Showing papers in "Microgravity Science and Technology in 2007"
TL;DR: In this paper, the authors describe several cooling techniques, including the application of miniaturized silicon and BiTe thermoelectric coolers and direct cooling with dielectric liquids through thin film evaporation.
Abstract: Driven by the continuing Moore’s Law evolution in chip technology, power dissipation of nanoelectronics chips could exceed 300W, with heat fluxes above 150W/cm2, within the next few years, along with localized, sub-millimeter zones with heat fluxes in excess of 1kW/cm2. New and novel cooling techniques, with the ability to selectively cool sub-millimeter “sun spots” while providing effective global cooling for high heat flux chips are needed. Several promising approaches, including the application of miniaturized silicon and BiTe thermoelectric coolers and direct cooling with dielectric liquids through thin film evaporation, will be described.
64 citations
TL;DR: In this paper, the wave characteristics of the water film flow over a vertical or an inclined plate with a heater have been studied and the fluorescence method was used to measure local instantaneous film thickness.
Abstract: Liquid films are encountered in space systems as well as in numerous industrial processes and everyday life. The present work is a part of the preparation of the SAFIR experiment of the European Space Agency onboard the International Space Station. Wave characteristics of the water film flow over a vertical or an inclined plate with a heater have been studied. The fluorescence method was used to measure local instantaneous film thickness. In addition to measure wave characteristics eight capacitance sensors were located as a line across the flow. The process of rivulet formation in a heated film was registered. Two zones of the heat flux effect on liquid film deformation were distinguished. At low heat fluxes, the film flow is hardly deformed. At high heat fluxes the thermocapillary forces provide formation of rivulets and a thin film between them. The measured values of the distance between rivulets depend slightly on the plate inclination angle. It was found that for a positive temperature gradient along the flow, heating may increase the wave amplitude because thermocapillary forces are directed from the valley to the crest of the wave. This effect was shown in the interrivulet zone, where relative wave amplitude and Marangoni number increase with a rise of the heat flux density.
40 citations
TL;DR: In this article, a fiber optical thickness probe was used to study the rupture of a subcooled water film flowing down an inclined plate with a 150×150 mm heater, where the main governing parameters of the experiment and their respective values are: Reynolds number (3.2-30.2), plate inclination angle from the horizon (3-90 deg), heat flux (0-1.53 W/cm2), and the threshold heat flux required for film rupture.
Abstract: Rupture of a subcooled water film flowing down an inclined plate with a 150×150 mm heater is studied using a fiber optical thickness probe. The main governing parameters of the experiment and their respective values are: Reynolds number (3.2–30.2), plate inclination angle from the horizon (3–90 deg), heat flux (0–1.53 W/cm2). The effect of the heat flux on the film flow leads to the formation of periodically flowing rivulets and thin film between them. As the heat flux grows the film thickness between rivulets gradually decreases, but, upon reaching a certain critical thickness, the film spontaneously ruptures. The critical film thickness is practically independent on the film Reynolds number as well as on the plate inclination angle and lies in the neighborhood of 60 µm (initial film thickness varies from 93 to 368 µm). The heater surface temperature prior to rupture is also independent of Re and Θ, and is about 45°C (initial film temperature is 24°C). The process of rupture involves two stages: 1) abrupt film thinning down to a very thin residual film remaining on the heater; 2) rupture and dryout of the residual film. The threshold heat flux required for film rupture is scarcely affected by the plate inclination angle but grows with the Reynolds number.
40 citations
TL;DR: In this article, the formation of dry patches in a subcooled liquid film flowing over a locally heated plate at small positive and negative plate inclination angles with respect to the horizon was studied.
