Improvement Potential Rate Research Articles

Analysis of drying characteristic, effective moisture diffusivity and energy, exergy and environment performance indicators during thin layer drying of tea in a convective-hot air dryer

The objective of this study is mainly to analyze the drying kinetic parameters, effective diffusivity, and thermodynamic performance indicators (energy, exergy, heat, and mass transfer coefficients) of tea under different drying conditions of different drying temperatures (DT) and thin layer thicknesses (TT). Experimental drying was conducted at drying temperatures of 70°C, 80°C, and 90°C with thin layer thicknesses of 10 mm, 15 mm, and 20 mm. The results show that a higher drying temperature and a lower thin layer thickness can increase evaporation moisture content and shorten drying time. By evaluating and comparing the fitting of five drying models adopted by the coefficient of determination (R2) and chi-square (χ2), it can be found that the logarithmic model is the best to describe drying behavior. The effective moisture diffusivity shows a positively correlated trend with the increase in DT and TT, with the value of activation energy ranging from 14.030 to 22.344 kJ mol−1 K−1. The specific moisture evaporation rate (SMER), energy efficiency, exergy efficiency, and sustainability index (SI) descend as the TT increases at all DT; the specific energy consumption (SEC) and improvement potential (IP) rate perform in an opposite manner, but the TT remains unchange. The conclusion drawn from the thermodynamic parameters is opposite to the aforementioned. As the TT increases, the heat and mass transfer coefficients show a significant decrease trend. In addition, the heat and mass transfer coefficients are given as functions of DT and TT, and further knowledge shows that the mass transfer coefficient is positively correlated with DT but the heat transfer coefficient is negatively correlated. In conclusion, this article provides new insights into the effects of drying characteristics, energy consumption characteristics and heat and mass transfer characteristics in the process of tea drying under different drying conditions, and provides certain theoretical reference bases for promoting the optimization of industrialized tea drying production machinery design and drying process optimization.

Energetic and exergetic metrics of a cargo aircraft turboprop propulsion system by using regression method for dynamic flight

Nowadays, the development of aviation in line with sustainability goals is one of the current challenges. Being a source of environmental impact, aero-engines have been the main research and design object for achieving these aims. In this study, thermodynamic analysis involving exergy and sustainability computations is performed at different flight conditions where Mach varies between 0 and 0.7 and altitude changes between 0 and 7.7 km. Based on this analysis, modeling exergy parameters for each component are carried out with multiple regression approach. The exergy efficiency of turboprop engine at dynamic flight conditions varies between 15% and 25.9% whereas it is measured between 76 and 77% for the combustor and between 93 and 99% for gas turbine. Moreover, exergy destruction of the turboprop engine changes between 2.15 MW and 7.55 MW. Exergetic improvement potential rate (IPR) of the combustor resides between 0.4 MW and 1.21 MW throughout flight conditions whereas it is found at orders of 0.1 MW or less for other components. On the other hand, linear and quadratic modelings are performed for several parameters of turboprop engine components including exergy efficiency, exergy destruction and IPR under dynamic flight conditions. The determination coefficient (R2) of the models changes between 0.69 and 0.98 in linear modeling, whereas R2 in quadratic modeling improves to 0.97 and 0.99 ranges. It is thought that component-based modeling by considering different flight conditions could contribute to determining points where component efficiency is the highest.

Thermodynamic responses of bleed air on separated flow high by-pass turbofan engine under constant speed and constant thrust cases

Gas turbine engines, especially turbofan, have been famous for their fuel economy and reliability attributes. Therefore, these have continued to be manufactured by updating their features. Therefore, thermodynamic analyses related to turbofan engines have drawn great attention, providing deeper insight into potential improvements. New generation aircrafts have been conceived to draw bleed air as little as possible from their aero-engines so as to provide lower fuel consumption. In this study, influences of bleed air ratio (BAR) ranging from 1 % to 6 % on high by-pass turbofan (HBT) engine are handled by considering constant speed (CS) and constant thrust (CT) cases. Specific fuel consumption of HBT engine changes between 20.68 g/kN and 22.25 g/kN at CT whereas varies between 20.63 g/kN and 21.9 g/kN at CS owing to variation of BAR. Moreover, exergy efficiency of HBT resides between 26.92 % and 25.02 % at CT while changes 26.99 % and 25.43 % at CS. It shows that to maintain thrust constant could slightly penalty the engine performance in terms of fuel efficiency. On the other hand, the higher BAR leads to lower exergy efficiency of the combustor, which changes 80.95 %–82.33 % ranges at CT and varies 80.77 %–82.31 % intervals at CS. Finally, improvement potential rate for the combustor is found higher 1 MW and increases with elevated BAR whereas that for other five components is measured less than 0.04 MW. It could be underscored that adverse effect of BAR for both cases is observed. It is thought that this study helps in observing what extent the engine is affected from usage of bleed air in terms of thermodynamic metrics.

