Flow electrification Flow electrification by cavity QEDby cavity QED

T. V. PrevenslikT. V. Prevenslik11F, Greenburg Court11F, Greenburg CourtDiscovery Bay, Hong KongDiscovery Bay, Hong Kong

ContentsContents

Historical backgroundHistorical backgroundContact electrification Contact electrification PurposePurposeQED Theory QED Theory Flow analysisFlow analysisConclusionsConclusions

Historical Historical backgroundbackground

19501950 Streaming current Streaming current Zeta potential Zeta potential induced by induced by impurity ionsimpurity ions

19801980 Electrification Electrification density ionic charges as density ionic charges as double double layer at the wall interfacelayer at the wall interface

20012001 Physiochemical corrosion-oxidation Physiochemical corrosion-oxidation ... No evidence of corrosion products... No evidence of corrosion products … … Streaming currents Streaming currents shear stress shear stress

Source never identifiedSource never identified

Contact electrificationContact electrificationContact and Balancing of Fermi levels Contact and Balancing of Fermi levels thermodynamic equilibrium thermodynamic equilibrium

Only one contact necessary for Only one contact necessary for equilibrium - independent of equilibrium - independent of materials.materials.

Experiment shows equilibrium is Experiment shows equilibrium is reached in a single contact only for reached in a single contact only for metals - many contacts are metals - many contacts are necessary to achieve equilibrium necessary to achieve equilibrium between metals and insulators.between metals and insulators.

Some mechanism - in addition to the Some mechanism - in addition to the balancing of Fermi levels - is at playbalancing of Fermi levels - is at play

Cavity QED Cavity QED induced photoelectric effectinduced photoelectric effect

Two-step model contact and Two-step model contact and separationseparation

Interface is a high frequency QED Interface is a high frequency QED cavity that inhibits low frequency IR cavity that inhibits low frequency IR radiation from thermal kT energy radiation from thermal kT energy inherent in atomic clusters. inherent in atomic clusters.

IR energy released concentrates to IR energy released concentrates to VUV levels in the surfaces of the VUV levels in the surfaces of the metal and insulatormetal and insulator

Electrons are produced by the Electrons are produced by the photoelectric effect.photoelectric effect.

Separation

Metal

Insulator_

+

e_

E

E

Contact

Metal

Insulator

PurposePurpose

Extend the cavity QED induced photoelectric effect Extend the cavity QED induced photoelectric effect in the Two-step model of contact in the Two-step model of contact

electrification to flow electrification. electrification to flow electrification.

Theoretical Theoretical backgroundbackground

Piping system and laminar flow Piping system and laminar flow QED cavities in hydraulic oilsQED cavities in hydraulic oils

Comparison of contact and flow Comparison of contact and flow electrificationelectrification

Available EM energyAvailable EM energyPhotoelectric effectPhotoelectric effect

Piping system Piping system Hydraulic fluid is pumped Hydraulic fluid is pumped

in laminar flow through in laminar flow through small diameter - long pipe small diameter - long pipe Loop is closed as the fluid Loop is closed as the fluid falls into an open falls into an open receiving tank and receiving tank and pumped back to the pumped back to the supply plenum.supply plenum.

Air enters the fluid in Air enters the fluid in falling into receiving tank falling into receiving tank - usually through the - usually through the pump .pump .

PumpReceiving tank

Pipe

Air Air

Laminar flow Laminar flow relationsrelations

2

2

12RrVV MxVelocityVelocity

RV

drdV M 4Frictional stressFrictional stress

Re48 3

2

2 Rx

RxVPP Matmx

PressurePressure

8

4RxPPAVQ atmx

MPoiseuille Eqn.Poiseuille Eqn.

Pipe w all

VM2R

L

PS Patm

x

PxA B

Laminar flow and QED Laminar flow and QED Cavities Cavities

Light and electron Light and electron emission occurs over emission occurs over dimensions from dimensions from walls less than 100 walls less than 100 mmLight emission Light emission precedes electron precedes electron emission - similar to emission - similar to photoelectric effectphotoelectric effect

Depth 1.5 mm

30 mm

Flow 10 mm

Microscope studies show Microscope studies show cavities form in laminar flocavities form in laminar flow near surface of boundariw near surface of boundarieses

Washio et al, Proc Washio et al, Proc Instn Mech Engrs, Instn Mech Engrs, 215 Part J, (2001) 215 Part J, (2001)

373373

QED cavities in hydraulic QED cavities in hydraulic oilsoils

Air clusters in flowing hydrocarbon Air clusters in flowing hydrocarbon liquidsliquids

