Ali Gungor

Exergoeconomic Analysis of a Heat Pump Tumbler Dryer

In this study, exergy and exergoeconomic analyses of a heat pump tumbler dryer are carried out by using actual thermodynamic and cost data. The wet cotton fabric is used as the test drying material. The results show that the specific moisture extraction rate (SMER) and evaporation rate of dryer are equal to 1.08 kg/kWh and 0.018 kg/s, respectively. Also, the respective exergetic efficiencies of the heat pump and overall system are equal to 0.07 and 0.11. A parametric study is then conducted in order to investigate the system performance and costs of the components, depending on the operating temperature and mass flow rate of air.

Exergoeconomic evaluation of a geothermal power plant

In this study, exergy and exergoeconomic analyses of the Dora II geothermal power plant (DGPP) with 9.5 MW net power output are carried out by using real thermodynamic and cost data. The exergetic efficiency of this plant is calculated to be 29.6%. The highest exergy destruction rate among the DGPP components occurs in the cooling towers followed by the turbines, vaporisers, preheaters and pumps. For exergoeconomic analysis, the cost balance equation for each component is written based on certain parameters and auxiliary equations to determine the cost values of exergy destruction. The costs of exergy destruction and electricity produced are determined based on the analysis and data used. The cooling tower I exhibits the greatest exergy destruction cost, followed by the turbines. The present results show that the unit cost of electricity produced and the exergy cost of geothermal fluid are 5.3 cents/kWh and 1.67 cents/kWh for DGPP, respectively.

Analysis and optimisation of a cascade active magnetic regenerative refrigeration system

In this paper, comprehensive thermodynamic analysis and optimisation of a cascade active magnetic regenerative refrigeration system are performed. A parametric study is conducted to investigate the effects of various design parameters on the cycle performance through energy and exergy efficiencies. A multi-objective optimisation method based on a fast and elitist non-dominated sorting genetic algorithm is applied to determine the best design parameters for the system. Two objective functions utilised in the optimisation study are the total cost rate of the system and the system exergy efficiency. The total cost rate of the system is minimised while the cycle exergy efficiency is maximised using an evolutionary algorithm. To provide insight, the Pareto frontier is shown for a multi-objective optimisation. The results show that exergy efficiency could be increased by 14.53% using exergy-based optimisation and the cost could be reduced by 12% using the cost-based optimisation.

Exergoeconomic Analysis of a Cascade Active Magnetic Regenerative Refrigeration System

In this paper, an exergoeconomic analysis of a cascade active magnetic regenerative (AMR) refrigeration system operating on a regenerative Brayton cycle is conducted with respect to various system design parameters. The finite difference method is used in order to solve the set of governing equations, which are highly nonlinear and coupled. In exergy analysis, a thermodynamic model is developed in order to determine exergy destruction rates and calculate the exergy efficiency of the system. In the economic analysis, investment cost rates are calculated with respect to equipment costs, which are determined by cost correlations for each system component, and capital recovery factors. Thus, by combining the two analyses, an exergoeconomic model is created whereby the exergy streams are identified and cost equations are allocated for each component. The results of both exergetic and exergoeconomic analyses show that increasing the fluid mass flow rate decreases the exergy efficiency, and increasing the specific exergetic cooling rate decreases the cost per unit of cooling.

THERMODYNAMIC ANALYSIS AND PERFORMANCE ASSESSMENT OF A CASCADE ACTIVE MAGNETIC REGENERATIVE REFRIGERATION SYSTEM

In the present study, a thermodynamic model is proposed to analyze and assess the performance, through energy and exergy, of a cascade active magnetic regenerative (AMR) refrigerator operation a regenerative Brayton cycle. This cascade refrigeration system works with GdxTb1–x alloys as magnetic materials where the composition of the alloy varies for different stages. In this model, the heat transfer fluid considered is a water– glycol mixture (50% by weight). The refrigeration capacity, total power consumption, coefficients of performance (COP), exergy efficiency and exergy destruction rate of a cascade AMR refrigeration (AMRR) system are determined. To understand the system performance more comprehensively, a parametric study is performed to investigate the effects of several important design parameters on COP and exergy efficiency of the system.

Energy and Exergy Analyses of an Active Magnetic Refrigerator

In this paper, a thermodynamic model for predicting the performance of active magnetic refrigerator (AMR) is developed using energy and exergy analyses. Through this model, the cooling power, total power consumption, as well as the coefficient of performance (COP), exergy efficiency and exergy destruction rates of an AMR are determined. The effects of increasing mass flow rate on the COP, exergy efficiency and exergy destruction rates of the system are investigated. The results are presented to show that when mass flow rate increases, the COP and exergy efficiency curves reach their maximum values and then slightly decreases with increasing mass flow rate. The rate of exergy destruction increases with increasing mass flow rate due to the pump power requirements. The numerical results show that in order to reach optimal performance, mass flow rate must be adjusted carefully regarding to different operating conditions.

Thermodynamic Performance Assessment and Comparison of Active Magnetic Regenerative and Conventional Refrigeration Systems

Comprehensive thermodynamic analyses, performance assessments, and comparative evaluations of active magnetic regenerative (AMR) and conventional vapor-compression-based refrigeration systems are presented in this study. The active magnetic regenerative (AMR) uses a magnetic material as a thermal storage medium and as a refrigerating medium. A parametric analysis is to investigate the influences of various operating conditions and/or parameters on the thermodynamic performance of the AMR cycle. In this regard, these performance results are compared with the published experimental data for a traditional refrigeration system with the same refrigeration capacity and temperature span. The results of this particular study show that the COP of the AMR cycle changes very little with varying hot source temperature. It is shown that the conventional vapor-compression-based refrigeration cycles offer better performance than the active magnetic regenerative refrigeration systems.

Exergy Analysis and Environmental Impact Assessment of a Geothermal Power Plant

Geothermal power plants are one of the environmentally benign systems among other types of power generation systems. In this chapter, the exergy efficiencies and exergy destruction rates are analyzed for the binary geothermal. In addition, greenhouse gas (GHG) emissions (in ton CO2-eq/kWh) during operation as well as the sustainability index are determined under various operating conditions. For the case study presented here, it is shown that the Dora II binary geothermal power plant produces no GHG emissions during operation since no fossil fuels are burned. For the same production capacity, it helps reduce the emissions by 56 Mega Ton CO2-eq/yr compared to a coal-fired power plant and 28 Mega Ton CO2-eq/yr compared to a natural gas combined cycle power plant.