Analysis of heat and mass transfer by CFD for performance enhancement in direct contact membrane distillation

Analysis of heat and mass transfer by CFD for performance enhancement in direct contact membrane distillation

This is the Accepted version of the following publication

Yu, Hui, Yang, Xing, Wang, Rong and Fane, Anthony G (2012) Analysis of heat and mass transfer by CFD for performance enhancement in direct contact membrane distillation. Journal of Membrane Science, 405-406. pp. 38-47.

ISSN 0376-7388

The publisher’s official version can be found at

http://www.sciencedirect.com/science/article/pii/S037673881200141X

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Downloaded from VU Research Repository https://vuir.vu.edu.au/25292/

Fig. 1. Schematic of axially-symmetry single fiber module in CFD simulating domain

Fig. 2. Schematic of heat transfer process in MD

Fig. 3. Heat-transfer coefficient distributions along the module length for membranes with different C values

(T_fi = 327.2 K, T_pi = 294.0 K, u_fi=0.06 m·s^-1, u_pi= 0.417 m·s^-1, C = 2.0×10^-7 to 1.0×10^-6 kg·m^-2·s^-1·Pa^-1)

0.00 0.05 0.10 0.15 0.20 0.25

1000 10000

Heat transfer coefficient (W.m-2 .K-1 )

x / m C = 2.0X10^-7 kg.m^-2.s^-1.Pa^-1: h

f ; h

p

h

m ; K

mo

C = 5.0X10^-7 kg.m^-2.s^-1.Pa^-1: h

m ; K

mo

C = 1.0X10^-6 kg.m^-2.s^-1.Pa^-1: h

m ; K

mo

0.00 0.05 0.10 0.15 0.20 0.25 0.4

0.5 0.6 0.7 0.8 0.9 1.0

C = 2.0X10^-7 kg.m^-2.s^-1.Pa^-1: Whout Baffle, With Baffle C = 5.0X10^-7 kg.m^-2.s^-1.Pa^-1: Whout Baffle, With Baffle C = 1.0X10^-7 kg.m^-2.s^-1.Pa^-1: Whout Baffle, With Baffle

TPC

x / m

Fig. 4. TPC distributions along the module length for non-baffled and baffled modules with membranes of different C values

(T_fi = 327.2 K, T_pi = 294.0 K, u_fi=0.06 m·s^-1, u_pi= 0.417 m·s^-1, C = 2.0×10^-7 to 1.0×10^-6 kg·m^-2·s^-1·Pa^-1)

0.00 0.05 0.10 0.15 0.20 0.25 0.000

0.001 0.002 0.003 0.004 0.005 0.006 0.007 0.008 0.009 0.010 0.011 0.012

C = 2.0E-7 kg.m^-2.s^-1.Pa^-1: Whout Baffle, With Baffle C = 5.0E-7 kg.m^-2.s^-1.Pa^-1: Whout Baffle, With Baffle C = 1.0E-6 kg.m^-2.s^-1.Pa^-1: Whout Baffle, With Baffle

N m / kg.m-2 .s-1

x / m

Fig. 5. N_m distributions along the module length for non-baffled and baffled modules with membranes of different C values

(T_fi = 327.2 K, T_pi = 294.0 K, u_fi=0.06 m·s^-1, u_pi= 0.417 m·s^-1, C = 2.0×10^-7 to 1.0×10^-6 kg·m^-2·s^-1·Pa^-1)

Fig. 6. Temperature distributions and flow fields at the shell side of 0.25m modules (local snapshots) (a) without baffles; (b) with baffles

(T_fi = 327.2 K, T_pi = 294.0 K, u_fi=0.06 m·s^-1, u_pi= 0.417 m·s^-1, C = 2.0×10^-7 kg·m^-2·s^-1·Pa^-1) (a)

(b)

280 300 320 340 360 0

200 400 600 800 1000 1200 1400 1600 1800

h MD

Tm (K)

Fig. 7. h_MD vs. membrane temperature T_m with C = 2.0×10^-7 kg·m^-2·s^-1·Pa^-1

280 300 320 340 360 -400

-200 0 200 400 600 800 1000 1200 1400 1600

f(T c)

Tm / K

313.9K

Fig. 8. Function f(T_c) at varied membrane temperatures T_m with C = 2.0×10^-7 kg·m^-2·s^-1·Pa^-1

300 320 340 0

10000 20000 30000

P = 11141

P = 4381

P = 7120

P / Pa

Tm / K

P = 2739

Fig. 9. The distribution of saturated vapor pressure difference ∆P at various membrane temperatures T_m

0.00 0.05 0.10 0.15 0.20 0.25 0.1

0.2 0.3 0.4 0.5 0.6 0.7 0.8

Tfi = 327.2K, T

pi = 294.0K: Without Baffle, With Baffle Tfi = 337.2K, T

pi = 304.0K: Without Baffle, With Baffle Tfi = 347.2K, T

pi = 314.0K: Without Baffle, With Baffle Tfi = 360.0K, T

pi = 326.8K: Without Baffle, With Baffle Tfi = 370.0K, T

pi = 336.8K: Without Baffle, With Baffle

TPC

x / m

Fig. 10. TPC distribution along the module length for non-baffled and baffled modules at varied feed/permeate inlet temperatures with a constant temperature difference

(∆T_in=33.2 K, u_fi=0.06 m·s^-1, u_pi= 0.417 m·s^-1, C = 2.0×10^-7 kg·m^-2·s^-1·Pa^-1)

