Multi-effect Desalination System Research Articles

Enviro-exergo-economic analysis and optimization of a nanofiltration-multi effect desalination, power generation and cooling in an innovative trigeneration plant

In this work, an innovative trigeneration system integrating the combined nano filtration - multi effect desalination system to absorption chiller for cooling, steam Rankine cycle for power output, parabolic trough collector, and auxiliary natural gas-fired heater for heat input. Energy, exergoeconomic, and environmental models are developed for the proposed plant. Comparison between systems with/without nanofiltration is conducted. Then, a parametric study is exhibited and discussed. Finally, multi-objective optimization process is carried out using genetic algorithm to achieve minimum investment cost rate and maximum exergetic efficiency. Results showed that the nanofiltration unit addition decreases the overall plant exergy destruction, investment cost rate and annual fuel consumption by 12.11%, 6.88% and 12.1% respectively. Moreover, the annual CO 2 emissions can be enhanced by about 9% with the heating steam temperature of the desalination unit. On the other hand, parametric study revealed that increasing the absorption generator temperature and the desalination unit number of evaporators is recommended from the energetic exegetic, and exergoeconomic points of view. While the plant investment cost per hour is negatively affected by number of evaporators increase. The annual CO 2 emissions avoided can be enhanced by about 9% with the NF-MED heating steam temperature increase. Optimization process showed that the optimal operation conditions can decrease the total product cost rates by 2.94% and increase the exergy efficiency by 5.26% compared to the base system.

Experimental and Numerical Study of Hydrodynamic and Heat Transfer Characteristics of Falling Film Over Metal Foam Layered Horizontal Tube

AbstractA novel nonintrusive technique based on an air-coupled ultrasonic transducer was used to study the hydrodynamic behavior of falling film over metal foam layered horizontal tube. Copper foam having a porosity of 90.5%, brazed over a copper tube of 25.4 mm diameter was used in this study. Falling film thickness distribution in the circumferential direction and the dynamic characteristics of falling film were studied in the falling film Reynolds number range of 356–715, and at a tube spacing of 5 mm and 15 mm. The falling film characteristics over metal foam layered horizontal tubes were compared with that over a plain horizontal tube surface. Heat transfer studies of falling film over metal foam layered tube were studied in an evaporator of a multi-effect desalination system by experiment. It was observed that the falling film heat transfer coefficient was enhanced 2.7 times by the application of metal foam over the plain horizontal tube. The measurements obtained from hydrodynamic and heat transfer studies were compared with the predictions made by a computational model and were found to be in good agreement. Metal foam properties required for the computational model were obtained using a microcomputed tomography-based study.

A new standalone single effect thermal vapor compression desalination plant with nano-filtration pretreatment

Thermal vapor compression is one of the most efficient techniques used in both small and medium scale desalination systems. However, the system works under vacuum pressure which is complex in design that uses expensive materials. Thus, a new system design is proposed to allow operation at atmospheric pressure to bypass scaling issues involving nano-filtration technology. The nanofiltration membrane is used as a pre-treatment, to rise the top brine temperature to almost 100 °C and operate the plant at atmospheric pressure. The proposed plant uses solar energy as the main source of thermal/electrical energy. To assess the performance of the new system, energy, exergetic, economic and environmental analysis are carried out for 500 m3/day standalone solar-nanofiltration-thermal vapor compression desalination plant (Solar-NF-TVC). In addition, the proposed system is tested under different operating conditions such as feed water temperature, compression ratio, salt rejection, recovery ratio and motive steam pressure. Results indicate that the plant exergetic efficiency is up to 10%, which is higher than the multi-effect desalination system, reverse osmosis, multi-effect evaporation mechanical vapor compression and multi-effect desalination thermal vapor compression. The compression ratio is found to be the most effective control variable that affects the plant performance ratio, and the feed water temperature has the most significant effect on exergetic efficiency. The saved amount of CO2 is equal 13661.2 ton/yr. Finally, the plant unit water price is found to be equal to 0.89 $/m3. Overall, the proposed cost-effective desalination plant is more suitable for remote areas due to its manufacturing from local available materials.

