Mehmet Kanoglu

Exergy analysis of a dual-level binary geothermal power plant

Exergy analysis of a 12.4 MW existing binary geothermal power plant is performed using actual plant data to assess the plant performance and pinpoint sites of primary exergy destruction. Exergy destruction throughout the plant is quantified and illustrated using an exergy flow diagram, and compared to the energy flow diagram. The causes of exergy destruction in the plant include the exergy of the working fluid lost in the condenser, the exergy of the brine reinjected, the turbine-pump losses, and the preheater–vaporizer losses. The exergy destruction at these sites accounts for 22.6, 14.8, 13.9, and 13.0% of the total exergy input to the plant, respectively. Exergetic efficiencies of major plant components are determined in an attempt to assess their individual performances. The exergetic efficiency of the plant is determined to be 29.1% based on the exergy of the geothermal fluid at the vaporizer inlet, and 34.2% based on the exergy drop of the brine across the vaporizer–preheater system (i.e. exergy input to the Rankine cycle). For comparison, the corresponding thermal efficiencies for the plant are calculated to be 5.8 and 8.9%, respectively.

Exergy analysis of vapor compression refrigeration systems

Abstract A computational model based on the exergy analysis is presented for the investigation of the effects of the evaporating and condensing temperatures on the pressure losses, the exergy losses, the second law of efficiency, and the coefficient of performance (COP) of a vapor compression refrigeration cycle. It is found that the evaporating and condensing temperatures have strong effects on the exergy losses in the evaporator and condenser, and on the second law of efficiency and COP of the cycle but little effects on the exergy losses in the compressor and the expansion valve. The second law efficiency and the COP increases, and the total exergy loss decreases with decreasing temperature difference between the evaporator and refrigerated space and between the condenser and outside air.

Exergetic performance investigation of a turbocharged stationary diesel engine

An exergetic assessment is reported of a turbocharged stationary diesel engine with a power output of about 19 MW. The system studied consists of a diesel engine, a turbine, a compressor, an intercooler and a radiator. The sites of exergy destructions are identified and quantified and the exergy efficiencies of various components are determined. The effects of inlet air temperature and pressure on the exergy efficiency and exergy destruction for the system components are investigated. The exergy efficiency of the engine is found to be 40.5%. The greatest exergy destruction occurs in the engine itself, which accounts for 84% of total exergy destruction in the system.

Thermodynamic analysis of a pyroprocessing unit of a cement plant: a case study

The cement industry is one of the most intensive energy and cost industries in the world that consumes about 3800 MJ per tonne of cement produced. To achieve an effective energy management scheme, energy and exergy analyses were employed on the pyroprocessing unit of Gaziantep Cement Plant in Turkey. Energy and exergy efficiencies are determined to be 52.2% and 35.9%, respectively. Application of insulation on the unit reduced rate of heat loss from 22.7 MW to 17.3 MW. This in turn increases both the energy and the exergy efficiency values to 63.6% and 47.3%, respectively. The effect of weather conditions on the efficiency values is studied. It is estimated that 1056.7 kW of electricity can be generated by using the waste heat from the unit. The application of waste heat recovery steam generator prevents the emission of 5183 tons of CO2 to the atmosphere, representing a reduction of 8.2%.

Thermodynamic analysis and optimization of various power cycles for a geothermal resource

ABSTRACT In this study, geothermal resources in Kutahya-Simav region having geothermal water at a temperature suitable for power generation is considered. The study is aimed to yield the method of the most effective use of the geothermal resource and a rational thermodynamic comparison of various cycles for a given resource. Maximum first law efficiencies vary between 6.9 to 10.6% while the second law efficiencies vary between 38.5 to 59.3% depending on the cycle considered. The maximum power output, the first law, and the second law efficiencies are obtained for Kalina cycle followed by combined cycle and binary cycle.

Performance assessment of an integrated absorption cooling-hydrogen liquefaction system using geothermal energy

An integrated geothermal based triple effect absorption cooling and Linde–Hampson system for hydrogen gas liquefaction is proposed and analysed thermodynamically. The effect of various operating conditions and parameters on the system performance is studied. The results show that the mass of hydrogen gas pre–cooled by the absorption system per unit mass flow rate of geothermal water flowing through the system (n) and the amount of hydrogen liquefied per unit mass flow rate of geothermal water flowing through the system (y) increase with an increase in the geothermal source temperature. Also, both energetic and exergetic coefficients of performance decrease from 1.33 to 0.12 and 0.92 to 0.08, respectively with an increase in the mass flow rate of geothermal water from 1.5 kg/s to 3.0 kg/s. The energetic and exergetic utilisation factors decrease from 0.06 to 0.009 and 0.19 to 0.006, respectively as the mass flow rate of geothermal water increases.

