Charles A. Ward Thermodynamics and Kinetics Laboratory, University of Toronto

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Charles A. Ward Thermodynamics and Kinetics Laboratory, University of Toronto Fluid Behavior In Absence Of Gravity: Confined Fluids and Phase Change Second g-jitter Meeting Victoria, British Columbia

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Charles A. Ward Thermodynamics and Kinetics Laboratory, University of Toronto. Fluid Behavior In Absence Of Gravity: Confined Fluids and Phase Change. Second g-jitter Meeting Victoria, British Columbia. Configuration of a Confined Fluid at g. 0. Prediction from thermodynamics. g. - PowerPoint PPT Presentation

Transcript of Charles A. Ward Thermodynamics and Kinetics Laboratory, University of Toronto

Page 1: Charles A.  Ward Thermodynamics and Kinetics Laboratory,  University  of Toronto

Charles A. Ward

Thermodynamics and Kinetics Laboratory,

University of Toronto

Fluid Behavior In Absence

Of Gravity: Confined Fluids and Phase Change

Second g-jitter Meeting

Victoria, British Columbia

Page 2: Charles A.  Ward Thermodynamics and Kinetics Laboratory,  University  of Toronto

Configuration of a Confined Fluid at gConfiguration of a Confined Fluid at g0

Liquid

g

Prediction from thermodynamics

Page 3: Charles A.  Ward Thermodynamics and Kinetics Laboratory,  University  of Toronto

Apparatus Used on the Space Shuttle

Page 4: Charles A.  Ward Thermodynamics and Kinetics Laboratory,  University  of Toronto

Position of the Apparatus and Observations on the Space Shuttle

Page 5: Charles A.  Ward Thermodynamics and Kinetics Laboratory,  University  of Toronto

Thermodynamic predictions

Measure the contact angle at the upper and lower interface...

Average SAMS reading

Average OARE reading

Average values from a confined fluid

Page 6: Charles A.  Ward Thermodynamics and Kinetics Laboratory,  University  of Toronto

ge>0

Pl >Pu

nSV)l >nSV)u

γSV)l <γSV)u

θl >θu

Summary of the Proposed Mechanism

Page 7: Charles A.  Ward Thermodynamics and Kinetics Laboratory,  University  of Toronto

Examine the Effect of Adsorption on the Contact Angle of the Water-Glass System

Page 8: Charles A.  Ward Thermodynamics and Kinetics Laboratory,  University  of Toronto

New Theory

Gibbs adsorption equation, Young Eq.

Statistical mechanics

Page 9: Charles A.  Ward Thermodynamics and Kinetics Laboratory,  University  of Toronto

Comparison of Isotherms with Measurements

Page 10: Charles A.  Ward Thermodynamics and Kinetics Laboratory,  University  of Toronto

Mechanism by Which Large Contact Angles on the Space Shuttle are Produced

5°C Space shuttle

observations compared to those in a ground-based laboratory.

Page 11: Charles A.  Ward Thermodynamics and Kinetics Laboratory,  University  of Toronto

Way it looks and the Way It Should Look!

nSV = f (T ,PV )⇒ θ = g(T ,PV )

PV − PL = γ LV (1R1

+1

R2)

μL = μ V = μ SV = μ SL

Page 12: Charles A.  Ward Thermodynamics and Kinetics Laboratory,  University  of Toronto

Experimental Apparatus Used to Study Liquid-Vapour Phase Change Processes

Page 13: Charles A.  Ward Thermodynamics and Kinetics Laboratory,  University  of Toronto

1. Measure in one     horizontal direction.

A. No evaporation when pressure was 820 Pa.

    B. Pressure in the vapor  775Pa,

j = 0.407±0.006 g/m2s

2. Without opening the      system, rotate the 3-     dimensional positioner      90° and measure in the      second horizontal      direction.