A comprehensive assessment of energetic and exergetic performance for the dehumidification system of a processed pistachio production unit

AbstractThe present study aims to conduct a comprehensive evaluation of the energetic and exergetic performance of a dehumidification system utilized in the processing of raw pistachios. The assessment involved the application of the first and second laws of thermodynamics to calculate the exergy aspects of each component of the system, including input and output exergy rates, output/input exergy efficiency, product/fuel exergy efficiency, exergy destruction rate, exergy loss rate, exergy improvement potential rate, and specific exergy consumption. Furthermore, the effect of variations in reference state temperature on the exergy parameters was also investigated. The results indicated that the pre‐dryer chamber had the highest input exergy rate among all the components of the dehumidification system. The product/fuel exergy efficiency is specified to be 35.10%, 9.47%, and 60.43%, for the electro‐fan, heater, and pre‐dryer chamber, respectively, while their output/input exergy efficiency are 87.87%, 22.10%, and 56.28%, respectively. The values of the exergy destruction rate of these components are 0.83, 147.14, and 1.12 kW whereas the exergy loss rate values are found to be 0.03, 4.12, and 9.24 kW, respectively. The improvement potential rate values of these components are obtained to be 0.10, 117.83, and 4.53 kW, while the amount of specific exergy consumption for the dehumidification system is determined as 481.85 kJ/kg. The study also reveals that the exergy parameters vary with changes in reference state temperature and that the exergy efficiencies decrease linearly as reference state temperature rises. Therefore, the findings of this investigation demonstrate the potential for using exergy analysis as an effective tool to improve the performance of dehumidification systems in industrial settings, specifically in the production of pistachios.Practical applicationsPistachio nut known as green gold because of its high economical value, is one of the popular nuts over the world. Dehumidification system based on drying technology could be used in food industry with many distinct advantages for processing of particulate crops like pistachios. For a comprehensive assessment of this system, analysis of the first and second laws of thermodynamics is applied. Exergy aspect based on the thermodynamic analysis the is an important stage for designing, modeling, optimizing, and performance assessment of the dehumidification system to produce processed pistachio. The results of this study show that the performance of dehumidification system could be improved by incorporating a steam compressor, a secondary heat exchanger, self‐heat recuperation technology, and a pinch method. It is believed that such a study would contribute to the industrial exploitation of pistachio which can provide insight into decreasing energy consumption and reducing capital costs for engineers and factory owners.

Effects of working fluid mixtures on the exergetic sustainability of a solar-biomass organic Rankine cycle power plant

This study assessed the effects of working fluid mixtures on the exergetic sustainability of a solar-biomass organic Rankine cycle (ORC) plant. The design features of a real ORC plant operational at Ottana (Italy) were employed for analyses. Although a lot of studies exist in the literature on thermo-economic implications of mixture working fluids in ORC plants, the aspect of sustainability is often left out. The desire to bridge this gap is the key motivation for this study. Zero-dimensional models were implemented in MATLAB for the design of all the hybrid plant units. The ORC design considered as working fluids the existing pure MM, and mixtures 0.1MM/0.9MDM, 0.8MM/0.2MDM, and 0.9MM/0.1MDMselected actively from the REFPROP database. Furthermore, established off-design models were incorporated into the ORC simulations. The exergetic sustainability index (ESI), the environmental effect factor (EEF), the exergetic improvement potential rate (IP), and the exergetic recoverability ratio (RECR) were adopted as sustainability performance indicators. Additionally, the destruction factor (DF) was used to assess the effects of a working fluid mixture on the sustainability performance of the ORC at the component level. Results showed that under design conditions, the mixture 0.1MM/0.9MDM had worse ESI than pure MM by about 1.5%, while the mixtures 0.8MM/0.2MDM and 0.9MM/0.1MDM improved ESI by about 1.6% and 2%, respectively. At off-design conditions, the optimum HTF mass flow rate with the highest ESI was obtained as about 7 kg/s for all the fluids. For the HTF temperature, 260 o C was obtained as the optimum for the mixture 0.8MM/0.2MDM, and 250 o C for all the other fluids. Also, decreasing the heat sink temperature in all fluids increases linearly the system ESI. Moreover, the ORC condenser showed the highest DF of over 70% for all the fluids, and the use of the best mixture (0.9MM/0.1MDM) as the ORC working fluid would increase the condenser DF by about 2 percentage points relative to pure MM. Future studies should seek to derive a set of general criteria that would aid the selection of cycle and working fluid mixture designs in favor of sustainability.