Thermo-economic comparison of two models of combined transcritical CO2 refrigeration and multi-effect desalination system

Combined refrigeration and boosted multi-effect desalination systems (B-MED) are very useful and energy efficient for water and cold cogeneration. This study aims to improve such an integrated system. An original system of a combined transcritical CO2 refrigeration and boosted multi-effect desalination is studied and analyzed at 85 ℃ inlet heat source temperature; the desalination cycle in the original system (1B-MED) consists of six effects and one booster module. The original model is modified by adding another booster module; the desalination cycle in the modified system (2B-MED) consists of six effects and two booster modules at 85 ℃. By increasing the inlet heat source temperature, the number of effects increases. A Thermo-economic analysis is obtained to analyze and assess the two systems at different inlet heat source temperatures 85–110 ℃ with a various number of effects 6–11 effects. The results show that the modified system with two booster modules is thermo-economically more efficient than the original one with one booster module since the freshwater production rate increases by around 65, 74, 82, 87, 97 and 104 m3 per day at 85, 90, 95, 100, 105, and 110 ℃, respectively, with an increasing rate of 22 % – 23 %. Moreover, the unit product cost UPC of the modified system decreases to reach its lowest value at 105, 110 ℃, with a decreasing rate of more than 25 % compared to the original model with one booster module.

Techno-economic, environmental and emergy analysis and optimization of integrated solar parabolic trough collector and multi effect distillation systems with a combined cycle power plant

In this investigation, the improvement of the combined power plant that is located in Qom province was studied based on using solar energy and multi-effect desalination system. In this regard, energy, exergy, exergoeconomic, exergoenvironmental, emergoeconomic, emergoenvironmental as (6 E) analysis has been performed. Also, multi -objective genetic algorithm (MOGA) was applied to optimization of the propose cycle in view of 6 E analysis. Due to the high complexity of the optimization problem and reduce the computation time, the combination of genetic programing and artificial neural network has been employed to generate exact correlation for objective functions. The initial results demonstrated that adding the solar-based-thermal system caused an improvement of about 1.91% in the exergetic efficiency of the base plant. Moreover, by simultaneous integration of solar unit and desalination system in the base plant, the new-designed plant could generate 33 kg/s freshwater. It was determined from optimization results that the exergetic efficiency of the proposed plant increased by 3.22%. Furthermore, after optimization and at the optimum operating condition, power generation costs, power generation's environmental impacts, freshwater generation's costs, freshwater production's environmental impacts, and the emergy of the proposed system decreased about 6.27%, 24.51%, 36.51%, 26.13%, and 1.87%, respectively.

Exergy, economic and pinch analyses of a novel integrated structure for cryogenic energy storage and freshwater production using ejector refrigeration cycle, desalination unit, and natural gas combustion plant

