Papers by Gokmen Demirkaya
ASME 2011 5th International Conference on Energy Sustainability, Parts A, B, and C, 2011
Improving the efficiency of thermodynamic cycles plays a fundamental role in reducing the cost of... more Improving the efficiency of thermodynamic cycles plays a fundamental role in reducing the cost of solar power plants. These plants work normally with Rankine cycles which present some disadvantages due to the thermodynamic behavior of steam at low pressures. These disadvantages can be reduced by introducing alternatives such as combined cycles which combine the best features of each cycle. In this paper a combined Rankine-Goswami cycle (RGC) is proposed and a thermodynamic analysis is conducted. The Goswami cycle, used as a bottoming cycle, uses ammonia-water mixture as the working fluid and produces power and refrigeration while power is the primary goal. This bottoming cycle, reduces the energy losses in the traditional condenser and eliminates the high specific volume and poor vapor quality presented in the last stages of the lower pressure turbine in the Rankine cycle. In addition, the use of absorption condensation in the Goswami cycle, for regeneration of the strong solution, ...
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Wiley Interdisciplinary Reviews: Energy and Environment, 2013
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Volume 6: Emerging Technologies: Alternative Energy Systems; Energy Systems: Analysis, Thermodynamics and Sustainability, 2009
A combined power/cooling cycle, which combines the Rankine and absorption refrigeration cycles, u... more A combined power/cooling cycle, which combines the Rankine and absorption refrigeration cycles, uses ammonia-water mixture as a working fluid and produces power and refrigeration while power is the primary goal. This cycle, also known as the Goswami Cycle, can be used as a bottoming cycle using waste heat from a conventional power cycle or as an independent cycle using low temperature sources such as geothermal and solar energy. This paper presents a parametric analysis of the combined cycle. Parametric study of the cycle was carried out in the commercial software Chemcad 6.1. The thermodynamic property data used in simulations were validated with experimental data. Chemcad model was also compared with simulations previously carried out in the process simulator Aspen Plus. The agreement between the two sets has proved the accuracy of the model developed in Chemcad. Then, optimum operating conditions were found for a range of ammonia concentration in the basic solution, isentropic ex...
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Energy, 2012
ABSTRACT
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Energy, 2010
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Applied Energy, 2011
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International Journal of Energy Research, 2010
Published online in Wiley InterScience (www.interscience.wiley.com). DOI: 10.1002/er.1750 ... Ana... more Published online in Wiley InterScience (www.interscience.wiley.com). DOI: 10.1002/er.1750 ... Analysis of a combined power and cooling cycle ... Gokmen Demirkaya1, Ricardo Vasquez Padilla1,2, D. Yogi Goswami1,Ã,y, Elias Stefanakos1 and Muhammad M. Rahman1 ...
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Development of innovative thermodynamic cycles is important for the efficient utilization of low-... more Development of innovative thermodynamic cycles is important for the efficient utilization of low-temperature heat sources such as solar, geothermal, and waste heat sources. Binary mixtures exhibit variable boiling temperatures during the boiling process, which leads to a good thermal match between the heating fluid and working fluid for efficient heat source utilization. This study presents a theoretical and an experimental analysis of a combined power/cooling cycle, which combines the Rankine and absorption refrigeration cycles, uses ammonia-water mixture as the working fluid and produces power and refrigeration, while power is the primary goal. This cycle, also known as the Goswami Cycle, can be used as a bottoming cycle using waste heat from a conventional power cycle or as an independent cycle using low to mid-temperature sources such as geothermal and solar energy. A thermodynamic analysis of power and cooling cogeneration was presented. The performance of the cycle for a range...
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Thermodynamic Cycles for Renewable Energy Technologies
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ASME 2017 11th International Conference on Energy Sustainability
Liquid Air Energy Storage (LAES) is one of the methods to store energy, which takes the advantage... more Liquid Air Energy Storage (LAES) is one of the methods to store energy, which takes the advantage of high expansion ratio of air from liquid state to gaseous state. It uses liquefied air to create a potential energy reserve, by storing air in liquid form at −196°C, in insulated, unpressurized vessels and exposing them to ambient temperatures followed by an electricity generation process by driving a turbine. Off-peak electricity is used to liquefy air, and liquid air will be drawn from the tank, pumped to high pressure and used to drive a turbine to generate electricity when this stored energy is needed. Thermal storage loops (cold recycle) within the cycle as well as integration of waste cold (using the cold released during regasification of LNG) or waste heat (utilizing a waste heat stream during the expansion of air) are the key benefits of this technology and strengthen its competitive position among other energy storage methods. In this paper, a grid scale, long duration energy...
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Entropy
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Journal of Energy Resources Technology
The Goswami cycle is a cycle that combines an ammonia–water vapor absorption cycle and a Rankine ... more The Goswami cycle is a cycle that combines an ammonia–water vapor absorption cycle and a Rankine cycle for cooling and mechanical power purposes by using thermal heat sources such as solar energy or geothermal steam. In this paper, a theoretical investigation was conducted to determine the performance outputs of the cycle, namely, net mechanical power, cooling, effective first law efficiency and exergy efficiency, for a boiler and an absorber temperature of 85 °C and 35 °C, respectively, and different boiler pressures and ammonia-water concentrations. In addition, an experimental investigation was carried out to verify the predicted trends of theoretical analysis and evaluate the performance of a modified scroll expander. The theoretical analysis showed that maximum effective first law and exergy efficiencies were 7.2% and 45%, respectively. The experimental tests showed that the scroll expander reached a 30–40% of efficiency when boiler temperature was 85 °C and rectifier temperatu...
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Combined power and refrigeration cycles have been explored for improving their overall energy con... more Combined power and refrigeration cycles have been explored for improving their overall energy conversion efficiency and decreasing the cost of energy produced. Bottoming cycles can be used to recover the waste heat or exhaust heat of gas turbines and conventional steam Rankine cycles and convert it to work and/or refrigeration. In most applications, refrigeration is the more expensive product than power because it requires refrigeration equipment as well as power to produce conventional refrigeration. Therefore, the additional output of refrigeration by the combined cycle provides greater benefit than conventional power systems. This paper presents a review of combined power and cooling cycles for effective utilization of heat sources. C
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Journal of Quantitative Spectroscopy and Radiative Transfer, 2005
ABSTRACT Monte Carlo method was used to predict the incident radiative heat fluxes on the freeboa... more ABSTRACT Monte Carlo method was used to predict the incident radiative heat fluxes on the freeboard walls of the METU 0.3 MWt atmospheric bubbling fluidized bed combustor based on the data reported previously. The freeboard was treated as a rectangular enclosure with gray interior walls and gray, absorbing, emitting and isotropically scattering medium. A Monte Carlo solver was developed and the performance of the solver was assessed by comparing its predictions with those of method of lines solution of discrete ordinates method and experimental measurements reported previously. Parametric studies were carried out to examine the effects of particle load and anisotropic scattering on the predicted incident radiative heat fluxes. The comparisons show that Monte Carlo method reproduces the measured incident radiative heat fluxes reasonably well for the freeboard problem.
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Journal of Energy Resources Technology, 2012
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Journal of Energy Resources Technology, 2012
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Papers by Gokmen Demirkaya