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[en] Solar thermal is a promising renewable energy supplying technology that is being introduced slowly in industrial activities. Integration of solar thermal energy in a complex process, in combination with other energy provision devices, must be evaluated carefully, in order to obtain its maximum capacity and performance. This study tackles the integration of the thermosolar technology in a dairy process, sited in a climatic zone where diffuse irradiation is the meaningful one, based on two well developed thermodynamic tools: pinch and exergy analysis. Both tools have been utilized in the context of a low and middle temperature for the production of hot water for the steps of the dairy process. A combined implementation of both methodologies, helped by economical estimation, provides a powerful tool that allows finding the best integration of thermosolar and, by this, taking substantial design decisions. - Highlights: ► Integration of solar thermal energy in an industrial process was assessed. ► Pinch and exergy analysis were used to determine the optimal energy supply configuration. ► Solar thermal energy reduces the fossil energy demand with a moderate investment.
[en] In this work we present the development and implementation of an integrated approach for mathematical exergoeconomic optimization of complex thermal systems. By exploiting the computational power of a professional process simulator, the proposed integrated approach permits the optimization routine to ignore the variables associated with the thermodynamic balance equations and thus deal only with the decision variables. To demonstrate the capabilities of the integrated approach, it is here applied to a complex cogeneration system, which includes all the major components of a typical thermal plant, and requires more than 800 variables for its simulation
[en] In this research, a vortex generator heat exchanger is used to recover exergy from the exhaust of an OM314 diesel engine. Twenty vortex generators with 30° angle of attack are used to increase the heat recovery as well as the low back pressure in the exhaust. The experiments are prepared for five engine loads (0, 20, 40, 60 and 80% of full load), two exhaust gases amount (50 and 100%) and four water mass flow rates (50, 40, 30 and 20 g/s). After a thermodynamical analysis on the obtained data, an optimization study based on Central Composite Design (CCD) is performed due to complex effect of engine loads and water mass flow rates on exergy recovery and irreversibility to reach the best operating condition. - Highlights: • A vortex generator heat exchanger is used for diesel exhaust heat recovery. • A thermodynamic analysis is performed for experimental data. • Exergy recovery, irreversibility are calculated in different exhaust gases amount. • Optimization study is performed using response surface method
[en] Highlights: • Hourly productivity improves by inserting the reticular porous layer in the basin. • The efficiency improves by inserting the reticular porous layer inside the basin. • The maximum exergy efficiency from the modified system is found as 7.33%. - Abstract: In this paper, an experimental study with the exergy analysis are performed to investigate the application of a reticular porous insert in a single slope solar still for performance improvement. Two single slope solar stills containing conventional and modified by inserting a reticular porous layer are fabricated and experimented together. Two stills have the same dimensions. The porous insert was made up by black sponge rubber. All tests were taken in Semnan with geographical coordinates of 35°33′N, 53°23′E, Iran. Hourly water and glass temperatures, productivity, and efficiency of two stills are measured and evaluated experimentally. Moreover, the exergy efficiencies of the solar stills are obtained and presented. Finally, a cost analysis is performed to investigate the modified still economically. It was concluded that the daily total water productions for one day of the experiment are 3263 and 3829 cc/m2 for the conventional and modified stills, respectively. Accordingly, the modified still produces about 17.35% more distilled water in comparison to the conventional one during one day. Finally, the costs per liter per square meter for the modified and conventional stills are 0.0095 and 0.0108 $/L/m2, respectively.
[en] An experimental investigation into an active magnetic regenerative (AMR) heat circulator based on self-heat recuperation technology, was conducted to evaluate its energy saving potential in heat circulation. In an AMR heat circulator, magnetocaloric effect is applied to recuperate the heat exergy of the process fluid. The recuperated heat can be reused to heat the feed process fluid and realize self-heat recuperation. In this paper, AMR heat circulator has newly been constructed to determine the amount of heat circulated when applied to self-heat recuperation and the energy consumption of the heat circulator. Gadolinium and water was used as the magnetocaloric working material and the process fluid, respectively. The heat circulated amount was determined by measuring the temperature of the process fluid and gadolinium. The net work input for heat circulation was obtained from the magnetizing and demagnetizing forces and the distance travelled by the magnetocaloric bed. The results were compared with the minimum work input needed for heat circulation derived from exergy loss during heat exchange. It was seen that the experimentally obtained value was close to the minimum work input needed for heat circulation. - Highlights: • AMR heat circulator has newly been constructed for experimental evaluation. • Heat circulation in the vicinity of Curie temperature was observed. • Energy consumption of an AMR heat circulator has been measured. • Energy saving for processes near Curie temperature of working material was seen
[en] Increasing expenditures for energy require an optimization of chemical processes with regard to energy efficiency. Energy efficiency is of course only one aspect of a multi-objective optimization during process development. It will be shown how methods for increasing energy efficiency are integrated in the workflow of BASF's process development for new and existing processes. Special focus will be on the use of exergy analysis and its high relevance to industrial chemical processes. It will be shown how exergy analysis might be used for comparison of different process concepts. Additionally examples will emphasize how an increase of energy efficiency by change of operational conditions can be reached. Also these measures can be interpreted in terms of reduced exergy losses. For all examples the additional investment, if needed, is justified by the savings, which were altogether approximately 7 million euro per year. Highlights: → Work flow for development of energy efficient processes for new and existing plants in the chemical industry is presented. → Exergy analysis has been used to identify favorable process concepts. → Examples with annual savings of about 7 million euro emphasize the use of the method.