Abstract: This study deals with the formation of dry patches in a subcooled liquid film flowing over a locally heated plate at small positive and negative plate inclination angles with respect to the horizon. Prior to film rupture appreciable thermocapillary deformations of the film surface appear, growing with the heat flux. Upon reaching a threshold heat flux the film rupture occurs. By means of high speed imaging it is found that the process of rupture involves two stages: 1) abrupt film thinning down to a thin residual film on the heater; 2) rupture and dryout of the residual film. As the plate inclination angle is reduced the threshold heat flux required for film rupture weakly decreases, however when the angle becomes negative the threshold heat flux begins to rise dramatically, which is associated with an increase of the stabilizing hydrostatic effect due to the growth of the film thickness. The characteristic time of rupture decreases as the threshold heat flux increases. At nucleation of the dry patch the speed of contact line can be as high as 220 mm/s. The results obtained, apart from their intrinsic importance for ground-based applications, can also be of interest for microgravity research as a film flow with different relative contribution of inertia, hydrostatic and thermocapillary forces is considered.
37 citations
TL;DR: The data indicate that plasmid exchange between microorganisms is occurring under space flight conditions, and more experiments are needed to evaluate the occurrence and implications of microbial adaptation and evolution via MGE.
Abstract: Mobile genetic elements (MGE) such as phages, plasmids and transposons play a crucial role in bacterial adaptation and evolution. These MGE mobilize and reorganize genes within a given genome or between bacterial cells. The impact of space flight conditions on these processes is largely unknown. The Mobilisatsia/Plasmida experiment was set up to investigate the impact of space flight conditions on plasmid-mediated conjugation. The experiment was done aboard the International Space Station during the Soyuz Mission 8S (April 19(th) until April 30(th) 2004). An experiment was performed with the Gram-positive Bacillus thuringiensis AND931 (carrying the conjugative plasmid pXO16), B. thuringiensis 4Q7 (with mobilizable plasmid pC194) and B. thuringiensis GBJ002 (final recipient). A second experiment was carried out with the Gram-negative Escherichia coli CM140 (carrying the conjugative plasmid RP4), E. coli CM1962 (with the mobilizable plasmid pMOL222) and Cupriavidus metallidurans AE815 (final recipient). It was observed by selective platings that plasmid exchange between the Gram-positive bacterial strains occurred in the space flight experiment. It is speculated that the latter plasmid exchange occurs more efficient than in the ground control experiment. No significant differences could be observed between space flight and ground control for the Gram-negative bacteria. The data indicate that plasmid exchange between microorganisms is occurring under space flight conditions. Since microorganisms are endogenous to any spacecraft and their presence considered as a possible jeopardy for manned space exploration, more experiments are needed to evaluate the occurrence and implications of microbial adaptation and evolution via MGE.
34 citations
TL;DR: In this article, experiments in the short channel oriented horizontally with the width 40 mm, height 1 mm and length 80 mm were performed and the two-phase flow pattern map was created.
Abstract: Recent developments in electronics and medicine generate an interest in capillary hydrodynamics and heat transfer in Microsystems. Microsystems also are very important for aerospace industry. In the present paper we focus upon experiments in the short channel oriented horizontally with the width 40 mm, height 1 mm and length 80 mm. New flow regimes are observed and the two-phase flow pattern map is created. The obtained results are compared with the data available in the literature.
29 citations
TL;DR: In this article, the authors presented an experimental study of rupture of a subcooled water film falling down an 1 m long heated copper plate with longitudinal grooves of 0.5×0.15 mm2 cross sectional area and 2 mm spacing, and found that the threshold heat flux at which an initial stable dry patch forms on the grooved surface is about two times higher than that on a smooth surface.
Abstract: This paper presents an experimental study of rupture of a subcooled water film falling down an 1 m long heated copper plate with longitudinal grooves of 0.5×0.15 mm2 cross sectional area and 2 mm spacing. It was found that the threshold heat flux at which an initial stable dry patch forms on the grooved surface is about two times higher than that on a smooth surface. Furthermore, the grooves prevent dry patches from spreading over the total heated surface thus essentially delaying the onset of the heat transfer crisis. The main governing parameters of the experiment and their respective values are: initial film temperature (20–95°C), heat flux (0–1.26 W/cm2) and volumetric flow rate (11.1–38.2 l/h) (Re=56.2–653.2).