Tearing of oil during flowTearing of oil during flowTearing and QED electrificationTearing and QED electrification

Source of EM energySource of EM energy

Air clusters in hydraulic oilAir clusters in hydraulic oil Oil Vapor bubbles POil Vapor bubbles Pxx < P < Pvapvap

Air bubbles PAir bubbles Pxx < P < Pair air Air bubbles likely as PAir bubbles likely as Pair air >> P>> Pvapvap

Air enters the system through the open tankAir enters the system through the open tank Solubility of air in hydraulic oils is significant [Ostwald Solubility of air in hydraulic oils is significant [Ostwald

coefficient ~ 10 coefficient ~ 10 by volume] by volume] Large air bubbles not likely by surface tension Large air bubbles not likely by surface tension

Air dissolved throughout oil as nano- clusters of air Air dissolved throughout oil as nano- clusters of air ( N( N22 and O and O22 molecules ) molecules )

Tearing of oil during flowTearing of oil during flowMaximum tension theory Maximum tension theory [ Joseph, J [ Joseph, J

Fluid Mech 366 (1998) 367]Fluid Mech 366 (1998) 367] Cavitation in laminar flow is explained as viscous Cavitation in laminar flow is explained as viscous

shear stress produces tensile stress at 45° to wall shear stress produces tensile stress at 45° to wall Tearing of oil occurs if nominal tensile stress is Tearing of oil occurs if nominal tensile stress is raised above the rupture stress of oil because of the raised above the rupture stress of oil because of the

stress concentration of air clusters stress concentration of air clusters Tearing separates oil from itself or boundary wall Tearing separates oil from itself or boundary wall

leaving an evacuated space with oil clusters leaving an evacuated space with oil clusters

Tearing and QED Tearing and QED electrificationelectrification

Tearing produces vacuum spaces Tearing produces vacuum spaces with oil clusters with oil clusters

Spaces are a high frequency QED Spaces are a high frequency QED cavities that briefly suppress low cavities that briefly suppress low frequency IR radiation from oil frequency IR radiation from oil clusters. clusters.

Suppressed IR energy loss is Suppressed IR energy loss is conserved by a gain to VUV levels conserved by a gain to VUV levels in adjacent oil and wall surfacesin adjacent oil and wall surfaces

Electrons are produced by the Electrons are produced by the photoelectric effect.photoelectric effect. 1D cavity

Oil cluster

FlowFlow

Source of EM Source of EM energyenergy

Oil molecule has thermal kT energyOil molecule has thermal kT energyMolecules are harmonic oscillatorsMolecules are harmonic oscillators

At ambient temperature, thermal kT At ambient temperature, thermal kT energy is equivalent to the molecule energy is equivalent to the molecule

emitting IR radiationemitting IR radiation

Oscillator and IR radiationOscillator and IR radiationAt T ~ 300 K, kT~0.025 At T ~ 300 K, kT~0.025 eVeV Saturation at Saturation at ~ 100 ~ 100 m m Most of IR energy in oil Most of IR energy in oil molecule occurs:molecule occurs:

> 20 > 20 m m If QED cavity confines IR If QED cavity confines IR radiation to radiation to < 20 < 20 m, m, most of thermal kT most of thermal kT energy is suppressed energy is suppressed

0.00001

0.0001

0.001

0.01

0.1

1 10 100 1000

Wavelength - microns

Pla

nck

ener

gy E

T - e

V kT

1exp

Tkhc

hc

ET

Oil cluster formation Oil cluster formation

Hydrostatic compression - IR uninhibited Hydrostatic compression - IR uninhibited Hydrostatic tension - IR inhibitedHydrostatic tension - IR inhibited

Surface tensionSurface tension S S limits the radius limits the radius RR of the of the oil cluster that can be formed, oil cluster that can be formed, RR > R> R00

Heptane Heptane RR00 ~ 0.4 ~ 0.4 m m

IR

2R0

STPSR 2

0

2R

IR energy in oil clusterIR energy in oil clusterSpherical cluster energySpherical cluster energy

