Hasan Yamık

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.

A Comparison of Engine Performance and the Emission of Fusel Oil and Gasoline Mixtures at Different Ignition Timings

Alcohols have been used as a fuel for engines since 19th century. Among the various alcohols, ethanol is known as the most suited renewable, bio-based and ecofriendly fuel for spark-ignition (SI) engines. In addition, ethanol has higher evaporation heat, octane number, and flammability temperature therefore it has positive influence on engine performance and reduces exhaust emissions. In this study, engine performance and emission levels of unleaded gasoline and unleaded gasoline-fusel oil blends in a spark ignition engine, under variable ignition timings are investigated. Engine torque increased and brake specific fuel consumption (bsfc) decreased with the ignition timings. For F0 and F10 blends, hydrocarbon emissions changed by 22% on average and carbon monoxide (CO) emissions changed by 9.2%. It was also observed that nitrogen oxide (NOx) emissions were reduced.

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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Optimum insulation thickness for piping system using exergy and environmental methods

). 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 Cooling Applications Through Exergy Analysis 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.

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.

Experimental examination of the effects of military aviation fuel JP-8 and biodiesel fuel blends on the engine performance, exhaust emissions and combustion in a direct injection engine

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.

Optimum insulation thickness determination using the environmental and life cycle cost analyses based entransy approach

Natural gas engine (Wartsila 18VSG) having meanly 5,993 kW electrical power output and used in a Trigeneration system located in Ankara was analyzed in terms of energy and exergy. Analysis, which is used actual data, was made to natural gas engine, heat recovery boiler and absorption chiller, while trigeneration system on full load operation conditions. Energy loss, energy efficiency, exergy destruction and exergy efficiencies of the trigeneration system was calculated. The energy and exergy efficiencies of system were determined as 64 and 39 % respectively. FESR (fuel energy saving ratio) and FESxR (fuel exergy saving ratio) were calculated as 27, 28 % respectively for Trigeneration facility.