28 citations
TL;DR: Fincke et al. as mentioned in this paper performed four experiments under isothermal conditions to determine: If a stream of honey injected into water would exhibit the Rayleigh-Tomotika instability and break into small drops.
Abstract: Miscible Fluids in Microgravity (MFMG) was a zero-upmass investigation performed on the International Space Station. The goal of MFMG was to determine if interfacial phenomena seen with immiscible fluids could be seen with miscible fluids. The experiments had to be performed with existing materials on the ISS. Honey and water were chosen as the fluids, and urine collection syringes were used as the vessels in which the experiments were performed. In March 2004 (Increment 8) Dr. Michael Foale performed four experiments under isothermal conditions to determine: If a stream of honey injected into water would exhibit the Rayleigh-Tomotika instability and break into small drops. If an aspherical drop of water in honey would spontaneously assume a spherical shape. The experiments were performed successfully. During Increment 9, Mike Fincke performed two runs in which a stream of honey was injected into water while the syringe was attached to the surface of the Commercial Generic Bioprocessing Apparatus (CGBA) at approximately 31° C. No change in the stream shape was observed. Two more runs were performed on Increments 10 and 11 but no additional phenomena were observed. No behavior beyond simple diffusion was observed. We performed simulations with the Navier-Stokes equations plus a Korteweg stress term. We estimated that the maximum possible value of the square gradient parameter was 10−12 N for the honey-water system.
27 citations
TL;DR: In this article, an experimental study of the spray impact on a heated target and of spray cooling has been performed in normal gravity and in microgravity conditions during parabolic flights, and the effects of spray parameters and of the gravity level on heat transfer have been investigated.
Abstract: An experimental study of the film produced by the spray impact on a heated target and of the spray cooling has been performed in normal gravity and in microgravity conditions during parabolic flights. A convex shape of the target allowed visualization of the film evolution and determination of the film characteristics using the image processing. The effects of the spray parameters and of the gravity level on heat transfer have been investigated. It has been found that the spray cooling efficiency depends on the water flow rate in a non-monotonous way. A range of spray parameters at which the effect of gravity level on heat transfer is significant has been determined. It has been found that the spray cooling is less effective in microgravity conditions in comparison with normal gravity and hypergravity.
25 citations
TL;DR: In this article, the effects of phase distribution in the condenser on the stability and reliability of the whole system were studied and a model is proposed for convective condensation at low mass fluxes in a microgravity-like situation.
Abstract: This paper deals with certain aspects of convective condensation phenomena and condenser behaviour in capillary-driven cooling loops (CPL or LHP) studied in the LAPLACE laboratory, Toulouse. The effects of phase distribution, in the condenser, on the stability and the reliability of the whole system were studied. A model is proposed for convective condensation at low mass fluxes in a microgravity-like situation. The numerical results are in good agreement with experimental data. On increasing the mass flux, both numerical and experimental results suggest that the stationary state no longer exists, and intrinsic instabilities occur and develop in the condenser. The effects of such instabilities, as well as flow regime transitions, on loop behaviour remain an open question.
22 citations
TL;DR: In this paper, a liquid layer of variable thickness is subject to a flow of inert gas and the non-uniform evaporation induced by the gas flow creates a temperature gradient parallel to the interface triggering in that way thermocapillary convection.
Abstract: In this paper, some of the preparatory experiments of the ESA sponsored space program CIMEX-1 are presented. A liquid layer of variable thickness is subject to a flow of inert gas. The non-uniform evaporation induced by the gas flow creates a temperature gradient parallel to the interface triggering in that way thermocapillary convection. The combined action of evaporation, thermocapillarity and gravity has been not completely clarified both theoretically and experimentally. The experiment presented in this work concerns a liquid layer of ethanol of 2.2 mm thickness in presence of a mass flow of Nitrogen whose intensity varies in the range of hundreds of milliliter per minute. The experiments were performed at an initial liquid temperature of 21°C. The patterns observed are strongly dependent on the flow rate of inert gas. A change in the instability patterns has been observed for a gas flow of about 1.7 l/min.