This study aims to investigate an innovative hybrid structure of electricity storage at off-peak hours and its application at on-peak hours. In this paper, a novel hybrid system for energy storage and freshwater production using air compression and liquefaction system, ejector refrigeration cycle (ERC), thermal multi-effect desalination (MED) system, and natural gas combustion unit (GCU) is developed. The wasted heat of the liquefaction cycle is stored at off-peak hours to provide heat to the ERC and thermal desalination system and preheat the inlet streams to the turbines at on-peak hours. Also, wasted refrigeration of liquid air stream and refrigeration resulting from liquefied natural gas (LNG) regasification operations are stored at on-peak hours and are utilized in compressed air liquefaction at off-peak hours. This integrated structure produces 83.12 kg/s liquid air and 38.91 kg/s freshwater at off-peak hours with 58.24 MW power consumption. During on-peak hours, the liquid air along with 2.681 kg/s LNG enters the turbines after preheating and combustion and generated 122.6 MW power. Round-trip and storage efficiencies are obtained as 64.91% and 75.96%, respectively. Also, the exergy efficiencies of the energy storage system at off-peak hours, energy production system at on-peak hours and the whole system are estimated as 78.13%, 75.85%, and 65.92%, respectively. The results of the exergy study illustrate the reactors (43.37%), heat exchangers (26.76%), and throttle valves (10.58%) have the highest contribution to exergy destruction in the proposed combined structure, respectively. This study provides the refrigeration cycle integration with process core as hot and cold composite curves and pinch analysis. Pinch investigation is conducted on the system multi-stream exchangers and the heat exchanger networks are extracted. The economic analysis illustrates that the investment return period, the levelized cost of the product, and net annual benefit in the hybridized system are 4.877 years, 0.0919 US$/kWh, 78.38 MMUS$/year, respectively. The results of sensitivity analysis indicate the round-trip efficiency increases up to 65.32% by raising the pressure of the on-peak power generation cycle.

Exergy, pinch, and reliability analyses of an innovative hybrid system consisting of solar flat plate collectors, Rankine/CO2/Kalina power cycles, and multi-effect desalination system

Nowadays due to increasing energy demand in the world, the use of energy systems with maximum efficiency is unavoidable. Thermal integration of the systems decreases the number of equipment employed and also raises the efficiency of the hybrid configuration. In the present study, an innovative hybrid system for cogeneration of power and desalinated water including organic Rankine unit, carbon dioxide power plant, Kalina power cycle based on the seawater temperature difference, and multi-effect desalination system is developed. Part of the heat required by the system is provided by solar flat plate collectors. The innovative hybrid system produces 849.5 MW power and 198.5 kg/s potable water. Exergy investigation of the system indicates that the most exergy destruction in the whole system belongs to the combustion chamber and heat exchangers, each of which is 46.60% and 34.91% of the total exergy destruction, respectively, which shows that more than 80% of exergy destruction is related to these two parts. The exergy efficiency of the whole system is 44.81%. Through the pinch method, the heat exchanger network related to the multi-stream heat exchangers of the hybrid system is extracted. The effect of air /fuel ratio (inlet to the combustion chamber) on system performance in the parametric analysis is examined. One of the main results is a 12.69% improvement compared to the initial state of total electrical efficiency of the structure in case of increasing the fuel input to the combustion chamber up to 62.00 kg/s. By system reliability analysis and examining different modes of failure and repair rates of different sections of the system, the probability of the structure operation in different cases is extracted.

A unique ocean and solar based multigenerational system with hydrogen production and thermal energy storage for Arctic communities

Arctic communities are suffering from food and energy shortages and their high logistic costs. An innovative ocean and solar-based energy, food, fuel, and water production system is developed for Arctic communities, including Nunavut's polar hamlets. The ocean thermal energy conversion (OTEC) with ammonia trilateral Rankine cycle, concentrated solar plant (CSP), bifacial photovoltaic (BiPV), cascaded heat pump, multi-effect desalination and polymer electrolyte membrane (PEM) electrolyzer and fuel cell systems are integrated with hydrogen production and utilization and two tanks thermal energy storage systems. A food production system that includes a fish farm, a greenhouse, and a food drying facility is integrated into the system. Water and hydrogen productions are carried out with multi-effect desalination and PEM electrolyzer systems, respectively. Two primary integrations are considered for polar daytime and polar nighttime. The overall system- and its subsystems and components are extensively analyzed through various methods and simulations using the software packages. Both energy and exergy approaches are used to carry out thermodynamic analyses. The transient (time-dependent) analyses are carried out in order to present more detailed analyses with various ambient and operational parameters. Moreover, commercially available solar plant components and actual meteorological data from different databases are taken into account in order to provide more insightful results. The overall energy and exergy efficiencies for the average ambient conditions are found to be 16.28% and 36.35%, respectively.

