Exergy

In the present research work, a mathematical model is obtained for predicting specific fuel consumption in a 1.4-liter Otto cycle engine with electronic injection without making modifications, when using as fuel gasoline mixtures with concentrations in volume of 0%, 25%, 50%, 75% and 100% of anhydrous ethanol. For the analysis of results, a simplex lattice reticular mixture experiment design was carried out, which was subject to an urban driving cycle in the city of Cuenca at 2558 m above sea level in a roller power bank. The data acquisition and the development of the algorithm were carried out through an analysis of descriptive statistical methods. The validation of the algorithm was performed through residual analysis. As a main result, there is a mathematical model that enables predicting the engine fuel consumption, for ranges of ethanol concentration from 0% to 100% in the gasoline without needing to conduct real tests. En la presente investigación se obtiene un modelo matemát...

Este manuscrito reúne conceitos fundamentais de Física, Físico-Química e Termodinâmica (Primeira Lei) que são apresentados aos alunos da UNESA na disciplina Física II, a qual faz parte da grade curricular dos cursos de Engenharia Civil e Engenharia Ambiental e Sanitária. Procuramos focar em conceitos e exercícios chaves, de forma a apresentar o conteúdo com a maior clareza possível. Assim, seguindo as estrofes da música "Comida" (Titãs, 1987) - "A gente não quer só comida. A gente quer comida, diversão e arte." - enfatizamos as noções de calor, trabalho, energia e as correlações.

A CO2 water to water heat pump system was used to investigate<br> the effects of throttle valve opening and water flow rates at higher<br> charge capacity (149% of the full charge). It was observed that the<br> throttle opening affects the gas cooler pressure (and inlet<br> temperature) where the less the opening the higher the pressure.<br> Although the increase in gas cooler pressure was improving the<br> gas cooler heat output and therefore the system efficiencies, there<br> is an optimum pressure which when exceeded, the system<br> performance deteriorates. This optimum pressure also is related to<br> a certain throttle opening which is approximately at 20% in this<br> study. Similarly, as the throttle valve is reduced, the overall system becomes more ideal as indicated by Lorentz efficiency.<br> On the other hand, the higher the flow rates the higher the performance although it's better to keep the chilling w...

Up to 2025, Indonesia will approximately utilize 150 MWe promising small scale of waste heat geothermal sources for electricity power plants. As the characteristic of the brine water is has a low grade of heat and low grade of enthalpy. Therefore, the Organic Rankine Cycle geothermal binary power plant system is well suited to maximize these potentials to construct low-capacity power plants to maximize the utility of geothermal power plant. The aim of this research is to examine a case study on the performance of the turbine of the 500 kW ORC power plant. The turbine is rotated by the working fluid. The working fluid used for this research is npentane. An exergy analysis is performed to reduce losses or energy wasted, especially on the turbine component. Results of analysis with random data collected in April to July 2018 from the turbine system. The result shows that the minimum efficiency of 56.24% is when inlet heat source temperature of 117oC and ambient temperature of 22oC. Whi...

The performance of turbochargers is heavily influenced by heat transfer. Conventional investigations are commonly performed under adiabatic assumptions and are based on the first law of thermodynamics, which is insufficient for perceiving the aerothermodynamic performance of turbochargers. This study aims to experimentally investigate the non-adiabatic performance of an automotive turbocharger turbine through energy and exergy analysis, considering heat transfer impacts. It is achieved based on experimental measurements and by implementing a novel innovative power-based approach to extract the amount of heat transfer. The turbocharger is measured on a hot gas test bench in both diabatic and adiabatic conditions. Consequently, by carrying out energy and exergy balances, the amount of lost available work due to heat transfer and internal irreversibilities within the turbine is quantified. The study allows researchers to achieve a deep understanding of the impacts of heat transfer on t...

The coal-fired thermal power plant with a capacity of 3x135 MW gross or a total of 405 MW is composed of two high-pressure, one deaerator-heater and four lowpressure feed water heaters arranged in cascading stages on each of the three units. The objectives of the study are to determine the performance of these feed water heaters, both HP and LP, using the American Society of Mechanical Engineers Performance Test Code (ASME PTC) 12.1 and Heat Exchange Institute (HEI) Inc. procedures with engineering report and comparative discussions. Performance indicators such as terminal temperature difference (TTD), drain cooler approach (DCA) and temperature rise (TR) across heater were used to determine each unit’s feed water heater system performance. The results showed that the high-pressure feed water heaters (HPH) were significantly more efficient compared to the low-pressure feed water heaters (LPH). An alarming off-design condition was encountered by the last stage heater, LPH7, in unit o...

Energy management systems are used to analyze the efficiency of energy systems and identify any problem areas to lower costs and save energy, typically using energy based performance measurements. Our aim was to use exergy parameters, instead, to see if more accurate information could be obtained about which ener?gy saving application would result in greater energy savings. Exergy analysis is based on the Second law of thermodynamics and focuses on the environment and the quality of the energy. Implementing an exergetic approach to analyze a steam heating system, we examined data related to exergy flows and exergy losses, and ultimately improved the performance of the system through this energy management model. The following seven energy saving applications were identified and ranked according to their improvement potentials: adjusting the air to fuel ratio ? 1, preventing steam leaks ? 2, installing an automatic blow down system ? 3, insulating the pipes ? 4, insulating valves and...

One of the most important methods for efficient hydrogen utilization is the proton exchange membrane fuel cell (PEMFC) because of its low environmental impact and easy maintenance. Depletion of fossil fuels along with global warming is all the more reasons for the researchers to seek new methods in converting primary energy into power, heating, etc.; fuel cells, in the meantime, are a promising method to convert energy into usable power. In the present paper, a proton exchange membrane fuel cell, utilizing hydrogen as a fuel is proposed as the main component of a power generation system. The waste heat of the fuel cell is then recovered via two scenarios, which are using the waste heat as the heat source of an organic Rankin cycle (ORC) or using it to be expanded in the gas turbine. A comprehensive energy and exergy analysis are carried out to find the effectiveness of the system along with the adverse conditions of the components. Results demonstrate that at operation conditions, t...

Due to environmental concern and high price of the fuel, waste heat recovery has become a central issue for the industrial and commercial energy user. Waste heat recovery by heat pipe heat exchanger (HPHE) is an excellent way of saving energy and cost, preventing the global warming and reduction of air pollution. A heat pipe heat exchanger (HPHE) is generally consists of three sections: evaporation, condensation and adiabatic section. From the different researchers, it has been experimentally found that, the filling ratio and variation of adiabatic region length has a great impact for increasing the thermal performance and effectiveness of HPHE. The main motivation of conducting this experimental work is to analysis and investigation of the potential effect and heat transfer performance of the heat pipe in water-to-water HPHE by varying the filling ratio and adiabatic length. Heat pipe is fabricated from the straight copper tube of 280 mm length (with inner and outer diameter of 13 mm and 15mm) by vacuum process and injecting the water as working fluid. In this study, six heat pipes are used vertically based on the principle of thermosiphon with 40-45% optimal filling ratio of water. The experiment was conducted without adiabatic section that's replace by a 2.5 mm metallic plate then it's conducted by varying the length and position of adiabatic section at 96 mm, 64 mm and 32 mm from the center of heat pipe. A water heater of 1000 W is placed in the evaporation section and atmospheric water is flown through the condensation section of the heat exchanger. The results show that the filling ratios, appropriate adiabatic length and position have significant effect on the thermal efficiency where filling ratio is more effective than adiabatic length. The maximum performance observes at optimum filling ratio of 45% with shorter adiabatic length of heat pipe.