TL;DR: In this article, the effects of the tube diameter, the flow directions, and the mass velocity on the tube quenching using liquid nitrogen are investigated systematically in the terrestrial conditions by using three inner diameters of the transparent heated tube (7, 10, 13.6 mm) for measuring fluid behavior observations and heat transfer measurements simultaneously.
Abstract: The gravity effects on quenching of tube by cryogenic fluids for the development of cryogenic fluid management on orbit are studied. In this paper, the effects of the tube diameter, the flow directions, and the mass velocity on the tube quenching using liquid nitrogen are investigated systematically in the terrestrial conditions. The experiments are performed by the mass velocity between 100–600 kg/m2s in downward and upward flow directions by using three difference inner diameters of the transparent heated tube (7, 10, 13.6 mm) for measuring fluid behavior observations and heat transfer measurements simultaneously. The results indicate that the difference between the minimum heat fluxes under downward and upward flow conditions increased as the mass velocity increased. These characteristics of heat transfer were caused by filamentary flow pattern that was found in only downward flow and high mass velocity conditions.
TL;DR: In this article, the authors present experimental tests about the performance of heat pipes filled with a self-rewetting fluid (alcohol aqueous solutions) and compare with conventional commercial water heat pipes.
Abstract: The work presents experimental tests about the performance of heat pipes filled with a “self-rewetting“ fluid (alcohol aqueous solutions). Comparison with conventional commercial water heat pipes is also considered. The used fluid exhibits an anomalous increase in the surface tension with increasing temperature. Along these lines, the fluid has been investigated as a possible means to improve heat transfer inside the heat pipes with a focus, in particular, on space applications (next generation satellites). The experiments have been carried out both in normal and in low-gravity conditions (attained onboard a ‘zero-g’ plane, during a parabilic flight campaign). The results have confirmed improved capability of the considered heat pipes with respect to traditional heat pipes filled with water.
TL;DR: In this paper, the authors investigated the effect of slip on heated liquid film driven by its own vapor in microchannel and found that the maximum of the slip velocity is located in the transition region.
Abstract: The development of compact, advanced cooling technology leads to problems involving two-phase flows at micro-scales. We investigate the effect of slip on heated liquid film driven by its own vapor in microchannel. The macroscopic interface shape is found to be sensitive to slip length comparable with the initial film thickness. The slip at the wall tends to elongate the transition film, and can have an effect on the mass flow rate. Calculations reveal that the maximum of the slip velocity is located in the transition region. The present work is a part o Studies of such liquid films in microchannels propose accurate models of the transition regimes between macro- and micro-scales that capable of predicting formation of dry patches and heat transfer in the micro-region near contact line and hence, in the localized hot spots with very intensive evaporation. The deviation of the gas flow from the continuum hypothesis is measured by Knudsen number. However, the concept of the mean free path is not useful for the liquids, and is more relevant to the liquids slipping at the wall. A review of recent experimental, numerical and theoretical works on slip effect can be found in [6]. In the present work we investigate the slip effect on evaporating liquid film driven by its own vapor in microchannel. f the preparation of the SAFIR experiment of the European Space Agency onboard the International Space Station.
TL;DR: In this article, the authors have modelled the thermal diffusion process under different microgravity environments using measured g-jitter data onboard the International Space Station (ISS) and FOTON-12.
