Gyeongsang National University
Hanshik Chung
CONTENTS
 Background of Study

Introduction & Objective
 Results and discussion
 Conclusions
Fresh Water Generation System ;
(Phase-change)
(Single-Phase)
Why and What is MED ?
• MSF
( Multi Stage Flash Desalination )
•MED
( Multi Effect Desalination )
(1) MED-TVC : MED by TVC (Thermo Vapor Compressor)
(2) MED-MVC : MED by MVC
(Mechanical Vapor Compressor)
MVC and MED System
Mechanical vapor compressor design.
Assumptions and Simulation Conditions
• Steady state conditions
• 3D periodic model with CFD software package (CFX 12)
• To reduce the computational cost, only single passage
• 119,291 nodes and 613,893 elements
NUMERICAL MODELING
3-Grid computational domain
The inlet boundary conditions;
•
•
•
•
Subsonic inlet, temperature and total pressure
The turbulence intensity : 5%.
Periodic boundary conditions were applied
Blade hub and shroud : adiabatic walls.
Governing Equation
• 3-D Reynolds averaged compressible Navier-Stokes equations
• SST k-ω turbulence model
Mass and momentum conservation equations

ui   0 (1)
xi

uiu j    p  p
xi
xi x j
  u u j 2 u  
  ij l  
   i 
  x j xi 3 xl  x j
  u u j  2 
ul  
i


 ij  (2)

  k  t
 t 


x

x
3

x
  j

i 
l 

u



k
( k )  ( U j k )   ij i   * k  [(    k t ) ] (3)
t
x j
x j
x j
x j
u



k
1 k 
( k )  ( U j k )   ij i   * k  [(    k t ) ]  2 (1  F1 ) 
(4)
t
x j
x j
x j
x j
 x j x j
Details of geometry and flow condition in inlet
Number of rotor blades @ each stage
Number of stator blades
14
15
Diameter impeller 1
Inside : 282 mm
Outside : 750 mm
Inside: 298 mm
Outside : 792 mm
Inside : 298 mm
Outside : 792 mm
3650 rpm
24.1 kPa
2.62×106J /kg
7.84 ×103 J /kg.K
64.1oC
Diameter impeller 2
Diameter guide vane
Basic rotating speed
Total pressure @ inlet
Specific enthalpy @ inlet
Specific entropy @ inlet
Static temperature @ inlet
Fluid properties
Properties of saturated steam.
PROPERTY
Molar mass
Critical Volume
Critical Temperature
Critical Pressure
Boiling temperature
Acentric Factor
VALUE
18.015 kg/kmol
55.95
cm3/mol
Boundary conditions.
SETTING
Inlet
Outlet
647.14 K
Interface Models
220.64 bar
Blade
64.1o C
0.344
TYPE
Total pressure, total temperature
Average static pressure
Mass flow out
Frozen Rotor
Heat transfer
Mass and Momentum
Wall roughness
adiabatic
no slip wall
smooth wall
RESULTS AND DISCUSSION
1.35
3000 rpm
3650 rpm
4000 rpm
1.30
4500 rpm
5000 rpm
Pressure ratio
1.25
1.20
1.15
1.10
0.0
0.2
0.4
0.6
Inlet mass flow rate (kg/s)
Compressors performance map at various rotational speeds.
0.85
t-t isentropic efficiency
0.80
0.75
0.70
0.65
0.60
0.55
3000 rpm
3650 rpm
4000 rpm
0.50
4500 rpm
5000 rpm
0.45
0.0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
Inlet mass flow rate (kg/s)
Mass flow rates and efficiencies for various Rotational speeds.
32
Discharge pressure (kPa)
31
30
29
28
27
3000 rpm
3650 rpm
4000 rpm
26
4500 rpm
5000 rpm
25
350
360
370
380
390
Outlet temperature (K)
.Temperature and discharge pressure at various rotational speeds.
guide vane blade
60
impeller stage 1
80
(a)
(b)
50
40
velocity
velocity
60
40
30
Shroud
20
1.0
20
Shroud 1.0
0.6
0.8
0
0
0.6
0.4
PS
0.8
0.6
0.4
1.0
PS
0.8
10
0.6
Hub
0.4
0.2
0.0
0.2
0.2
0.2
Hub
0.4
0.8
0.0
0.0
SS
0.0
SS
impeller stage 2
(c)
70
60
velocity
50
40
30
20
Shroud
1.0
10
0.8
0
0.6
0.4
1.0
PS
0.8
0.6
0.2
0.4
0.2
Hub
0.0
0.0
SS
Flow field at blade in blade passage at (a) 16.6%, (b) 50%, and (c) 83.3%
Contour of static entropy and plot of velocity vector for 4500 rpm rotational speed
at low suction mass flow rate.
(b)
(a)
(d)
(c)
Three-dimensional flow structure in flow passage (a, b, and c) and blade
loading at rotor and stator at low suction mass flow rate.
CONCLUSION
• The effects of various operating conditions on the
compressor performance have been investigated.
At a high discharge pressure, the blockage effect was
very dominant, restricting the flow rate.
• A detailed flow analysis was performed in this
simulation, along with an examination of secondary
phenomena.
• The results clearly show the flow characteristics inside
the compressor under different operating conditions.
• This simulation showed that the widest stable operating
zone was located at a high rotational speed.