Avoidable and unavoidable exergy destruction and exergoeconomic evaluation of the thermal processes in a real industrial plant

Exergy analysis is a universal method for evaluating the rational use of energy. It can be applied to any kind of energy conversion system or chemical process. An exergy analysis identifies the location, the magnitude and the causes of thermodynamic inefficiencies and enhances understanding of the energy conversion processes in complex systems. Conventional exergy analyses pinpoint components and processes with high irreversibility. To overcome the limitations of the conventional analyses and to increase our knowledge about a plant, advanced exergy-based analyses are developed. These analyses provide additional information about component interactions and reveal the real potential for improvement of each component constituting a system, as well as of the overall system. In this paper, a real industrial plant is analyzed using both conventional and advanced exergy analyses, and exergoeconomic evaluation. Some of the exergy destruction in the plant components is unavoidable and constrained by technological, physical and economic limitations. Calculations related to the total avoidable exergy destruction caused by each component of the plant supplement the outcome of the conventional exergy analysis. Based on the all-reaching analysis, by improving the boiler operation (elimination of approximately 1 MW of avoidable exergy destruction in the steam boiler) the greatest improvement in the efficiency of the overall system can be achieved

Exergoeconomic evaluation of real processes for coffee roasting

Exergoeconomic methods provide an effective approach for identifying, evaluating and reducing thermodynamic inefficiencies and costs in an energy system. The aim of this paper is to show the potential for cost reduction on the demand side, using the exergoeconomic method in the example of real processes for coffee roasting. More than 6.5•109 kg of coffee beans is roasted worldwide annually, mostly in batch roasters. Near the end of the roast, roasting coffee emits volatile organic compounds, carbon monoxide and other pollutants, which in many industrialized countries have to be oxidized in afterburners. Afterburners release exhaust gases with a temperature of 250-450°C, depending on the roasting process and the method of exhaust gas cleaning. The aim of this paper is to use exergy analysis and exergoeconomic performance evaluation to determine the energy use for coffee roasting and the afterburning process, and evaluate the way to utilize waste heat and reduce costs in the factory. For roasters with the capacity of up to 4 tons of green coffee beans per hour, the potential of heat recovery is 1.1 MW and the possibility to save money is around 60,000 € per year. This case study is similar to many others worldwide, and the results of this analysis could lead to more general conclusions

Improving eco-sustainable characteristics and energy efficiency of evaporative fluid cooler via experimental and numerical study

This paper presents an on-going research project that aims to identify possibilities for wider use of evaporative cooling in process industry, especially the use of evaporative fluid cooler units. Experimental study is performed on small scale evaporative fluid cooler, while the correlation based model has been carried out to explore the detailed heat and mass transfer processes inside this unit. Numerical integration of mathematical model is executed by new approach, based on differential, collocation Simpson method. Proposed models have been verified by comparing the computed results with those obtained by the experimental measurements. The results of research will enable the creation of more comprehensive simulation software, with wider range of operating and construction parameters

EFFECTS OF IMPLEMENTATION OF CO-GENERATION IN THE DISTRICT HEATING SYSTEM OF THE FACULTY OF MECHANICAL ENGINEERING IN NIŠ

Implementation of co-generation of thermal and electrical energy in district heating systems often results with higher overall energy efficiency of the systems, primary energy savings and environmental benefits. Financial results depend on number of parameters, some of which are very difficult to predict. After introduction of feed-in tariffs for generation of electrical energy in Serbia, better conditions for implementation of co-generation are created, although in district heating systems barriers are still present. In this paper, possibilities and effects of implementation of natural gas fired co-generation engines are examined and presented for the boiler house that is a part of the district heating system owned and operated by the Faculty of Mechanical Engineering in Niš. At the moment, in this boiler house only thermal energy is produced. The boilers are natural gas fired and often operate in low part load regimes. The plant is working only during the heating season. For estimation of effects of implementation of co-generation, referent values are taken from literature or are based on the results of measurements performed on site. Results are presented in the form of primary energy savings and greenhouse gasses emission reduction potentials. Financial aspects are also considered and triangle of costs is shown