Abstract: Microgravity environments may provide perspective platforms for studying the phenomenon of thermal diffusion. It is, however, noted that the residual microaccelerations (g-jitters) in space laboratories may affect the accuracy of experiments due to convections that they induce. An appropriate interpretation of experimental results from the Space relies on a thorough understanding of the influence of g-jitters on thermal diffusion. In this paper, we have modelled the thermal diffusion process under different microgravity environments using measured g-jitter data onboard the International Space Station (ISS) and FOTON-12. The fluid system consists of a rectangular cavity filled with a ternary mixture of methane, n-butane and dodecane (50∶20∶30 mol%). A lateral heating condition is applied. Various case scenarios have been studied with respect to different locations in the ISS and FOTON; and a detailed analysis is made in comparison with the ideal zero gravity (0-g) scenario. It is found that the diffusion process is only slightly affected by the g-jitters in both platforms. Recommendations are made according to the findings from this study for the improvement of the accuracy of diffusion experiments in Space.
TL;DR: An overview of the research program in Heat and Mass Transfer coordinated by the European Space Agency (ESA) can be found in this paper, where the authors describe the experiments performed up to now as well as their main results.
Abstract: This paper gives an overview of the research programme in Heat and Mass Transfer coordinated by the European Space Agency (ESA). This research programme consists of six projects involving more than 30 partners, both academia and industry, spread in 11 countries in Europe, Canada and Israel. The microgravity experiments performed up to now are recalled as well as their main results. Finally, the experiments planned for the coming years, particularly in the Fluid Science Laboratory (FSL) on the International Space Station (ISS), are briefly described.
TL;DR: In this article, the pool boiling heat transfer of FC-72 on a plain plate with a heating area of 15*15 mm2 in different pressure and subcooling has been studied experimentally both in normal gravity on the ground and in microgravity aboard the Chinese recoverable satellite SJ-8.
Abstract: The pool boiling heat transfer of FC-72 on a plain plate with a heating area of 15*15 mm2 in different pressure and subcooling has been studied experimentally both in normal gravity on the ground and in microgravity aboard the Chinese recoverable satellite SJ-8. A quasi-steady heating method is adopted, in which the heating voltage is controlled as an exponential function with time. Three modes of heat transfer, namely single-phase natural convection, nucleate boiling, and transition boiling, are observed, while the nucleate pool boiling are the major subject for discussion in the present paper. In normal gravity, the present data is compared with those obtained by other researchers, and a satisfactory agreement is evident and warrants reasonable confidence in the data. Compared with terrestrial experiments, the boiling curves in microgravity are considerably gentle, and CHF is no more than 40% of that in terrestrial condition. In microgravity, influences on boiling curves of the pressure and subcooling are similar with those in normal gravity, namely that the heat transfer coefficient and CHF will increase with subcooling for the same pressure, and that they will also increase with pressure for the same subcooling. Keywords: microgravity, pool boiling, subcooling, plate heater
TL;DR: In this paper, the effect of surface instability and internal flow on the internal flow structure of a large droplet was investigated using Particle Image Velocimetry (PIV) technique.
Abstract: Under the microgravity environment, production of new and high quality material is expected. Large droplet is preferable for such a containerless processing in microgravity environment. There are a lot of previous studies for droplet levitation [1]. However, effect of surface instability and internal flow appear remarkable when the droplet becomes large. Elucidation of effect of surface instability and internal flow of the levitated droplet is required for the quality improvement of new material. The objective of present study is to clarify critical conditions of the occurrence of the internal flow and the surface instability. At first, the condition between the stable region and the unstable region of the droplet levitation was evaluated by using the existing critical Weber number theory. The experimental result agreed well with the theory. It was suggested that the stability of droplet can be evaluated by using the theory for the interfacial instability. Finally, two-dimensional visual measurement was conducted to investigate the internal flow structure in a levitated droplet. The effect of physical properties on the internal flow structure of the droplet is investigated by Particle Image Velocimetry (PIV) technique. As the result, it is indicated that the internal flow structure is affected by the physical property such as viscosity.
TL;DR: In this paper, an electronic nose specifically designed for air quality control in closed environment is under development, which has been tested during the ENEIDE mission on board of the International Space Station.
