Application of artificial neural network method for prediction of osmotic pretreatment based on the energy and exergy analyses in microwave drying of orange slices

The study targeted towards drying of cantaloupe slices with various thicknesses in a microwave dryer. The experiments were carried out at three microwave powers of 180, 360, and 540 W and three thicknesses of 2, 4, and 6 mm for cantaloupe drying, and the weight variations were determined. Artificial neural networks (ANN) and adaptive neuro-fuzzy inference systems (ANFIS) were exploited to investigate energy and exergy indices of cantaloupe drying using various afore-mentioned input parameters. The results indicated that a rise in microwave power and a decline in sample thickness can significantly decrease the specific energy consumption (SEC), energy loss, exergy loss, and improvement potential (probability level of 5%). The mean SEC, energy efficiency, energy loss, thermal efficiency, dryer efficiency, exergy efficiency, exergy loss, improvement potential, and sustainability index ranged in 10.48–25.92 MJ/kg water, 16.11–47.24%, 2.65–11.24 MJ/kg water, 7.02–36.46%, 12.36–42.70%, 11.25–38.89%, 3–12.2 MJ/kg water, 1.88–10.83 MJ/kg water, and 1.12–1.63, respectively. Based on the results, the use of higher microwave powers for drying thinner samples can improve the thermodynamic performance of the process. The ANFIS model offers a more accurate forecast of energy and exergy indices of cantaloupe drying compare to ANN model.

Water shows a strong tendency to absorb the energy of wavelengths of 3 and 6 µm, which are in the infrared (IR) range. Therefore, IR dryers are used to dry food and fruits that have a high‐water content. Thus, modeling and optimizing energy and exergy parameters of terebinth drying in an IR–rotary drum (RD) dryer were evaluated using the response surface methodology. Independent factors included IR power and rotary rotation speed, and response factors were specific energy consumption (SEC), energy efficiency (EFF), exergy efficiency (EXEFF), specific exergy loss (EXLOSS), and exergy improvement potential (EIP). According to the obtained results, the range of EFF and EXEFF was between 28.93%–9.11% and 0.88%–6.62%, respectively. As IR power and RD speed increased, SEC (123.75–39.21 MJ/kg), EXLOSS (3.97–2.97 MJ/kg), and EIP (3.62–1.009 MJ/kg) decreased, while EFF and EXEFF increased. The results obtained in this study showed that the optimal IR drying power is 616.39 W, and the optimal rotary rotation speed is 13.46 rpm.

In this study, exergy analysis, energy analysis, and mathematical modeling are performed in a 35 MW solar‐fossil fuel power plant. The losses of exergy and energy in different components and also changes of the efficiency of exergy and energy are analyzed at a specific day, 20th June. The assumed power plant in this study is Solar Electric Generating Station VI (SEGS VI), located in California's Mojave Desert. A parametric study, under different working conditions, including different working pressures, temperatures, collector output temperature, steam flow rate, and heat transfer fluid (HTF) flow rate is studied and the effect of variation of parameters on the performance of the plant is investigated. Authors found that, the maximum exergy loss happens in the collector and the maximum energy loss occurs in the condenser. Energy analysis shows that 47% of the total loss energy in the cycle happens in the condenser, as the main component that wastes energy. From exergy analysis, the collector and then boiler are the main components wasting exergy where 68.32% of total exergy loss occurs in these two components in hybrid mode (solar‐fossil fuel). Exergy and Energy efficiency variations throughout the day show that minimum exergy efficiency (32.7%) and maximum energy efficiency (23%) occurs at 12 am. Exergy efficiency variation versus turbine inlet pressure shows that the maximum exergy efficiency (26%) accure at 95 bar. The changes of the absorbed heat and solar irradiation of the 20th of June shows a good agreement with the measured data in validated reference.

