Transient and thermo-economic analysis of MED-MVC desalination system

Journal Article · Mon Oct 29 04:00:00 EDT 2018 · Energy (Oxford)

DOI:https://doi.org/10.1016/j.energy.2018.10.145· OSTI ID:1593985

Elsayed, Mohamed L. ^[1]; Mesalhy, Osama ^[2]; Mohammed, Ramy H. ^[2]; Chow, Louis C. ^[3]

---

1. Univ. of Central Florida, Orlando, FL (United States). Dept. of Mechanical and Aerospace Engineering; Zagazig Univ., Zagazig (Egypt). Dept. of Mechanical Power Engineering; Savengy Technologies
2. Univ. of Central Florida, Orlando, FL (United States). Dept. of Mechanical and Aerospace Engineering; Zagazig Univ., Zagazig (Egypt). Dept. of Mechanical Power Engineering
3. Univ. of Central Florida, Orlando, FL (United States). Dept. of Mechanical and Aerospace Engineering

An exergo-economic model is used to assess the performance of a multi-effect desalination plant integrated to a mechanical vapor compressor unit (MED-MVC) with a water production capacity of 1500 $m^3$/day. The results show that the second law efficiency ($$\eta_{II}$$) 2.8%. The MVC and evaporator units are responsible for about 39 and 52% of the total exergy destruction, respectively. The total water price (TWP) is 1.70 $$\$$/m^3$ when calculated using a simple conventional economic model and 1.63 $$\$$/m^3$ when calculated using an exergy-based cost model. Increasing the number of effects from 1 to 6 results in a 39% reduction in the specific power consumption (SPC), a 70% increase in $$\eta_{II}$$ and a 24% decrease in TWP. A dynamic model is developed to investigate the effect of fluctuations of compressor work ($$\dot{W}_c$$) and inlet seawater temperature ($$T_{sw}$$) on the plant behavior and performance. The dynamic model results show that the disturbance in $$\dot{W}$$ has a significant effect on the plant transient behavior and may cause the plant to cease operation while a disturbance in $$T_{sw}$$ has only a moderate impact. Increasing $$T_{sw}$$ above a certain value of the steady-state condition without proper control on the plant response could lead to evaporator dry out. In term of performance, a reduction in $$\dot{W}_c$$ causes a decrease in the plant production capacity and SPC, while it increases the plant performance ratio (PR). On the other hand, a reduction in the inlet $$T_{sw}$$ causes a reduction in the plant production capacity and PR and an increase in SPC for the same compressor work. Furthermore, a comparison between a MED-MVC system and a MED integrated to a thermal vapor compressor system (MED-TVC) reveals that the latter system is rather sensitive to the reduction in $$T_{sw}$$ due to the presence of the condenser unit in the MED-TVC. The response of the MED-MVC system is slower than the MED-TVC which is due to the high thermal capacity of the preheaters for the feed in the MED-MVC.

• Research Organization: Savengy Technologies, LLC, Orlando, FL (United States)
• Sponsoring Organization: USDOE Office of Science (SC); Egyptian Ministry of Research and Higher Education
• Grant/Contract Number: SC0015809
• OSTI ID: 1593985
• Alternate ID(s): OSTI ID: 1636548
• Journal Information: Energy (Oxford), Journal Name: Energy (Oxford) Journal Issue: C Vol. 167; ISSN 0360-5442
• Publisher: Elsevier
• Country of Publication: United States
• Language: English

Related Subjects

32 ENERGY CONSERVATION, CONSUMPTION, AND UTILIZATION
Cost diagram
Dynamic disturbance
Mechanical vapor compression (MVC)
Seawater