To solve the modeling problem of altitude ground test facility (AGTF) exhaust systems, which is caused by nonlinearity along the gas path and the difficulty of ejection factor calculation, a ...multi-cavity iterative modeling method is presented. The components of exhaust systems, such as the exhaust diffuser and cooler, are built with a series of volumes. It overcomes the disadvantage that traditional lumped-parameter models have, whereby they cannot calculate the dynamic parameters along the gas path. The exhaust system model is built with an iterative method based on multi-cavity components, and simulations are carried out under experimental conditions. The simulation results show that the maximum error of pressure is 2 kPa in the steady state and less than 6 kPa in the transient process compared with experimental data. Closed-loop simulations are also carried out to further verify the accuracy and effectiveness of the multi-cavity iterative exhaust system modeling method.
•Concentrated solar collectors are used in multigeneration of power and commodities.•Energy and exergy analyses of system and subsystems are described and conducted.•Performance comparisons of ...multigeneration system to referenced baseline system (power only) are done.•The present system helps improve the use of renewable sources for better sustainability.
In this study, a multigeneration system is proposed to integrate a solar-driven gas turbine with an organic Rankine cycle, a small capacity absorption refrigeration system, single stage flash desalination, and direct space heating. Three concentrated solar collectors with rated concentration ratios of 300, 500, and 800, at a solar insolation of I=800W/m2, produce 1000°C air at the gas turbine inlet. Heat recovery from compressor intercooling and exhaust streams supply heat to the absorption refrigeration system generator, desalination process, and organic Rankine cycle boiler. These subsystems include secondary power generation, chilled water storage for space cooling, and domestic hot water production from heated desalinated water. Space heating is obtained through heat exchange with warm waste brine from the desalination process. The proposed system is compared to a reference system integrating the same solar power system with a Kalina cycle at energy and exergy efficiencies of 0.275 and 0.29. The multigeneration system indicates energetic and exergetic efficiencies of 0.284 and 0.27, respectively. Although the solar gas turbine-Kalina system suggests similar efficiency results, the multigeneration system provides a more sustainable and promising for additional commodity production from a single heat source at suitable levels for community or small commercial applications, which would otherwise require additional primary energy sources.
•A steady-state thermodynamic model is developed for absorption refrigeration in a ship.•Operation profile of B.Delta37 bulk carrier is used as an initial data.•Suitability of water-LiBr and ...ammonia-water working pairs were validated.•Coefficient of performance (COP) was studied in ISO and tropical conditions.•Estimated energy savings were 47 and 95tons of fuel every year.
This work presents a steady-state thermodynamic model for absorption refrigeration cycles with water-LiBr and ammonia-water working pairs for purpose of application on a ship. The coefficient of performance was studied with different generator and evaporator temperatures in ISO and tropical conditions. Absorption refrigeration systems were examined using exhaust gases, jacket water, and scavenge air as energy sources. Optimal generator temperatures for different refrigerant temperatures were found using different waste heat sources and for the absorption cycle itself. Critical temperature values (where the refrigeration power drops to zero) were defined. All of these values were used in order to evaluate the cooling power and energy production possibilities in a bulk carrier. The process data of exhaust gases and cooling water flows in two different climate conditions (ISO and tropical) and operation profiles of a B. Delta37 bulk carrier were used as initial data in the study. With the case ship data, a theoretical potential of saving of 70% of the electricity used in accommodation (AC use) compressor in ISO conditions and 61% in tropical conditions was recognized. Those estimates enable between 47 and 95tons of annual fuel savings, respectively. Moreover, jacket water heat recovery with a water-LiBr system has the potential to provide 2.2–4.0 times more cooling power than required during sea-time operations in ISO conditions, depending on the main engine load.
Nowadays, the high-power density and high efficiency of marine diesel engines make the requirements of high boost pressure and wide-range intake flow increased. In this study, a two-stage sequential ...turbocharging (TSST) system is presented as a method for increasing the power density and broadening the efficient working range of diesel engines. Through experimental and analysis methods, the relationships of intake and exhaust energy migration and exhaust energy distribution in the turbocharging mode switching process of the TSST system are investigated, and the optimal control strategy for the switching valves is obtained. The experimental results show that the optimized valve control strategy can achieve a reasonable distribution and efficient utilization of exhaust energy during the switching process. More specifically, the boost pressure error function is only 0.0003 kPa2·s, the engine speed fluctuation amplitude is less than 6 r/min, and the speed transition time is less than 8 s. A smooth switching between the turbocharging modes of the TSST system is achieved, exhaust energy loss is minimized, and the fuel economy and power performance of marine diesel engines over the entire range of operating conditions are effectively improved.
