RUBI: Boiling with an isolated bubble in microgravity on-board ISS (Data Processing and Analysis: Issues and Challenges)

RUBI: Boiling with an isolated bubble in microgravity on-board ISS

(

Data Processing and Analysis: Issues and Challenges

)

Institut de Mécanique des Fluides de Toulouse

(CNRS-INP-UPS)

Mohammad Qaisar Raza, Julien Sebilleau, Catherine Colin

Colloque du GDR MFA 2799

 Contribution to heat transfer during boiling • Microlayer evaporation below the bubble

• Unsteady conduction during rewetting

• Forced convection between nucleation sites  Boiling is a complex process

 Several mechanism and parameters are involved  Accurately modelling still remains a challenge

Heater surface

(Kurul & Podowski, 1990; Basu et al., 2005,

Yeoh et al., 2008, Neptune CFD code):

Richenderfer et al. ETFS 2018

Modelling of Heat Transfer

Rewetting

 Buoyancy masks the role of different underlying mechanism

• Small growth time and fast detachment of bubbles In earth gravity  Study at individual bubble scale in microgravity

• Large bubble and longer growth time facilitate understanding

50X Slow

 Accurate modelling of heat transfer requires an estimation of several other parameters:

Bubble departure diameters, frequency of detachment, waiting time, density of active nucleation site

𝑞" ~𝑔𝑛 where 𝑛~0.3 − 1.5  In microgravity (μg) condition

𝑞"~ 0

𝑞" ↑

𝑞" ↓

mUltiscale Boiling Investigation) is planned on-board International

Space Station under the framework of ESA project BOILING.

 Launch Date: 25 July, 2019

RUBI is installed in FSL module of ISS

Honeycomb Heater Pump P re -h ea ter Flow meter Microthermocouple rack

High Voltage Electrode

HS

IR

• Single bubble pool boiling; • Microscale processes; • Impact of shear flow; • Impact of electric field.

Current Science Team: • TUD-TTD (DE), • Aix-Marseille University (FR), • ENEA (IT), • EPFL (CH), • IMFT (FR), • Kobe University (JP), • Kutateladze IT (RU), • LAPLACE (FR), • ULB-TIPs (BE), • University of Hyogo (JP), • University of Padova (IT), • University of Pisa (IT), • University of Maryland (US) • University of Ljubljana • AUTH

• Fluid N-Perfluorohexane

• Pressure : 500 mb,750 mb,1000 mb • Subcooling : 3K, 5K and 10 K

• Wall heat flux : 0.5, 0.75, 1, 1.5 W/cm2

• Liquid flow rate : 0.1, 0.3 and 0.5 l/mn • Mean velocities 0.8, 2.5 and 4.1 cm/s

• t_wait = time between the heater supply and the laser pulse

5

 In the framework of MAP program (Multiscale Analysis of Boiling ) supported by ESA, a comprehensive boiling experiments, namely RUBI (Reference mUltiscale Boiling Investigation) is planned aboard International Space Station

 Goals: Study of nucleate boiling on a single nucleation site in the international space station - heat transfer at the bubble foot

- growth and detachment for different subcooling, overheating wall in a shear flow and/or electric field

Predict bubble detachment diameter

RUBI Experiments

7

5X Slow

BW Image Processing

Subject Image

Background Image

 Image binarization technique is used to extract

the bubble contour

Clean Binary Image

Contact

points

 Challenges:

Reflection at the bubble top and at the base of the bubble

 Based on the clean binary image boundary fit was obtained

 Contact points corresponding to neck formation at the bubble base was determined to identify the contact line

 At both the contact points, linear fit of 10 pixels were used to estimate the contact angles

 Bubble volume and diameter Deq

BW Image Processing

Circle_Fit_1

Circle_Fit_2

Circle_Fit_3

Circle_Fit_1 was obtained based on the points of the Boundary fit

Circle_Fit_2 passes through the contact points and apex of the bubble (These three points were same as obtained from the

Boundary fit)

Circle_Fit_3 passes through the diametrical end points and apex of the bubble (These three points were same as obtained from the Boundary fit)

𝜃

𝜃

𝑝

𝐷/2

𝑐𝑜𝑠𝜃

= 2 ∗ 𝑝/𝐷

 In addition to the

Boundary fit

, 3 circle fit was also made to the bubble interface to estimate different parameters

𝜃 =?

