Pong Device

HJR EnvironmentalHeather Nelson

Jeannette Harduby

Rudi Schuech

HJR

Project Goals

• To design a constant flow control device capable of handling turbid water– Easy to operate and maintain– Not prone to clogging– Inexpensive to build

• Build and test preliminary model

• Analyze data and make recommendations for further research

Flexible tubing

Removable adapters w/ internal mesh screens

Sand pipe

Sealing pipe

Pong pipe

Tubing-pipe adapter

Tubing-pipe adapter

Dramatization. Actual droplets may be smaller.

Head that ping pong ball must retain

Driving head for sand column

Height of sand

Initial water height

Perforated Baffle

Pour water in here

What happens when user stops adding water?

Sand colum

nHJR

Holding container (bucket or glass column)

Pong pipe

Sealing pipe

Driving pressure for sand column

Upflow prevents trapped air

(keyword: “prevent”)!

Force Balance

WPB

DB

sDssP

FFFF

VF

RHVLRF

0

])[(

1

202

2

θ2

θ1

Rs

Rp

Rp

Rp

Ls

sealing pipe (not to scale!)

Static pressure force = γH0

L2

L1

Rp - L1

Rp - L2

Vd1

Vd2

Vc2

Vc1

Volumes of top and bottom spherical sections are Vp2, Vp1

H0

Total pressure head ≈ 25 cm

→ Sealing pipe diameter = 7 mm!

Does it leak?

Not really – leaks about 7 mL/day (.04% of 20 L/day target!)

Ice cream = Ice cream cone – cone !

poreL 2

w pore

32 LVh

gD

Sand colum

n

1

2

0 poreV V

1/3

pore sandgrainD D1

L

Assuming # pores = # sand grains, and

Porosity = θ = Vpores/Vtotal = Apores / Atotal……

z1-z2

2 21 1 2 2

1 22 2 L

p V p Vz z h

g g

= hL!

1 2 0 (z z ) V Q Flow Rate Through Sand Column

0

10

20

30

40

50

60

70

0 1 2 3 4 5 6

Driving Pressure Head (cm)

Flo

w R

ate

(L

/day)

10 cm hL → 20 L/day

expected 1.5 cm → sand diameter < 0.4 mm

The Ithaca Effect(air bubbles)

10

12

14

16

18

20

22

24

0 5 10 15 20

Elapsed Time (hrs)

Flo

w R

ate

(L

/da

y)

Clean Water

12

12.5

13

13.5

14

14.5

15

15.5

16

16.5

17

0 2 4 6 8 10 12

Time (hrs)

Flo

w R

ate

(L

/da

y)

Dirty Water (150 NTU)

10

12

14

16

18

20

22

24

0 2 4 6 8 10 12

Elapsed Time (hrs)

Flo

w R

ate

(L/d

ay)

Testing Conclusions

• Pong Device very sensitive to movement, needs to be designed more rigidly

• Flow rate fluctuates over time

• Possible cause: air bubbles forming in tubing – sand column needs to be shaken approximately every 6 hours

• With dirty water flow rate decreases steadily over time

Further Reflections

• Bubbles won’t be a problem when water is at equilibrium with outside temperature

Recommendations

• Develop rigid Pong Device design

• Test in field conditions

• Contact NGO’s and other organizations working on similar research projects to fill gap in primary sources

Questions?