Parabolic Flight Experiments

Analysing the two-phase flow behaviour of cryogenic propellants like LH 2-VH 2 and the accompanying flow regime utilizing volume fraction is made easier by the current analysis. Additionally, two phases of liquid hydrogen (LH 2) in different inlet velocities and temperatures have been described in the current work. With the aid of the commercial CFD program Ansys Fluent, a two-dimensional computer model of a cryogenic feed line, has been created for the present study. To characterize the two-phase flow of LH 2 and to accurately estimate hydrodynamic and thermodynamic properties under various situations, the volume of fluid (VOF) approach based on an Eulerian flow scheme incorporated with an energy equation is used. These models have been validated with experimental data, and the trend of volume fraction captured matches the computational result. The flow visualization and the volume fraction has evaluated along with bulk mean temperature (Tb) and velocity analysis. Therefore, the current methodology may be used to estimate the flow shape and phase distribution at different initial conditions.

An experimental study of a flat plate pulsating heat pipe has been performed under various gravity conditions during ESA 69 parabolic flight campaign. A molybdenum plate, with 14 milled rectangular channels with cross-section of 3×3 mm, was covered with a sapphire window, and tested in vertical position with ethanol as working fluid. If operation in normal and hyper-gravity conditions were characterized by nucleate boiling regime, FP-PHP working like in looped thermosyphon mode, transition into microgravity was accompanied by a flow pattern change into slug/plug regime with thin film evaporation, due to absence of buoyancy forces. Hydrodynamic instabilities, accompanied with short-term periods of emergence of nucleate boiling under microgravity, were observed during several parabolas. Formations of long vapor slugs in the channel lead to thin film evaporation. Combined optical and infrared visualizations showed velocity and amplitude increase of the menisci motions.

Pulsating Heat Pipes are thermally driven two-phase passive devices mainly based on phase change phenomena (film evaporation, flow boiling, film condensation), and influenced by capillary and gravity forces. They consist of a meandering capillary tube closed in a loop, evacuated and partially filled with a working fluid at saturation conditions. Once the heat load is applied, the fluid motion starts and an oscillating pattern of alternating vapour bubbles and liquid plugs forms inside the tube. As it is widely accepted, complex flow patterns, ranging from slug flow to annular flow, occur in the adjacent tubes of pulsating heat pipes (PHP), initiated by local pressure instabilities ((Khandekar et al. 2003) and (Liu et al. 2007). Such flow patterns have obviously effects on the total heat flux transferred from the heated to the cooled ends of the PHP. Many parameters have also a direct influence on their operation (Charoensawan et al. 2003): number of turns, PHP dimensions, filling ra...

This work describes the thermal characterization on ground and under a varying gravity field (parabolic flights) of a large diameter Pulsating Heat Pipe (PHP) especially designed for its future implementation on the heat transfer host module of the International Space Station (ISS) for long term microgravity experiments. A multi-turn compact closed loop PHP is made of aluminum and partially filled with FC-72 (50% vol.). The 3mm tube internal diameter is larger than the static capillary limit evaluated on ground conditions for the above working fluid, with the objective of dissipating larger heat power inputs compared to smaller diameter channels, under microgravity conditions, allowing the typical slug flow pattern of PHPs to occur. To provide a detailed insight on the thermo-hydraulics phenomena during the device start-up under the occurrence of microgravity, the PHP is equipped with a transparent sapphire tube insert, two miniature pressure transducers and two microthermocouples. ...

Effects of nanostructured defects of copper solid surface on the bubble growth in liquid argon have been investigated through a hybrid atomistic-continuum method. The same solid surfaces with five different nanostructures, namely, wedge defect, deep rectangular defect (R-I), shallow rectangular defect (R-II), small rectangular defect (R-III) and no defect, have been modeled at molecular level. The liquid argon is placed on top of the hot solid copper with superheat of 30 K after equilibration is achieved with CFD-MD coupled simulation. Phase change of argon on five nanostructures has been observed and analyzed accordingly. The results showed that the solid surface with wedge defect tends to induce a nanobubble relatively more easily than the others, and the larger the size of the defect is the easier the bubble generate.

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An experimental study of a flat plate pulsating heat pipe has been performed under various gravity conditions during ESA 69 th parabolic flight campaign. A molybdenum plate, with 14 milled rectangular channels with cross-section of 3×3 mm 2 , was covered with a sapphire window, and tested in vertical position with ethanol as working fluid. If operation in normal and hyper-gravity conditions were characterized by nucleate boiling regime, FP-PHP working like in looped thermosyphon mode, transition into microgravity was accompanied by a flow pattern change into slug/plug regime with thin film evaporation, due to absence of buoyancy forces. Hydrodynamic instabilities, accompanied with short-term periods of emergence of nucleate boiling under microgravity, were observed during several parabolas. Formations of long vapor slugs in the channel lead to thin film evaporation. Combined optical and infrared visualizations showed velocity and amplitude increase of the menisci motions.

