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LOW ENERGY DIRECT CONTACT MEMBRANE DISTILLATION: TOWARDS
OPTIMAL FLOW CONFIGURATION
Isam Janajreh, Dana Suwwan
Mechanical and Materials Engineering Department,
Masdar Institute of Science and Technology,
Abu Dhabi, UAE
Masdar Institute Waste to Energy lab
Oman, Mascut
1
POTABLE WATER
• THE WORLD DEMANDS ON POTABLE WATER IS NOTICEABLY INCREASING DUE TO HUMAN
DEVELOPMENTS
• BASED ON WWI , 2/3 OF THE WORLD’S POPULATION WILL FACE POTABLE WATER
SHORTAGE IN 2025.
Introduction
Scope of the work
Model Anatomy and Equations
Results
Conclusion
2 Ref.: earth.rice.edu
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)
• SWEEPING GAS MEMBRANE DISTILLATION (SGMD)
Introduction
Scope of the work
Model Anatomy and Equations
Results
Conclusion
Feed In
Feed out
Membrane
Permeate
out
Permeate
in
DCMD
Feed In
Feed out
Coolant
out
Coolant in
LGDCMD Membrane Conducting
plate
Liquid gap
Feed In
Feed out
Membrane
Condenser VMD Permeate
Vacuum pump
Feed In
Feed out
Membrane
Permeate
out
Sweep
gas in
SGMD Sweep
gas out
Product
Feed In
Feed out
Coolant
out
Coolant in
AGCMD Membrane Condensing
plate
Air gap
SCOPE OF WORK DEVELOP A VALIDATED NUMERICAL DCMD MODEL FOR PARALLEL
AND COUNTER FLOW CONFIGURATIONS THROUGH WHICH
PARAMETRIC STUDY CAN BE CARRIED OUT:
Introduction
Scope of the work
Model Anatomy and Equations
Results
Conclusion
• 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
Introduction
Scope of the work
Model Anatomy and Equations
Results
Conclusion
Continuity: c
i
i Sx
u
t
Momentum: ii
j
ij
j
jii Sgxx
uu
t
u
Energy: h
j
jj
it
tp
i
i
i
SJhx
TcK
xpeu
x
])
Pr[()]([
5
Parameter Symbol
(unit) Value
Length x height L (m)x h(m) 0.21x0.001
Knudsen &
Poiseuille fluid
model
α T , β T 1
Molar Weight Mw(kg/mol) 0.018
Membrane
Thickness δm (μm) 130
Gas Constant 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
kp(W/mK) 0.178
Table 1: Selected Parameter for the model
• 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 𝑥𝑙 = 0.05 Re D)
• STEADY, INCOMPRESSIBLE, BUT NON-ISOTHERMAL FLOW
• 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
Introduction
Scope of the work
Model Anatomy and Equations
Results
Conclusion
6
ASSUMPTIONS
GOVERNING EQUATIONS
MASS FLUX:
𝐽′′ = 𝑐𝑚 𝑃𝑓𝑠𝑎𝑡 − 𝑃𝑝
𝑠𝑎𝑡 [1]
𝑃𝑖 𝑝𝑢𝑟𝑒𝑠𝑎𝑡 𝑇 = EXP 23.1964 −
3816.44
𝑇−46.13 , 𝑖 ∈ 𝑓, 𝑝 [2]
𝑃𝑖𝑠𝑎𝑡 𝑥, 𝑇 = 𝑥𝑤𝑎𝑤𝑃𝑖 𝑝𝑢𝑟𝑒
𝑠𝑎𝑡 , 𝑖 ∈ 𝑓, 𝑝 [3]
𝑎𝑤 = 1 − 0.5𝑥𝑁𝑎𝐶𝑙 − 10𝑥𝑁𝑎𝐶𝑙2 [4]
𝑐𝑚 = 𝑐𝑘 + 𝑐𝑝 = 1.064 𝛼 𝑇 𝑟
𝜏 𝛿𝑚
𝑀𝑤
𝑅 𝑇𝑚𝑡+ 0.125 𝛽 𝑇
𝑟2
𝜏 𝛿𝑚 𝑀𝑤 𝑃𝑚
𝑅 𝑇𝑚𝑡 𝜂𝑣 [5]
Introduction
Scope of the work
Model Anatomy and Equations
Results
Conclusion
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 Sceince, 330 (2009)279-287
7
GOVERNING EQUATIONS CONT’D HEAT FLUX:
𝑄𝑚 = 𝑄𝑣 + 𝑄𝑐 [6]
𝑄𝑣 = 𝐽′′Δ𝐻 = 𝐽′′(𝐻𝑚,𝑓 − 𝐻𝑚,𝑝) [7]
𝐻𝑚,𝑖 = 1.7535 𝑇𝑚,𝑖 + 2024.3, 𝑖 ∈ 𝑓, 𝑝 [8]
𝑄𝑐 = −𝑘𝑚
𝛿𝑚𝑇𝑚,𝑓 − 𝑇𝑚,𝑝 [9]
𝑘𝑚 = 𝜀𝑘𝑔 + 1 − 𝜀 𝑘𝑏 [10]
𝑘𝑔 𝑇𝑚 = 0.0144 − 2.16 × 10−5 TM + 273.15 + 1.32 × 10−7 TM + 273.15 2 [11]
Introduction
Scope of the work
Model Anatomy and Equations
Results
Conclusion
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
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.
