scholarly journals Assessing the Impact of Operating Conditions on the Energy and Exergy Efficiency for Multi-Effect Vacuum Membrane Distillation Systems

Water ◽  
2021 ◽  
Vol 13 (11) ◽  
pp. 1500
Author(s):  
A. Najib ◽  
J. Orfi ◽  
H. Alansary ◽  
E. Ali
Keyword(s):  
Energy Consumption ◽  
Pilot Plant ◽  
Membrane Distillation ◽  
Exergy Efficiency ◽  
Operating Conditions ◽  
Performance Ratio ◽  
Cold Temperatures ◽  
Energy And Exergy ◽  
Vacuum Membrane Distillation ◽  
The Impact

A comprehensive study was conducted to elucidate the effect of operating conditions on the performance of a multi-effect vacuum membrane distillation pilot plant. A theoretical assessment of the energy and exergy efficiency of the process was achieved using a mathematical model based on heat and mass transfer, which was calibrated using experimental data obtained from the pilot plant. The pilot plant was a solar vacuum multi-effect membrane distillation (V-MEMD) module comprising five stages. It was found that a maximal permeate mass flux of 17.2 kg/m2·h, a recovery ratio of 47.6%, and a performance ratio of 5.38% may be achieved. The resulting gain output ratio (GOR) under these conditions was 5.05, which is comparable to previously reported values. Furthermore, the present work systematically evaluated not only the specific thermal energy consumption (STEC), but also the specific electrical energy consumption (SEEC), which has been generally neglected in previous studies. We show that STEC and SEEC may reach 166 kWh/m3 and 4.5 kWh/m3, respectively. We also observed that increasing the feed flow rate has a positive impact on the process performance, particularly when the feed temperature is higher than 65 °C. Under ideal operational conditions, the exergetic efficiency reached 21.1%, and the maximum fraction of exergy destruction was localized in the condenser compartment. Variation of the inlet hot and cold temperatures at a constant differential showed an interesting and variable impact on the performance indicators of the V-MEMD unit. The difference with the lowest inlet temperatures exhibited the most negative impact on the system performance.

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 Multiphysics Modeling and Analysis of a Solar Desalination Process Based on Vacuum Membrane Distillation

Membranes ◽  
2021 ◽  
Vol 11 (6) ◽  
pp. 386
Author(s):  
Benjamin N. Shuldes ◽  
Mona Bavarian ◽  
Siamak Nejati
Keyword(s):  
Salt Concentration ◽  
Saturation Pressure ◽  
Membrane Distillation ◽  
Exergy Efficiency ◽  
Operating Conditions ◽  
Recovery Ratio ◽  
Permeate Flux ◽  
Element Analysis ◽  
Vacuum Membrane Distillation ◽  
Polarization Phenomena

A hollow fiber vacuum membrane distillation (VMD) module was modeled using finite element analysis, and the results were used to conduct an exergy efficiency analysis for a solar-thermal desalination scheme. The performance of the VMD module was simulated under various operating conditions and membrane parameters. Membrane porosity, tortuosity, pore diameter, thickness, and fiber length were varied, along with feed temperature and feed configuration. In all cases, polarization phenomena were seen to inhibit the performance of the module. Under VMD operation, polarization of salt concentration was seen to be the main determining factor in the reduction of permeate flux. Within the boundary layer, salt concentration was seen to rapidly increase from the feed mass fraction of 0.035 to the saturation point. The increase in salt concentration led to a decrease in saturation pressure, the driving force for separation. Charging the feed into the shell instead of the lumen side of the membranes resulted in a further decrease in permeate flux. It is shown that adding a baffling scheme to the surface of the fibers can effectively reduce polarization phenomena and improve permeate flux. Increasing the overall recovery ratio was seen to increase the exergy efficiency of the system. Exergy efficiency was seen to have almost no dependency on membrane parameters due to the low recovery ratio in a single pass and the high heating duty required to reach the desired temperature for the feed stream.

scholarly journals Enhanced Performance of Membrane Distillation Using Surface Heating Process

