LOW ENERGY DIRECT CONTACT
MEMBRANE DISTILLATION: TOWARDS
OPTIMAL FLOW CONFIGURATION
Oman, Mascut
Isam Janajreh, Dana Suwwan
Mechanical and Materials Engineering Department,
Masdar Institute of Science and Technology,
Abu Dhabi, UAE
[email protected]
Masdar Institute
Waste to Energy lab
1
POTABLE WATER
• THE WORLD DEMANDS ON POTABLE WATER IS NOTICEABLY INCREASING DUE TO HUMAN
DEVELOPMENTS
Introduction
• BASED ON WWI , 2/3 OF THE WORLD’S POPULATION WILL FACE POTABLE WATER
SHORTAGE IN 2025.
Scope of the work
Model Anatomy
and Equations
Results
Conclusion
Ref.: earth.rice.edu
2
•
•
•
•
•
•
•
•
Introduction
Scope of the
work
Model
Anatomy and
Equations
Results
DESALINATION
MULTI-STAGE FLASH (MSF)
MULTI-EFFECT DISTILLATION (MED)
VAPOR COMPRESSION (VC)
FREEZING, HUMIDIFICATION/DEHUMIDIFICATION,
SOLAR STILLS
ELECTRO-DIALYSIS (ED)
REVERSE OSMOSIS (RO)
MEMBRANE DISTILLATION (MD):
• DIRECT CONTACT MEMBRANE DISTILLATION (DCMD)
• AIR GAP MEMBRANE DISTILLATION (AGMD)
• VACUUM MEMBRANE DISTILLATION (VMD)
Conclusion
• SWEEPING GAS MEMBRANE DISTILLATION (SGMD)
Feed In
Membrane
DCMD
Permeate
out
Feed In
Membrane
Feed out
LGDCMD
Coolant
out
Conducting
plate
Liquid gap
Feed out
Permeate
Feed In
Feed In
VMD
Membrane
Condenser
Permeate
Feed out
Coolant in
SGMD
Sweep
gas out
Membrane
Feed out
Vacuum pump
Permeate
out
Product
Sweep
Feed In
AGCMD
Membrane
Feed out
Coolant
out
Condensing
plate
Air gap
Coolant in
SCOPE OF WORK
Introduction
Scope of the
work
Model
Anatomy and
Equations
Results
Conclusion
DEVELOP A VALIDATED NUMERICAL DCMD MODEL FOR PARALLEL
AND COUNTER FLOW CONFIGURATIONS THROUGH WHICH
PARAMETRIC STUDY CAN BE CARRIED OUT:
• Varying Velocity (v=0.01 m/s initially)
• 1v, 2v, 4v, 6v
• Flow configuration
• Parallel
• Counter
• Inlet Temperatures
• Membrane properties:
• Thickness
• Conductivity
• Channel Length (x=0.21 m)
• 0.5x, 0.75x, 1x, 2x, 4x, 6x
4
MODEL SETUP
Parameter
Symbol
(unit)
Value
Length x height
L (m)x h(m)
0.21x0.001
Knudsen &
Poiseuille fluid
model
Molar Weight
α T ,β T
Introduction
Scope of the
work
Model
Anatomy and
Equations
Mw (kg/mol)
0.018
Membrane
Thickness
Gas Constant
δm (μm)
130
R(J/mol. K)
8.3143
Pores Radius
r(nm)
50
Gas Viscosity
ηv (Ns m2 )
9.29e-6
Porosity
ε
0.7
Membrane
Thermal
Conductivity
k p (W/mK)
0.178
Table 1: Selected Parameter for the model
Results
Conclusion
Continuity:
Energy:
    ui

 Sc
t
xi
Momentum:
1
  u i  u i u j  ij


  gi  Si
t
x j
x j
c p  t T


[u i (  e  p)] 
[( K 
)
  h j J j ]  Sh
xi
xi
Prt
xi
j
ASSUMPTIONS
Introduction
Scope of the
work
Model
Anatomy
and
Equations
• TWO-DIMENSIONAL IN CARTESIAN COORDINATES OF X AND Y
DIRECTIONS
• IN THE INLET REGION, THE CHANNEL HEIGHT (Y-DIRECTION) IS
ASSUMED TO BE VERY SMALL WITH RESPECT TO THE CHANNEL
LENGTH (210mmx2mm)
• THE VELOCITY PROFILES IS CONSIDERED FOR THE FULLY
DEVELOPED FLOW (PARABOLIC PROFILE AS  = 0.05 Re D)
• STEADY, INCOMPRESSIBLE, BUT NON-ISOTHERMAL FLOW
Results
Conclusion
• THE FEED STREAM IS CONSISTED OF A MIXTURE OF TWO
MISCIBLE BRINE SOLUTION, WHILE THE PERMEATE STREAM
COMPROMISES OF SINGLE SPECIE OF FRESH WATER
• NO SLIP CONDITION AT THE MEMBRANE AND CHANNEL WALLS
6
GOVERNING EQUATIONS
Introduction
MASS FLUX:
′′ =   − 
[1]
Scope of the
work