Multi-Response Design Optimisation of a Combined Fluidised Bed-Infrared Dryer for Terebinth (Pistacia atlantica L.) Fruit Drying Process Based on Energy and Exergy Assessments by Applying RSM-CCD Modelling

The present investigation aimed to perform an optimisation process of the thermodynamic characteristics for terebinth fruit drying under different drying conditions in a fluidised bed-infrared (FBI) dryer using response surface methodology (RSM) based on a central composite design (CCD) approach. The experiments were conducted at three levels of drying air temperature (40, 55, and 70 °C), three levels of drying air velocity (0.93, 1.765, and 2.60 m/s), and three levels of infrared power (500, 1000, and 1500 W). Energy and exergy assessments of the thermodynamic parameters were performed based on the afirst and second laws of thermodynamics. Minimum energy utilisation, energy utilisation ratio, and exergy loss rate, and maximum exergy efficiency, improvement potential rate, and sustainability index were selected as the criteria in the optimisation process. The considered surfaces were evaluated at 20 experimental points. The experimental results were evaluated using a second-order polynomial model where an ANOVA test was applied to identify model ability and optimal operating drying conditions. The results of the ANOVA test showed that all of the operating variables had a highly significant effect on the corresponding responses. At the optimal drying conditions of 40 °C drying air temperature, 2.60 m/s air velocity, 633.54 W infrared power, and desirability of 0.670, the optimised values of energy utilisation, energy utilisation ratio, exergy efficiency, exergy loss rate, improvement potential rate, and sustainability index were 0.036 kJ/s, 0.029, 86.63%, 0.029 kJ/s, 1.79 kJ/s, and 7.36, respectively. The models predicted for all of the responses had R2-values ranging between 0.9254 and 0.9928, which showed that they had good ability to predict these responses. Therefore, the results of this research showed that RSM modelling had acceptable success in optimising thermodynamic performance in addition to achieving the best experimental conditions.

Performance of Exergetic, Energetic and Techno-Economic Analyses on a Gas-Type Industrial Drying System of Black Tea

The purpose of this research work is to perform detailed exergetic, energetic and techno-economic analysis of the black tea drying process in the gas-type industrial dryer. Exergy–energy and techno-economic methodology was applied to investigate the heat loss, exergetic and energetic performance, exergy efficiency, improvement potential rate, sustainability index and techno-economic performance of a drying system. The results showed that the heat loss of exhaust air in the late drying process played a main contributing role in the heat loss and exergy loss of the whole drying system. Therefore, the exergy efficiency of the initial drying period and the redrying period varied from 38.08% to 65.09% and 24.76% to 26.97%, respectively. In addition, the improvement potential rate and sustainability index of the whole system varied from 6.93 kW to 12.94 kW and 1.33 to 2.86, respectively. The improvement potential obtained in the present work indicated that the drying operation is greatly in need of exergy performance improvement. Finally, the net present value and payback period obtained from techno-economic analysis were 179,442.03 USD and 5.3 years, the result is useful for investors or contractors to refer to and make investment decisions.