•The brake efficiency of the engine with TSST system was improved under entire conditions.•Transient exhaust energy flow during the switching process was studied by experiment.•The speed fluctuation first decreases and then increases with increasing delay time.•Energy distribution during the switching process was optimized by valve control.
•1-D numerical TEG model in diesel freight vehicles exhaust pipe.•Over 800W of electrical power for the heavy-duty vehicle.•Plain fins provide better performance than offset strip fins.•The height of ...the thermocouple legs plays a significant role.•2% maximum efficiency needs further improvements.
A parametric study and optimization approaches of a thermoelectric generator (TEG) for the recovery of energy from the exhaust gas in Diesel vehicles used in freight transport is reported. The TEG is installed in the tailpipe of a commercial vehicle (3.5tonnes) and a heavy-duty vehicle (40tonnes). The exhaust gas is used as the heat source and the cooling water as the heat sink. Two different heat exchanger configurations are considered: plain fins and offset strip fins. The influence of the height, length and spacing of the fins on the electrical and net power is analysed for the fixed width and length of the TEG. The influence of the length and width of the TEG and of the height of the thermocouple legs is also investigated. According to the criteria used in this study, plain fins are the best choice, yielding a maximum electrical power of 188W for the commercial vehicle and 886W for the heavy-duty vehicle. The best recovery efficiency is about 2%, with an average thermoelectric material efficiency of approximately 4.4%, for the light-duty vehicle. Accordingly, there is significant room for further improvement and optimisation based on the thermoelectric modules and the system design.
This paper presents the parametric optimization and performance analysis of the organic Rankine cycle (ORC) system for waste heat recovery from marine engine exhaust. The engine exhaust heat under ...operating conditions has been field-measured and evaluated. The thermo-economic optimization based on multi-objective evaluations is conducted numerically. This study aims to determine the optimal design evaporation temperature and condensation temperature, and to select suitable working fluids. The cooling water loop is taken into accounted for the whole ORC system. The parametric optimization with objective functions is compared. The economic objective function is defined as the ratio of net power output to total heat exchanger area, and the comprehensive objective function is determined as the weight-sum of exergy efficiency and economic objective function. The results show that there is the optimal evaporation temperature under the fixed expansion ratio in the ORC system for achieving the maximum thermal efficiency. The optimal condensation temperature for achieving the maximum economic objective function or comprehensive objective function is determined respectively. The parametric optimization with comprehensive objective function is better. With multi-objective evaluations, R141b performs the most satisfactorily with the maximum net power output of 97 kW, followed by R113 and cyclohexane, and R600a performs the least favorably. The optimized ORC system with R141b under various operating conditions is technically feasible and economically attractive.
•Diesel engine parameters under various operating conditions are field-measured.•The cooling water loop for the ORC system is taken into accounted.•Optimal evaporation temperature and condensation temperature are determined.•ORC parameters and working fluids are optimized with multi-objective evaluations.
Transshipment of compacted soybean is characterized by labor-intensive processes, long operating times, and a great amount of dust that cannot be collected by sealed devices. This dust significantly ...reduces air quality of the workshop and represents a great threat to human health. Solving this problem has been a great challenge in the soybean storage industry. For this reason, in the present study the concept of a transshipment system for soybean clearance was proposed. This system can simultaneously achieve real-time transshipment of falling materials and air curtain control of fugitive dust. The main factors influencing the performance of the air curtain dust control system were investigated using numerical simulation, and the effects of the exhaust-to-pressure ratio K and air curtain outlet velocity V on dust control efficiency were determined. Results showed that the width of the dust-collecting paths increased with increasing K and V values. We also found out that dust-escape paths were mainly concentrated in the transition height between the complete air curtains and local air curtains. At the beginning of the process, dust control efficiency rapidly increased and the increment rate became slower as K increased. When K = 1.5 and V = 5–6 m/s, dust control efficiency reached values up to 95.54–96.27%. Based on numerical simulation results, the prototype transshipment system for soybean clearance was developed, and the effectiveness of air curtain dust control was validated via smoke tracing experiments. After the application of the developed system, occupational lung disease can be significantly reduced, and transshipment efficiency per clearance can be enhanced by approximately 67% (about 50,113￥ can be saved in terms of energy consumption and labor resources). An extra granary can be saved after using the newly developed system for 36.5–52.1 clearances.