303

4 RU IR

Energy densityEnergy density3/

21

kTNdof

dofN ~ Degrees of freedom

k ~ Boltzmann’s constant

VUV energy emitted by VUV energy emitted by clustercluster

Cavity QED Cavity QED momentarily momentarily suppresses IR suppresses IR

radiation from clusterradiation from clusterConservation of Conservation of

energy requires the energy requires the prompt release of IR prompt release of IR

radiationradiationMulti-IR photons Multi-IR photons combine to VUV combine to VUV

levels levels kTRRRE

0

20 Electrons and VIS Electrons and VIS

photons producedphotons produced

E

E

Ree--D

Wall--

Oil cluster

FlowFlow Air cluster

+ VISPhoton

R0

Photoelectric effectPhotoelectric effect

0.001

0.01

0.1

1

10

100

0 1 2 3 4 5

Cluster radius - microns

Elec

troni

c ch

arge

- nC

Y = 1

Y = 0.1

NNdof dof = 6= 6EEVUVVUV = 4.9 = 4.9

eVeV

VUVdof

VUV

IRVUV E

kTRNEUN

30

32

Number of VUV Number of VUV photonsphotons

pVUVe NN

Number of electronsNumber of electrons

eVEVUVp 10,1

Electron YieldElectron Yield

Flow electrificationFlow electrification Oil clusters and Oil clusters and

fragments in contact with fragments in contact with wall separate at entrance wall separate at entrance IR radiation is suppressed IR radiation is suppressed and released as VUV and released as VUV Electrons are freed from Electrons are freed from oiloilWall is charged negative Wall is charged negative and oil positiveand oil positive

FragmentFragment

ClusterCluster

1-D Resonance 1-D Resonance ~ 2 D~ 2 DSuppression of IRSuppression of IR

D < 10 D < 10 mm

DD

FlowFlow

WallWall

dd

-

e-++

EE

SummarSummaryy

Flow electrification occurs as oil ruptures in a tearing actionFlow electrification occurs as oil ruptures in a tearing actionRupture takes place if the tensile stress at a point exceeds the Rupture takes place if the tensile stress at a point exceeds the pressure at which the air dissolved in oil, usually atmospheric pressure at which the air dissolved in oil, usually atmospheric

pressurepressureAir clusters uniformly distributed throughout the Air clusters uniformly distributed throughout the volumevolume of the of the

oil act as local stress concentrators for ruptureoil act as local stress concentrators for ruptureElectron charge Electron charge Number of oil clusters Number of oil clusters volume volume

Electrical current is proportional to volume flow rate [ Current Electrical current is proportional to volume flow rate [ Current = Charge density x volume flow rate] = Charge density x volume flow rate]

Current not proportional to surface area of the wall Current not proportional to surface area of the wall

Flow Flow AnalysisAnalysis Streaming currentStreaming current

II Re Re x -x - flow experiment flow experiment

I I AA( ( PPxx -- PPatmatm ) - electrical analogy ) - electrical analogy

NNeeQQ replaces the flow replaces the flow QQ NNee is the electron density is the electron density

Since Since NNee NNOC OC PPxx-1-1

NNcc PPxx-1-1

222

1RQx

PRQxN

RxQNI

xOCe

23

2

8Re4RQxx

RPPAI atmx - Poiseiulle - Poiseiulle

Volumetric current Volumetric current density density

00.2

0.40.6

0.81

1.21.4

0 500 1000 1500 2000

Reynold's number Re

Cur

rent

den

sity

I /

Q

x

104

C/m

3

0.24 mm

0.58 mm

1.25 mm

Re 43

2

2

Rx P

Rx

QI

atm

Chen et al, Ind Eng Chen et al, Ind Eng Chem Res. 35 (1996) Chem Res. 35 (1996)

3195 3195

Total current Total current

00.5

11.5

22.5

33.5

0 500 1000 1500 2000

Reynold's number Re

Curr

ent

I x 1

011 A

0.24 mm

0.58 mm

1.25 mmRe4

Re

3

2

RxP

Rx

I

atm

ConclusionConclusions s

Flow and contact electrification obey the same physics - Flow and contact electrification obey the same physics - Inhibited IR to VUV by cavity QED Inhibited IR to VUV by cavity QED QED cavity is an evacuated space containing oil clusters that QED cavity is an evacuated space containing oil clusters that briefly forms as the oil ruptures and tears under tensile stressbriefly forms as the oil ruptures and tears under tensile stressTearing is governed by the tensile stress given by the maximum Tearing is governed by the tensile stress given by the maximum tension theory tension theory Cavity QED converts thermal kT energy to VUV Cavity QED converts thermal kT energy to VUV The analytical The analytical II and and II / / QQ relations derived are reasonable relations derived are reasonable approximations of flow electrification data for a approximations of flow electrification data for a volume chargevolume charge relation. An area charge relation does not correlate with the data relation. An area charge relation does not correlate with the data