Exergy Characteristics Research Articles

선박용 디젤엔진의 배기가스 열회수 시스템 (II) - R245fa 및 Water 의 작동유체에 대한 엑서지 분석 -

대형 선박의 추진용 디젤엔진에서 버려지는 배기가스의 열을 회수하기 위한 랭킨사이클이 적용된 발전시스템에 대하여 R245fa 및 water 의 작동유체에 따른 그 엑서지 특성을 분석하였다. 그 이론적인 계산 결과로, R245fa 에 대하여 터빈입구의 압력이 증가할수록 엑서지 효율 및 시스템의 엑서지 효율이 증가하였고, 엑서지 파괴율은 주로 응축기 및 증발기에서 상대적으로 높게 나타났다. 그리고 질량유량의 증가에 따라 시스템의 엑서지 효율이 증가하는 특성을 보였다. Water 의 경우에, 증발기에서의 엑서지 파괴율은 R245fa 의 경우와 유사하게 나타났지만, 터빈입구의 압력 및 질량유량 비율의 변동에 대하여 열원에 대한 엑서지 손실률이 가장 큰 폭으로 변동하였다.

Effects of air psychrometrics on the exergetic efficiency of a wind farm at a coastal mountainous site – An experimental study

In this paper, the most important energy and exergy characteristics of wind energy were examined. Atmospheric variables as air temperature, humidity and pressure and their effects on the wind turbine output were investigated toward wind energy exploitation. It was shown that these usually disregarded meteorological parameters while planning new WFs (Wind Farms), in fact, do play an important role in the farm’s overall exergetic efficiency. The wind potential around a coastal mountainous area was studied based on field measurements. Understanding atmospheric parameters variation appears to be of great importance for estimating energy yield in rough terrain and in this paper special focus was given to that.

Exergoecological analysis of processing of SO2-containing gases from zinc production

AbstractAn energy and technological study of processing SO2-containing metallurgical gases from zinc production to sulfuric acid production using the exergy method of thermodynamic analysis has bean carried out. A real operating installation since 2003 at the KCM-SA, Plovdiv, Bulgaria, has been used as the model scheme. The principal production stages have been analyzed. The absolute and the relative exergy characteristics of the separate stages as well as of the process as a whole have been calculated. The results have been used to evaluate the influence of sulfuric acid production on the environment. The results obtained have been compared with previous studies on similar processes both in zinc and in copper production. The studied installation of sulfuric acid production has good exergoecological indices, defining it as an effective process both in thermotechnical and in ecological aspects.

Exergy analysis of thermal processes in the building materials industry

A method is proposed to calculate the chemical exergy with allowance for the chemical composition and the ambient temperature. The exergy analysis of cement clinker burning is performed. It is found that the maximal energy saving for a rotary cement kiln can be achieved by decreasing the sludge humidity and optimizing the fuel combustion and the clinker cooler operation. The analysis of thermal processes in terms of exergy characteristics is demonstrated to be more efficient than that in terms of thermal parameters, since the optimization and intensification of industrial kilns requires not only heat loss reduction but also more efficient use of heat.

New Spatio-Temporal Wind Exergy Maps

In this paper, energy and exergy characteristics of wind energy are investigated. The effects of wind speed and air temperature and pressure at the inlet of a wind turbine on windchill temperature are examined. We also investigate energy and exergy efficiencies of the wind energy generating system and verify the models through a case study on a 100 kW wind generating system for 21 climatic stations in the province of Ontario, Canada. New energy and exergy efficiency maps of the wind energy generating system are introduced to provide a common basis for regional assessments and interpretations. These efficiency maps are plotted for 4 months of the year (January, April, July, October), which are taken to be representative months of the seasons. The results show that aerial differences between energy and exergy efficiencies are approximately 20%–24% at low wind speeds and approximately 10%–15% at high wind speeds.

Influence of blast-furnace process thermal parameters on energy and exergy characteristics and exergy losses

The technology ‘blast furnace—converter’ dominates at present in the production of steel all over the world. Therefore, the blast-furnace process is continuously being improved, among others, by raising the thermal parameters, such as temperature and oxygen-enrichment of the blast, as well as the addition of auxiliary fuels. The changes in the consumption of coke go together with changes in the consumption of blast, the production of top-gas and its consumption in Cowper stoves, as well as the production of electricity in the recovery turbogenerator utilizing the waste exergy of the top-gas due to raised pressure. Related to a unit of pig iron production, these values are called energy (exergy) characteristics of the blast-furnace plant. They serve as a quantity measure of the thermal improvement of the blast-furnace process. This paper presents an algorithm of the process exergy analysis of simulative investigations of the influence of increased thermal parameters on the thermodynamic perfection of the process and the blast-furnace plant. This algorithm bases on the theoretical empirical balance method of the ‘input–output’ type. By means of this algorithm the influence of increased thermal parameters of the process not only on the saving of coke but also of the blast can be determined, as well as of the production and composition of top-gas, the consumption of top-gas in the Cowper stoves and the production of electric energy in the recovery turbine. The blast-furnace process displays a high exergy efficiency, whereas the process of compressing and preheating the blast is characterized by rather high exergy losses due to the application of the combustion process. It has been shown that the internal exergy losses in the blast furnace are comparable with the exergy losses in the processes of compressing and preheating of the blast. Calculations were carried out for a modern Polish blast furnace with a volume of 3200 m3. Copyright © 2005 John Wiley & Sons, Ltd.