The dairy industry needs new and more energy-efficient technological procedure for milk pasteurization. This article introduces a comparative efficiency assessment of various milk pasteurization technologies and electrotechnological means. The study featured milk, which was heated from 20 to 75°C with a capacity of 1000 kg/h at an estimated power of 58.95 kW. The treatment involved a steam-to-milk pasteurizer with electric indirect or direct heating, an induction pasteurizer, and a thermosiphon pasteurizer with direct or indirect electric heating. The study relied on the methods of energy and exergy analyses. The system of steam-to-milk pasteurizer with electric indirect (elemental, induction) or direct (electrode) heating demonstrated the following indicators: exergy loss – 1.29 kW, power consumption – 71.29 kW, exergy efficiency – 0.99, energy efficiency – 0.827. The thermosiphon pasteurizer with direct or indirect electric heating demonstrated the following properties: exergy loss – 1.29 kW, power consumption – 60.92 kW, exergy efficiency – 0.99, energy efficiency – 0.9676. The induction pasteurizer had the least competitive parameters: exergy loss – 10.8 kW, power consumption – 70.43 kW, exergy efficiency – 0.867, energy efficiency – 0.837. The thermosiphon pasteurizer with direct or indirect electric heating was able to increase the energy efficiency of milk pasteurization, while the induction pasteurizer proved to be a promising R&D direction.

Thermodynamic (energy and exergy) analysis of steam cooling process in the marine steam propulsion plant is presented in this research. Steam cooling is performed by using Desuperheater which inject water in the superheated steam to obtain wet steam. Wet steam is used in auxiliary heaters for various heating purposes inside the marine steam propulsion system. Auxiliary heaters require wet steam due to safety reasons and for easier steam condensation after heat transfer. Analysis of steam cooling process is performed for a variety of steam system loads. Mass flow rates of cooling water and superheated steam in a properly balanced cooling process should have the same trends at different system loads - deviations from this conclusion is expected only for a notable change in any fluid temperature. Reduction in steam temperature is dependable on the superheated steam temperature (at Desuperheater inlet) because the temperature of wet steam (at Desuperheater outlet) is intended to be almost constant at all steam system loads. Energy losses of steam cooling process for all observed system loads are low and in range between 10–30 kW, while exergy losses are lower in comparison to energy losses (between 5–15 kW) for all loads except three the highest ones. At the highest system loads exergy losses strongly increase and are higher than 20 kW (up to 40 kW). The energy efficiency of a steam cooling process is very high (around 99% or higher), while exergy efficiency is slightly lower than energy efficiency (around 98% or higher) for all loads except the highest ones. At the highest steam system loads, due to a notable increase in cooling water mass flow rate and high temperature reduction, steam cooling process exergy efficiency significantly decreases, but still remains acceptably high (between 95% and 97%). Observation of both energy and exergy losses and efficiencies leads to conclusion that exergy analysis consider notable increase in mass flow rate of cooling water which thermodynamic properties (especially specific exergies) strongly differs in comparison to steam. Such element cannot be seen in the energy analysis of the same system.

The energy assessment must be made through the energy quantity as well as the quality. But the usual energy analysisevaluates the energy generally on its quantity only. However, the exergy analysis assesses the energy on quantity as well asthe quality. The aim of the exergy analysis is to identify the magnitudes and the locations of real energy losses, in order toimprove the existing systems, processes or components. The present paper deals with an exergy analysis performed on anoperating 50MWe unit of lignite fired steam power plant at Thermal Power Station-I, Neyveli Lignite Corporation Limited,Neyveli, Tamil Nadu, India. The exergy losses occurred in the various subsystems of the plant and their components havebeen calculated using the mass, energy and exergy balance equations. The distribution of the exergy losses in several plantcomponents during the real time plant running conditions has been assessed to locate the process irreversibility. The Firstlaw efficiency (energy efficiency) and the Second law efficiency (exergy efficiency) of the plant have also been calculated.The comparison between the energy losses and the exergy losses of the individual components of the plant shows that themaximum energy losses of 39% occur in the condenser, whereas the maximum exergy losses of 42.73% occur in the combustor.The real losses of energy which has a scope for the improvement are given as maximum exergy losses that occurredin the combustor.

Modeling and assessing the sustainability of machining systems has been considered to be a crucial approach to improving the environmental performance of machining processes. As the most common machining system, the computer numerical control (CNC) milling system is a typical man–machine cooperative system where the activities of the machine tool and operator generate material and energy consumption. However, the energy consumption of the operator in the CNC milling system has often been ignored in most existing research. Therefore, existing methods fail to provide a comprehensive understanding of the sustainability of the CNC milling system. To fill this gap, an exergy loss assessment method is proposed to investigate the sustainability of the CNC milling system, where the energy consumption of the operator, the energy consumption of the machine tool, and material consumption are taken into consideration. The key performance indexes of the energy consumption of the operator, the energy consumption of the machine tool, the exergy loss, and the specific exergy loss (SEL) are analyzed and modeled. To demonstrate the feasibility of the proposed method, a case study was carried out on a three-axis machining center (XH714D), in which the energy consumption of the operator, the energy consumption of the machine tool, the exergy loss of energy consumption, the exergy loss of chips, the exergy loss of compressed air, the exergy loss of cutting tool wear, the exergy loss of cooling liquid dissipation, and the SEL were found to be 169,750 J, 758,211 J, 603,131 J, 2,031,404 J, 22,023 J, 301,868 J, 2673 J, and 88.04 J/mm3, respectively. The proposed method is effective to assess the sustainability of the CNC milling system, and the established exergy loss models build a good basis for exergy efficiency optimization.