Membranes ◽  
2021 ◽  
Vol 11 (11) ◽  
pp. 866
Author(s):  
Fei Han ◽  
Shuxun Liu ◽  
Kang Wang ◽  
Xiaoyuan Zhang
Keyword(s):  
Energy Consumption ◽  
Energy Performance ◽  
High Energy ◽  
Membrane Distillation ◽  
Operating Conditions ◽  
Surface Heating ◽  
Commercial Application ◽  
Heating Process ◽  
Temperature Polarization ◽  
Vacuum Membrane Distillation

Membrane distillation (MD) is a thermally driven desalination process that has excellent application prospects in seawater desalination or hypersaline wastewater treatment, while severe temperature polarization (TP) and the resulting relatively high energy consumption have become principal challenges limiting the commercial application of MD. Therefore, the design of novel systems to overcome the shortage of conventional MD requires urgent attention. Here, we developed three surface heating vacuum membrane distillation systems, namely, SHVMD-1, SHVMD-2, and SHVMD-3, according to the different positions of the thermal conducting layer in the cell. The distillate flux, TP, and energy performance of these systems under different operating conditions were investigated. All three systems showed stable performance, with a salt rejection >99.98% for 35 g/L NaCl, and the highest flux was close to 9 L/m2·h. The temperature polarization coefficients were higher than unity in SHVMD-2 and SHVMD-3 systems, and the SHVMD-2 system produced the lowest specific energy consumption and the highest thermal efficiency. In addition, we tested the intermittent surface heating process, which can further improve energy performance through reducing specific electrical energy consumption in vacuum membrane distillation. This paper provides a simple and efficient membrane system for the desalination of brines.

The Impact of Electric Hybrid Compressor to Make Transport Environmentally Friendly

2013 ◽  
Vol 391 ◽  
pp. 207-212
Author(s):  
Maciej Bajerlein
Keyword(s):  
Energy Consumption ◽  
Operating Conditions ◽  
Vehicle Speed ◽  
Suspension Systems ◽  
Actual Operating ◽  
Vehicle Operation ◽  
Total Energy Balance ◽  
The Impact ◽  
Road Emission ◽  
Speed Engine

This paper presents the investigations, whose aim was to determine the influence of the operation of electric and mechanical compressors on the energy consumption of city buses in public transport. The tests were performed on pneumatic systems used in city transit vehicles whose underlying component is a compressor generating pressure for the brake and suspension systems. Owing to the application of a portable analyzer - SEMTECH DS the emissions (with a secondly resolution) of CO, HC, NOx, CO2 in the exhaust gases were measured. The on-road emission tests were performed in the actual operating conditions in SORT driving tests. These tests reflect the actual vehicle operation in a real task through preset procedures of their realization and measurements determining the energy consumption and exhaust emissions or the influence of the vehicle accessories and all variables (vehicle speed, engine load, acceleration or distance covered) on the total energy balance. The on-road tests were performed on a runway of the Bednary airstrip in Poland.

A review on membrane applications and transport mechanisms in vacuum membrane distillation

2017 ◽  
Vol 34 (1) ◽  
Author(s):  
Rakesh Baghel ◽  
Sushant Upadhyaya ◽  
Kailash Singh ◽  
Satyendra P. Chaurasia ◽  
Akhilendra B. Gupta ◽  
...  
Keyword(s):  
Membrane Fouling ◽  
Membrane Separation ◽  
Critical Evaluation ◽  
Experimental Studies ◽  
Membrane Distillation ◽  
Permeate Flux ◽  
Separation Processes ◽  
Vacuum Membrane Distillation ◽  
Polarization Coefficient ◽  
The Impact

AbstractThe main aim of this article is to provide a state-of-the-art review of the experimental studies on vacuum membrane distillation (VMD) process. An introduction to the history of VMD is carried out along with the other membrane distillation configurations. Recent developments in process, characterization of membrane, module design, transport phenomena, and effect of operating parameters on permeate flux are discussed for VMD in detail. Several heat and mass transfer correlations obtained by various researchers for different VMD modules have been discussed. The impact of membrane fouling with its control in VMD is discussed in detail. In this paper, temperature polarization coefficient and concentration polarization coefficient are elaborated in detail. Integration of VMD with other membrane separation processes/industrial processes have been explained to improve the performance of the system and make it more energy efficient. A critical evaluation of the VMD literature is incorporated throughout this review.