Experimental study on an open cycle desiccant cooling system

This paper presents the design and construction of an experimental desiccant cooling system that uses natural zeolite as the desiccant. This is the first use of this desiccant in an actual or experimental system. The primary system components are originally designed and constructed. The paper provides a sufficient detail on the design procedure of the components as well as the methods of measurements. Experiments are conducted to cover a wide range of system and operating parameters. For the investigated cases, the coefficient of performance, the cooling capacity, and the moisture removal capacity take maximum values of 0.95, 16 kW/kg dry air, and 6.5 g/kg dry air, respectively. Exergy analysis is performed for a typical operation of the unit and the exergy destructions and exergy efficiencies are calculated. The greatest exergy destruction occurs in the desiccant wheel and the exergy efficiency of the unit is 3.3 percent.

An Investigation of Energy Versus Exergy Based Optimization for Power Cycles

A comparison of optimization studies based on energy and exergy methods and for the ideal and actual working models of common power cycles are performed. The cycles considered include the simple gas-turbine cycle, the regenerative gas-turbine cycle, the regenerative gas turbine cycle with reheating and intercooling, the simple steam cycle, the reheat steam cycle, and the combined gas-vapor cycle. The optimization is performed to determine the optimum pressure ratios in gas-turbine cycles and the optimum boiler pressures in steam cycles that maximize the thermal efficiency of the cycle in energy method and the exergy efficiency in exergy method. The optimum points are also searched for maximizing the net work of the cycle in both energy and exergy methods. The results show that the optimum boiler pressures that maximize the network are identical based on both energy and exergy approaches and for both ideal and actual operating models in simple steam and reheat steam cycles. The optimum boiler pressures that maximize the cycle efficiency are about the same based on both energy and exergy approaches when ideal operations are considered in simple and reheat steam cycles. The optimum points differ when actual operations are considered for these cycles. The optimum pressure ratios that maximize the network are identical based on both energy and exergy approaches but different depending on the selection of an ideal or actual model in simple and regenerative gas-turbine cycles, and in combined cycle. No agreement with respect to the optimum pressure ratios that maximize the cycle efficiency is observed for all types of gas-turbine cycles including the combined cycle.

Exergy-based industrial ecology assessment of integrated and separated power and heat production systems

In this paper, exergy-based industrial ecology concept is demonstrated in terms of exergetic rate of resource depletion by analysing two different combined heat and power productions systems: the CGAM system and a Diesel Engine Powered Cogeneration (DEPC) system. The analysis indicates that exergy-based industrial ecology concept can be successfully applied to cogeneration systems, demonstrating advantages of integrated generation. The weighted depletion number for separate productions of electricity and steam is determined to be 0.673 whereas the value for the integrated CGAM system is 0.532. The corresponding depletion numbers for the DEPC system are determined to be 0.590 and 0.480, respectively. It is clear from these numerical results that separate power and heat production system causes greater non-renewable resource depletion when compared with integrated systems.

Thermodynamic Evaluation of First and Second Law Performance of Evaporative Cooling Schemes for Regenerative Gas Turbines

In this study, effect of evaporative cooling on performance of regenerative gas turbine cycle is investigated considering simple regenerative cycle and regenerative cycle with intercooling and reheating. Evaporative cooling is applied to inlet air in simple regenerative cycle while it is applied to compressor inlet air and air between the compressor stages in reheat regenerative cycle. The first and second law performances of the cycles incorporating evaporative cooling are compared to the corresponding conventional cycles. Effects of the temperature and relative humidity of the ambient air, the turbine inlet temperature, and the pressure ratio on the net work, the thermal efficiency, and the second-law efficiency of the cycles are investigated. It appears that evaporative cooling increases thermal efficiency, net work, and optimum pressure ratio. With respect to simple regenerative cycle at a turbine inlet temperature of 1400 K and at a pressure ratio of 20, the thermal efficiency and the net work increase by 1.5 percent and 4 percent, respectively by inlet cooling in simple regenerative cycle while they increase by 18.3 percent and 12.2 percent, respectively by inlet cooling and intercooling in reheat regenerative cycle. With respect to conventional regenerative cycle with intercooling and reheating, evaporative cooling applied to inlet air and for intercooling provides essentially no increase in thermal and second-law efficiencies while it increases the net work 8.2 percent to 17.8 percent depending on the ambient conditions. Increasing turbine inlet temperature gives a linear increase in the optimum pressure ratio. As the ambient temperature increases and the relative humidity decreases, evaporative cooling becomes more effective in improving cycle performance.