scholarly journals Exergy Efficiency Promotion for the System of CO2 Hydrogenation to Methanol in Habitable Confined Space

2021 ◽  
Vol 9 ◽  
Author(s):  
Kai Xiong ◽  
Yong-Li Yin ◽  
Yong Cao ◽  
Xiao-Tian Liu
Keyword(s):  
Carbon Dioxide ◽  
Energy Consumption ◽  
Working Condition ◽  
Space Velocity ◽  
High Energy ◽  
Exergy Efficiency ◽  
Total System ◽  
Exergy Destruction ◽  
Confined Space ◽  
External Energy

Excess hydrogen and carbon dioxide will be produced during the operation of life support systems in the habitable confined space (HCS), and to eliminate the two excess gases by converting them into methanol is of great significance for maintenance of atmospheric balance and protection of crew’s life safety. Due to the limited energy supply ability within the HCS, it is important for the system of carbon dioxide hydrogenation to methanol (CDHM) to operate with high energy efficiency to reduce unnecessary external energy consumption and internal energy loss. In this paper, the exergy analysis method is adopted for exergy efficiency improvement. Specifically, a parametric study on the exergetic performance of the CDHM system is conducted based on the three key working condition parameters that have a huge impact on the reaction process and energy utilization quality, which is used to find the favorable working condition with low external energy consumption and exergy destruction per unit gas elimination and high exergy efficiency. Within the chosen three reaction parameters which are reaction pressure, temperature, and space velocity ranging from 5 to 8 MPa, from 483.15 to 543.15 K, and from 2,800 to 4000 h−1, respectively, the gas elimination of carbon dioxide and hydrogen increases by 13.3, 19.58, and 30.58%, respectively. Moreover, the input power, cold energy consumption, and exergy destruction per molar synthetic methanol all grow to some extent, leading to a 0.06% decline, a 0.46% promotion, and a 0.15% decrease, respectively, in the exergy efficiency. The results show that the high exergy efficiency can be realized with relatively low pressure, high temperature, and low space velocity in the working condition. Besides, the exergy destructions of each component in the CDHM system are also presented in this paper. The exergy destructions in the methanol synthesis reactor, heater, and heat exchanger hot end are found to be the three biggest, whose summation accounts for more than 90% of the total system exergy destruction. Thus, the exergy efficiency also can be improved by reducing the three biggest exergy destructions.

scholarly journals 4E Analysis of a Fuel Cell and Gas Turbine Hybrid Energy System

2020 ◽  
Vol 11 (1) ◽  
pp. 7568-7579
Keyword(s):  
Fuel Cell ◽  
Cell Voltage ◽  
Energy System ◽  
High Energy ◽  
Exergy Efficiency ◽  
Combined Cycle ◽  
Net Energy ◽  
Exergy Destruction ◽  
Molten Carbonate ◽  
Ambient Temperatures

Exergy analysis of the expansion turbine hybrid cycle of integrated molten carbonate fuel cells is presented in this study. The proposed cycle was used as a sustainable energy curriculum to provide a small hybrid power plant with high energy efficiency. To generate electricity with the system mentioned above, and externally repaired fusion carbon fuel cell was used located at the top of the combined cycle. Moreover, the turbine and steam turbine systems are considered as complementary and bottom layers for co-generation, respectively. The results showed that the proposed system could reach net energy of up to 1125 kilowatts, while the total exergy efficiency (including electricity and heat) for this system is more than 68%. Moreover, the energy supplied and exergy efficiency derived from the proposed cycle are stable versus changes in ambient temperatures. Besides, the effect of increasing the current density on the cell voltage and the total exergy destruction was considered. Also, the new approaches of the exergoeconomics and exergoenvironmental analysis are implemented in this system. The results show that the hybrid system can decrease the exergy destruction costs more than 16%, and the environmental footprint of the system more than 23.4%.

