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Cogeneration has improved sustainability as it can improve the energy utilization efficiency significantly. In this paper, a novel ammonia-water cycle is proposed for the cogeneration of power and refrigeration. In order to meet the different concentration requirements in the cycle heat addition process and the condensation process, a splitting /absorption unit is introduced and integrated with an...
Energy recovery devices can have a substantial impact on process efficiency and their relevance to the problem of conservation of energy resources is generally recognized to be beyond dispute. One type of such a device, which is commonly used in thermal power plants and air conditioning systems, is the rotary air preheater. A major disadvantage of the rotary air preheater is that there is an unavoidable...
This paper aims at analyzing energy and exergy efficiencies in the Chinese transportation sector. Historical data is used to investigate the development of efficiencies from 1980 to 2009. Firstly, we calculate energy consumption values in PJ (petajoule) for nine transportation modes of five transportation sub-sectors. Then, the weighted energy and exergy efficiencies for each transportation mode,...
A new way to evaluate the energetic performance of lime shaft kilns is proposed. Two new exergy-based indicators are introduced for the evaluation, one to assess the exergy efficiency of limekilns and the other indicator to assess the effectiveness of the exergy consumption of the dissociation reaction. The combination of both indicators provides a clear picture of the energetic performance of the...
In this paper, the performance of wind energy system is assessed thermodynamically, from resource and technology perspectives. The thermodynamic characteristics of wind through energy and exergy analyses are considered and both energetic and exergetic efficiencies are studied. Wind speed is affected by air temperature and pressure and has a subsequent effect on wind turbine performance based on wind...
The main results of a theoretical work on the use of a low temperature heat source for power generation through a carbon dioxide transcritical power cycle are reported in this paper. The procedure for analyzing the behaviour of the proposed cycle consisted in modifying the input pressure to the turbine from 66 bar, maintained constant each evaluated temperature (60 °C, 90 °C, 120 °C and 150 °C) until...
The present work concerns the parametric study and optimization of regenerative Clausius and organic Rankine cycles (ORC) with two feedwater heaters. For the parametric optimization, thermal efficiency, exergy efficiency and specific work are selected as the objective functions, so the mentioned parameters are calculated for different values of the outlet pressures from the second and third pumps...
In this study, energy and exergy analyses are carried out for the charging period of an ice-on-coil thermal energy storage system. The present model is developed using a thermal resistance network technique. First, the time-dependent variations of the predicted total stored energy, mass of ice, and outlet temperature of the heat transfer fluid from a storage tank are compared with the experimental...
This paper examines the performance of a new Marnoch heat engine, which uses dry air and a pneumatic piston assembly to convert thermal energy to electricity. The system has unique capabilities of operating over temperature differentials less than 100 K. Unlike a common Stirling engine, the heat exchangers and piston assembly are not co-located, which is beneficial for positioning of heat exchangers...
In this paper, an exergy analysis is applied to indicate the exergy efficiency and irreversibility of common models of evaporative cooling. Exergy analysis of conditioned air are based on the results of experimental investigations on the direct, indirect, and two-stage indirect/direct evaporative cooling for six cities in Iran, each having various weather conditions. For this purpose, exergy balances...
In the present work, a multi-parameter optimization approach of Isopropanol–Acetone–Hydrogen (IAH) chemical heat pump is developed based on the entransy theory. In the optimization process, the total low-temperature heat consumed by the heat pump system generally decreases while the high-temperature heat recovered by the heat pump increases remarkably. When the temperatures of the reboiler and endothermic...
In this study, a novel approach is proposed to determine the maximum amount of exergy from the sun when applied to a conventional photovoltaic (PV) system in order to formulate its exergy efficiency. The variations of exergy efficiency are investigated for two cases using actual experimental data obtained from an installed PV system in Turkey. A new computer program is written in the Matlab-Simulink...
Exergy analysis is applied to assess the energy conversion processes that take place in the human body, aiming at developing indicators of health and performance based on the concepts of exergy destroyed rate and exergy efficiency. The thermal behavior of the human body is simulated by a model composed of 15 cylinders with elliptical cross section representing: head, neck, trunk, arms, forearms, hands,...
Grate coolers are widely used in cement industries to recover heat from hot clinker, coming out from the rotary kiln. This study focuses on improving the energy, exergy and recovery efficiencies of a grate cooling system through the optimization of its operational parameters such as masses of cooling air and clinker, cooling air temperature, and grate speed. It has been found that the energy and recovery...
An exergy analysis of the Dora II geothermal power plant (DGPP) with 9.5 MW net power output is carried out by using actual plant data to evaluate plant performance and pinpoint the locations of exergy destructions/losses. It aims to determine exergy efficiencies, and exergy destructions in each component of the plant. Exergy destructions in each of the components of the whole plant are determined...
This present paper deals with exergoeconomic results of the Wind Turbine Power Plants (WTPPs) for the first time to our knowledge. Ratio of exergy loss rate to capital cost-exergy efficiency graph and correlation are presented. Monthly exergoeconomic results are also presented for the three turbines. Ratio of exergy loss rate to capital cost and ratio of energy loss rate to capital cost depending...
By using exergy efficiency as an objective function, the performances of three different organic Rankine cycles (ORCs) systems including the basic ORC (BORC) system, the single-stage regenerative ORC (SRORC) system and the double-stage regenerative ORC (DRORC) system using six different working fluids under the same waste heat condition are examined. The genetic algorithm (GA) is chosen as a novel...
This study proposes a new concept called the cascade Rankine cycle, which recovers LNG (liquefied natural gas) cold energy for power generation, optimizes the cycle by investigating the effects of key parameters on its performance, and compares its thermal efficiency, exergy efficiency and economic evaluation to those of the conventional alternatives. The cascade Rankine cycle consists of multiple...
The aim of this work is to apply performance indicators for individuals under physical activity based on the concepts of exergy destroyed and exergy efficiency. The cardiopulmonary exercise test is one of the most used tests to assess the functional capacity of individuals with varying degrees of physical training. To perform the exergy analysis during the test, it is necessary to calculate heat and...
The thermal performance of supercritical pressure ORCs (Organic Rankine Cycles) is related to the critical temperature of the organic fluids. The heat source in this investigation was flue gas with an inlet temperature of 150 °C and an outlet temperature of 70 °C. The working fluids were R218, R134a and R236fa. An integrated-average temperature difference was used to quantify the thermal match between...
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