(a) N_m distribution along the module length

0.00 0.05 0.10 0.15 0.20 0.25

0.002 0.003 0.004 0.005 0.006 0.007 0.008 0.009 0.010 0.011 0.012

0.013 T_fi = 327.2K, T_pi = 294.0K: Without Baffle, With Baffle T_fi = 337.2K, T_pi = 304.0K: Without Baffle, With Baffle T_fi = 347.2K, T_pi = 314.0K: Without Baffle, With Baffle T_fi = 360.0K, T_pi = 326.8K: Without Baffle, With Baffle T_fi = 370.0K, T_pi = 336.8K: Without Baffle, With Baffle

N m / kg.m-2 .s-1

x / m

Fig. 11. N_m results for non-baffled and baffled modules at

varied feed/permeate inlet temperatures with a constant temperature difference ∆T_in

(a) N_m distribution along the module length; (b) Local mass fluxes N_m comparison x=0.125m (∆T_in=33.2 K, u_fi=0.0602 m·s^-1, u_pi= 0.417 m·s^-1, C = 2.0×10^-7 kg·m^-2·s^-1·Pa^-1)

(b) Local mass fluxes N_m comparison (x=0.125m)

320 330 340 350 360 370

0.001 0.002 0.003 0.004 0.005 0.006 0.007

Local flux N

m x=0.125m w/o baffles

w baffles

N m / kg.m-2 .s-1

Tfin / K

0.00 0.05 0.10 0.15 0.20 0.25 0.1

0.2 0.3 0.4 0.5 0.6 0.7 0.8

Tfi = 327.2K, T

pi = 294.0K: Without Baffle, With Baffle Tfi = 337.2K, T

pi = 304.0K: Without Baffle, With Baffle Tfi = 347.2K, T

pi = 314.0K: Without Baffle, With Baffle Tfi = 360.0K, T

pi = 326.8K: Without Baffle, With Baffle Tfi = 370.0K, T

pi = 336.8K: Without Baffle, With Baffle

 h

x / m

Fig. 12. η_h distribution along the module length for non-baffled and baffled modules at varied feed/permeate inlet temperatures with a constant temperature difference

(∆T ×

0.00 0.05 0.10 0.15 0.20 0.25 0.50

0.55 0.60 0.65 0.70

0.75 u

fi = 0.0602 m.s^-1, u

pi = 0.417 m.s^-1 Tfi = 329K, T

pi = 314K, T

in = 15K Tfi = 344K, T

pi = 334K, T

in = 10K Tfi = 334K, T

pi = 314K, T

in = 20K Tfi = 344K, T

pi = 329K, T

in = 15K

TPC

x / m

Fig. 13. TPC distributions along the module length at varied feed/permeate inlet temperatures T_fi/ T_pi and temperature differences ∆T_in

(u_fi=0.06 m·s^-1, u_pi= 0.417 m·s^-1, C = 2.0×10^-7 kg·m^-2·s^-1·Pa^-1)

0.00 0.05 0.10 0.15 0.20 0.25 0.0010

0.0012 0.0014 0.0016 0.0018 0.0020 0.0022

ufi = 0.0602 m.s^-1, u

pi = 0.417 m.s^-1 Tfi = 329K, T

pi = 314K, T

in = 15K Tfi = 344K, T

pi = 334K, T

in = 10K Tfi = 334K, T

pi = 314K, T

in = 20K Tfi = 344K, T

pi = 329K, T

in = 15K

N m / kg.m-2 .s-1

x / m

Fig. 14. N_m distributions along the module length at varied feed/permeate inlet temperatures T_fi/ T_pi and temperature differences ∆T_in

×

0.00 0.05 0.10 0.15 0.20 0.25 0.54

0.56 0.58 0.60 0.62 0.64 0.66 0.68 0.70 0.72 0.74

ufi = 0.0602 m.s^-1, u

pi = 0.417 m.s^-1 Tfi = 329K, T

pi = 314K, T

in = 15K Tfi = 344K, T

pi = 334K, T

in = 10K Tfi = 334K, T

pi = 314K, T

in = 20K Tfi = 344K, T

pi = 329K, T

in = 15K

 h

x / m

Fig. 15. η_h distributions along the module length at varied feed/permeate inlet temperatures T_fi/ T_pi and temperature differences ∆T_in

(u_fi=0.06 m·s^-1, u_pi= 0.417 m·s^-1, C = 2.0×10^-7 kg·m^-2·s^-1·Pa^-1)

Table. 1. The temperature comparison of experimental data and simulation results (u_fi=0.06 m·s^-1, u_pi= 0.417 m·s^-1, C = 2.0×10^-7 kg·m^-2·s^-1·Pa^-1)

L (m) T_fi (K) T_fo (K) Error (%) T_pi (K) T_po (K) Error (%)

0.25 Exp. 327.2 325.7 - 294.0 301.4 -

Sim. - 325.9 0.0614 300.9 -0.166

0.25 Exp. 333.9 331.6 - 294.4 302.8 -

Sim. 332.5 -0.271 303.2 0.132

0.25 Exp. 334.8 333.8 - 312.8 317.7 -

Sim. - 333.6 -0.0599 318.3 0.189

0.25 Exp. 337.6 334.8 - 294.3 304.1 -

Sim. 336.2 0.418 304.2 0.0329

0.25 Exp. 337.6 336.4 - 304.0 311.1 -

Sim. 336.3 -0.0297 312.1 0.321