Exergetic analysis of a continuous plant for the hydrothermal reduction of CO2 into formate

Carbon capture and utilization can mitigate the problems caused by CO2 emissions, at the same time that valuable products are obtained from the conversion of CO2. By reduction of CO2 in hydrothermal conditions (T = 275°C, P = 200 bar), high yields of conversion of CO2 to formate of up to 70% can be achieved in reaction times of 1 h. This technology can be implemented as a continuous process in large CO2 production sites, and for this purpose the energy optimization of the process is essential to make it technically and economically feasible. Therefore, the objective of this work is to evaluate the thermodynamic efficiency and the cost of the different units involved in the hydrothermal conversion of CO2 into formate. Exergy balances were applied to the main units of a continuous plant for the hydrothermal reduction of CO2 into formate. The exergy efficiency, exergy improvement potential rate, the exergoeconomic costs and the sustainability index were calculated along with the exergy destruction rate in the main process units. The specific exergy destroyed per kg of formate produced was calculated as 6260 kJ/kg. The results showed that the major exergy destruction rate took place in the reactor, representing the 69% of the total exergy destruction in the plant. Although this destruction rate increased with the conversion in the reactor, in terms of the overall efficiency and exergetic cost of the process, a high conversion above 70% is advisable. The exergetic efficiency of each unit was also evaluated along with the exergetic improvement potential rate. The lowest efficiency was identified in the pump with a value of 0.44. In the case of the exergoeconomic performance, the reactor showed the highest cost rate representing the 67% of the total costs. The total exergoeconomic cost rate was 2.3 €/kg of formate produced.

Production of animal feed from food waste or corn? Analyses of energy and exergy

The aim of the study was to investigate the energy and exergy consumption of the food waste dryer and then to compare the energy required to produce animal feed with the waste drying method and conventional methods. The required waste from the kitchens has been collected so that each collection period was considered as a block due to having different moisture content. The results showed that the amount of energy consumed increased along with increasing temperature to 29.23 kJ, also wasted exergy and the rate of recovery was significantly increased, but the efficiency of the device decreased significantly. Over time, energy consumption, energy consumption ratio, improvement potential rate have increased, but exergy efficiency reduced. Obtained results suggest that the conversion of food waste into animal feed requires 1.8 MJ per kg less energy. Finally, feed production from food waste is more affordable than agriculture because not only we need less energy than but also we don't spend money to get initial materials.

Advanced exergy analysis of the turbojet engine main components considering mexogenous, endogenous, exegenous, avoidable and unavoidable exergy destructions

In this study, exergy dynamic and advanced exergy analyses are applied to the turbojet engine to assess its mexogenous, endogenous, exogenous, avoidable and unavoidable exergies under the environment conditions of 15 °C temperature and 1 bar pressure. The maximum exergy point in the turbojet engine is found for the combustor in which C11H23 (Jet-A1) fuel is combusted with air, while the minimum one is determined for the air compressor head where the free air enters. The combustion chamber has the maximum fuel, product and irreversibility rates and the air compressor has the minimum fuel and product exergy values, while the minimum irreversibility is found for the turbine. Maximum improvement potential rate is found for the combustion chamber (5141.27 kW), while minimum rate is determined for the turbine of system (6.95 kW). Also, the turbine component has the highest exergy efficiency (97.20%) due to its expansion process, while combustion chamber component has the lowest exergy efficiency (55.39%) due to low efficient combustion process of the fuel. Furthermore, the mexogenous exergy destructions from maximum to minimum are found for the combustion chamber, air compressor and gas turbine units, respectively. Considering exergy dynamic analysis, the mexogenous exergy destruction rates of the combustion chamber, air compressor and gas turbine are found as 184.4 kW, 103.97 kW and 9.99 kW, respectively. Considering all results, the combustion chamber is the primer component to be handled for better efficiency and improvement.

Modeling and Optimization of Energy and Exergy Parameters of a Hybrid-Solar Dryer for Basil Leaf Drying Using RSM

This study deals with the optimization of energetic and exergetic parameters of a hybrid-solar dryer to dry basil leaves under determined experimental conditions at three air temperatures (40 °C, 55 °C, and 70 °C) and three bed thickness levels (2, 4, and 6 cm). The optimization of the thermodynamic parameters was performed using the response surface method (RSM) based on the central composite design (CCD) and the desirability function (DF) to maximize the drying rate, exergy efficiency, improvement potential rate and the sustainability index, and to minimize the energy utilization, energy utilization ratio and exergy loss rate. These parameters were calculated on the basis of the first and second laws of thermodynamics as the response variables. Based on the results obtained, it was determined that the optimal conditions for basil drying were at a drying air temperature of 63.8 °C and a bed thickness of 2 cm. At this point, the parameters of the drying rate, energy utilization, energy utilization ratio, exergy efficiency, exergy loss rate, improvement potential rate and sustainability index were obtained with the maximum utility function (D = 0.548) as 0.27, 0.019 (kJ/s), 0.23, 65.75%, 0.016 (kJ/s), 1.10 (kJ/s) and 0.015, respectively.