Effect of TiO2/MO Nano-lubricant on Energy and Exergy Savings of an Air Conditioner using Blends of R22/R600a

2020 ◽  
Vol 17 (4) ◽  
pp. 8283-8297
Author(s):  
M.E. Abdur Razzaq ◽  
J. U. Ahamed ◽  
M.A. M. Hossain
Keyword(s):  
Energy Consumption ◽  
Power Consumption ◽  
Tio2 Nanoparticles ◽  
Volume Fraction ◽  
Exergy Efficiency ◽  
Operating Conditions ◽  
Coefficient Of Performance ◽  
Air Conditioner ◽  
Exergy Destruction ◽  
Nano Lubricant

This experimental study determines the energetic and exergetic performances of an air conditioner using blend of R22/R600a (60:40 by mass) for different volume fractions (0.1 %, 0.2 %, 0.3 %, and, 0.4 %) of TiO2 nanoparticles dispersed into mineral oil (MO). Energetic and exergetic parameters investigated in this experiment including power consumption, cooling effect, discharge pressure and temperature, coefficient of performance (COP), exergy destruction (irreversibility), irreversibility in the component, sustainability index (SI) and exergy efficiency at different operating conditions. The k-type thermocouples and pressure gauge were used to measure the temperature and pressure at different locations of the air conditioner. Thermodynamic characteristics of the refrigerant were collected using REFPROP 7. Results showed that the lowest power consumption and total exergy destruction were observed in the system with 0.4% volume fraction of TiO2 nanoparticles charge in the TiO2/MO lubricant with refrigerant blend; these values of energy consumption and total exergy destruction were 12.76 % and 7.5 % respectively, which is lower than R22/Polyol ester (POE) lubricant. The COP for the blend was increased by 6.5% to 8.3% compared to R22 and with nano-lubricant COP for the blend was increased by 17.9% to 19.9% compared to R22/POE. The air conditioner using blend charge with 0.4% TiO2/MO lubricant has the maximum COP and exergy efficiency among the selected nano-lubricants. These values of COP and exergy efficiency were 19.9 % and 35.07 % respectively, greater than that of R22/POE. Again, compressor discharge temperature was found to be decreased with the introduction of nano-lubricants compared to the original system, and the expectancy of compressor life may be extended with TiO2/MO nano-lubricant. Among the components, the compressor was found to be maximum exergy destroyer (at 60 %), followed by the condenser (at 25.4 %) and evaporator (at 13.3 %). Overall, the study found that refrigerant blend with nano-lubricant minimised the energy consumption and exergy destruction and the system operated safely with nano-lubricant without any system modification.

scholarly journals Efficiency and Losses Analysis of Steam Air Heater from Marine Steam Propulsion Plant

Energies ◽  
2018 ◽  
Vol 11 (11) ◽  
pp. 3019 ◽  
Author(s):  
Josip Orović ◽  
Vedran Mrzljak ◽  
Igor Poljak
Keyword(s):  
Ambient Temperature ◽  
Power Plants ◽  
High Energy ◽  
Exergy Efficiency ◽  
Flue Gases ◽  
Exergy Destruction ◽  
Air Heater ◽  
Air Heating ◽  
Wide Range ◽  
Steam System

Air heaters are commonly used devices in steam power plants. In base-loaded conventional power plants, air heaters usually use flue gases for air heating. In this paper, the air heater from a marine steam propulsion plant is analyzed, using superheated steam as a heating medium. In a marine propulsion plant, flue gases from steam generator are not hot enough for the air heating process. In a wide range of steam system loads, the analyzed steam air heater has low energy power losses and high energy efficiencies, ranging from 98.41% to 99.90%. Exergy analysis of the steam air heater showed that exergy destruction is quite high, whereas exergy efficiency ranged between 46.34% and 67.14%. Air heater exergy destruction was the highest, whereas exergy efficiency was the lowest at the highest steam system loads, which was an unexpected occurrence because the highest loads can be expected in the majority of marine steam plant operations. The change in the ambient temperature significantly influences steam air heater exergy efficiency. An increase in the ambient temperature of 10 °C reduces analyzed air heater exergy efficiency by 4.5%, or more, on average.