  = EXP 23.1964 −
3816.44
−46.13
,  ∈ , 
[2]
Model Anatomy
and Equations
 ,  =   
 ,  ∈ , 
[3]
Results
2
 = 1 − 0.5 − 10
Conclusion
 =  +  = 1.064  

 
[4]

 
+ 0.125  
  2  
    
[5]
Tzahi Y. Cath, “Experimental study of desalination using DCMD: A new approach to flux enhancement”, J. Membrane7Science,
228 (2004)5-16
Tsung-Ching Chen, Chii-Dong Ho, Ho-Ming Yeh, “ Theoretical and experimental analysis of direct contact membrane desalination”,
J. Membrane Sceince, 330 (2009)279-287
GOVERNING EQUATIONS CONT’D
HEAT FLUX:
Introduction
 =  + 
[6]
Scope of the
work
 = ′′ Δ = ′′(, − , )
[7]
Model Anatomy
and Equations
, = 1.7535 , + 2024.3,
Results
 = −
Conclusion
 =  + 1 −  


, − ,
 ∈ , 
[8]
[9]
[10]
  = 0.0144 − 2.16 × 10−5 TM + 273.15 + 1.32 × 10−7 TM + 273.15
2
[11]
Tzahi Y. Cath, “Experimental study of desalination using DCMD: A new approach to flux enhancement”, J. Membrane Science,
228 (2004)5-16
Tsung-Ching Chen, Chii-Dong Ho, Ho-Ming Yeh, “ Theoretical and experimental analysis of direct contact membrane
desalination”, ”, J. Membrane Science, 330 (2009)279-287
8
TEMPERATURE POLARIZATION
Introduction
Scope of the
work
IT IS KNOWN THAT THE DCMD EFFICIENCY IS LIMITED BY THE HEAT TRANSFER
THROUGH THE BOUNDARY LAYERS. IN ORDER TO DEFINE AND QUANTIFY THE
BOUNDARY LAYER RESISTANCE OVER THE TOTAL HEAT TRANSFER RESISTANCE, THE
TEMPERATURE POLARIZATION IS USED.
, −,
=
[12]
, −,
0.001
0.001
0.0525
0.105
0.0005
0.1575
0
300
0.21
302
304
306
308
310
-0.0005
1v
Results
-0.001
312
Vertical distance (m)
Model Anatomy
and Equations
Vertical distance (m)
0.0525
0.105
0.0005
0.1575
0.21
0
300
302
0.001
0.21
0
300
302
304
306
308
310
312
-0.0005
-0.001
Vertical distance (m)
Vertical distance (m)
0.1575
0.157
5
0.21
302
304
306
308
-0.0005
4v
Temperature (°C)
-0.001
312
0.052
5
0.105
0.0005
0
300
310
Temperature (°C)
0.0525
0.105
308
2v
-0.001
Temperature (oC)
0.0005
306
-0.0005
0.001
Conclusion
304
310
312
6v
Temperature (°C)
9
MESH SENSITIVITY
Introduction
Mesh
Scope of the
work
Model
Anatomy
and
Equations
Results
Very Fine 800 by 92
147,200 cells
Fine
Baseline
Coarse
Conclusion
Statistics
400 by 92
73,600 cells
400 by 46
36,800 cells
200 by 46
18,400 cells
Mean
Temperature ok
Error
316.7
Reference
316.9
0.07%
313.3
1.1%
301.8
4.7%
10
VALIDATION: TEMPERATURE PROFILES
314
Introduction
Tb,f
312
310
Tm,f
Scope of the
work
308
306
Model
Anatomy
and
Equations
Vmax=0.0191 m/s
Vmax=0.0382 m/s
Vmax=0.0575 m/s
Tm,p
304
302
300
Tb,p
Results
298
Experimental Results (Chen et al. )
0
0.05
0.1
0.15
0.2
Length (m)
Simulation Results
Conclusion
• Inlet velocity sensitivity: Baseline temperatures Tf=40oC and Tp=25oC
• Both experimental and simulation follow the same trend
• Larger inlet velocity results in larger temperature gradient across the membrane
T.-C. Chen et al. / Journal of Membrane Science 330 (2009) 279–287
11
TEMPERATURE PROFILES-COUNTER FLOW
314
Introduction
Tb,f
312
310
Tm,f
Scope of the
work
Model
Anatomy
and
Equations