Exergy, exergoeconomic and multi-objective optimization of a clean hydrogen and electricity production using geothermal-driven energy systems

In this research paper, comprehensive thermodynamic modeling of an integrated energy system consisting of a multi-effect desalination system, geothermal energy system, and hydrogen production unit is considered and the system performance is investigated. The system's primary fuel is a geothermal two-phase flow. The system consists of a single flash steam-based power system, ORC, double effect water–lithium bromide absorption cooling system, PEM electrolyzer, and MED with six effects. The effect of numerous design parameters such as geothermal temperature and pressure on the net power of steam turbine and ORC cycle, the cooling capacity of an absorption chiller, the amount of produced hydrogen in PEM electrolyzer, the mass flow rate of distillate water from MED and the total cost rate of the system are studied. The simulation is carried out by both EES and Matlab software. The results indicate the key role of geothermal temperature and show that both total exergy efficiency and total cost rate of the system elevate with increasing geothermal temperature. Also, the impact of changing absorption chiller parameters like evaporator and absorber temperatures on the COP and GOR of the system is investigated. Since some of these parameters have various effects on cost and efficiency as objective functions, a multi-objective optimization is applied based on a Genetic algorithm for this system and a Pareto-Frontier diagram is presented. The results show that geothermal main temperature has a significant effect on both system exergy efficiency and cost of the system. An increase in this temperature from 260 C to 300 C can increase the exergy efficiency of the system for an average of 12% at various working pressure and also increase the cost of the system by 13%.

Effects of surface roughness and temperature on non-equilibrium condensation and entrainment performance in a desalination-oriented steam ejector

• Wet steam model was built and effects of surface conditions were fully studied. • Increase of roughness reduces the ejector performance and condensation intensity. • The performance varies within 4% as the wall temperature changes from 30 to 150 °C. • The condensation droplets occur on the inner wall when it has poor adiabatic properties. Ejectors usually act as thermal compressors to recover the superfluous water vapor in multi-effect desalination systems. However, the influences of wall conditions on the steam ejector performances were not fully understood. To investigate the effects of the surface roughness and temperature on non-equilibrium condensation and entrainment performance in the steam ejector, a wet steam model was built by a computational fluid dynamics software. Simulation results indicate that the increase of roughness height reduces the ejector performance and attenuates the non-equilibrium condensation phenomenon significantly. Furthermore, as the wall temperature changes in the range of 30–150 °C, the ejector performance varies merely within 4%; however, condensation droplets which may cause erosion damage occurs on the internal surface when the wall has poor adiabatic properties. Therefore, the wall roughness and temperature should be fully considered to enhance the ejector performance and mitigate potential condensation on the wall.

Design and exergy based optimization of a clean energy system with fuel Cell/MED and hydrogen storage option

The principal aim of the current research is the design and optimization of a multi-generation unit capable of generating electricity and potable water and hydrogen. The system comprises a gas turbine unit, a high-temperature solid-oxide fuel cell (SOFC), a combustion chamber, and a multi-effect desalination (MED) system. The pressurized steam and fuel enter the anode side of high-temperature SOFC and the air goes to the cathode side. Due to reactions inside the SOFC, a high amount of electricity produces, and excess H2 enters the combustion chamber. Hot flue gases can run a gas turbine and a MED unit to generate more electrical power and desalinated water. The study illustrated the impact of current density on voltage losses and output power and output voltage of SOFC. A parametric examination is also conducted to demonstrate the influence of primary design variables on the system performance. Exergo-economic multi-criteria optimization is used to determine the optimized parameters to obtain the higher efficiency and lower cost of fuel and equipment. Calculations represented that the suggested arrangement is able to generate 53.46 kg/s desalinated water, and 54.8 MW electricity and 7.43 kg/h hydrogen energy. The system exergy efficiency under this condition is about 36.45% but the results of optimization showed that this value could rise up between 50.8% and 61.17% with the lowest system cost.