Abstract: Long-term manned space missions requires a continuous monitoring of the air quality inside the spacecraft. For this scope, among several different solutions, electronic noses have been considered. On behalf of European Space Agency an electronic nose specifically designed for air quality control in closed environment is under development. After several ground experiments concerning the monitoring of a biofilter efficiency, the instrument has been tested during the ENEIDE mission on board of the International Space Station. in this paper the instrument main concepts and its performance in ground and space experiments are illustrated.
TL;DR: In this article, a problem of condensation on curvilinear fin is considered with taking into account the essential influence of the capillary forces and non uniform temperature of the fin.
Abstract: Some aspects of the ESA space program EMERALD are presented. A problem of the film type condensation on curvilinear fin is considered with taking into account the essential influence of the capillary forces and non uniform temperature of the fin. Disjoining pressure effect on condensate film flow is studied numerically, because of very thin film of condensate on the fin tip. Value of the groove flooding depth changes significantly the condensate outflow from the condenser. Calculations for water condensation predict a very high value of the heat transfer coefficient, more than 50 kW/m2K, on a quite important part of the surface area and confirm the idea of proposed condenser and Double Capillary Pumped Loop.
TL;DR: The hypothesis tested by this project is that space flight increases the incidence and duration of herpes virus reactivation and shedding in saliva and that an immune response may not be necessary for reactivation.
Abstract: The hypothesis tested by this project is that space flight increases the incidence and duration of herpes virus reactivation and shedding in saliva. Saliva, urine, and blood samples were collected from 3 crew members who participated in a 14-day Odessa Soyuz taxi mission. Saliva samples were collected before, during, and after the mission, and blood and urine were collected before and after the mission. The saliva and urine samples were analyzed using the polymerase chain reaction to detect the presence of 3 important herpes viruses. Epstein-Barr virus (EBV) and varicella-zoster virus (VZV) were tested in saliva, and cytomegalovirus (CMV) was measured in urine samples. Plasma antibodies levels to these viruses were determined by enzyme-linked immunosorbent assay before and after flight. EBV reactivated before, during, and after flight; CMV reactivated before and after flight; and VZV reactivated during and after flight. In other studies, greater frequencies of positive samples and greater numbers of copies of viral DNA have been found. No increases in titer of antibodies to these viruses were found, suggesting that an immune response may not be necessary for reactivation.
TL;DR: In this article, the authors summarize the results of the few research carried out on FBHT in microgravity, with special emphasis to the recent research carried at ENEA, in the frame of an ESA (European Space Agency) project.
Abstract: Flow boiling heat transfer (FBHT) allows high performance heat transfer due to latent heat transportation and its use is therefore important to reduce size and weight of space platforms and satellites. Its knowledge is also important for the safe operation of existing single-phase systems in case of accidental increase of heat generation rate. The number of existing researches on flow boiling in reduced gravity is very small due to both larger heat loads and available room in a 0-g apparatus for experiments. Consequently, coherence in existing data is somewhat missing. This lecture will summarize the results of the few research carried out on FBHT in microgravity, with special emphasis to the recent research carried out at ENEA, in the frame of an ESA (European Space Agency) project.
TL;DR: The experiment LSO (Lightning and Sprite Observations) on board of the International Space Station was the first experiment dedicated to nadir observations of sprites from space as discussed by the authors.
Abstract: The experiment LSO (Lightning and Sprite Observations), on board of the International Space Station, was the first experiment dedicated to nadir observations of sprites from space. Such observations are innovative as sprites are generally observed at the horizon. At the nadir, sprites are superimposed with lightning flashes and the observation concept is based on a spectral differentiation of sprites and lightning by using an adapted filter. The experiment is composed of two micro-cameras, fixed on a station window. One camera is equipped with a filter and measures the sprites in the N2 1P most intense sprite emission line, which coincides also to the atmospheric absorption band of the molecular oxygen. The second microcamera provides observations of lightning flashes in the visible. Measurements were performed during four ESA missions: Andromede, Odissea, Cervantes and Delta. During 19h of effective observations, 180 flashes were analyzed and several possible sprites were identified, demonstrating the interest of this differentiation method. In addition during sunset and sunrise conditions when the lower atmosphere is in the dark, LSO observed the airglow of the secondary ozone maximum at about 90 km modulated by gravity wave activity.