Separation of Biologically Active Compounds by Membrane Operations

2017 ◽  
Vol 23 (2) ◽  
pp. 218-230 ◽  
Author(s):  
Xiaoying Zhu ◽  
Renbi Bai
Keyword(s):  
Energy Consumption ◽  
Bioactive Compounds ◽  
Membrane Fouling ◽  
Membrane Separation ◽  
Separation Efficiency ◽  
High Energy ◽  
Separation Processes ◽  
Membrane Processes ◽  
Separation Technology ◽  
Pressure Driven

Background: Bioactive compounds from various natural sources have been attracting more and more attention, owing to their broad diversity of functionalities and availabilities. However, many of the bioactive compounds often exist at an extremely low concentration in a mixture so that massive harvesting is needed to obtain sufficient amounts for their practical usage. Thus, effective fractionation or separation technologies are essential for the screening and production of the bioactive compound products. The applicatons of conventional processes such as extraction, distillation and lyophilisation, etc. may be tedious, have high energy consumption or cause denature or degradation of the bioactive compounds. Membrane separation processes operate at ambient temperature, without the need for heating and therefore with less energy consumption. The “cold” separation technology also prevents the possible degradation of the bioactive compounds. The separation process is mainly physical and both fractions (permeate and retentate) of the membrane processes may be recovered. Thus, using membrane separation technology is a promising approach to concentrate and separate bioactive compounds. Methods: A comprehensive survey of membrane operations used for the separation of bioactive compounds is conducted. The available and established membrane separation processes are introduced and reviewed. Results: The most frequently used membrane processes are the pressure driven ones, including microfiltration (MF), ultrafiltration (UF) and nanofiltration (NF). They are applied either individually as a single sieve or in combination as an integrated membrane array to meet the different requirements in the separation of bioactive compounds. Other new membrane processes with multiple functions have also been developed and employed for the separation or fractionation of bioactive compounds. The hybrid electrodialysis (ED)-UF membrane process, for example has been used to provide a solution for the separation of biomolecules with similar molecular weights but different surface electrical properties. In contrast, the affinity membrane technology is shown to have the advantages of increasing the separation efficiency at low operational pressures through selectively adsorbing bioactive compounds during the filtration process. Conclusion: Individual membranes or membrane arrays are effectively used to separate bioactive compounds or achieve multiple fractionation of them with different molecule weights or sizes. Pressure driven membrane processes are highly efficient and widely used. Membrane fouling, especially irreversible organic and biological fouling, is the inevitable problem. Multifunctional membranes and affinity membranes provide the possibility of effectively separating bioactive compounds that are similar in sizes but different in other physical and chemical properties. Surface modification methods are of great potential to increase membrane separation efficiency as well as reduce the problem of membrane fouling. Developing membranes and optimizing the operational parameters specifically for the applications of separation of various bioactive compounds should be taken as an important part of ongoing or future membrane research in this field.

scholarly journals Current Knowledge and Future Directions for Improving Subsoiling Quality and Reducing Energy Consumption in Conservation Fields

Agriculture ◽  
2021 ◽  
Vol 11 (7) ◽  
pp. 575
Author(s):  
Shangyi Lou ◽  
Jin He ◽  
Hongwen Li ◽  
Qingjie Wang ◽  
Caiyun Lu ◽  
...  
Keyword(s):  
Energy Consumption ◽  
Cover Crops ◽  
Current Knowledge ◽  
High Energy ◽  
Field Application ◽  
Research Progress ◽  
Monitoring And Control ◽  
Future Directions ◽  
Tillage Depth ◽  
And Control

Subsoiling has been acknowledged worldwide to break compacted hardpan, improve soil permeability and water storage capacity, and promote topsoil deepening and root growth. However, there exist certain factors which limit the wide in-field application of subsoiling machines. Of these factors, the main two are poor subsoiling quality and high energy consumption, especially the undesired tillage depth obtained in the field with cover crops. Based on the analysis of global adoption and benefits of subsoiling technology, and application status of subsoiling machines, this article reviewed the research methods, technical characteristics, and developing trends in five key aspects, including subsoiling shovel design, anti-drag technologies, technologies of tillage depth detection and control, and research on soil mechanical interaction. Combined with the research progress and application requirements of subsoiling machines across the globe, current problems and technical difficulties were analyzed and summarized. Aiming to solve these problems, improve subsoiling quality, and reduce energy consumption, this article proposed future directions for the development of subsoiling machines, including optimizing the soil model in computer simulation, strengthening research on the subsoiling mechanism and comprehensive effect, developing new tillage depth monitoring and control systems, and improving wear-resisting properties of subsoiling shovels.

