Single-effect Mechanical Vapor Compression Research Articles

Performance investigation of standalone multi-effect mechanical vapor compression desalination system powered by cascade photovoltaic/thermal-photovoltaic solar field-assisted heat pump system

A new stand-alone system of modified multi-effect mechanical vapor compression (ME-MVC) desalination unit powered by photovoltaic/thermal-photovoltaic (PVT-PV) collectors is studied The system incorporates solar-assisted heat pumps (HPs), an external preheater, and electrical and thermal energy storage subsystems. The system is investigated under different seawater feed configurations, effects number, and HP evaporator temperatures. It is compared with the conventional PV-powered single-effect mechanical vapor compression (SE-MVC) desalination system. The designed system is modeled and solved using MATLAB under weather conditions of Alexandria, Egypt, in terms of energy and economics impacts. Results indicate that the combined subsystem of the solar-assisted HPs and ME-MVC of parallel/cross feed and four effects has the lowest electricity consumption of 6.39 kWh/m3 while the value for SE-MVC is 7.58 kWh/m3. The average daily freshwater production of the proposed system is 86.4 m3 in summer and 72.89 m3 in winter with a freshwater cost of 5.11 $/m3. Yearly PVT-PV electrical efficiencies are 20.51 % and 19.35 %, respectively, whereas PVT thermal efficiency is 46.65 % and the overall solar system combined efficiency is 20.31 %. The proposed system's electricity consumption is 15.7 % lower, its solar system's efficiency is 23.54 % larger, and its freshwater cost is 3 % lower than that of the PV-powered SE-MVC.

Comparative performance evaluation of two compression ways of a single-effect mechanical vapor compression desalination system

Comparative performance evaluation of two compression ways of a single-effect mechanical vapor compression desalination system

Brine Management: Techno-economic Analysis of a Mechanical Vapor Compression Energy System for a Near-Zero Liquid Discharge Application

Fresh water availability is gradually decreasing and may limit the primary needs of drinking water and irrigation, as well as other activities, such as energy conversion, tourism, etc. A high number of desalination plants are being built to provide clean water. One of the main strategies is the brine volume minimization by means of either membrane or thermal processes. The present study focuses on the development of a techno-economic analysis of a Single Effect-Mechanical Vapor Compression (SE-MVC) system for purposes of brine volume minimization. The aim is to evaluate the thermodynamic and economic performances as well as the capital and operating expenditures of the brine concentrator when being part of a near zero liquid discharge (near-ZLD) application. This is achieved by developing the thermodynamic and economic models of the system, which are then combined together in a single integrated procedure. Brackish water analysis is used as starting point for this work. Water properties are modeled using Pitzer's equations as well as correlations found in the literature. The economic evaluation of the investment is performed by calculating the Net Present Value and Internal Rate of Return, key parameters to assess the investment viability of the project. The evaporator model provides the necessary input variables for the economic model. For a feed flow of 10.147 kg∙s-1 and a heat duty of 18080 kW, the annualized capital cost of equipment is 594.93 k€∙y-1, while the operating expenses are 854.40 k€∙y-1 The total annualized cost of the process is 1449.33 k€∙y-1.

Design analysis of MVC desalination unit powered by a grid connected photovoltaic system

The use of solar energy especially for desalination of seawater is well adapted for the Saharan region where the fresh water is scarce and solar energy potential is high. This paper presents a design analysis of a single-effect mechanical vapor compression (MVC) desalination unit powered by a grid connected photovoltaic (PV) solar system. The aim of this work is to define, as function of the freshwater needs and site specificity, the embodiment of the MVC components and the PV panels’ size. The proposed approach is based on MVC components models coupled with a solar energy estimation model. The results are illustrated using a case study in Dakhla city sited at the south of Morocco; they show that the embodiment of the global system depends greatly on the temperature of brine and distillate streams. A large gap between these design variables reduces the heat transfer area, but increases the size of the PV system.

On thermoeconomic analysis of a single-effect mechanical vapor compression desalination system

The current study is focused on thermoeconomic analysis of a single effect mechanical vapor compression (MVC) desalination system operating with and without brine recirculation. For this purpose, first- and second-law analyses are carried out to estimate the energy consumption and second-law efficiency of the plant. A single stage seawater reverse osmosis plant is also presented for the sake of comparison. For thermal systems, a detailed heat exchanger design is provided to calculate an overall heat transfer coefficients, heat transfer areas, and the pressure drops on the cold- and hot-sides of the heat exchangers. Besides, the product cost is calculated and compared by using two different cost estimation methods. Moreover, it is demonstrated that the cost-flow method of economic analysis is more elaborative and useful because it enables the component level cost optimization. The calculations reported the values of specific energy consumption (SEC), second law efficiency and product cost to be 10 to 13kWh/m3, 8 to 9% and 1.7 to 2.3$/m3, respectively. Furthermore, it is shown that the input parameters like cost index factor, electricity cost, compressor efficiency and the heat transfer areas have a remarkable influence on the product cost and must be selected carefully for accurate cost estimation.

