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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

ijanajreh@masdar.ac.ae

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