A wickless passive two phase closed loop heat transfer device especially designed for a future implementation on the heat transfer host module of the International Space Station is tested in relevant environment on board a parabolic flight. The tube internal diameter (3mm) is larger than the static capillary threshold evaluated in normal gravity for this working fluid (FC-72), leading the device to work as a loop thermosyphon on ground and in hypergravity conditions, and as a Pulsating Heat Pipe when micro-gravity occurs. Novel start up tests, where the heat load has been provided after the occurrence of microgravity, show that the 20s microgravity period is enough for the device activation and, most important, that the device activation is purely thermally induced and not affected by the previous acceleration field. Two miniaturized pressure transducers and direct fluid temperature measurement via two micro-thermocouples, allow to provide a detailed insight on the fluid local thermodynamics states both in the evaporator and in the condenser zone during microgravity. It is shown that the two-phase fluid close to the evaporator and the condenser is subjected to several degrees (up to 5 K) of superheating or subcooling. The level of subcooling seems to increase with the heat input level both in terms of temperature difference and in terms of percentage time with respect to the whole microgravity period.

A large tube may still behave, to a certain extent, as a capillary in a micro-gravity environment. This very basic concept is here applied to a two-phase passive heat transfer device to obtain a new family of hybrid wickless heat pipes. Indeed, a Loop Thermosyphon, which usually consists of a large tube, closed end to end in a loop, evacuated and partially filled with a working fluid and intrinsically gravity assisted, may become a capillary tube in space condition and turn its thermo-fluidic behavior into a Pulsating Heat Pipe. This work presents the results obtained on such a hybrid device heated at 200 W both on board a sounding rocket (ESA REXUS 22, microgravity period ~120 s), and on ground in vertical and anti-gravity orientation. Since no steady state occurred in microgravity conditions, the comparison between flight and ground data focuses on the startup phenomenon, whereas the thorough ground test campaign describes the limits and performances of the device working in thermosyphon mode. The expected thermal behavior in microgravity conditions is between that of a purely conductive tube in anti-gravity conditions on ground and that of a gravity assisted thermosyphon. Since a microgravity period of approximately 120s is not sufficient to reach a pseudo steady state regime, further investigation on a longer-term weightless condition is mandatory.

A Single Loop Pulsating Heat Pipe (SLPHP) with an inner diameter of 2 mm is tested in hyper/micro gravity conditions during the 68 ESA Parabolic Flight Campaign. The system is designed with two sapphire tubes that connect the heated and the cooled section, allowing simultaneous fluid flow high-speed visualization, and a direct to fluid IR analysis by using respectively a high-speed camera and a Medium-Wave Infrared Camera (MWIR). Three independent heaters are positioned at the evaporator in order to vary the power distribution and to promote different flow motions with specific heating configurations. Furthermore, two highly accurate pressure transducers measure the pressure drop between the condenser and the evaporator. Additionally, twelve thermocouples mounted on the external tube wall record local temperatures during parabolic flight tests. Such a complete thermo-fluid dynamic analysis at different gravity levels, coupled with the acquisition of high-speed and infrared images in...

A Pulsating Heat Pipe specifically designed to be hosted on board the Heat Transfer Host of the International Space Station is tested in hyper-gravity and microgravity during Parabolic Flights. The device is realized bending an annealed aluminium tube with an inner diameter of 3 mm. The geometry is a three-dimensional closed loop with 14 turns. The external temperatures of the device are measured in the adiabatic zone with a high-speed infrared camera, recording images at 50 frames per second and with a spatial resolution of 1280x1024 pixel. The images are thereafter post-processed and utilized to extrapolate space and time-varying local heat fluxes on the tube internal surface in contact with the fluid, solving the inverse heat conduction problem in the pipe wall. It is found that the local heat flux can reach values up to 10 kW/m during the start-up of the device in weightlessness. These results point out that in this dynamic thermofluidic system, the temperature difference betwee...

This work describes the thermal characterization on ground and under a varying gravity field (parabolic flights) of a large diameter Pulsating Heat Pipe (PHP) especially designed for its future implementation on the heat transfer host module of the International Space Station (ISS) for long term microgravity experiments. A multi-turn compact closed loop PHP is made of aluminum and partially filled with FC-72 (50% vol.). The 3mm tube internal diameter is larger than the static capillary limit evaluated on ground conditions for the above working fluid, with the objective of dissipating larger heat power inputs compared to smaller diameter channels, under microgravity conditions, allowing the typical slug flow pattern of PHPs to occur. To provide a detailed insight on the thermo-hydraulics phenomena during the device start-up under the occurrence of microgravity, the PHP is equipped with a transparent sapphire tube insert, two miniature pressure transducers and two microthermocouples. ...