Analysis of potassium nitrate purification with recovery of solvent through single effect mechanical vapor compression

Analysis of purification of potassium nitrate with incorporation of single effect mechanical vapor compressor for solvent recovery was done. Analysis focused on the effect of concentration and temperature of mother liquor on the energy efficiency of the process and the amount of recovered solvent. Performance coefficient of mechanical vapor compressor ranged between 1.5 and 7.5 depending primarily on the temperature of mother liquor. It was found that with increase in temperature of mother liquor through pre-heating, the power of the compressor, compression ratio and amount of heat supplied to the evaporator decrease. For a 40% concentrated feed solution and mother liquor temperature above 80 °C, performance coefficient is higher than 4. It is therefore concluded that preheating mother liquor and reduction of the effect of concentration of both mother liquor and concentrated waste stream through other methods reduces the power consumption of purification process.

Analysis of a single-effect mechanical vapor compression desalination system using water injected twin screw compressors

The mechanical vapor compression (MVC) desalination system is very attractive and competitive for small and medium scale water production. This paper presents a comprehensive analysis of a single-effect MVC desalination system using water injected twin screw compressors. The operational characteristics of the twin screw compressor including inlet volume flow rate, compressor pressure ratio, and mass fraction of injected water are investigated. The specific power consumption and the specific heat transfer area of the MVC system are then analyzed based on these characteristics. The results are comparable with data reported in literature for similar single-effect MVC desalination systems. Further comparison is performed for a single-effect MVC system using a twin screw compressor with/without water injection. The results demonstrate that the single-effect MVC desalination system using water injected twin screw compressor is a very promising technology for water production capacities less than 600m3/d. It also shows that the temperature difference between boiling vapor and compressed vapor at compressor exit can be as high as 10°C.

Research on an evaporator-condenser-separated mechanical vapor compression system

Initial experimental results on a new single-effect mechanical vapor compression (MVC) system which separates the evaporator from the condenser by employing a rotating disk evaporator were presented. The separated structure is designed to provide enhanced heat transfer, descaling and antiscaling. Specifically, experiments were performed on an evaporator-condenser-separated MVC system with a rated capacity of 1.5m3/day, which has two sets of rotating evaporators. The performance of the system was evaluated under different values of compressor frequency and evaporating temperature. It was shown that the evaporator and condenser pressures fall gradually with increases in compressor frequency under a constant distillate production. It was found that the COP increases with increasing evaporating temperature, and the highest COP obtained was 20.98.

Distillation of oil field produced water for reuse on irrigation water: evaluation of pollutants removal and ecotoxicity

Desalination is one of the earliest forms of saline water treatment and it is still used throughout the world. In this work, a single-effect mechanical vapor compression (MVC) process was investigated to produce water for irrigation of non-edible cultures from oil-field produced water. Distillation was able to produce a condensate presenting very low amounts of 84 analyzed pollutants. Ecotoxicological assays with Pseudokirchneriella subcapitata algae, Danio rerio fish, lettuce (Lactuca sativa) and earthworm (Eisenia fetida) were performed in condensate. The condensate was non-toxic for all tested organisms, except for P. subcapitata algae that showed some level of chronic toxicity caused by ammonium nitrogen. This toxic effect was confirmed by conducting a series of ecotoxicological assays with condensate samples after ammonia removal (stripping). The condensate presented quality acceptable for irrigation of non-edible crops.

Toxicity assessment of oil field produced water treated by evaporative processes to produce water to irrigation.

During the productive life of an oil well, a high quantity of produced water is extracted together with the oil, and it may achieve up to 99% in the end of the well's economical life. Desalination is one of mankind's earliest forms of saline water treatment, and nowadays, it is still a common process used throughout the world. A single-effect mechanical vapor compression (MVC) process was tested. This paper aims to assess the potential toxicity of produced water to be re-used in irrigation. Samples of both produced and distilled water were evaluated by 84 chemical parameters. The distilled produced water presented a reduction up to 97% for the majority of the analyzed parameters, including PAHs. Toxicity bioassays were performed with distilled produced water to evaluate the growth inhibition of Pseudokirchneriella subcapitata algae, the acute toxicity to Danio rerio fish, the germination inhibition of Lactuca sativa vegetable and the severity of toxicity, as well as behavior test with Lumbricid Earthworm Eisenia fetida. The ecotoxicological assays results showed no toxicity, indicating that the referred evaporative process can produce water to be reused in irrigation.