TL;DR: In this paper, the authors describe a "space-first" test of bacterial fuel cells onboard the International Space Station using the Rhodoferax ferrireducens strain, and test if it is possible to use a bacterial fuel cell in 1g and under both simulated (RPM) and real microgravity conditions.
Abstract: Bacterial Fuel Cells are innovative energy systems that use bacteria to transform carbohydrates anaerobically into free electrons and waste products. The bacteria deposit the electrons on the anode and hence create a potential difference between the anode and the cathode, yielding a ‘bacterial battery’. This principle may be favourably influenced by enhanced bacterial productivity or bacterial growth in microgravity conditions, as is shown before in several other studies on bacteria in microgravity. Nonetheless, bacterial fuel cells have not been tested in space before. Currently foreseen applications are very promising for space flight and include waste disposal in manned space vehicles. This study describes a ‘space-first’test of bacterial fuel cells onboard the International Space Station using the Rhodoferax ferrireducens strain. We test if it is possible to use a bacterial fuel cell in 1g and under both simulated (RPM) and real microgravity conditions. Due to differences in magnitude of the output the data had to be normalized and cumulatively plotted. In all, it can be concluded that bacterial fuel cells show similar phases in the output under different gravitational conditions. Hence it can be concluded from a biological point of view that bacterial fuel cells do operate in space.
TL;DR: In this paper, the behavior of growing/collapsing vapor bubble ejected to subcooled liquid bath was focused and the instability emerged over the surface of the growing and collapsing vapor is discussed as functions of the degree of subcooling, and the temperature and ejection speed of the vapor.
Abstract: Behavior of growing/collapsing vapor bubble ejected to subcooled liquid bath was focused. Test fluid was purified water in the present study. Vapor bubble was produced inside the heated tube of 1.5 mm in inner diameter by supplying the test fluid to the tube by microsyringe. This system enabled the authors to observe interaction between the vapor and the liquid in the condensing process extracted from the boiling phenomenon consisting of liquid-gas-solid interactions. The bubble behavior was detected by employing a high-speed camera with up to 100,000 fps. The instability emerged over the surface of the growing and collapsing vapor is discussed as functions of the degree of subcooling, and the temperature and ejection speed of the vapor. The present study aims to understand and control the micro-bubble emission boiling known as MEB.
TL;DR: In this article, a theoretical model to predict time dependent film condensation heat transfer in 2D geometries for different channel shapes is presented, where surface tensions, curvature induced pressures, gravitational forces and shear stresses at liquid-wall interfaces are taken into account.
Abstract: This paper presents a theoretical model to predict time dependent film condensation heat transfer in 2-dimensional geometries for different channel shapes. Surface tensions, curvature induced pressures, gravitational forces and shear stresses at liquid-wall interfaces are taken into account. Local and mean heat transfer coefficients, liquid film thickness distribution and cross sectional void fraction are evaluated as a function of time. The predicted results for condensation of R134a vapor in a circular channel (1mm diameter), a square channel (1mm side), and an equilateral triangular channel (1mm side) are presented.
TL;DR: It is confirmed that high levels of motility behaviour are necessary to produce significant decreases in fly longevity, and a likely consequence of the cold transport step, no effects on the life spans of the flown flies were detected.