Results
Temp (oK)
308
Vmax=0.0575 m/s
306
Vmax=0,0382 m/s
304
Vmax=0.0191 m/s
Tm,p
302
Tb,p
300
Conclusion
298
0
0.05
0.1
0.15
0.2
Length (m)
I. Inlet velocity sensitivity: Baseline temperatures Tf=40oC and Tp=25oC
Larger inlet velocity results in larger temperature gradient across the membrane
12
MASS FLUX- PARALLEL VS COUNTER FLOW
22
Vmax=0.0382 m/s
Vmax=0.0191m/s
Vmax=0.0575m/s
(Counter) Vmax=0.0382 m/s,
(Counter) Vmax=0.0191m/s
(Counter) Vmax=0.0575m/s
20
18
Model
Anatomy
and
Equations
Mass Flux (Kg/m 2.hr)
Scope of the
work
Mass flux (kg/m2.hr)
Introduction
16
14
12
10
Vc=0.057
Vc=0.038
Vc=0.019
Vp=0.057
Vp=0.038
Vp=0.019
8
6
4
Results
Conclusion
2
0
0.05
0.1
0.15
0.2
0.25
Length (m)
Length(m)
Velocity inlet(m/s)
Parallel
Counter
Mass flux (kg/hr.m2) Mass flux (kg/hr.m2)
V1 = 0.05744
1.744
1.84
+5.5%
V2= 0.0382
1.60
1.73
+8.1%
V3=0.01925
1.11
1.21
+9.0%
Inlet velocity and configuration : Parallel < Counter flow for Baseline temp (40 and 25oC)
13
MASS FLUX: PARALLEL VS COUNTER FLOW
Scope of the
work
Model
Anatomy
and
Equations
Mass flux (kg/m2.hr)
Introduction
Tc=80
Tp=80
Tc=60
Tp=60
Tc=40
Tp=40
Results
Length (m)
Conclusion
Inlet Temperature
(c)
Parallel
Mass flux(kg/m2.hr)
Counter
Mass flux(kg/m2.hr)
40
1.744
1.84
+5.5
60
7.13
8.87
+24.5
80
21.01
23.65 +12.5
Inlet Temperature: Parallel < counter flow Baseline velocity 0.0191m/s
16
HEAT FLUX
-500
Vp=0.019
-1000
Vp=0.038
-1500
Vp=0.057
Introduction
Model
Anatomy
and
Equations
Heat flux(w/m2)
Scope of the
work
Heat Flux (W/m 2)
-2000
Vc=0.019
-2500
Vc=0.038
-3000
Vc=0.057
-3500
Vmax=0.0382 m/s
Vmax=0.0191m/s
Vmax=0.0575m/s
(Counter) Vmax=0.0382 m/s,
(Counter) Vmax=0.0191m/s
(Counter) Vmax=0.0575m/s
-4000
-4500
-5000
Results
-5500
0
0.05
0.1
Length (m)
0.15
0.2
0.25
Length(m)
Inlet velocity
Conclusion
Heat flux
Parallel (w/m2)
Heat flux
Counter (w/m2)
V1 = 0.05744 486.2
507.3
V2= 0.0382
396.8
454.8
V3=0.01925
332.6
362.3
Parallel vs counter flow configuration at Baseline temp (40 and 25oC)
15
HEAT FLUX (CHANGING FEED FLOW TEMPERATURE)
Tc=40
Tp=40
Tc=60
Scope of the
work
Model
Anatomy
and
Equations
Heat flux(w/m2)
Introduction
Tp=60
Tc=80
Tp=80
Results
Length (m)
Conclusion
Inlet temperature
(oC)
Parallel
Heat flux (w/m2)
Counter
Heat flux (w/m2)
40
333
362
60
1015
1068
80
4234
4513
Inlet Temperature: Parallel < counter flow Baseline velocity 0.0191m/s
16
TEMPERATURE POLARIZATION: FLOW VELOCITY
0.75
0.7
=
0.65
Introduction
Vmax=0.0382 m/s
Vmax=0.0191m/s
Vmax=0.0575m/s
(Counter) Vmax=0.0382 m/s,
(Counter) Vmax=0.0191m/s
(Counter) Vmax=0.0575m/s
, −,
, −,
Model
Anatomy
and
Equations
Temperature Polarization
Scope of the
work
Temp. Polarization
0.6
0.55
0.5
0.45
0.4
0.35
0.3
Results
0.25
0
0.05
0.1
0.15
0.2
0.25
Length(m)
Length (m)
Conclusion
Mass/velocity
inlet
Total /average Temp
polarization parallel
V1 = 0.05744 0.32
V2= 0.0382
0.29
Total/average Temp
polarization counter
0.34
0.325
V3=0.01925 0.28
0.32