The influence of fresh water production rate on the economics of two dual-purpose power/water plants: a case study

ABSTRACT The technical and economic analysis of the dual-purpose power/water Solar Rankine Cycle (SRC) coupled with Multi-Effect Desalination (MED) system was investigated. The influence of using Thermal Vapor Compression (TVC) on the unit costs of the generated power and water was also studied. Due to the population increase in the southern touristic coastal region of Iran and decreasing trend of the fuel price subsidy over the recent years, the government interest is shifting to the use of solar thermal energy and integrating the MED or MED-TVC desalination units with the conventional Rankine cycles, and to apply the solar thermal energy to reduce the fuel consumption. The water production rate of the MED or MED-TVC plants integrated into the SRC can significantly affect the electrical performance and consequently the fresh water and electricity unit of costs which has been rarely reported in the literature. In this regard, a comparison was made between the SRC-MED and SRC-MED-TVC configurations under two different scenarios of 6 and 12 hours of thermal energy storage. The output temperature of the LF solar field was considered to be regulated by defocusing the field mirrors and changing the working fluid mass flow rate. The unit costs of electricity (COE) and fresh water (COW) for both plants were determined under different scenarios of the water production capacities. Based on the results, COE and COW range from 0.20$/kWh to 0.25$/kWh and from 1.25$/to 3$/, respectively, for different water production rates. Also, for water production rates of more than 80,000/day, the SRC-MED plant has lower COE and COW as compared to the S‌RC-MED-TVC plant. While the COE and COW of the SRC-MED-TVC plant are less than those of the other plant for water production rates of less and equal to 36,000/day.

An Efficient Energy Utilization of Biomass Energy-Based System for Renewable Hydrogen Production and Storage

Abstract The increasing environmental limits and carbon emissions taxes are substantial to develop the efficient systems for offering an effective energy utilization. This study proposed a new biomass-based gasification-assisted configuration for the renewable hydrogen production system offering efficient energy utilization. A multi-effect desalination system is employed for water desalination which is converted to steam and fed to the entrained flow gasifier. The integrated heat recovery steam generator gains the additional heat from the syngas to generate steam using fresh water from the desalination unit. The produced hydrogen is supplied to the multistage compression unit that stores hydrogen at high pressure. Industrial aspen plus software V9 version is employed for the simulation under the RK-SOAVE property method. The production of hydrogen before the water gas shift reactor is 129.5 mol/s and after the water gas shift reactor is found to be 171 mol/s. The thermodynamic performance of the biomass energy-assisted system is determined through overall energetic and exergetic efficiencies that are revealed to be 40.86% and 38.63%. Numerous sensitivity studies are performed to explore the performance of the designed system and presented and discussed.

Investigation on a small‐scale vertical tube evaporator multieffect desalination system: Modeling, analysis, and optimization

AbstractA growing population with depleting water resources has increased the requirement for desalination systems. Large‐scale desalination plants have seen a growth in the recent period; however, the small‐scale (SS) decentralized desalination plants' need has not been realized for the rural population. Low specific heat consumption for multieffect desalination systems makes it suitable for such decentralized operation. The challenge now lies in determining the system capacity and optimal operational range for the SS requirements. In this study, the thermoeconomic model for an SS multieffect desalination system for various configurations is developed. Optimization of the SS plant for the number of effects is performed to determine the optimal operational range of motive steam pressure, motive steam flow rate, and feed water flow rate. Total distillate production and freshwater cost are focused on objectives and constraints imposed over the input parameters with SS production. The results reveal that for a distillate production of 750 L/day, the motive steam flow requirement is estimated to be 25–35 kg/h with a pressure range of 2–5 bar. This study provided an overview for selecting the number of effects based on the commercial aspect of total production requirements.