Abstract: Human exploration of outer space will eventually take place. In preparation for this endeavour, it is important to establish the nature of the biological response to a prolonged exposure to the space environment. In one of the recent Soyuz Missions to serve the International Space Station (ISS), the Spanish Soyuz mission in October 2003, we exposed four groups of Drosophila male imagoes to microgravity during the almost eleven days of the Cervantes mission to study their motility behaviour. The groups were three of young flies and one of mature flies, In previous space experiments, we have shown that when imagoes are exposed to microgravity they markedly change their behaviour by increasing their motility, especially if subjected to these conditions immediately after hatching. The constraints of the current Soyuz flights made it impossible to study the early posthatching period. A low temperature cold transport was incorporated as a possible way out of this constraint. It turned out that on top of the space flight effects, the cold treatment by itself, modifies the motility behaviour of the flies. Although the four groups increased their motility, the young flies did it in a much lower extent than the mature flies that had not been exposed to the low temperature during transportation. Nevertheless, the flies flown in the ISS are still more active than the parallel ground controls. As a consequence of the lower motility stimulation in this experiment, a likely consequence of the cold transport step, no effects on the life spans of the flown flies were detected. Together with previous results, this study confirms that high levels of motility behaviour are necessary to produce significant decreases in fly longevity.
TL;DR: The first International Caenorhabditis elegans Experiment (ICE-First) was carried out using a Russian Soyuz spacecraft from April 19–30, 2004 and investigated the following aspects of the organism: whether meiotic chromosomal dynamics and apoptosis in the germ cells were normal under microgravity conditions, and the effect of the space flight on muscle cell development.
Abstract: The first International Caenorhabditis elegans Experiment (ICE-First) was carried out using a Russian Soyuz spacecraft from April 19-30, 2004. This experiment was a part of the program of the DELTA (Dutch Expedition for Life science Technology and Atmospheric research) mission, and the space agencies that participate in the International Space Station (ISS) program formed international research teams. A Japanese research team that conducted by Japan aerospace Exploration Agency (JAXA) investigated the following aspects of the organism: (1) whether meiotic chromosomal dynamics and apoptosis in the germ cells were normal under microgravity conditions, (2) the effect of the space flight on muscle cell development, and (3) the effect of the space flight on protein aggregation. In this article, we summarize the results of these biochemical and molecular biological analyses.
TL;DR: In this article, temperature measurements during flow boiling of R134a in a 0.96 mm single circular channel are reported in order to provide a criterion for the determination of the critical conditions in the channel.
Abstract: Temperature measurements during flow boiling of R134a in a 0.96 mm single circular channel are reported in order to provide a criterion for the determination of the critical conditions in the channel. The flow boiling heat transfer is obtained by using a secondary fluid; the wall temperature displays larger fluctuations in the zone where dryout occurs. These temperature fluctuations in the wall denote the presence of a liquid film drying up at the wall with some kind of an oscillating process. These temperature fluctuations never appear during condensation tests, neither are present during flow boiling at low vapour qualities. The fluctuations also disappear in the post-critical condition zone.
TL;DR: Findings indicate the importance of maintaining a vigorous scientific program in the ISS to understand the consequences of the modified environment in outer space on living organisms.
Abstract: If exploration of outer space is going to be a major human enterprise in the future, it is important to establish the nature of the biological response to the space environment. In one of the recent Soyuz missions to serve the ISS, the Spanish Soyuz Mission in October 2003, we sent a group of Drosophila pupae that underwent almost complete development there. Microarray analyses of the RNAs extracted from flies fixed in the ISS revealed that a relatively large set of genes (15% of the total number assayed) suffered a significant expression change in these conditions. Furthermore, the samples had to be transported to the launch site and it was necessary to slow down their development by exposing them to a lower temperature, fully compatible with pupal development. Such a pre- exposure had an effect by itself on the pattern of gene expression observed after pupal development at normal temperature, but the two environmental factors seemed to act synergistically together with the containment in the type I container. These findings indicate the importance of maintaining a vigorous scientific program in the ISS to understand the consequences of the modified environment in outer space on living organisms.