Less than 5%

Comparison of Bubble Parameters

Less than 2%

Less than 3%

Volume

_Diameter

_{Foot Diameter}

Contact Angle

Contact Angle Comparison

Linear fit of 10 pixel points

Circle Fit

 Linear fit of 10 pixel points is not a suitable approach of measuring contact angle

 Circle fit is suitable approach for measuring the contact angle

[⁰]

Subcooling

Flow

Largest

More

Less

Insignificant

3 ℃

10 ℃

100

ml/min

500

ml/min

EASdDdC00cDc_01

EASdDdC00aDc_01

EASdBc000cBc_02

EASdBc000aBc_02

Effect of Refraction

R

R

p

B

B’

𝑑𝑃

𝐷

= 2 𝑅

EASdDdC00cDc_01

∆𝑇

= 10℃

500 ml/min

 Apparent contact line (blue color) was shifted at the new location

(green color) to compensate for the effect of refraction

C

D

E

O

A

A’

ACL

SCL

0.8 mm

Refraction compensation

Effect of Refraction

___

B’

A’

A

B

𝜃

= 𝐴𝑑𝑣𝑎𝑛𝑐𝑖𝑛𝑔

𝜃

= 𝑅𝑒𝑐𝑒𝑑𝑖𝑛𝑔

C

D

E

R

p

p

R

𝜃

𝜃

O

O

As an approximation, Circle fit was made to the left-half and right-half of the bubble which passes through points A’CD and B’ED, respectively. The contact angles were calculated using following

formulae-𝜃

= cos

(𝑝

/𝑅

)

𝜃

= cos

(𝑝

/𝑅

)

𝑝

and 𝑝

is the vertical distance of the center of the circles from

the new contact points A’ and B’, respectively. 𝑅

and 𝑅

are the

radius of the left and right circle, respectively.

15

Flow

Linear fit approach

LR Circle approach

(500ml/min) EASdBc000cBc_01

Shear Flow

Comparison of Benchmark Tests

 Benchmark tests were selected to compare the image processing codes

 Several international teams are involved such as from University of Pisa, Froth Institute of Computer Science, Aristotle University of Thessalonik, among others

X

_X

IR Camera Calibration Issue

[℃] 𝑡 (𝑠) Heating Initiates @ t=0 Nucleation Site Boiling Region

∆𝑇

𝑡

𝑇

𝑇

17

Velocity Distribution

Temperature Distribution

Constant heat flux

Liquid in

_{Liquid out}

Substrate

Liquid

Liquid in

Liquid out

IR Camera Calibration

 2D Study in COMSOL

COMSOL

IR Camera

Boiling Region

𝑇

𝑇

𝑞” = 1 W/cm2

𝑝 = 1000 mbar

Q = 100 ml/min Δ𝑇𝑠𝑢𝑏 = 5𝐾

𝐷_𝑒𝑞 = 𝑘 𝑡

𝑡_{𝑤𝑎𝑖𝑡} = 5 𝑠

 Constant 𝑘 captures the rate of bubble growth, and depends on the superheat of the heated wall, and liquid properties

𝑘 = 𝑓(𝐽𝑎)

 Large value of 𝑘 suggests faster growth of bubble

Shear Flow Results

Evaporation Condensation Heat transfer mechanism in microgravity Superheated layer 𝛿 𝛿 (𝑚𝑚) 19

Events Status

Phase-I  Experiments completed (March 2020)

 Data processing and analysis is underway

Phase-II  Experiments under progress

 To be finished by the end of 2020

Conclusions

 We are studying boiling with isolated bubbles in microgravity condition

 High speed BW and IR camera images are being analyzed to get the physical insights about individual bubble  Improved fundamental understanding of boiling will

 facilitate accurately model the heat transfer  facilitate validation of numerical simulations

Thank you

 Acknowledgements