and kinds of waste heat energy, may be used for cooling. This paper presents the simulation of a single stage solar absorption chiller operating with an Ammonia–Water mixture under steady state conditions. This simulation is based on heat and mass balances for each component. The heat and mass transfers in the absorber, the condensation of binary vapor of Ammonia–Water in the condenser and a thermosyphon desorber placed under the purification column were modeled. The numerical model was compared and validated with experimental data obtained with a solar absorption chiller. The calculated results agree well with experimental data. Simulations based on experimental data were used to predict the temperature and concentration profiles in each heat exchanger. A parametric study was conducted to investigate the effect of evaporator and desorber temperature on the absorption chiller's performance. The COP decreases by 25% with a decrease of 10 °C in evaporator temperature and the COP increases by 4% with an increase of 10 °C in desorber temperature.
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experimental study of an Ammonia Water absorption chiller
International Journal of Refrigeration-revue Internationale Du Froid, 2012Co-Authors: Brice Le Lostec, Nicolas Galanis, Jocelyn MilletteAbstract:Abstract This paper presents the performance of an Ammonia-Water absorption chiller. This single-stage 10 kW absorption chiller is cooled with a Water-ethylene glycol solution. The required heat source is hot Water between 75 °C and 85 °C. Different operating conditions can be imposed by varying temperatures and flow rates of secondary circuits and the flow of the rich solution. This equipment, designed for solar air conditioning applications, was tested under various operating conditions to assess its performance. This study shows that the performance of the absorption chiller decreases significantly with the evaporator temperature. This is due to a problem of partial evaporation in the evaporator when the absorption machine is operated outside its design specifications. Cooling capacity oscillations, caused by refrigerant expansion control, were also observed. Absorption chiller performance is also influenced by heat source temperature, cooling temperatures and flow of the rich solution.