𝜃 =𝑇𝑚,𝑓−𝑇𝑚,𝑝
𝑇𝑏,𝑓−𝑇𝑏,𝑝 [12]
Introduction
Scope of the work
Model Anatomy and Equations
Results
Conclusion
9
-0.001
-0.0005
0
0.0005
0.001
300 302 304 306 308 310 312
Vert
ica
l d
ista
nce (m
)
Temperature (oC)
0.0525
0.105
0.1575
0.21
-0.001
-0.0005
0
0.0005
0.001
300 302 304 306 308 310 312
Vert
ica
l d
ista
nce (m
)
Temperature (°C)
0.0525
0.105
0.1575
0.21
-0.001
-0.0005
0
0.0005
0.001
300 302 304 306 308 310 312
Vert
ica
l d
ista
nce (m
)
Temperature (°C)
0.0525
0.105
0.1575
0.21
-0.001
-0.0005
0
0.0005
0.001
300 302 304 306 308 310 312
Vert
ica
l d
ista
nce (m
)
Temperature (°C)
0.05250.105
0.15750.21
1v 2v
4v 6v
MESH SENSITIVITY
Mesh Statistics Mean
Temperature ok
Error
Very Fine 800 by 92
147,200 cells
316.7 Reference
Fine 400 by 92
73,600 cells
316.9 0.07%
Baseline 400 by 46
36,800 cells
313.3 1.1%
Coarse 200 by 46
18,400 cells
301.8 4.7%
Introduction
Scope of the work
Model Anatomy and Equations
Results
Conclusion
10
VALIDATION: TEMPERATURE PROFILES
0 0.05 0.1 0.15 0.2 0.25298
300
302
304
306
308
310
312
314
Vmax=0.0382 m/s Vmax=0.0191 m/s
Tb,f
Tm,f
Vmax=0.0575 m/s
Tm,p
Tb,p
Simulation Results Experimental Results (Chen et al. )
Introduction
Scope of the work
Model Anatomy and Equations
Results
Conclusion
T.-C. Chen et al. / Journal of Membrane Science 330 (2009) 279–287
Length (m)
11
• 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
TEMPERATURE PROFILES-COUNTER FLOW
0 0.05 0.1 0.15 0.2 0.25298
300
302
304
306
308
310
312
314
Vmax=0.0575 m/s
Vmax=0,0382 m/s
Vmax=0.0191 m/sTm,p
Tm,f
Tb,p
Tb,fIntroduction
Scope of the work
Model Anatomy and Equations
Results
Conclusion
Length (m)
Tem
p (
oK
)
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
0 0.05 0.1 0.15 0.2 0.252
4
6
8
10
12
14
16
18
20
22
Length(m)
Mass F
lux (
Kg/m
2.h
r)
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/sIntroduction
Scope of the work
Model Anatomy and Equations
Results
Conclusion
Inlet velocity and configuration : Parallel < Counter flow for Baseline temp (40 and 25oC)
Velocity inlet(m/s) Parallel
Mass flux (kg/hr.m2)
Counter
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%
Length (m)
Ma
ss f
lux (kg
/m
2.h
r)
13
Vp=0.057
Vp=0.038
Vp=0.019
Vc=0.038 Vc=0.019
Vc=0.057
MASS FLUX: PARALLEL VS COUNTER FLOW
Introduction
Scope of the work
Model Anatomy and Equations
Results
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
Length (m)
Ma
ss f
lux (kg
/m
2.h
r)
Inlet Temperature: Parallel < counter flow Baseline velocity 0.0191m/s 16
Tp=80
Tp=60
Tp=40
Tc=60
Tc=40
Tc=80
HEAT FLUX
0 0.05 0.1 0.15 0.2 0.25-5500
-5000
-4500
-4000
-3500
-3000
-2500
-2000
-1500
-1000
-500
Length(m)
Heat
Flu
x (
W/m
2)
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
Introduction
Scope of the work
Model Anatomy and Equations
Results
Conclusion
Inlet velocity 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
