DSD-INT 2015 - Bridging the gab in future sanitation - Adithaya Thoa Radhakrishnan

1 Challenge the future

D-SHIT Adithya Thota Radhakrishnan

Domestic Slurry Hydraulics In Transport systems

[email protected]

Bridging the gap in future sanitation!

2 Challenge the future [email protected]


Introduction 1 Objective 2 Rheology 3 Modelling 4

Sanitation systems

Planned 5

• Simple to Complex

• Industrialised countries

• High water consumption

• Expensive treatment

• Loss of resource



Objective 2 Rheology 3 Modelling 4

New sanitation concept

Introduction 1 Planned 5

Source separation

Resource recovery

Low water consumption




New sanitation: elements

Treatment

Transport

Collection

Source Separation

Vastly overlooked

Planned 5

D-SHIT project??

Transport design for domestic slurry of Grinded Kitchen Waste + Feces + Urine?

Collection tank

WWTP D-SHIT




What does this mean for us?

Planned 5

Increase in

total solid

concentration

Vacuum toilets +

Kitchen grinder

Example: Ketchup vs. Water




D-SHIT Objective?

Planned 5

• To study the flow of domestic slurry at various solid concentration and temperature

• To determine the optimum design conditions for the slurry transport

• To determine the optimum dilution for the slurry


Rheology

Rheology of Concentrated Domestic Slurry A mixture of Brown water (Faeces + Urine) and Grinded Kitchen Waste



Introduction 1 Modelling 4

Complexity of CDS

Planned 5

0

0,2

0,4

0,6

0,8

1

1,2

0 50 100 150 200 250 300 350

Shear

stre

ss (

Pa)

Shear rate (1/s)

Water Low mix Medium mix High mix

Non-Newtonian

Objective 2 Rheology 3




Rotating viscometer

Rotating viscometer to measure Torque vs Rotation speed

Shear stress vs Shear rate Yield stress

Temperature Solid concentration Slurry lifetime

Influence of

Output

Rheological model

Sisko model

Herschel-Bulkley

Combined Herschel-Bulkley

Planned 5



Introduction 1 Objective 2 Modelling 4

0

1

2

3

4

5

6

0 100 200 300 400 500

Sh

ea

r str

ess (

Pa

)

Shear rate (1/s)

GKW 6% GKW 11% Fit 6% Fit 11%

0

5

10

15

20

25

30

35

40

45

0 50 100 150 200 250 300

She

ar

str

ess (

Pa)

Shear rate (1/s)

GKW 18% Fit 18%

At temperature 10º C At temperature 10º C

Combined Herschel-Bulkley model

Bingham model

Viscosity increases with concentration

Rheology 3 Planned 5




0

0,5

1

1,5

2

2,5

0 100 200 300

Sh

ea

r str

ess (

Pa

)

Shear rate (1/s)

BrW 1.8% BrW 3% BrW 4%

Sisko 1.8% Sisko 3% Sisko 4%

0

10

20

30

40

0 50 100 150 200 250 300

Sh

ea

r str

ess (

Pa

)

Shear rate (1/s)

GKW 18% Combined Herschel-Bulkley 18%

Sisko model

Combined Herschel-Bulkley model

At temperature 10º C At temperature 10º C

Viscosity increases with concentration





0

2

4

6

8

10

12

14

16

18

20

0,1 1 10

Defo

rmation (

rad)

Stress (Pa)

GKW 6% GKW 11% GKW 18%

0

2

4

6

8

10

12

14

16

18

20

0,1 1 10

De

form

ation

(ra

d)

Stress (Pa)

Mix 3.4% Mix 7% Mix 11%

Yield stress increases with concentration





0

5

10

15

20

25

30

35

40

45

0 100 200 300

Sh

ea

r str

ess (

Pa

)

Shear rate (1/s)

18% 10C 18% 20C 18% 30C 18% 40C 18% 60C

0

2

4

6

8

10

12

14

0 2 4 6 8 10 12 14

De

form

ation

(ra

d)

Stress (Pa)

18% 10C 18% 20C 18% 30C 18% 40C 18% 60C

Viscosity and yield stress decreases with temperature



Modelling

Why? To aid the design process. How to model Concentrated Domestic Slurry?




How to model domestic slurry?

Multiphase

models

Eulerian-

Eulerian

Eulerian-

Lagrangian

Inhomogeneous Homogeneous

Torque derieved from the shear stress being a bulk property; comparing the measured shear stress to the one simulated provides a valid measure for the verification of the model.

0

10

20

30

40

50

60

70

80

0 100 200 300 400 500 600

Shear

stre

ss (

Pa)

Shear rate (/s)

Secondary flow

Planned 5



Introduction 1 Objective 2 Rheology 3 Planned 5

Single-phase Homogeneous fluid!

25

30

35

40

45

50

55

60

65

70

75

100 200 300 400 500

Shear

stre

ss (

Pa)

Shear rate (1/s)

Results from CFD, comparing the shear rate and stresses, derived from Torque and Rotational rate

Modelling 4


Planned

Preparation of Artificial Slurry. Pressure drop experiments. Turbulence pressure drop model for slurries.



Introduction 1 Objective 2 Rheology 3 Modelling 4 Planned 5

Rheological models

Bingham

Sisko

Herschel-Bulkley

Combined Herschel-Bulkley

Different models for same slurry




Experimental setup Appropriate pipe lengths are provided to reach a completely developed flow




Experimental setup

• Tank capacity of 4m3 to provide require

NPSHA and fill the system

• Di of 0.20m

• 6 to 8 pipe lengths for the development of

flow

• Components

• Horizontal pipe

• Vertical pipe

• Inclined pipe 60°

• Inclined pipe 45°

• Butterfly valve

• Gate valve

• Bend 90°

• Bend 180°




Artificial slurry

Preparation of artificial slurry to mimic the rheological behaviour of the CDS • To mimic the yield stress • To mimic the power law behaviour

Criteria for artificial slurry

• Environmentally friendly • Easily disposable • Easily preparable • Preferably transparent

Possible mixtures of

• Bentonite, Xanthum gum, glucose




Pipeline experiment

Single phase experiments

•Pressure drop for non-Newtonian fluids •Velocity range of 1 – 2 m/s •For different slurry concentrations

Multiphase experiments

•Pressure drop for non-Newtonian fluids + gas (air) •Studying the flow regimes at different superficial velocities •For different slurry concentrations




Turbulence pressure drop model for slurries

Pressure loss using hydraulic friction factor

Using mixing length theory to derive the velocity gradient in the boundary layer

Assumption At high velocity, due to near wall lift force, only water is predominantly present.

Kinetic energy

Friction coefficient




Turbulence pressure drop model for slurries

Comparing this with the standard friction loss for water flow using Darcy-Weisbach friction, we can find a relative measure for pressure loss

Integrating we get an expression for

velocity difference

But, one problem! Verification of the assumption is required.




Model approach!

Equation of continuity

Equation of motion

Integrating using non-Newtonian viscosity relation

Adopting the energy loss equations.

Equation for pressure drop in the turbulence regime.



Summary

For CDS •Viscosity and yield stress increase with concentration •Viscosity and yield stress decrease with temperature (higher thermal motion) •CDS can be modelled as a single-phase homogeneous fluid represented by its bulk viscosity and density

Planned •Preparation of artificial slurry •Performing the single phase experiments •Building the turbulence model

Thank you!

Software

DSD-INT 2015 - Bridging the gab in future sanitation - Adithaya Thoa Radhakrishnan