Optimization of parallel/cross flow multi-effect desalination system with flue gas pre-heating considering thermo-vapor compression coupling

To reduce the energy consumption of low-temperature multi-effect distillation (LT-MED), a new scheme was proposed by combining the thermo-vapor compression (TVC) and utilizing the low-grade heat of flue gas in the thermal power generating unit for feed brine preheating. For further improvement, the concept of the mass fraction is especially proposed and considered. Taking the gained output ratio (GOR) and water production cost as the objective functions, the effects of temperature difference, TVC positions were investigated by thermodynamic and economic analysis. The optimal effect number was selected for the LT-MED system under the lowest investment. The results indicated that GOR increased and the water production cost decreased with the backward movement of TVC. The lowest water production cost was obtained under the conditions that N = 5 and TVC was at the 4th effect with the mass fraction Rmf is 0. Thermodynamic, economic, and exergy analysis was performed on the selected systems and the control group. It was concluded that the new proposed system was superior to the others in both the water production and the water production cost. GOR increased from 9.67 to 10.94 and the water production cost fell from 3.13 $/m3 to 2.84 $/m3.

Exergoeconomic and multi-objective optimization analyses of an organic Rankine cycle integrated with multi-effect desalination for electricity, cooling, heating power, and freshwater production

Efficient utilization of waste heat to run a power and desalination systems is a key technology to mitigate the energy-water crisis. Organic Rankine Cycle (ORC) is one of the promising systems that can exploit low-grade waste heat. So, this paper introduces a novel ORC-based poly-generation system driven by waste heat to produce electrical, cooling, and heating power. The poly-generation system is integrated with multi-effect desalination (MED) system for freshwater production as well. Energy, exergy, and exergo-economic (3E) investigations are made to assess the feasibility of integration of the proposed novel ORC to MED cycle. The new ORC has an adjustable three-way valve to control the seasonal requirement of electrical, heating, and cooling power. Performance of the suggested multi-generation ORC/MED is evaluated by calculating the plant electrical efficiency (ηelec), energy utilization factor (EUF), overall exergy efficiency (ηex), total product unit cost (cp,tot), electricity cost Celec, total water price (TWP), and exergo-economic factor fk. It is found that the base case of the proposed multi-generation ORC/MED plant could produce electrical power of 8.055 MW at a cost of 1.035 ¢/kWh, cooling power of 5.239 MW, heating power of 7.579 MW, and freshwater of 66.55 m3/h for 0.4136 $/m3. While the ηelec,EUF,ηex,andcp,tot are 13.38%, 53.27%, 37.22%, and 2.877 $/GJ, respectively. The parametric study indicates that adjusting the ratio of electric power generation to cooling power production has a significant impact on the thermo-economic efficiency of the ORC/MED plant and does not have any effect on the freshwater production. The multi-objective optimization analyses show that the electrical power, cooling power and EUF of the optimized case improve by 16%, 306.6% and 50%, respectively, and the cp,tot and Celec decrease by 16% and 9.5%, respectively.

Performance evaluation of a co-production system of solar thermal power generation and seawater desalination

Increasing power cycle efficiency is an important way to reduce the cost of the solar thermal power generation. The power generation system using a supercritical carbon dioxide (s-CO2) Brayton cycle has the advantages of high cycle efficiency, small equipment size and low corrosion. Then, low temperature waste heat generated by the s-CO2 Brayton cycle can be used as the low temperature heat source for multi-effect desalination. This paper discusses a s-CO2 Brayton cycle integrated with a multi-effect seawater desalination system. The heat input of the s-CO2 Brayton cycle is from a central-tower solar receiver. The residual heat of the s-CO2 Brayton cycle is the heat input of the multi-effect distillation system. The results show that the integration of multi-effect desalination system does not affect the s-CO2 Brayton cycle efficiency. With the increase of split ratio of the compressor, Brayton cycle efficiency increases and then decreases, and the water production decreases and then increases. With the increase of turbine inlet temperature, Brayton cycle efficiency increases while freshwater production varies insignificantly. After optimizing the design of the cogeneration system, solar thermal power efficiency is 24.04%, the cost of electricity generation can be reduced, the LCOE is 0.081$/kWh. by using the waste heat generated from the power cycle. realized electricity-water cogeneration, the fresh water production from 5-effect MED is 459m3/day, and the unit cost of freshwater UPC of 0.81$/m3.

