Hadi Ganjehsarabi

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.

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.

Numerical Simulation of Building Wall Integrated with Phase Change Material: A Case Study of a Mediterranean City Izmir, Turkey

Nowadays, improving the energy efficiency of buildings without decreasing the comfort of its occupants is of great importance in the whole world. The most widespread passive energy control strategy is the utilization of insulation materials with low thermal transmittance. This chapter proposes an alternative control strategy that would help to create more stable temperatures inside a room. This is changing the thermal capacity of a common wall with the integration of phase change material (PCM). To evaluate the performance of the PCM, user-defined scripts are coded in commercial CFD solver ANSYS FLUENT to simulate one-dimensional heat transfer through a wall within a detached cabin in a city with Mediterranean climate for 1 day in the hot season. The placement and amount of PCM in the building element are changed and analyzed. The results show a decrease in the indoor wall temperature up to 6 °C, which is promising for further research.

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.

Energy and exergy analyses of a solar assisted combined power and cooling cycle

In this study, a thermodynamic analysis of a solar assisted Rankine-Goswami integrated cycle is carried out for a range from 230 to 240 MW sizes. To illustrate the performance characteristics of these integrated cycle, an exergy analysis is conducted to pinpoint the losses due to internal and external irreversibilities of each component. In addition, the effect of design parameter such as condenser pressure on the performance of the integrated cycle is examined. The results shows that the variation of condenser pressure from 4 kPa to 24 kPa greatly reduces the exergy efficiency of the system. Moreover, it is found the exergy efficiency of standard solar assisted Rankine cycle case is 42.8% whereas the exergy efficiency of solar Rankine-Goswami multigeneration system is 47.03%.