Page 14: Charles A.  Ward Thermodynamics and Kinetics Laboratory,  University  of Toronto

Near the Interface During Steady State Water Evaporation

PIV =593±34Pa

TIL =−0.4±0.05°C

TIV =2.6±0.05°C

j =1.017g/sm2

PIL =617.3Pa

Psat(TIL )=593Pa

Psat(TIV )=766.6Pa

Page 15: Charles A.  Ward Thermodynamics and Kinetics Laboratory,  University  of Toronto

Temperature During Steady State Evaporation of Water

1. Uniform temperature     layer in the liquid     near the interface.

2. Thermal conduction      below the uniform      temperature layer.

3. How does the energy     cross the uniform     temperature layer?

°

PIV =181.0±0.5Pa

TIL =−16.20±0.02°C

TIV =−10.45±0.01°C

j =1.520±0.003g/ sm2

Page 16: Charles A.  Ward Thermodynamics and Kinetics Laboratory,  University  of Toronto

Does Marangoni Convection Alone Explain the Uniform Temperature Layer?

Page 17: Charles A.  Ward Thermodynamics and Kinetics Laboratory,  University  of Toronto

Interfacial Properties During Steady State Evaporation

Page 18: Charles A.  Ward Thermodynamics and Kinetics Laboratory,  University  of Toronto

Assumed Velocity Profile Near the Interface

Page 19: Charles A.  Ward Thermodynamics and Kinetics Laboratory,  University  of Toronto

σ (R0 ,θ ) = η (1r

∂vr

∂θ+

∂vr

∂r−

r) r=R0

∇γLV • iθ =1R0

(dγ LV

dTIL

)(dTI

L

dθ)€

∇γLV • iθ = σ (R0 ,θ )

vθ (R0 ,θ ) = −1η

(dγ LV

dTIL

)(dTI

L

dθ) ln(1−

2δu

R0

)

Determine Tangential Speed from Measured Temperature Profile

Equate tangential surface tension gradient with viscous shear stress

Surface Tension is only a function of temperature

Viscous Shear Stress

Expression for the fluid speed:

v(2δu ,θ ) = 0

Page 20: Charles A.  Ward Thermodynamics and Kinetics Laboratory,  University  of Toronto

Tangential Speed Determined from Thickness of the Uniform-Temperature Layer and Measured Interfacial Temperature Gradient

Page 21: Charles A.  Ward Thermodynamics and Kinetics Laboratory,  University  of Toronto

Image of Interface and Probe During Steady State Evaporation

Page 22: Charles A.  Ward Thermodynamics and Kinetics Laboratory,  University  of Toronto

Results Suggest Marangoni Flow is Unstable

j = 0.407g

m2sVapor-phase pressure: 776.1 Pa

Page 23: Charles A.  Ward Thermodynamics and Kinetics Laboratory,  University  of Toronto

Effect of Marangoni Convection on Evaporation

Page 24: Charles A.  Ward Thermodynamics and Kinetics Laboratory,  University  of Toronto

Comparison of Speed Determined by Two methods

Page 25: Charles A.  Ward Thermodynamics and Kinetics Laboratory,  University  of Toronto

Probe Position as a Function of Time

When Evaporation is Occurring at Different

(Steady) Rates

Page 26: Charles A.  Ward Thermodynamics and Kinetics Laboratory,  University  of Toronto

Power Spectra of Probe Oscillations

Page 27: Charles A.  Ward Thermodynamics and Kinetics Laboratory,  University  of Toronto
Page 28: Charles A.  Ward Thermodynamics and Kinetics Laboratory,  University  of Toronto

If there is no Marangoni

convection, energy conservation is not satisfied!

Page 29: Charles A.  Ward Thermodynamics and Kinetics Laboratory,  University  of Toronto

Conclusions

1. A fluid confined in a cylindrical container and exposed to the acceleration field of the Shuttle adopts the two-interface configuration, but not the configuration it would be expected to adopt if the system were in equilibrium and the acceleration were ~10-6g0. The configuration adopted corresponds to the configuration expected under equilibrium conditions if the acceleration were greater than 10-4g0.

2. During water evaporation, thermocapillary (or Marangoni) convection exists at the interface. Even in a ground-based laboratory the flow parallel to the interface is oscillatory. At higher evaporation rates, the thermocapillary convection can become turbulent.