scholarly journals Energetic and exergetic analysis of a convective drier: A case study of potato drying process

2020 ◽  
Vol 5 (1) ◽  
pp. 563-572
Author(s):  
Iman Golpour ◽  
Mohammad Kaveh ◽  
Reza Amiri Chayjan ◽  
Raquel P. F. Guiné
Keyword(s):  
Energy Consumption ◽  
Research Work ◽  
Specific Energy Consumption ◽  
Exergy Efficiency ◽  
Operating Conditions ◽  
Energy Utilization ◽  
Convective Drying ◽  
Drying Time ◽  
Energy And Exergy ◽  
Exergy Losses

AbstractThis research work focused on the evaluation of energy and exergy in the convective drying of potato slices. Experiments were conducted at four air temperatures (40, 50, 60 and 70°C) and three air velocities (0.5, 1.0 and 1.5 m/s) in a convective dryer, with circulating heated air. Freshly harvested potatoes with initial moisture content (MC) of 79.9% wet basis were used in this research. The influence of temperature and air velocity was investigated in terms of energy and exergy (energy utilization [EU], energy utilization ratio [EUR], exergy losses and exergy efficiency). The calculations for energy and exergy were based on the first and second laws of thermodynamics. Results indicated that EU, EUR and exergy losses decreased along drying time, while exergy efficiency increased. The specific energy consumption (SEC) varied from 1.94 × 105 to 3.14 × 105 kJ/kg. The exergy loss varied in the range of 0.006 to 0.036 kJ/s and the maximum exergy efficiency obtained was 85.85% at 70°C and 0.5 m/s, while minimum exergy efficiency was 57.07% at 40°C and 1.5 m/s. Moreover, the values of exergetic improvement potential (IP) rate changed between 0.0016 and 0.0046 kJ/s and the highest value occurred for drying at 70°C and 1.5 m/s, whereas the lowest value was for 70°C and 0.5 m/s. As a result, this knowledge will allow the optimization of convective dryers, when operating for the drying of this food product or others, as well as choosing the most appropriate operating conditions that cause the reduction of energy consumption, irreversibilities and losses in the industrial convective drying processes.

scholarly journals Nanoscale optical writing through upconversion resonance energy transfer

2021 ◽  
Vol 7 (9) ◽  
pp. eabe2209
Author(s):  
S. Lamon ◽  
Y. Wu ◽  
Q. Zhang ◽  
X. Liu ◽  
M. Gu
Keyword(s):  
Graphene Oxide ◽  
Energy Transfer ◽  
Energy Consumption ◽  
Data Storage ◽  
High Capacity ◽  
Resonance Energy Transfer ◽  
Resonance Energy ◽  
High Energy ◽  
Optical Data ◽  
Upconversion Nanoparticles

Nanoscale optical writing using far-field super-resolution methods provides an unprecedented approach for high-capacity data storage. However, current nanoscale optical writing methods typically rely on photoinitiation and photoinhibition with high beam intensity, high energy consumption, and short device life span. We demonstrate a simple and broadly applicable method based on resonance energy transfer from lanthanide-doped upconversion nanoparticles to graphene oxide for nanoscale optical writing. The transfer of high-energy quanta from upconversion nanoparticles induces a localized chemical reduction in graphene oxide flakes for optical writing, with a lateral feature size of ~50 nm (1/20th of the wavelength) under an inhibition intensity of 11.25 MW cm−2. Upconversion resonance energy transfer may enable next-generation optical data storage with high capacity and low energy consumption, while offering a powerful tool for energy-efficient nanofabrication of flexible electronic devices.