Modeling of a MED-TVC desalination system by considering the effects of nanoparticles: energetic and exergetic analysis

In this study, the energetic and exergetic analysis of a multi-effect desalination system with a thermal vapor compression desalination system has been numerically evaluated. For this purpose, the mass, energy, and exergy balance equations for the thermo-compressor, first effect as well as middle effects, and condenser have been developed. The effects of motive steam pressure and number of effects on yield, gained output ratio (GOR), performance ratio (PR) and irreversibility have been examined. Nanoparticles were used to improve the heat transfer properties at different stages. The highest rate of exergy destruction with 61.67% is concerned with thermo-compressor, owing to the large difference between the motive steam pressure and the entrained steam. The lowest exergy losses rate among the various components was 4.89% for the condenser, due to the fact that much of the final distillate steam entrained the thermo-compressor. As the number of effects increased from 1 to 7, the yield, GOR as well as PR, improved by approximately 590% and the irreversibility reduced by 1.88%. As the motive steam pressure increased from 400 to 1290 kPa, the yield decreased by 25.45% while the GOR and PR improved by 12.62 and 14.8%, respectively. From the second law viewpoint, irreversibility intensified by 16.11% which in turn diminished the second efficiency by 3.17%.

Exergoeconomic analysis of a geothermal steam turbine combined with multi-effect desalination and reverse osmosis

An exergoeconomic analysis is reported of a geothermal-based combined system for electricity and freshwater in which a geothermal steam turbine is integrated with multi-effect desalination and reverse osmosis systems. The article includes an exergy analysis, an economic assessment and an exergoeconomic (i.e., exergy-based economic) evaluation. The specific exergy costing method is used for the analysis of the system to determine the effects of various design criteria on the cost rates and then to incorporate feasible improvements for enhanced cost effectiveness. The results of the exergoeconomic analysis can assist in the design, optimization and improvement of geothermal-based electricity-freshwater production combined systems. It is found that the exergoeconomic factors for the reverse osmosis, multi-effect desalination and steam turbine are high, all exceeding 85%. Thus, reducing the investment costs for these components is merited. This can be done by any of the following measures, among others: reducing heat transfer area in the multi-effect desalination system, using less expensive pumps and membranes in reverse osmosis, and lowering the expansion ratio, turbine inlet temperature and isentropic efficiency for the steam turbine.

Operation Rule of Steam Ejector and Influence Analysis of Ejection Position

In order to analyze the operation rule of steam ejector used in sewage treatment field, this paper established the mathematical model of steam ejector, simulated the internal flow state, analyzed the influence rule of external parameters on the performance of steam ejector, and analyzed the influence rule of ejector position on the water production ratio of steam ejector multi-effect evaporation desalination system. The research results show that under the same steam ejector structure, as the pressure of the working steam increases, the mixing and disturbance of the working steam and the ejected steam become more intense, and the diamond shock wave structure increases. As the pressure of the ejected steam increases, the momentum exchange effect of the shear blending of working steam and ejected steam is accelerated, and the speed increase rate becomes larger, and the diamond shock wave structure gradually gathers toward the nozzle. As the pressure rise of the ejected steam inlet and outlet increases, the backflow phenomenon near the wall in the mixing chamber becomes more serious, and the diamond shock wave structure is reduced. With the forward movement of the ejector position of the thermal steam compressor, the pressure of the ejected steam increases, and the water production ratio of the steam ejector multi-effect evaporation seawater desalination system shows a downward trend. Therefore, choosing appropriate working condition parameters can effectively improve the working performance of steam ejector and improve its operating efficiency in the field of sewage treatment.