Exergetic and techno‐economic analysis of Moroccan horehound leaves (Marrubium vulgare L.) in forced convection solar and microwave drying

AbstractThis paper aims to analyze solar and microwave drying of Horehound leaves (Marrubium vulgare) from an exergetic point of view. Solar drying tests in forced convection were performed at airflow rates (150 and 300 m3/h) and air‐drying temperatures (60°C, 70°C, and 80°C), where the microwave tests were performed in microwave powers ranging from 50 to 450 kW. Four performance parameters were investigated: exergy of evaporation, exergy loss, and exergy efficiency, sustainability index, and the improvement potential rate of the drying chamber and drying process. The results show that the exergy efficiency increases with the increase of aerothermal conditions. Exegetic performances essentially depend on the drying air temperatures and the airflow rates. The exergy efficiency of the drying process is higher than that of the drying chamber. The drying characteristics of Horehound leaves treated under microwave irradiation is a crucial process to predict its moisture content design so as to optimize the drying process. The exergetic analysis presented in this manuscript shows an improvement in the sustainability index of the drying processes and the reducing losses due to the irreversibility of large‐scale production of dry plants by using solar dryer systems. The techno‐economic analysis performed on the solar dryer including the calculation of the cost of production of 1 kg of dried product shows the economic profitability of drying this kind of product using the convective solar dryer.

Impacts of biomass hybridization on exergetic sustainability of a solar organic Rankine cycle power plant

Due to the low thermo-economic performance of solar ORC plants, several studies are ongoing to investigate the potential merits/demerits of biomass hybridization as a retrofit. Although many of such studies have examined the technical and economic viabilities of various hybrid solar-biomass concepts, due attention has not been directed to the area of their sustainability based on the Second Law of Thermodynamics. This study was aimed at investigating the potential effects of biomass hybridization on the exergetic sustainability of an organic Rankine cycle (ORC) power plant. Design data of an existing solar ORC plant currently operational at Ottana (Italy) were employed for analysis. The referenced ORC plant is rated at about 630 kWe, powered at the moment solely by a concentrated solar power (CSP) field, which integrates linear Fresnel collectors with two-tank thermal energy storage (TES) device. Five different exergetic sustainability indicators were employed in this study to assess the aforementioned ORC plant when fed by hybrid solar-biomass energy resources. Results showed the hybrid plant's destruction factor (DF), exergetic sustainability index (ESI), environmental effect factor (EEF), improvement potential rate (IPR), and recoverability ratio (RECR) of 89.40%, 0.119, 8.435, 4744.8 kW, and 0.89, respectively. Additionally, a comparison of the solar-only and the hybrid solar-biomass schemes revealed that biomass hybridization would improve the exergetic sustainability of the ORC plant. Nevertheless, the high value of IPR obtained suggests that ample opportunities would yet exist to further enhance sustainability indices of the studied ORC plant post biomass hybridization. In sum, biomass hybridization of the solar ORC plant considered in this study would enhance sustainability performance but more opportunities would yet exist to further optimize the system.

Energy, exergy, economic, environmental, energy based economic, exergoeconomic and enviroeconomic (7E) analyses of a jet fueled turbofan type of aircraft engine

In this study, energy, exergy, economic, environmental, energy based economic, exergoeconomic and enviroeconomic analyses (namely the 7E analysis) are performed to the gas turbine type of aero engines used in the civil and military aviation industries. The energy efficiency of the system is determined as 19.37%, and the exergy efficiency of the system is computed as 18.25%, whereas the exergetic improvement potential rate, fuel waste exergy rate, productivity lack ratio, improved exergetic efficiency and the improvement percentage of exergetic efficiency of the system are calculated as 36.456 GJ/h, 81.75%, 447.91%, 55.02% and 201.47%, respectively. Also, the exergy efficiencies of the components of the fan, fan duct nozzle, air compressor, combustion chamber, high pressure turbine, low pressure turbine and exhaust duct nozzle are estimated as 88.11%, 96.19%, 89.62%, 49.75%, 98.76% 98.42%, and 98.61%, respectively. The annual loss energy rate of the overall system is estimated to be 16010909.67 kWh/year, while the present worth of the system is 2478509.293 US$ and the energy based economic parameter is obtained to be 6.46 kWh/US$-year. The unit exergy cost rate of the overall engine’s product is calculated as 98.441 US$/GJ and the exergy cost rate of the engine is computed to be 980.111 US$/h.