I want here to thanks all the people who made possible the accomplishment of this thesis. First of all I thanks prof. Sauro Filippeschi who proposed me this challenging work. I know him since the time in which I organized with his support great conferences, like the one with ESA astronaut Paolo Nespoli. Esteem and respect is ever growing since that moment and this thesis further developed our relationship. He also made possible my nice experience at ENEA in Rome, giving me the economic support I needed. Thanks to dr. Mauro Mameli, who spent a lot of time behind me and my work. He is very passionate of what he does and transmitted this passion to me. Furthermore, he taught me important things both on technical/scientific and human side. Thanks to Prof. Anastasios Georgoulas for he shared his code and competences with me, patiently answering to all my questions, even in the middle of the night.Thanks to Dr. Giuseppe Zummo for he shared his experimental results and hosted me a week in ENEA and, with him, all the people of his laboratory in Rome, who received and treated me as a long time friend. Thanks to Dr. Davide della Vista, who spent a lot of time setting up work station remote connection. Finally, thanks to all my family (present and past) and all the people who supported me during these years. A special mention goes to Sister Rosetta, who-I am sure-is watching me from heaven: dear Sister, I haven't still gone to the Moon, but I remembered the promise I made you.

A Pulsating Heat Pipe specifically designed to be hosted on board the Heat Transfer Host of the International Space Station is tested in hyper-gravity and microgravity during Parabolic Flights. The device is realized bending an annealed aluminium tube with an inner diameter of 3 mm. The geometry is a three-dimensional closed loop with 14 turns. The external temperatures of the device are measured in the adiabatic zone with a high-speed infrared camera, recording images at 50 frames per second and with a spatial resolution of 1280x1024 pixel. The images are thereafter post-processed and utilized to extrapolate space and time-varying local heat fluxes on the tube internal surface in contact with the fluid, solving the inverse heat conduction problem in the pipe wall. It is found that the local heat flux can reach values up to 10 kW/m during the start-up of the device in weightlessness. These results point out that in this dynamic thermofluidic system, the temperature difference betwee...

A Pulsating Heat Pipe specifically designed to be hosted on board the Heat Transfer Host of the International Space Station is tested in hyper-gravity and microgravity during Parabolic Flights. The device is realized bending an annealed aluminium tube with an inner diameter of 3 mm. The geometry is a three-dimensional closed loop with 14 turns. The external temperatures of the device are measured in the adiabatic zone with a high-speed infrared camera, recording images at 50 frames per second and with a spatial resolution of 1280x1024 pixel. The images are thereafter post-processed and utilized to extrapolate space and time-varying local heat fluxes on the tube internal surface in contact with the fluid, solving the inverse heat conduction problem in the pipe wall. It is found that the local heat flux can reach values up to 10 kW/m during the start-up of the device in weightlessness. These results point out that in this dynamic thermofluidic system, the temperature difference betwee...

A numerical investigation on the effect of wettability characteristics on a single bubble growth during saturated flow boiling conditions within a microchannel, is conducted in the present paper. The numerical simulations are conducted with the open-source toolbox OpenFOAM, utilising a user-enhanced Volume OF Fluid (VOF) solver. The proposed solver enhancements involve a treatment for spurious velocities dampening (a well-known defect of VOF methods), an improved dynamic contact angle treatment to accurately account for wettability effects as well as the implementation of a phase-change model in the fluid domain, accounting for conjugate heattransfer with a solid domain. The predictions of the simulations show that the local Nusselt number (Nu) is more depended on wettability characteristics for low heat fluxes, and less dependent on higher heat fluxes. In more detail, it seems that the local, instantaneous heat transfer coefficient is higher for super-hydrophilic cases in comparison to hydrophilic. However, as the applied heat flux increases, hydrophilic and super-hydrophilic cases show a similar heat transfer enhancement with respect to the single-phase heat transfer in the considered micro-channel. Finally, superhydrophobic cases, show lower heat transfer performance with respect to the single-phase case. This is due to the fact that a vapour blanket is rapidly formed immediately after the nucleation, acting as an insulator of the heated solid surface.

Manned operations in an orbiting laboratory for extended periods of time has many characteristics in common with work in the deep sea, and is accompanied by a number of similar problems. In this paper the scenario of manned payload operations in space will be addressed : some aspects with their parallel in deep-sea work become evident. The analysis results from a study carried out with the ESA/ESTEC in preparation for the Columbus programme, and uses as a baseline the lessons learned from past manned miSSIons. Some highlights of these results are presented here.