Design of single-effect mechanical vapor compression

This paper presents a comprehensive design model of the single effect mechanical vapor compression process. Previous literature models focused on determination of the heat transfer area and compressor power consumption. Several new design features included in this study are the evaporator dimensions, demister dimensions, dimensions of the non-condensable gases venting orifice, and capacity of the vacuum system. The model equations include fundamental mass and energy equations; power consumption of the vapor compressor; and a well tested set of correlations for calculations of the physical properties of the vapor and liquid streams, heat transfer coefficients, and thermodynamic losses. Dependence of system variables on temperature and salinity makes the system equations nonlinear and requires an iterative solution. System performance is discussed as a function of the product flow rate, brine boiling temperature, temperature difference of the saturated boiling brine and compressed vapor, and length of the evaporator tube. Comparison of the design results against available field data shows good agreement for the predictions of specific power consumption and specific heat transfer area.

Visual basic computer package for thermal and membrane desalination processes

A visual basic computer package was developed for the design and analysis of thermal and membrane desalination processes. The package includes conventional processes, i.e., reverse osmosis, single-effect mechanical vapor compression, multiple-effect evaporation with/without thermal or mechanical vapor compression, and multi-stage flash evaporation. The models for these systems provide detailed design data that include flow rates, stream salinity, temperatures, heat transfer or membrane area, ejector dimensions, and bundle dimensions. The model predictions are based on detailed energy and material balances and well tested correlations for the heat transfer coefficient, thermodynamic losses, and physical properties of the seawater and water vapor. The visual basic interface provides displays for profiles of system variables across the effects, stages, or membrane modules, which may include salinity, flow rates, etc. Also, displays for the process flow diagram and design results are generated simultaneously. The design results include the unit product cost, process capital, performance ratio or specific power consumption, the flow rate of cooling water, the heat transfer or the membrane area, and a number of thermodynamic losses.

Visual basic computer package for thermal and membrane desalination processes

A visual basic computer package was developed for the design and analysis of thermal and membrane desalination processes. The package includes conventional processes, i.e., reverse osmosis, single-effect mechanical vapor compression, multiple-effect evaporation with/without thermal or mechanical vapor compression, and multi-stage flash evaporation. The models for these systems provide detailed design data that include flow rates, stream salinity, temperatures, heat transfer or membrane area, ejector dimensions, and bundle dimensions. The model predictions are based on detailed energy and material balances and well tested correlations for the heat transfer coefficient, thermodynamic losses, and physical properties of the seawater and water vapor. The visual basic interface provides displays for profiles of system variables across the effects, stages, or membrane modules, which may include salinity, flow rates, etc. Also, displays for the process flow diagram and design results are generated simultaneously. The design results include the unit product cost, process capital, performance ratio or specific power consumption, the flow rate of cooling water, the heat transfer or the membrane area, and a number of thermodynamic losses.

Plastic/compact heat exchangers for single-effect desalination systems

Use of plastic materials and compact heat exchangers remains to be found on a limited scale in the desalination industry. This work focuses on performance evaluation of plastic and compact heat exchangers in the single-effect mechanical vapor compression desalination system. The analysis considers a number of tubing materials that includes PTFE plastic, high steel alloys, Cu Ni 90 10 and Cu Ni 70 30 , and titanium. The analysis includes determination of the specific power consumption and the evaporator and preheaters specific heat transfer area for various materials. Analysis is made as a function of variations in the condensate and the brine boiling temperatures. The specific cost is evaluated for various construction materials. Results show that the specific power consumption is independent of the construction material and depends only on the compression range. Also, the lowest specific heat transfer area is calculated for Cu Ni 90 10 . However, the lowest cost is obtained for the PTFE system because of the much lower cost of the material. Corrosion considerations and the associated reduction in the cost of corrosion inhibitors give an added adge for the use of PTFE plastic. Other factors that favor the use of plastic evaporators and preheaters include ease of construction and machining, lower installation and erection cost, ability to operate at higher top brine temperatures without fear of the effects of scale formation, use of acid cleaning, and virtual elimination of in-leakage problems. These merits of the plastic and compact heat exchangers and the analysis results should encourage the industry to take active steps in adopting these systems.

An electronic-mechanical analogue for the design of solar heating plant : Benseman, R. F. United Nations Conference on New Sources of Energy, Rome, 1961, 12 p., Illus.

A visual basic computer package was developed for the design and analysis of thermal and membrane desalination processes. The package includes conventional processes, i.e., reverse osmosis, single-effect mechanical vapor compression, multiple-effect evaporation with/without thermal or mechanical vapor compression, and multi-stage flash evaporation. The models for these systems provide detailed design data that include flow rates, stream salinity, temperatures, heat transfer or membrane area, ejector dimensions, and bundle dimensions. The model predictions are based on detailed energy and material balances and well tested correlations for the heat transfer coefficient, thermodynamic losses, and physical properties of the seawater and water vapor. The visual basic interface provides displays for profiles of system variables across the effects, stages, or membrane modules, which may include salinity, flow rates, etc. Also, displays for the process flow diagram and design results are generated simultaneously. The design results include the unit product cost, process capital, performance ratio or specific power consumption, the flow rate of cooling water, the heat transfer or the membrane area, and a number of thermodynamic losses.