Two-PhaseFlow Heat Transfer Experiments in Tubes Under Microgravity Conditions

Activityresponsible: Dr. Giuseppe ZUMMO
Address:ENEA C.R. Casaccia, Institute of Thermal FluidDynamics, Via Anguillarese 301 (S.P. 092), 00060 S. M. di Galeria RM,Italy 
Phone:+39 06 3048 4567 Fax:+39 06 3048 3026



Themain objective ofthisexperimental activity is to study two-phase flow cooling systems inmicrogravity environment. Two-phase flow heat transfer is the mostappropriate cooling method for those components characterised by highheat fluxes, which are expected to be used in space systems.Experimental activity will cover the main aspects of two-phase flow:heat transfer, pressure drop, CHF, and flow pattern visualization, insubcooled and saturated flow boiling.
In flow boiling systems (subcooled and saturated flow boiling),microgravity affects vapour bubble size, coalescence and formation aswell as flow pattern. These influences tend to disappear for increasingvalues of liquid velocity and for decreasing flow channel diameter.
The aim of the experimental campaign is to study the effect of tubediameter and flow velocity on flow boiling systems in low gravityconditions in order to define the limit conditions at which thegravitational forces do not have any influence on the physicalmechanisms of flow boiling. The results of the experimental campaignwill be useful in defining the design tools for two-phase flowcomponents in low gravity environment. The design tools are defined interms of heat transfer correlations, pressure drop correlations, CHFcorrelations.
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Schematic of the Experimental Facility
Schematic ofthe experimental loop

Picture of theMICROBO facility in flight configuration during the 38th ESA ParabolicFlight Campaign in October 2004

The MICROBO (MICROgravityBOiling) facility is designed in order toperform flow boiling and quenching experiments in 1-g and 0-g. Threetubular tests sections are used: 2.0 mm, 4.0 mm, and 6.0mm, while the process fluid is FC-72. Each tube is madeby Pyrex, which will allow flow visualization and the measurement ofheattransfer coefficient at the same time. The Pyrex tube is heated with aheatermade of a metal spring attached to the outer surface of the tube.
The characteristics of theexperimental apparatus are summarisedhereafter.

Dimensions:66 cm x 194 cm x 54 cm (Height x Length x Depth)
Overallmass: 210 kg
WorkingFluid: FC-72
Systempressure: 1.6 – 2.2 bar
Massflow rate range: 50 ml/min – 450 ml/min
Electricalpower: 180 Watt
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Two experimentalcampaigns were carried out in October 2004 (38th ESA parabolic flightcampaign) and March 2005 (39thESA parabolicflight campaign).Theexperimental activitywas performed aboard ofthe Novespace Airbus A300 Zero-G, located in Bordeaux, France. Theexperimental team was composed by:
Gian Piero Celata, MarcoGervasi, Alberto Lattanzi, Luca Simonetti, andGiuseppe Zummo.

ENEA team of October 2004 ESAPF 38 campaig (from the left): Luca Simonetti, Gian Piero Celata, MarcoGervasi, Alberto Lattanzi, andGiuseppe Zummo

ENEA Flying team of October 2004 ESA PF 38campaign (fromthe left): Luca Simonetti, Marco Gervasi, and Giuseppe Zummo

The MICROBOfacility wasused for the first time in the October 2004 campaign with the 6.0 mmtest section and all components weretested during the flights. Thefacility worked successfully and it allowed to perform all 93 scheduledexperiments on 93 parabolas. Inthe three flight days, the experiments during all parabolas weresuccessfully recorded, included the initial parabola of each day, for atotalof 93 tests. Among these tests, 74 were dedicated to flow boiling and15 toquenching.

In the March 2005campaign theexperiments were performed with the 4.0 mm test section. All 93scheduled tests were carried out successfully (84 dedicated to flowboiling and 9 to quenching). In this campaign Dr. Anne Pacros of ESAjoined the ENEA team and performed the experimental activity on boardof the ZERO-G airplane.

Flyingteam of March 2005 ESA PF39 campaign: Anne Pacros, Giuseppe Zummo,Marco Gervasi, and Luca Simonetti

Duringeach parabola video sequences of flow structure were recordedwith an ultra rapid shutter video camera on a digital video recorderwith afrequency of 50 frames per second. The frame recorded by the videocamera islocated near the exit section of the flow channel. The video imagesobtainedare able to provide information on the flow pattern at the exit of theheatedtube and can be analysed to determine the vapour bubble dimensions andvelocities for different values of gravity. With this video system itispossible to compare flow structures in microgravity and in normalgravity atthe same operational conditions (mass flow rate, inlet fluidtemperature,system pressure, and electrical power).

1-gbubbly flow
0-gbubbly flow
Typicalflow pattern observed in 1-g and 0-g at low mass flow rate

1-gbubbly flow
   0-gslug flow
Typicalflow pattern observed in 1-g and 0-g at intermediate vapour quality

Allvideos are in AVI format visible with almost all video players
Bubblyflow with low mass flow rate clickhere
Bubblyflow with high mass flow rate clickhere

Plot of walltemperature timetrace for low mass flow rate

Plot of walltemperature timetrace for high mass flow rate

Typicalplots ofthe walltemperature and acceleration level versustime. Theheattransfer regime is saturated flow boiling at different mass flow rates. In thesegraphs,the horizontalaxesrepresents time in seconds while the left vertical axes represents thewalltemperature in °C, and the right vertical axes represents theaccelerationlevel: 1 is normal g (9.81 m/s2). In the uppergraph walltemperature is not influenced by the gravity level, while in the bottomgraph there is a significant influence of gravity on temperatures.

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NovespaceAirbus A300 ZEROG

Forfurther details about NOVESPACE activities please visit their home page.

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The microgravityenvironment iscreatedaccording to the aircraft manoeuvres described in the figure.

Typical parabola of theAirbus A300 ZERO-G

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Collection of images of theparabolic flights

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Collection of articles andinterviews
(to read a pdf version just click on the below images)

Press releases from Agencies

"IL Sole 24 Ore"

"La Repubblica"

Video Interview to Dr. G.P. Celata on IES TV TG (May 2011) 

Interview to Dr. G.P. Celata on RADIO RAI1 (17/03/2005,18.35) 
Interview to Dr. G.P. Celata on RADIO RAI1 (12/05/2005,18.35) 

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European Space Agency Home Page

ESA - ParabolicFlights Home Page

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