scholarly journals Thermodynamic Study of Energy Consumption and Carbon Dioxide Emission in Ironmaking Process of the Reduction of Iron Oxides by Carbon

Energies ◽  
2021 ◽  
Vol 14 (7) ◽  
pp. 1999
Author(s):  
Guanyong Sun ◽  
Bin Li ◽  
Hanjie Guo ◽  
Wensheng Yang ◽  
Shaoying Li ◽  
...  
Keyword(s):  
Carbon Dioxide ◽  
Energy Consumption ◽  
Iron Oxides ◽  
Volume Fraction ◽  
Minimum Energy ◽  
Carbon Dioxide Emission ◽  
Reduction Reactions ◽  
Co2 Output ◽  
Coupling Parameters ◽  
Ironmaking Process

Carbon included in coke and coal was used as a reduction agent and fuel in blast furnace (BF) ironmaking processes, which released large quantities of carbon dioxide (CO2). Minimizing the carbon consumption and CO2 output has always the goal of ironmaking research. In this paper, the reduction reactions of iron oxides by carbon, the gasification reaction of carbon by CO2, and the coupling reactions were studied by thermodynamic functions, which were derived from isobaric specific heat capacity. The reaction enthalpy at 298 K could not represent the heat value at the other reaction temperature, so the certain temperature should be confirmed by Gibbs frees energy and gas partial pressure. Based on Hess’ law, the energy consumption of the ironmaking process by carbon was calculated in detail. The decrease in the reduction temperature of solid metal iron has been beneficial in reducing the sensible heat required. When the volume ratio of CO to CO2 in the top gas of the furnace was given as 1.1–1.5, the coupling parameters of carbon gasification were 1.06–1.28 for Fe2O3, 0.71–0.85 for Fe3O4, 0.35–0.43 for FeO, respectively. With the increase in the coupling parameters, the volume fraction of CO2 decreased, and energy consumption and CO2 output increased. The minimum energy consumption and CO2 output of liquid iron production were in the reduction reactions with only CO2 generated, which were 9.952 GJ/t and 1265.854 kg/t from Fe2O3, 9.761 GJ/t and 1226.799 kg/t from Fe3O4, 9.007 GJ/t and 1107.368 kg/t from FeO, respectively. Compared with the current energy consumption of 11.65 GJ/t hot metal (HM) and CO2 output of 1650 kg/tHM of BF, the energy consumption and CO2 of ironmaking by carbon could reach lower levels by decreasing the coupled gasification reactions, lowering the temperature needed to generate solid Fe and adjusting the iron oxides to improve the iron content in the raw material. This article provides a simplified calculation method to understand the limit of energy consumption and CO2 output of ironmaking by carbon reduction iron oxides.

scholarly journals Exergy efficiency of thermochemical syngas-to-ethanol production plants

2021 ◽  
Vol 3 (5) ◽  
Author(s):  
Marcos Paulo Gabriel da Costa e Silva ◽  
Júlio Cesar de Carvalho Miranda
Keyword(s):  
Ethanol Production ◽  
Process Improvement ◽  
Second Generation ◽  
Exergy Efficiency ◽  
Exergy Destruction ◽  
Exothermic Reactions ◽  
Production Processes ◽  
Different Temperatures ◽  
Exergy Analyses ◽  
Second Generation Ethanol

Abstract This work presents exergy analyses applied in four different conceptual second-generation ethanol production processes through a thermochemical route using catalysts based on Molybdenum (P-1), Copper (P-2), and Rhodium (P-3 and P-4), aiming to assess their exergetic efficiencies. The results show that the conceptual processes have satisfactory exergy efficiencies in both cases, when compared among themselves and when compared with other processes reported in literature. The processes’ efficiency for P-1, P-2, P-3 and P-4 were, respectively, 52.4%, 41.4%, 43.7% and 48.9%. The reactors were the sections in which exergy destruction was more significant, due to the exothermic reactions and mixing points (where streams with different temperatures were mixed). Such results show the potential of thermochemical ethanol production, besides opening the possibilities of process improvement. Graphic abstract

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