Energy–exergy analysis and optimisation of a model sugar factory in Turkey

Thermodynamic assessment of photovoltaic systems

Energy and exergy analysis of hydrogen production by solid oxide steam electrolyzer plant

Energy, exergy analysis in a hybrid power and hydrogen production system using biomass and organic Rankine cycle

Ensuring high economic indicators of power plants of various purposes, which include waste gas heat utilization systems, is possible with the use of effective heat utilization equipment. One of the criteria for evaluating the thermodynamic perfection of power plants is the amount of exergy losses in the structural elements of the plant. A decrease in exergy losses corresponds to an increase in exergy efficiency. Determination of the structural elements in the heat utilization system, in which the maximum exergy losses are localized, will allow to influence them in a targeted manner in order to increase the exergy efficiency of the installation. The paper presents the results of the development of complex methods for calculating local exergy losses in the processes of heat transfer through flat and cylindrical walls of air-heated heat exchangers, which are included in the heat utilization systems of power plants of various purposes. Complex methods are based on integral equations for calculating exergy losses, as well as differential equations of heat transfer theory when applied to heat utilization systems. The classification of exergy losses for heat utilization systems of power plants has been carried out, and the location and type of local exergy losses have been determined. Three types of local exergy losses are considered: losses during heat transfer from the heat carrier to the wall, heat transfer from the wall to the heat carrier, and exergy losses in heat conduction processes. A system of integrodifferential equations was developed and analytical expressions were obtained for the calculation of local exergy losses in heat transfer processes through the flat and cylindrical walls of air-heating heat exchangers. The introduction of new complex research methods expands the possibilities of using exergy analysis methods to increase the exergy efficiency of heat utilization systems. Research using the specified methods will allow to develop heat utilization systems with high indicators of energy and exergetic efficiency.

Exergy analysis and economic estimate of a novel solar and gas combined system

Hydrocarbons being natural fluid have drawn much attention of the scientists and researchers for the application as a sustainable material for the vapor compression refrigeration system. This paper presents a comparison of the energetic and exergetic performances of a domestic refrigerator using pure butane and isobutane as refrigerants. The thermodynamic performances such as exergy destruction or losses, exergy efficiency, and coefficient of performances (COP) were investigated. These parameters were measured at varied operating conditions. Exergy and energy efficiencies of isobutane were found to be 50% and 175% higher than that of R-134a. The analysis shows that the performances of butane and isobutane as refrigerants are comparable with HFC134a. It has also been found that at higher evaporating temperatures, the exergy losses are minimal. The maximum exergy loss occurred in the compressor and the value was 69% of the whole losses in the system. Highest sustainability index was found for butane compared to that of R134a and R600a, respectively.

Energy and exergy balances were done on a novel solar bi-ejector refrigeration system with R123, whose circulation pump is replaced by an injector. The analysis result of the novel system was compared with that of the original one. The effect of operation condition on system energy efficiency, exergy efficiency and exergy loss was analyzed, and the dynamic performance of a designed solar bi-ejector refrigeration system was also studied. The comparative results indicate that under the same operating condition, the novel system and the original system have equal energy efficiency, exergy efficiency and exergy loss, and the only difference between them is the exergy losses of the generators and the added injector. The other conclusions mainly include: the solar collector has the largest exergy loss rate of over 90% and for the bi-ejector refrigeration subcycle, the ejector has the largest exergy loss rate of about 5%; the total exergy loss changes inversely proportional to the evaporation temperature and positively proportional to the condensation temperature; when the other parameters are fixed, there exists an optimum generation temperature, at which the overall energy and exergy efficiencies are both the maximum and the total exergy loss is the minimum. The study points out the direction for optimizing the novel solar bi-ejector refrigeration system. Copyright © 2009 John Wiley & Sons, Ltd.