Inlet velocity and configuration : Parallel < Counter flow for Baseline temp (40 and 25oC)
17
TEMPERATURE POLARIZATION (CHANGING
FEED FLOW TEMPERATURE)
0.75
Introduction
0.7
=
Temperature Polarization
Model
Anatomy
and
Equations
Temp. Polarization
0.65
Scope of the
work
Tf,in = 40 C
Tf,in = 60 C
Tf,in = 80 C
(Counter) Tf,in = 40 C
(Counter) Tf,in = 60 C
(Counter) Tf,in = 80 C
, −,
, −,
0.6
0.55
0.5
0.45
0.4
Results
Vc
0.35
0.3
Conclusion
0.25
Vp
0
0.05
0.1
Length
(m)
Length(m)
0.15
0.2
0.25
Inlet temperature and configuration : Insensitive for the inlet temperature
Parallel flow the polarization temp goes beyond the recommended levels, whereas the counter
flow remains within the recommended range.
18
APPARATUS SET UP
19
CONCLUSIONS
Introduction
Scope of the
work
Model
Anatomy
and
Equations
Results
Conclusion &
Future work
• THE COMPUTATIONAL FLUID DYNAMICS WAS APPLIED TO DETERMINE A HIGH
FIDELITY ANALYSIS FOR THE DCMD.
• THE MODEL RETURNS THE BULK TEMPERATURES, AND MEMBRANE TEMPERATURES
FOR BOTH FEED FLOW AND PERMEATE FLOW.
• THE TEMPERATURE GRADIENT CREATED A DIFFERENCE IN THE SATURATION
PRESSURE BETWEEN THE MEMBRANE SIDES, WHICH DRIVES MASS AND ENERGY
TRANSFER THROUGH THE MEMBRANE FROM THE FEED TO THE PERMEATE SIDE.
• SENSITIVITY IN THE INLET MASS AND TEMPERATURE SHOWS MUCH MORE
PRONOUNCED EFFECT DUE TO TEMPERATURE AND ALWAYS FAVOR COUNTER
FLOW CONFIGURATIONS.
• TEMPERATURE POLARIZATION DECREASES ALONG THE CHANNEL LENGTH AS
THE TEMPERATURES REACH ASYMPTOTIC VALUE
20
INTRODUCTION
Introduction
Materials
and Methods
Results and
Discussion
Conclusion
21
PARALLEL CONFIGURATION
0.36
4
0.34
0.32
v
0.3
2v
4v
0.28
6v
0.26
Total Mass flow (kg/hr.m2)
Avergae Temperature Polarization
4.5
3.5
3
v
2.5
2v
2
4v
1.5
6v
1
0.5
0.24
0
0.5
1
1.5
Column plot (0.5x, 0.75x, x, 2x, 4x and 6x) (m)
0.8
0.76
Mass flow (kg/hr.m2)
0.72
0.68
0.64
v
0.6
2v
0.56
4v
0.52
6v
0.48
0.44
0.4
0
0
0.5
1
Column plot (0.5x, 0.75x, x, 2x, 4x and 6x) (m)
1.5
Channel length
m
Velocity
m/s
0.5x
0.105
-
-
0.75x
0.1575
-
-
1x
0.21
1v
0.01
2x
0.42
2v
0.02
4x
0.84
4v
0.04
6x
1.26
6v
0.06
column plot (0.5x, 0.75x, x, 2x, 4x and 6x) (m)
22
COUNTER FLOW
0.34
v
0.33
2v
4v
0.32
6v
0.31
Total Mass flow (kg/hr.m2)
0.35
6
5.5
5
4.5
4
3.5
3
2.5
2
1.5
1
0.5
0
V
2v
4v
6v
0
0.3
0
0.5
1
1.5
0.5
1
1.5
Column plot (0.5x,0.75x, x, 2x, 4x, and 6x) (m)
Column plot (0.5x, 0.75, x, 2x, 4x and 6x) (m)
0.8
0.7
Mass flow (kg/hr.m2)
Average Temperature Polarization
0.36
0.6
0.5
v
0.4
2v
0.3
4v
0.2
6v
0.1
0
0
0.5
1
Column plot (0.5x,0.75x, x,2x,4x and 6x) (m)
1.5
23
THERMAL CONDUCTIVITY ON MASS FLOW
Introduction
Scope of the
work
Model
Anatomy
and
Equations
Results
Conclusion
24
THICKNESS OF THE MEMBRANE
Introduction
Scope of
the work
Model
Anatomy
and
Equations
Results
Conclusion
25
OUTLINE
• INTRODUCTION
• SCOPE OF WORK
• MODEL ANATOMY AND EQUATIONS
• RESULTS
• CONCLUSIONS
26
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LOW ENERGY DIRECT CONTACT MEMBRANE DISTILLATION: TOWARDS OPTIMAL FLOW CONFIGURATION