Membrane Distillation Desalination System With Gap Circulation and Cooling Using a Built-in Heat Exchanger

2020 ◽  
Vol 143 (1) ◽  
Author(s):  
Atia E. Khalifa
Keyword(s):  
Energy Consumption ◽  
Heat Exchanger ◽  
Specific Energy Consumption ◽  
Membrane Distillation ◽  
Operating Conditions ◽  
Water Desalination ◽  
Module Design ◽  
Membrane Surfaces ◽  
Best Value ◽  
Feed Temperature

Abstract A comprehensive experimental investigation is conducted to evaluate the performance of a new flux-enhanced compact water gap membrane distillation (WGMD) module design with gap circulation and cooling for water desalination. The new design uses a separate circulation loop to circulate the gap water, and a built-in heat exchanger coil implanted inside the coolant stream channel for cooling the circulated gap water. The WGMD modules with circulation and with circulation and cooling are compared with conventional WGMD without circulation. Variations of distillate flux, temperatures, and energy consumption are presented at different design operating conditions. Circulation and cooling of the gap water greatly enhance the output flux due to gap water motion and increase the temperature difference between membrane surfaces. However, the enhancement in flux was achieved at the expense of energy consumption. Circulation and cooling of gap water are more effective with bigger gap widths. Feed flowrate showed significant effects with gap water circulation and cooling. The electrical specific energy consumption (SEC) showed the best value of 7.9 and 8.8 kWh/m3 at a feed temperature of 70 °C for both conventional WGMD and WGMD with circulation modules, while the best value of SEC for the WGMD module with gap circulation and cooling was 9.4 kWh/m3 at a feed temperature of 80 °C.

Optimization of four models flatbread bakery machines in Iran

2019 ◽  
Vol 30 (6) ◽  
pp. 3399-3434 ◽  
Author(s):  
Soroush Sadripour ◽  
Mohammad Estajloo ◽  
Seyed Abdolmehdi Hashemi ◽  
Ali J. Chamkha ◽  
Mahmoud Abbaszadeh
Keyword(s):  
Energy Consumption ◽  
Exergy Efficiency ◽  
Experimental Investigations ◽  
Content Type ◽  
Numerical Studies ◽  
Excess Air ◽  
High Preference ◽  
Energy And Exergy ◽  
Traditional Bread ◽  
Wasted Energy

Purpose The purpose of this study is to reduce energy consumption in bakeries. Due to fulfill this demand, quite a few parameters such as energy and exergy efficiency, energy waste and fuel consumption by different traditional flatbreads bakeries (Sangak, Barbari, Taftun and Lavash should be monitored and their roles should not be neglected. Design/methodology/approach In the present study, experimental measurements and mathematical modeling are used to scrutinize and investigate the effects of the aforementioned parameters on energy consumption by bakeries. Findings The results show that by doing reported methods in this paper, the wasted energy of the walls can be decreased by about 65 per cent; and also, by controlling the combustion reaction to perform with 5 per cent excess air, the wasted energy of excess air declines by about 90 per cent. And finally, the energy and exergy efficiency of bakeries is increased, and as a result, the annual energy consumption of Sangak, Barbari, Taftun and Lavash bakeries diminish about 71, 59, 57 and 40 per cent, respectively. Originality/value As evidenced by the literature review, it can be observed that neither numerical studies nor experimental investigations have been conducted about energy and exergy analyses of Iranian machinery traditional flatbread bakeries. It is clear that due to a high preference of Iranians to use the traditional bread and also the popularity of baking this kind of bread in Iran, if it is possible to enhance the traditional oven conditions to decrease the loss of natural gas instead of industrializing the bread baking, the energy consumption in the country can be optimized.

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.

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