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•An effective method to solve the soybean blanking dust collection is proposed.•The dust collection method ensures smooth ventilation inside the granary.•Dust collection efficiency reaches 95.54%.•The method is validated by industrial experiments.
A recurrent concern in nature conservation is the potential competition for forage plants between wild bees and managed honey bees. Specifically, that the highly sophisticated system of recruitment ...and large perennial colonies of honey bees quickly exhaust forage resources leading to the local extirpation of wild bees. However, different species of bees show different preferences for forage plants. We here summarize known forage plants for honey bees and wild bee species at national scale in Denmark. Our focus is on floral resources shared by honey bees and wild bees, with an emphasis on both threatened wild bee species and foraging specialist species. Across all 292 known bee species from Denmark, a total of 410 plant genera were recorded as forage plants. These included 294 plant genera visited by honey bees and 292 plant genera visited by different species of wild bees. Honey bees and wild bees share 176 plant genera in Denmark. Comparing the pairwise niche overlap for individual bee species, no significant relationship was found between their overlap and forage specialization or conservation status. Network analysis of the bee-plant interactions placed honey bees aside from most other bee species, specifically the module containing the honey bee had fewer links to any other modules, while the remaining modules were more highly inter-connected. Despite the lack of predictive relationship from the pairwise niche overlap, data for individual species could be summarized. Consequently, we have identified a set of operational parameters that, based on a high foraging overlap (>70%) and unfavorable conservation status (Vulnerable+Endangered+Critically Endangered), can guide both conservation actions and land management decisions in proximity to known or suspected populations of these species.
•We carried out full-scale fire tests on platform in a station hub.•The temperature and CO volume fraction were investigated during the tests.•We conducted CFD simulations in the full-scale ...platform.•The smoke movement characteristic was analyzed.•The effect of velocity at stairway on smoke movement was also explored.
Smoke movement is more complex in a station fire hub than in a common situation, and it is also difficult to deal with. In this paper, full-scale experiments were conducted to investigate the ceiling temperature, smoke-layer thickness and the temperature distribution within the station. The effect of smoke exhaust system and the velocity at staircase on smoke flow were investigated when the fire source located near the staircase, using a series of FDS numerical simulation. From the full-scale experiment and simulation results, several conclusions were made: (1) The full-scale experiment results showed that the sprinkler system was capable of confining the temperature rise if it is activated; (2) Meanwhile, it also proved that the propagation of smoke could be effectively controlled when the mechanical smoke exhaust system is switched on; (3) Based on the simulation results, smoke spread rapidly in the platform floor at the early stage and then it entered into the staircase when the smoke exhaust system was absent; (4) Even though the exhaust and supply system opened, smoke could still propagate through the staircase if there’s no downward airflow at the entrance; (5) When the downward airflow existed, smoke still cannot be effectively discharged without the smoke exhaust system.
Nitrogen isotope (δ15N) monitoring is a potentially powerful tool in tracing atmospheric nitrogen oxides (NOx); however, the isotopic fingerprint of vehicle exhaust remains poorly interpreted. This ...deficiency limits our understanding of the origin of atmospheric haze pollution, especially in China. In this study, we systemically explored the δ15N-NOx fingerprints of various vehicle exhausts (n = 137) in China. The δ15N-NOx values of vehicle exhausts ranged from −18.8‰ to +6.4‰, presenting a significant correlation with NOx concentrations (p < 0.01). The highest δ15N-NOx values were observed for liquefied petroleum gas vehicles (−0.1 ± 1.8‰), followed by gasoline vehicles (−7.0 ± 4.8‰) and diesel vehicles (−12.7 ± 3.4‰), all of which displayed a rising trend as emissions standards were continuously updated. The δ15N-NOx values under working conditions followed the trend warm start (−5.9 ± 5.0‰) > driving (−7.3 ± 5.9‰) > cold start (−9.2 ± 2.7‰). By establishing a suitable model for assessing representative δ15N-NOx values, the δ15N-NOx values of various vehicles, including different fuel types with different emission standards, were evaluated. A model of δ15N-NOx associated with motor vehicle data was developed, which estimated the national δ15N-NOx value of vehicle emissions to be −12.6 ± 2.2‰, but there was considerable variation among different target areas in China.
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