Length (m)
Hea
t flux(w
/m
2)
Parallel vs counter flow configuration at Baseline temp (40 and 25oC) 15
Vp=0.057
Vp=0.038
Vp=0.019
Vc=0.038
Vc=0.019
Vc=0.057
HEAT FLUX (CHANGING FEED FLOW TEMPERATURE)
Introduction
Scope of the work
Model Anatomy and Equations
Results
Conclusion Inlet temperature
(oC)
Parallel
Heat flux (w/m2)
Counter
Heat flux (w/m2)
40 333 362
60 1015 1068
80 4234 4513
Length (m)
Hea
t flux(w
/m
2)
16 Inlet Temperature: Parallel < counter flow Baseline velocity 0.0191m/s
Tp=80
Tp=60
Tp=40
Tc=60
Tc=40
Tc=80
TEMPERATURE POLARIZATION: FLOW VELOCITY
0 0.05 0.1 0.15 0.2 0.250.25
0.3
0.35
0.4
0.45
0.5
0.55
0.6
0.65
0.7
0.75
Length(m)
Tem
pera
ture
Pola
rization
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
Introduction
Scope of the work
Model Anatomy and Equations
Results
Conclusion Mass/velocity
inlet
Total /average Temp
polarization parallel
Total/average Temp
polarization counter
V1 = 0.05744 0.32 0.34
V2= 0.0382 0.29 0.325
V3=0.01925 0.28 0.32
𝜃 =𝑇𝑚,𝑓−𝑇𝑚,𝑝
𝑇𝑏,𝑓−𝑇𝑏,𝑝
17
Length (m)
Tem
p. Pola
riza
tion
Inlet velocity and configuration : Parallel < Counter flow for Baseline temp (40 and 25oC)
TEMPERATURE POLARIZATION (CHANGING FEED FLOW TEMPERATURE)
0 0.05 0.1 0.15 0.2 0.250.25
0.3
0.35
0.4
0.45
0.5
0.55
0.6
0.65
0.7
0.75
Length(m)
Tem
pera
ture
Pola
rization
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
Introduction
Scope of the work
Model Anatomy and Equations
Results
Conclusion
𝜃 =𝑇𝑚,𝑓−𝑇𝑚,𝑝
𝑇𝑏,𝑓−𝑇𝑏,𝑝
18
Length (m)
Tem
p. Pola
riza
tion
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.
Vp
Vc
APPARATUS SET UP
19
CONCLUSIONS
• 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
Introduction
Scope of the work
Model Anatomy and Equations
Results
Conclusion & Future work
20
INTRODUCTION
21
Introduction
Materials and Methods
Results and Discussion
Conclusion
PARALLEL CONFIGURATION
22
0.24
0.26
0.28
0.3
0.32
0.34
0.36
0 0.5 1 1.5
Ave
rga
e T
em
pera
ture
Pola
riza
tion
Column plot (0.5x, 0.75x, x, 2x, 4x and 6x) (m)
v
2v
4v
6v
0
0.5
1
1.5
2
2.5
3
3.5
4
4.5
0 0.5 1 1.5
Tota
l M
ass
flo
w (kg
/hr
.m2
)
Column plot (0.5x, 0.75x, x, 2x, 4x and 6x) (m)
v
2v
4v
6v
0.4
0.44
0.48
0.52
0.56
0.6
0.64
0.68
0.72
0.76
0.8
Ma
ss f
low
(kg
/hr
.m2
)
column plot (0.5x, 0.75x, x, 2x, 4x and 6x) (m)
v
2v
4v
6v
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
COUNTER FLOW
23
0.3
0.31
0.32
0.33
0.34
0.35
0.36
0 0.5 1 1.5
Ave
rag
e T
em
pera
ture
Pola
riza
tion
Column plot (0.5x, 0.75, x, 2x, 4x and 6x) (m)
v
2v
4v
6v
0
0.5
1
1.5
2
2.5
3
3.5
4
4.5
5
5.5
6
0 0.5 1 1.5
Tota
l M
ass
flo
w (kg
/hr
.m2
)
Column plot (0.5x,0.75x, x, 2x, 4x, and 6x) (m)
V
2v
4v
6v
0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0 0.5 1 1.5
Ma
ss f
low
(kg
/hr
.m2
)
Column plot (0.5x,0.75x, x,2x,4x and 6x) (m)
v
2v
4v
6v
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