DEHYDRATION BEHAVIOR AND THERMODYNAMIC ANALYSIS OF KIWIFRUIT SLICES IN CONVECTIVE TRAY DRYER

The present study was concerned with convective drying of kiwifruit slices. The influences of drying air temperature and flow rate on dehydration behavior of the samples and thermodynamic performance of the process were investigated. The results showed that the process duration was significantly decreased with the increasing temperature and flow rate. The entire dehydration process took place in the falling rate period and no constant period was observed. Using the nonlinear regression procedure, four well-known mathematical models were fitted into the experimental drying curves and the Midilli model represented the best description. The results of thermodynamic analyses indicated that, following the increment in air temperature, the energy utilization and energy utilization ratio values increased from 2.91 to 15.05 kJ s-1 and from 0.24 to 0.47, respectively. The exergy loss and exergy efficiency were specified to be in the ranges of 50-280 J s-1 and 55.89% to 84.13%, respectively. The exergy improvement potential rate and sustainability index varied from and from 12.28 J s-1 to 36.39 J s-1 and from 12.28 J s-1 to 36.39 J s-1, respectively. Generally, despite of energetic indices, higher temperatures of drying air resulted in better exergetic performance.

Advanced Exergy Analyses of a Solar Hybrid Food Dehydrator

In this study, for the first time an advanced exergy analysis was applied to a solar hybrid food dehydrator to find out the causes of the inefficacies and to assess the actual improvement potential. The dryer was integrated with an evacuated solar tube collector and gas burner as a heating sources. Drying experiments were performed using bell pepper at 55 °C under three heating options i.e., gas, solar and dual. The rates of exergy destructions were split into unavoidable (EdUN) and avoidable (EdAV) which further split into four parameters termed unavoidable endogenous (EdUN,EN), unavoidable exogenous (EdUN,EX), avoidable endogenous (EdAV,EX) and avoidable exogenous (EdAV,EN). Conventional exergy analysis revealed that drying chamber possess lower improvement potential rate (IP) than heating components while outcomes of advanced exergy analysis showed that both the design and system components interaction of heating unit imparted a major effect on its efficiency. Optimizing the operating conditions of the heating sources could reduce their higher amount of inefficiencies. The values of exergy efficiency for the overall system were calculated to be 86.66%, 84.18%, 83.74% (conventional) and 97.41%, 95.99%, 96.16% (advanced) under gas, dual and solar heating modes respectively.

Energy and Exergy Analyses of Rice Drying in a Novel Electric Stationary Bed Grain-Drying System with Internal Circulation of the Drying Medium.

In our study, we developed a system to reduce both energy consumption and pollutant discharge during the drying process. We present a new technology, a stationary bed grain-drying test device based on the internal circulation of the drying medium (ICODM). A rice-drying experiment was carried out inside of it, and the influences of air temperature (AT) and air velocity (AV) on the energy and exergy efficiencies (EEE) as well as the improvement potential rate (IPR) and the sustainability index (SI) of the rice-drying process were studied. The following conclusions were obtained: when the rice was dried at a temperature of below 55 °C and an AV across the grain layer of 0.5 m/s, the average EEE during the drying process was 48.27–72.17% and 40.27–71.07%, respectively, demonstrating an increasing trend as the drying medium temperature increased. When the rice was dried using an AV across the grain layer in the range of 0.33–0.5 m/s and a temperature of 40 °C, the two values were 39.79–73.9% and 49.66–71.04%, respectively, demonstrating a decreasing trend as the drying medium flow velocity increased. IPR and SI were 4.1–8.5 J/s and 1.9–2.7, respectively, at a drying temperature of 30–55 °C and an AV of 0.33–0.5 m/s. These conclusions can provide helpful guidance for the optimization and control of the rice-drying process in terms of saving energy.

