Emin Açıkkalp

Limits and Optimization of Power Input or Output of Actual Thermal Cycles

In classical thermodynamic, maximum power obtained from system (or minimum power supplied to system) defined as availability (exergy), but availability term is only used for reversible systems. In reality, there is no reversible system, all systems are irreversible, because reversible cycles doesn’t include constrains like time or size and they operates in quasi-equilibrium state. Purpose of this study is to define limits of the all basic thermodynamic cycles and to provide finite-time exergy models for irreversible cycles and to obtain the maximum (or minimum) available power for irreversible (finite-time exergy) cycles. In this study, available power optimization and performance limits were defined all basic irreversible thermodynamic cycles, by using first and second law of thermodynamic. Finally, these results were evaluated in terms of cycles’ first and second law efficiency, COP, power output (or input) and exergy destruction.

Modeling and optimization of maximum available work for irreversible gas power cycles with temperature dependent specific heat

Abstract In classical thermodynamics, the maximum power obtained from a system is defined as exergy (availability). However, the term exergy is used for reversible cycles only; in reality, reversible cycles do not exist, and all systems are irreversible. Reversible cycles do not have such restrictions as time and dimension, and are assumed to work in an equilibrium state. The objective of this study is to obtain maximum available work for SI, CI and Brayton cycles while considering the aforementioned restrictions and assumptions. We assume that the specific heat of the working fluid varies with temperature, we define optimum compression ratios and pressure ratio in order to obtain maximum available work, and we discuss the results obtained. The design parameter most appropriate for the results obtained is presented.

Assessment of thermodynamic performance and exergetic sustainability of turboprop engine using mixture of kerosene and methanol

In this study, first and second laws of thermodynamics were performed in the turboprop and is analysed and discussed with the mathematical model of sustainability performance of a turboprop engine using a mixture of alternative fuel (Methanol CH3OH) and conventional fuel (Kerosene C12H26). The results showed when the excess air is kept constant, with the increases of the alternative fuel, mixture is enriched with oxygen as a source of methanol and the actual air-fuel ratio decreased was determined. When the rate of alternative fuel in mixture was increased, it was observed that the fuel flow started to increase, because Lower Heating Value of methanol is lower than kerosene. Therefore, increasing of fuel consumption was found to obtain the same power in propeller as negative effect. ESIs - waste exergy ratio, exergy destruction factor and environmental effect factor - is increased with the increasing ratio of methanol in the mixture.

Comparative Analysis of Thermoeconomic Evaluation Criteria for an Actual Heat Engine

Abstract In the present study, an actual heat engine is investigated by using different thermoeconomic evaluation criteria in the literature. A criteria that has not been investigated in detail is considered and it is called as ecologico-economical criteria ( FEC

Energy and Exergy Evaluation of an Air Separation Facility: A Case Study

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Exergy and Energy Analysis of an Aircraft Air Cycle Machine at Designated Altitude

). It is the difference of power cost and exergy destruction rate cost of the system. All four criteria are applied to an irreversible Carnot heat engine, results are presented numerically and some suggestions are made.

Optimum insulation thickness for piping system using exergy and environmental methods

In this study, an air separation plant working according to the principle of separation of two columns and producing argon, nitrogen, and oxygen with a daily capacity of 250 tons was analyzed in detail with respect to the first and second laws of thermodynamics and the results were evaluated. The energy and exergy values for each point defined in the system were obtained. By using these values, thermodynamic evaluations for both the whole system and also its components were made. The efficiency values of energy and exergy, the values of energy losses and exergy destruction rates, the EIP (energetic improvement potential rate), ExIP (exergetic improvement potential rate), and the production of entropy values were found as 0.453, 0.79, 4368.475 kW, 10535.875 kW, 2391.535 kW, 3800.485 kW, and 35.347 kW/K, respectively. The energy and exergy efficiencies of the plant were found to be 45.3% and 13.1% respectively.

Optimum Insulation Thickness for Cooling Applications Through Exergy Analysis and Environmental Methods

In this paper, energy and exergy analyses are performed on an aircraft air cycle machine. Air cycle machine is essential to ventilate aircraft cabin during commercial flights. Exergy destruction rates and energy parameters of each component are investigated at a designated aircraft cruise altitude which is 10,789 meters and ambient air that is −55 °C. The thermodynamic parameters used here to obtain the results are real ones from actual devices. Exergy flow supplied to the air cycle machine is found as 235.392 kW. Exergy destruction rate of primary heat exchanger is calculated as 33.839 kW. Exergy destruction rate of turbine, compressor, and secondary heat exchanger section is calculated to be 55.65 kW.

Energy and Exergy Analysis of a Trigeneration Facility with Natural Gas Engine

Optimum insulation thickness for a piping system is investigated using a novel method that combines exergy and environmental analysis. Rockwool and glasswool are chosen as insulation materials for the system and the analysis was carried out for the city of Bilecik, located in the Marmara Region of Turkey. Investigation is performed for the different nominal pipe sizes (NPS or diameter nominal: DN) of 50, 100 and 150. The environmental impacts of the various parameters are described. Results for the environmental impact of the system, the net environmental saving, exergetic heat loss, the net exergy saving, fuel consumption and CO2 emissions according to insulation thickness are presented. Optimum points are calculated as 0.109 m, 0.126 m and 0.137 m for DN 50, 100, and 150, respectively for the glasswool. Optimum insulation thickness for the rockwool was determined as 0.064 m, 0.073 m and 0.079 for DN 50, 100, and 150, respectively.

Advanced exergoeconomic analysis of an electricity-generating facility that operates with natural gas

In this study, optimum insulation thickness is investigated for cooling applications in Antalya/Turkey. Antalya has hot climate and it is located in the Mediterranean Region of the Turkey. A novel method is presented to evaluate environmental impact of considered system. Energy and exergy analyses are used and they are combined with environmental impact factors. Two different wall types and two different insulation materials are chosen. Electricity is assumed as main energy source at the calculations. Results are presented and the optimum insulation thicknesses are researched according to novel method we proposed.