Analysing soccer using perturbation attempts

Dynamical systems theory describes how behaviours can deviate through a series of states (stable or unstable) before returning to an original stable state. It has been suggested that squash performance exhibits properties akin to a dynamical system and demonstrated that squash experts were able to reliably discriminate weak or strong shots that gave one player a distinct advantage over their opponent. They argued that experts were essentially identifying “perturbations” which they defined as incidents that change a system state from a stable to an unstable situation or vice versa. Similarly, in this paper we examine ball possession in soccer and consider those where neither team has a distinct advantage as being a stable situation and perturbation attempts as those where an effort is made to gain a distinct advantage. This study assessed the relative frequency and success rate of perturbation attempts in relation to the match status (match score at the time of the incident). A hand notation system was designed to record the variables of interest (players involved, pitch locations, behaviours performed and behaviour outcomes). Eight domestic league matches from the 2007/2008 season involving a Coca-Cola League One team were analysed. Results indicated that the home team made significantly less perturbation attempts (11.78% of total possessions) compared to the away teams (17.54%) but that generally perturbation attempts were more likely to be unsuccessful than successful (Z = 2.37, p < 0.05). Future studies need to assess if the frequency of perturbation attempts and perturbation success rates are related to playing standard

Exergy and exergoeconomic analysis of a steam boiler

Relying on coal as primary fuel in thermal power plants represents an unsustainable concept due to limited coal reserves and a negative environmental impact. Efficient utilization of coal reserves and a request for minimization of irreversibilities are imperative for thermal power plants operation. Numerous studies have shown that a steam boiler is a thermal power plant component with the highest irreversibility. The idea of this paper is to quantify the amounts and sources of irreversibilities within a steam boiler and its components, serving a 348.5MWe thermal power plant. Having this in mind, exergy and exergoeconomic analysis of a steam boiler is presented in this paper. Exergy destruction and exergy efficiency of all boiler components and of the boiler as a whole were calculated. Based on exergy flows and economic parameters (cost of the boiler, annual operation hours of the unit, maintenance factor, interest rate, operating period of the boiler), exergy analysis resulted in the cost of produced steam. The obtained results show that the boiler exergy efficiency is at 47.4%, with the largest exergy destruction occurring in the combustion chamber with a value of 288.07 MW (60.04%), and the smallest in the air heater with a value of 4.57 MW (0.95%). The cost of produced steam is calculated at 49,356.7 $/h by applying exergoeconomic analysis

Impact of a building shape factor on space cooling energy performance in the green roof concept implementation

The reduction of energy demand for space cooling requires adequate solutions at building and built environment scales in order to achieve sustainability goals. Since many existing buildings have inadequate envelopes for reducing heat gains in summer and heat losses in winter, environmentally friendly renovation techniques have to be considered. The roofs of existing buildings were identified as a field of intervention which could contribute to providing both energy savings and environmental benefits. The aim of the paper was to evaluate the contribution of green roofs to energy savings for space cooling depending on the building shape factor. Two groups of building models, with vertical and horizontal expansions, were analysed. The comparative analyses of the building models with conventional and green roofs showed small reduction of energy consumption less than 1% in case of well-insulated roofs with the addition of the extensive green roof. The comparison of different building models with green roofs of the same volume, which is in this case the same cooling area, indicated a more effective solution for green roofs implementation with the aim to improve energy performances of existing buildings using this passive design technique

Novel methylene modified cyclohexyl ethylenediamine-N,N '-diacetate ligands and their platinum(IV) complexes. Influence on biological activity

This paper focuses on the synthesis, characterization and biological activity of new N,N'-methylene modified cyclohexyl ethylenediamine-N,N'-diacetate (edda)-type ligands and their Pt(IV) complexes. Both the ligands and complexes were characterized by infrared, UV-vis, ESI-MS, 1D (H-1, C-13, Pt-195) and 2D (COSY, HSQC, HMBC) NMR spectroscopy and elemental analysis. The possible correlation between the reduction potentials and the cytotoxicity of the complexes was examined. The potential antitumoral activity of all compounds was tested in vitro on human melanoma A375, human glioblastoma U251, human prostate cancer PC3, human colon cancer HCT116, mouse melanoma B16 and mouse colon cancer CT26CL25 cells, as well as primary fibroblasts and keratinocytes. The results obtained revealed strong antitumor potential of the newly synthesized drugs with preserved efficacy against cisplatin resistant lines and less toxicity towards nonmalignant counterparts. The mechanism found to be responsible for the observed tumoricidal action of each synthesized compound was induction of apoptosis generally accompanied with caspase activation. Taken together, the effective response to the treatment of a wide range of different cell lines, including cisplatin resistant subclones, as well as induction of apoptosis, as the mechanism suggested to be the most desirable way of eliminating malignant cells, represents a great advantage of this novel group of drugs in comparison to other members in this metallo-drug family. (C) 2012 Elsevier Inc. All rights reserved