Thermodynamic Evaluation of the Forced Convective Hybrid-Solar Dryer during Drying Process of Rosemary (Rosmarinus officinalis L.) Leaves

This study aimed to examine the energy and exergy indices of the rosemary drying process in a hybrid-solar dryer (HSD) and the effects of air-drying parameters on these thermodynamic indices. Drying experiments were carried out at four levels of air temperature (40, 50, 60, and 70 ∘C) and three levels of air velocity (1, 1.5, and 2 m/s). Energy and exergy were calculated by application of the first and second laws of thermodynamics. Based on the principal laws, energy efficiency, exergy losses, and exergetic improvement potential rate, were evaluated. The results showed that the energy utilization ratio (EUR) ranged from 0.246 to 0.502, and energy utilization (EU) ranged from 0.017 to 0.060 (kJ/s). Exergy loss and efficiency varied from 0.009 to 0.028 (kJ/s) and from 35.08% to 78.5%, respectively, and increased with increased temperature and air velocity. It was found that the exergy loss rate was affected by temperature and air velocity because the overall heat transfer coefficient was different under these conditions. By comparison, with increasing temperature and air velocity, the exergy efficiency increased. Because most energy is used to evaporate moisture, this behavior may be explained by improved energy utilization. The drying chamber sustainability index ranged from 0.0129 to 0.0293. This study provides insights into the optimization process of drying operations and operational parameters in solar hybrid dryers that reduce energy losses and consumption.

Impact of different fuel usages on thermodynamic performances of a high bypass turbofan engine used in commercial aircraft

In this study, energy, exergy, and sustainability analyses are performed for the PW4056 engine to observe the different fuel effects on the thermodynamic performance of a turbofan engine. For this purpose, energy and exergy analyses are performed at the same dead state conditions, and then sustainability analyses are conducted for kerosene and hydrogen-powered engine and its main components. Also, nineteen thermodynamic performance metrics are adapted for the purpose of the study and used to compare the fuel performances. It is found that the fuel mass flow of the hydrogen fuel (1.03 kg/s) is lower than the kerosene fuel (2.85 kg/s), the exhaust gases mass flow of the hydrogen fuel (117.14 kg/s) is lower than the kerosene fuel (118.96 kg/s). The minimum exergy efficient component is determined as the combustion chamber in both cases, which are 64.24 % for kerosene case and 58.20 % for hydrogen case. The lowest relative exergy loss ratio is calculated to be 28.28 % for Fan outlet loss for hydrogen case, while the maximum relative exergy consumption ratio is calculated to be 51.93 % for combustion chamber for hydrogen case. The maximum productivity lack ratio is computed as 161.65 % for combustion chamber for hydrogen case, whereas the minimum relative fuel exergy waste ratio is computed as 0.02 % for high pressure turbine for hydrogen case, The highest exergetic improvement potential rate is obtained to be 24231.48 kW for combustion chamber for hydrogen case, while the lowest product ratio indicator is found to be 17.03 % for low pressure compressor for kerosene case. Furthermore, the minimum exergetic sustainability index is obtained to be 1.39 for the combustion chamber for the hydrogen case, whereas the maximum environmental effect factor is obtained to be 0.72 for combustion chamber for hydrogen case. On the other hand, with the usage of hydrogen fuel; it is observed that the exergy efficiency of the overall engine decreases from 26.9 % to 24.3 %, the ecological effect factor of the overall engine goes up from 3.712 to 4.113, the exergetic sustainability index of the overall engine rises from 0.321 to 0.369, and the waste exergy cost flow of the overall engine increases from 17.41 × 10 −3 US$/kW to 19.09 × 10 −3 US$/kW.

Turbofan engine performances from aviation, thermodynamic and environmental perspectives

In this paper, JT15D turbofan engine and its main subcomponents are assessed with the aviation, energy, exergy, environmental, and sustainability analyses. In the first stage, the system's specific thrust and specific fuel consumption of the engine are found as 315.9 N s/kg and 15.8 g/kN.s, respectively. Then, system's energetic efficiency is estimated as 21.15% and exergetic efficiency is accounted to be 19.919%. The system's exergetic improvement potential rate, productivity lack ratio and fuel exergy waste ratio are determined as 1573.535 kW, 402.024% and 80.081%, respectively. The ecological and environmental effect factors of the turbofan system are computed to be 5.020 and 4.020, respectively, while the sustainable efficiency factor and exergetic sustainability index rates are found as 1.249 and 0.249, respectively. Finally, among the system parts, the Combustion Chamber (CC) has minimum rates of sustainable efficiency factor, exergetic efficiency and sustainability index, while it has utmost rates of ecological and environmental effect factors, fuel exergy waste ratio, irreversibility and productivity lack ratios. As a general conclusion, the combustion chamber and low pressure compressor components should be optimized for better performance of the system.