The inescapable human desire to move further in space exploration is leading towards higher spacecraft power levels and electronics miniaturization. This trend not only affects power systems but also thermal control ones in terms of higher amount of heat to be dissipated and higher heat fluxes. PHP, a two phase passive device working in the confined flow region, is a promising solution in that it meets all of a future space mission requirements: it is simple, light, cheap, passive and exhibits adequate thermal performance. Recently an hybrid type of PHP (called LTS/PHP) has been proposed for space use only. This pointed out that the effect of gravity on flow confinement inside two phase wickless devices is not fully understood yet. A CFD approach to the problem is a powerful tool to unveil the secrets of this phenomenon. The VOF model developed by prof. A. Georgoulas and implemented in OpenFOAM was adopted. As a first step toward the microgravity validation of his model, the present work deals with the simulation of a recent parabolic flight experiment by dr. G. Zummo (ENEA). Considering a quasi-2D axysimmetric geometry of the 4 mm ID test section, the setup for the validation of the code is tested for saturated and subcooled conditions. Comparison of the saturated case with the experiment is given together with an highlight of the limitations of the model in subcooled cases.

In conjunction with the upcoming MlR'96 Russo-German manned space mission, a parabolic flight campaign was planned in order to verify some of the experiments to be carried out. The principal driver for the campaign is the Medex facility, which will be used for various human life science experiments during the MlR'96 mission. This parabolic flight campaign differs from the previous ones carried out in Europe, in that the scientists and experiments came to Star City, where the llyushin-76 is stationed and normally flies. This paper describes the technical, organizational, and logistics aspects of preparing such a campaign. A brief summary is given of the scientific experiments and operational tests carried out.

For the first time in the history of parabolic flight in Europe, a series of parabolic flights in a large aircraft took place over the North Sea in May, 1990. A group of more than 20 scientists and researchers from seven institutions participated in this parabolic flight campaign, carrying out a series of scientific and technical experiments during three days of flights. The flights were organized and carried out by OHB-System in Bremen, using the CNES Caravelle and their CEV crew. The range of experiments was wide, covering physiological and psychophysical experiments on human subjects , astronaut support equipment, biological equipment, and testing of new microgravity technology systems in the fields of fluid flow measurement, materials processing, and

Chapter 21 Operational Evaluation of the Exemsi Project:
In general the EXEMSI project has proved to be very successful mission. It has demonstrated that it is indeed possible to perform a major and useful project in a short time and on a moderate budget. In addition to achieving the scientific objectives, this simulation project provided valuable experience in the training of members of chamber crew and ground control crew for their tasks. It covered all aspects of a mission from call for experiment proposals, crew selection and training, integration and testing of the facility and its equipment, to daily monitoring and managing of the mission, and finally post-isolation data collection and evaluation. These other activities were accomplished by a small team of experts in the astoundingly short time of 8 months. What was lacking in manpower, time and funds, was more than made up for by enthusiasm, expertise, team spirit, hard work and long hours well beyond the call of duty of all those involved. In addition to the specific and technological objectives reached, many lessons learned in this operation have been identified, which could help to improve future missions. The experience has shown pitfalls to be avoided in future mission, as well as points where some small increase in effort can make a considerable difference. With the prospect of long-term manned spaceflights looming in the near future and the ever increasing costs of such endeavors, the possibilities offered by running simulated missions on the ground should be seriously considered. Such simulations permit the study of scientific and operational aspects of a space mission prior to its actual implementation. A ground based simulation of an extended space mission may be run at a fraction of the cost of an in-orbit precursor mission of even one-week duration. However, careful planning of the simulation mission is required so that it may yield relevant information and useful experience. Lessons learned from the EXEMSI project should be taken into account in such planning. At the start clear goals should be formulated, that can provide clear guidelines for building up the infrastructure and defining the operational scenario. A long duration mission simulating the conditions on the Russian space station MIR could provide a valuable source of information and experience in preparing for the MIR '95 Mission.

Test results of the performance of the RAPUNZEL tether deployer in zero-gee. The RAPUNZEL deployer is based on a tether spool and a magnetic hysteresis brake that controls deployment by applying a precisely maintained tension profile. A torque arm with variable spring is used as tension sensor, in a feedback loop with the hysteresis brake, tension could be precisely controlled during parabolic flight. However, the mechanism is complex and may not be so scalable and limited to low levels of deployment tension (<2 N in this test). It could perhaps be used as a first stage of a tension system in combination with a capstan tension multiplier.