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I. Horuz – One of the best experts on this subject based on the ideXlab platform.

  • A comparison between Ammonia–Water and Water-lithium bromide solutions in absorption heat transformers
    International Communications in Heat and Mass Transfer, 2001
    Co-Authors: E. Kurem, I. Horuz

    Abstract:

    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.

  • A comparison between Ammonia–Water and Water-lithium bromide solutions in vapor absorption refrigeration systems
    International Communications in Heat and Mass Transfer, 1998
    Co-Authors: I. Horuz

    Abstract:

    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.

  • thermodynamic performance assessment of an Ammonia Water rankine cycle for power and heat production
    Energy Conversion and Management, 2010
    Co-Authors: W. R. Wagar, Calin Zamfirescu, Ibrahim Dincer

    Abstract:

    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.

  • Thermodynamic performance assessment of an Ammonia–Water Rankine cycle for power and heat production
    Energy Conversion and Management, 2010
    Co-Authors: W. R. Wagar, Calin Zamfirescu, Ibrahim Dincer

    Abstract:

    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.

  • thermodynamic analysis of a novel Ammonia Water trilateral rankine cycle
    Thermochimica Acta, 2008
    Co-Authors: Calin Zamfirescu, Ibrahim Dincer

    Abstract:

    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.

  • assessment of pinch point characteristics in heat exchangers and condensers of Ammonia Water based power cycles
    Applied Energy, 2014
    Co-Authors: Kyoung Hoon Kim, Kyoungjin Kim

    Abstract:

    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.

  • effects of Ammonia concentration on the thermodynamic performances of Ammonia Water based power cycles
    Thermochimica Acta, 2012
    Co-Authors: Kyoung Hoon Kim, Chul Ho Han, Kyoungjin Kim

    Abstract:

    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.