SURFACE TENSION DRIVEN WATER PUMPING

byJ. Fraser & R.T. DobsonUniversity of Stellenbosch

Energy Postgraduate Conference 2013

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South African Heat Pipe Association Energy Postgraduate Conference EPC2013, 11-14 Aug 2013

Overview

• Introduction

• Background and Objectives

• Main Theory

• Problems

• Why it works

• Conclusion

Falling water droplet

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South African Heat Pipe Association Energy Postgraduate Conference EPC2013, 11-14 Aug 2013

Introduction

• Nature has adapted of millions of years

• Humans can learn much from nature

• Biomimicry = nature inspired design

• Examples:– Elephant trunk– Gecko feet– Shark skin– Lotus leaves– Beehive structure– Insect Nano robots – And many more

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South African Heat Pipe Association Energy Postgraduate Conference EPC2013, 11-14 Aug 2013

Introduction (cont.)

• Surface tension: similar to elastic membrane on fluid surface

• Nature found myriad of exploitations:

– Small insects stride on water– Bacteria releases surfactant for driving force– Some larva employs vector control for propulsion

• Recent applications:

– Small object propulsion– Nano-robots maneuverability– Capillary action– Micro pumping– etc

• Plant life thrived on Earth for thousands of years

• Pump water seemingly effortlessly

• Giant Redwoods grow up to 100 m tall

• Useful mechanism for water pumping

• In a time of water shortages, climate change, power consumption and emmision concerns

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South African Heat Pipe Association Energy Postgraduate Conference EPC2013, 11-14 Aug 2013

Background &Objectives

• Plant Leaves:– Photosynthesis: water + carbon dioxide + energy carbohydrates

+oxygen• Ingenious water transport mechanism of plants• Capillary-driven heat pipe technology mechanisms• Construct mechanical/artificial pump • First step in a larger project:

– wherein hydrogen, food (carbohydrates) and fuel are artificially produced.

• For this project:– build mechanically-constructed experimental simulation working

model of transport mechanism– Theoretical thermal-hydraulic simulation model + validation against

experimental model.

• After validation use of such a water pump in an artificial photosynthesis program to be established.

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South African Heat Pipe Association Energy Postgraduate Conference EPC2013, 11-14 Aug 2013

Main Theory Overview

• Water Transport in trees Transpiration pull

• (TACT)– Transpiration– Adhesion– Cohesion– Tension

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South African Heat Pipe Association Energy Postgraduate Conference EPC2013, 11-14 Aug 2013

Problems

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South African Heat Pipe Association Energy Postgraduate Conference EPC2013, 11-14 Aug 2013

Why it works

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South African Heat Pipe Association Energy Postgraduate Conference EPC2013, 11-14 Aug 2013

Why it works

• Secret Strong adhesion forces Strong cohesion forces Evaporation Surface tension forces

• Must prevent nucleation sites – Prevent embolisms

• Require a continuous channel of water:– Rerouting– Dissolve bubbles

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South African Heat Pipe Association Energy Postgraduate Conference EPC2013, 11-14 Aug 2013

In Conclusion

• Nature offers many lessons and techniques

• Surface tension useful mechanism

• Tree water pumping mechanism investigation

• Theory, build, experiment & validate

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South African Heat Pipe Association Energy Postgraduate Conference EPC2013, 11-14 Aug 2013

Acknowledgements

•Mr. Dobson

•Family

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South African Heat Pipe Association Energy Postgraduate Conference EPC2013, 11-14 Aug 2013

END

THANK YOU