[en] Highlights: • An approach is developed to optimize ATP problem based on flow pattern construction. • The heat conduction is optimized using entropy generation minimization principle. • Exergy analysis is carried out to evaluate the optimized heat conduction process. • The conductive path consisting of high conductivity material is constructed. - Abstract: An optimization approach is developed to optimize the “area to point” heat conduction problem based on the concept of flow pattern construction. As the key point of the approach, an optimal temperature field for heat conduction process is necessary to be constructed firstly (also known as the flow pattern construction). To construct the optimal temperature field, the heat conduction is optimized using the entropy generation minimization principle in a thermodynamics point of view. After optimization, the average and maximum temperature of the heating surface decreases, and, simultaneously, the exergy efficiency increases as well. Then the second step of the present optimization approach is to design a conductive path consisting of high conductivity materials to enhance heat transfer, according to the optimal temperature field. With the conductive path, the average and maximum temperature of the heating domain is found to decrease.
[en] In this paper we present an analysis of energy and exergy utilization in the transportation sector of Saudi Arabia by considering the sectoral energy and exergy flows for the years of 1990-2001. Energy and exergy analyses are conducted for its three subsectors, namely road, air and marine, and hence the energy and exergy efficiencies are obtained for comparison. Road subsector appears to be the most efficient one compared to air and marine subsectors. It is found that the energy efficiencies in air and marine subsectors are found to be equal to the corresponding exergy efficiencies due to the values of exergy grade function. A comparison of the overall energy and exergy efficiencies of Saudi Arabian transportation sector with the Turkish transportation sector is also presented for the year 1993 based on the data available. Although the sectoral coverage is not same for both countries, it is still useful to illustrate the situation on how subsectoral energy and exergy efficiencies vary over the years. Turkish transportation sector appears to be a bit more efficient for that particular year. It is believed that the present technique is practical and useful for analyzing sectoral energy and exergy utilization to determine how efficient energy and exergy are used in transportation sector. It is also be helpful to establish standards, based on exergy, to facilitate applications in industry and in other planning processes such as energy planning
[en] Highlights: • Advanced exergoeconomic analysis is done on a new helium extraction process. • Cost of exergy destruction and exergy destruction rate are calculated. • Three different strategies are suggested to improve performance of the components. - Abstract: An advanced method of exergoeconomic analysis was applied to a newly developed process configuration used for recovering helium from natural gas. In this process, a three stage propane refrigeration cycle is incorporated to provide a portion of the required refrigeration. Sensitivity analysis was also carried out for exergoeconomic factors and exergy destruction cost of the effective devices. In comparison with the existing processes, the proposed process has better performance in extracting the helium from the feed gas. Based on the results of conventional method, HE-105 and HE-104 heat exchangers have the highest extent of exergy destruction cost equal to 1889.68 $/hr and 1263.58 $/hr, respectively. The outcome of the advanced exergoeconomic analysis suggests that the exergy destruction cost (investment cost) of the compressors is avoidable while it is not true for the heat exchangers. Moreover, the exergy destruction costs induced from the remaining components are not considerable, thus the interactions among the process equipment is not strong.
[en] A comparative study on transcritical carbon dioxide refrigeration cycle with ejector and with throttling valve was performed by the first and second laws of thermodynamics in theory. The effects of the entrainment ratio of the ejector, heat rejection pressure, outlet temperature of gas cooler and evaporating temperature on the coefficient of performance (COP) and exergy loss were investigated in transcritical carbon dioxide refrigeration cycle with ejector and with throttling valve. It is found that ejector instead of throttling valve can reduce more 25% exergy loss and increase COP more 30%. In addition, critical entrainment ratio of the ejector, optimal heat rejection pressure and critical outlet temperature of gas cooler affects COP greatly for the transcritical carbon dioxide refrigerating cycle with ejector. - Research highlights: →Transcritical CO2 refrigeration cycle with ejector was analyzed by the laws of thermodynamics. → The ejector instead of throttling valve reduces more 25% exergy loss and increases COP more 30% in transcritical CO2 refrigeration cycle. → COP of transcritical CO2 refrigeration cycle with ejector was affected greatly by entrainment ratio of ejector, rejection pressure and outlet temperature of gas cooler. → Running condition of transcritical CO2 refrigeration cycle with ejector is limited by critical entrainment ratio of the ejector.